Rathbone's Use &
Care Of Batteries & Chargers:
A very valuable guide for the buyer or user of
rechargeable and primary battery packs in your organization.
Also the later part is a detailed collection of discussions from
true experts in the battery cell field regarding "Memory Effect".
This handbook is supported by manufacturers battery
cell specification sheets. Reference information pulled from
Anton Bauer, Cadex, Christie, Gates, GE, Saft, Sanyo, PAG, and
Panasonic manuals or specification sheets, as well as our own
in-depth knowledge and experience in the battery and analyzer
The following information is applicable in any market
that requires primary
or rechargeable battery packs and chargers. We will use the main
battery packs of one particular market for the illustration.
Battery Packs and Cells.
The use and care of these battery packs is also the same for
rechargeable battery packs in any other market. In this market
there are approximately five standard types of battery packs
to choose from:
1. NP1 Series
2. BP-90 Series
3. Brick Series, ( Unsealed screw together & Sealed)
4. Battery Belts
5. Film Lunch Box Battery Packs
There are approximately four companies building good chargers.
One is considered a high end “smart” charger and three manufacture
Battery Management Analyzer Systems? All four of these systems are better and best type
There are approximately three companies that provide complete battery
and charger systems manufactured by themselves.
There are dozens of street vendor battery assemblers manufacturing
battery packs with varying if any quality.
some of these street vendors are very good providing quality
at a profit but some are marketers providing product at a
The buyer for your product will do better to go to a quality aftermarket
company who supports their product with black and white manufacturers
battery cell specification sheets and listed prices of the batteries and chargers for your system. You
will receive better product and better price from a black and white
vendor hard copy. Stay away from vendors with vague or
generalized product descriptions and who do not list their prices for
all to see. Always ask for
specification sheets on the product you are considering. The exact
specifications should also be on the purchase order, packing slip and
invoice. If the vendor has specification sheets, you are on the
correct road! If the vendor supplies you the sales pitch in
writing you may still be on an acceptable road. Look closely at
the written sales pitch and verify the authority of the writing
person then pay attention to the purchase order, packing slip and
If the vendor
does not understand why you need specification sheets in writing
before giving them your purchase order or money, you have a company
selling product for profit. There are a few of these street
vendors that have been around a long time and some of those close,
open, and close again under the same or a different name.
customer education of the product is NOT in that vendors best
consideration in your choice of battery cells is this:
Negative Delta V Charge:
( “Sales Pitch”)...., If you are using a Smart charger or a Battery
Management System, you can use a press negative or brand name but low end
"economical" cell or a
high end sinter cell technology. Using a smart charger or
charger will allow you to use the less expensive cell with no harm to
that cell pack from the more sophisticated charger.
This is true...,
But, the charge rate can damage a battery cell if the battery cell is
not designed to accept the heat generated by faster rate of charge or
from a trickle (overnight) charger. The smart
chargers and our Analyzer charger units use a negative delta V charging
technique and cut off the fast charge at the voltage peak so
the press negative cell is not damaged.
Some manufacturers’ chargers go to, or use, a “trickle” charge
technique giving a constant very low charge and teach this as “not
harmful” to your battery pack.
Continually heating the insulator between
the positive and negative plates of any battery cell will cook the insulator. The
insulator becomes brittle, breaks apart and allows the negative and
positive plates to touch, allowing the battery cell to short.
A crock pot placed on its lowest setting. You place a fresh
roast in the crock pot and leave it there all day. You can go
by the pot and touch the pot anytime through the day. It will
be warm but will not burn you.
Yet that evening
the fresh juicy red roast is no longer red but dark and a finished
cooked product. That is what a trickle charge does to the
insulator between the negative and positive plates of the high
quality or low quality battery
cell in your battery pack.
Also, most people we are exposed to as a user or dealer focus
on the charge system used on the battery pack and make allowance for
lower end cells (with a sophisticated charging system), but forget to
consider the DISCHARGE rate of the battery pack. The number one enemy
of your battery cell is heat! A heavy or long term discharge
rate on a
battery pack is much more destructive to the cells than an
unsophisticated charger and certainly a sophisticated charger. Cell
quality is important! “You do get what you pay for.” The
press negative cell has more internal resistance than the sinter cell
A NO, NO, NO!
Another trick we see is “patching” or "Fixing" battery packs. When a
battery pack is somewhat new and still under warranty, it is
acceptable to change a cell in an assembly
environment using a welder, not a solder gun. A welder does
not harm the cell but a solder gun placed to the cell will burn the
insulator between the two
plates. A welder will not cause a voltage drop but a solder
joint will always cause a voltage drop. Several voltage drops
will damage the performance of the battery pack and create problems
for a sophisticated charger system. The charger system cannot
get an accurate reading of the battery pack due to false readings
because of the voltage drops.
another problem with patching is that you have several different
cells in series or parallel as the case may be, each with a different
capacity reading and strength. The newest cell placed in the
pack becomes the lead and
attempts to do the work of every cell that is not up to the same
standards. This will cause the new cell to wear down rapidly to
the performance levels of the other cells in that pack. It is
like placing a new dog at the front of a team of dogs who have been
run all day and telling that new dog to take that old team and run
all night. The new dog wears himself out trying to pull the
tired dogs along with him. Your battery pack is only as strong
as the weakest cell!
economy television stations, professional film and video companies,
freelance people and anyone else in the industry responsible
to maintain and replace the rapidly changing technology have many
things they must consider. Many of these are of no importance
to the salesperson trying to supply the package they represent.
In the tough competitive market today, many salespeople look for
areas to remove cost and become the favored low bid with all the
bells and whistles. (Of course, that salesperson is not
concerned with your long range forecast except to offer a replacement
somewhere in the future and only then to supply you with a specific
battery for that new system.)
more appropriate choice for you would be to select a battery system
that can be rebuilt and continue to grow with your change in
equipment technology. This will greatly reduce your accessory
purchases and expense budget. Smart buying in a long range plan
a flexible battery pack that will work with your existing system and
future system needs.
charger system that will work for multiple battery packs, and,
cheap, “Analyizer \ Conditioners”, that
battery pack and Waste your Charge Discharge Cycles. Many times the
salesperson may suggest that you reduce your expense so they can be
the low bid and this will most likely be in the battery and charger
A smart buyer
(and a smart, well intended, salesperson) should ask the following
ever change systems again and can you use this same battery and
charger system on more than one style of camera?
Will you be suing more than one manufacturers battery packs or
Will you ever
change the way you run the business again, i.e., more news, or more
outside production etc? This could mean more or different
camera systems. You want to keep your expense at a minimum
with a consistent and flexible battery and charger system that will work on
current systems as well as any other systems you purchase in the
future. Your decision regarding battery packs and chargers is
battery packs require different styles of chargers. Universal style
battery packs can utilize the same charger system. A system
like the, CADEX 7000, Christie CASP 2500, or PAG ACS. Saving
you $$$ that can be invested elsewhere, like more battery packs from
As an example, the BP- 90 is a better alternative than the NP1 Series
for versatility of Sony Product.
In a large
environment you may need the versatility of all five of the major
battery types. Because of this, chargers used in-house, Like
the CADEX 7000, Christie CASP, or PAG ACS can be
purchased with the versatility of managing all the different types of
battery packs while the user in the field will have a less expensive
but versatile unit for their battery. However, the
potential for completely changing systems or adding an additional
system down the road suggest reason for more flexible choices or
A good example
of adding flexibility to your TV news needs with minimal expense:
Use an Anton
Bauer or PAG manufactured adapter plate and have your choice of
vendor provide bricks for these systems. Then, no matter what
you do, all you need for versatility is a new adapter plate for an
additional system and you continue to use your existing brick style
Whether it is a screw together battery unit or a sealed
battery unit you may
significantly reduce your future replacement expenses by purchasing
inserts from Rathbone Energy
, Inc. and rebuilding the units
in-house or by allowing Rathbone Energy
, Inc. to
rebuild the unsealed or sealed battery pack for you. We can also
assist your technician by telephone in the opening of a sealed unit
as we supply you the inserts for those sealed units. Other
points of interest:
reduce the need for different types of chargers unless you are
adding equipment for a new crew.
the battery does or does not have temperature protection and or
voltage/current protection fuses internally (depending on the
Series batteries have no thermal protection exposing your systems
to potential damage.
Brick Style Batteries can come in several qualities.
Brand Name is
not all to consider as every brand name has high end cells and low
We sell all high end Battery Management Analyzer Chargers:
CADEX, PAG ACS and Rathbone Energy.
We still design
and can manufacture chargers similar to our retired Analyzer+300 &
After charger is plugged in, turned on and system has run diagnostic
codes and all lights are off, then place
NP1 Batteries on
We can custom design, sell boards, and sell a license on our products
and software as well as private label.
Christie, CADEX, PAG, Rathbone Energy are the only sophisticated
charging systems that qualify as a battery management analyzer charging
companies do produce “smart chargers” for particular markets in mass
volume, like for cellular phones or communications radios.
These are individual units, again produced in Very Mass Volume for
that particular market.
The others we
know off develop similar multi-port systems for One Specific Market,
can be simple software to semi complex software. Almost all are
simple smart software.
There are three basic types of charging systems for Ni-CD cells or
1. Time charge
2. Temperature charge method
3. Negative delta V cut off methods.
dT/dT for Nickel Metal Hydride
Constant Current / Constant Voltage for Lithium Ion
strictly a timing mechanism that is set to charge at a particular
rate for a set time and then either turn completely off or reduce the
charge rate to a lower charge rate for a set or indefinite time.
Method is a design that requires a temperature sensor in series built
into the battery pack itself. The temperature charger method looks
for this temperature sensor to open.
This “open” in
the current path tells the temperature charger to either reduce or
turn off the charge current to the battery pack. These can be
very simple to more complex designs with detail for levels of
reduction in current path by placing several temperature sensors in
the pack with different calibrations producing different results in
the current flow.
If the battery
is below a certain temperature do not charge. If the battery is
between A & E charge at this rate, if another sensor tells you the
battery is between D+ & J charge at this rate and so on.
Negative Delta V is the beginning of a simple smart
Negative Delta V is programmed to look for a particular voltage peak
in the battery cell or battery pack. It is much more accurate
than the other two methods.
Most Negative Delta V systems look for a voltage peak at
approximately .2V to .3 V above the voltage peak and tell the charger
the next instructions. For example, to turn off or to go to a reduced
charge current or something of that nature.
charger system will incorporate all of these three methods in their
charger routine as safety backup to the first charge routine.
This would be to
use the negative delta V charge method for
initial charge routine and for a safety on the battery and charger to
protect the battery, the charger and the product you would back up
the negative delta V charge routine with the temperature sensor to
detect too much dissipating heat or to detect a battery that is too
cold and prevent the charge routine until the battery has reached a
safe temperature environment.
Third would be
the back up of the timing routine at one and one half times the
needed charge time for the said battery pack. Thus if the
negative delta V fails and the temperature sensor fails the system
will still turn off when the battery as charged for one and one half
combination of these routines you develop a simple to semi-complex
The more complex
methods use the above mentioned routines in combination with
algorithms and other criteria to develop a battery management system.
We will not go into any heavier detail at this point as not to expose
our patients or trade secrets.
systems require very sophisticated chips and a strong EE with a
strong software background, strong background and understanding
of the battery chemical and battery cell itself.
“Analyzer \ Conditioner”
usually goes with a simple charger system that has some type of fuel
gauge to analyze an approximate capacity of the cell or battery pack.
The condition routine is a very simple routine to “deep” discharge
the battery pack to 1.0V per cell one or more times to reduce what
was once called the “memory effect”. They are very simple and
almost always a waste of money. Beware of any system that will
discharge a cell below .7 volts (per engineering specs. you can
damage the cell).
(Discussions by experts are in the last 20% of this article)
only approximately 10% of the demon it was 10 years ago.
of memory is simple. The battery cell has an electrolyte
chemical between the positive and negative cells placed on a gauge or
The moving of this electrolyte from one side to the other is the
chemical reaction that generates the energy or current from the
battery cell or battery pack.
When a battery pack is not thoroughly used in the field every time it
will, over time, develop a chemical change called a crystallization
build up on the insulator.
electrolyte changes in chemical form to this crystallization, it will
move through the
insulator gauge and will not create the desired chemical reaction.
Thus, you will not have the same intensity of energy generation.
developed several “witch” remedies such as to deep discharge the
battery with a lamp or allow the system to run until the product will
not operate anymore, not even to power any LED.
create several damaging effects to the battery cell or pack and
“memory” would always be blamed for these problems. As the
smoke screen of memory is removed we find that these techniques to
remove “memory” were actually doing more damage to the cells and
battery packs than anything else including analyzer conditioners.
Trickle (overnight) chargers increase this problem.
person or company telling you that there is such a thing as memory
is simply promoting low end cells or does not know batteries.
Either way, they should not be in the battery business.
When the battery
pack or cell is discharged below 1.0V per cell ( per engineering
specification manuals) you create the opportunity for reverse
discharge cells and or extremely unbalanced cells.
We discussed these effects and the correct procedures previously
using the analogy of the team of dogs.
A new battery
may be safely used with no unwarranted abuse or misuse of the battery
pack if the following options are used.
1. The product manufacturer should have a voltage cutoff method at
1.0V per cell designed into there product, and the product should
shut completely down at this point. Meaning, when the battery
reaches 1.0V per cell the system shuts completely down. The
unit should also have a “approaching” voltage shut down warning at
about 2 to 3 minute before actual shut down. Or say, an
(audible and or visual) voltage cut off warning at 1.02 V per cell
and a voltage shut down at 1.0 or .9 V per cell.
Some companies design product with a voltage shut down system, but
the product itself will continue to draw power from the battery pack.
If the user does not “turn off” the unit or “pull” the battery pack,
the unit will continue to draw power from the battery even down to
0.0V per cell. This is the greatest cause of reversed discharge
or extremely unbalanced battery cells or battery packs. If this is
done on a regular basis the user will definitely damage the battery
cell or pack very early in the battery charge discharge cycle life.
2. If the
manufacture has not added these design features to save the consumer
frustration and money:
Use the battery pack until the system does not operate properly and
then place the back up battery in the unit, and recharge the first
unit creating a battery rotation.
The charge time
of the charging battery depends on what type of charger is used and
the discharged level of the battery pack. If the charger has a
cut off at full charge then you have no immediate worry. If the
charger just continually charges with no cut of point you need
to check the manual and see how long it takes to fully charge a
electronic electrical wall timer and set that timer for 2 hours more
than the manual specifications ( rule of thumb). This connects
with the other sections that reference the analogy of the crock pot.
3. If the
manufactured product comes with a sophisticated charger system such a
one from Rathbone Energy, that we design, develop and can
produce, the customer only uses his battery and places it on our
system. We usually develop systems with a standard charge
routing and a battery management system routine. The customer
places his or her battery pack on a six week maintenance schedule.
With a proper system such as what we design and develop, the customer
only needs to run the Analyzer routine every 6th week.
We feel that
they will keep their battery as clean as is possible with the least
amount of maintenance using our battery management chargers and this
If you use a
system that fully discharges the battery cell or pack to 1.0V per
cell every single time you use the product you still greatly reduce
the battery life expectancy by abusing the charge discharge cycle
life of the battery pack.
Suppose you use the unit and only use 10% of the run time capacity
and then discharge the battery pack. You wasted 90% of that one
cycle. Most battery packs used in the medical industry are
designed for 500 to 700 charge discharge cycles. It will not
take a long time to process that battery pack through its anticipated
charge discharge cycle life if this type processing
Also, to keep the battery pack on a continual charge charger will
cook the insulator, make the insulator brittle, breaking up and
allowing the positive and negative plates to touch creating a shorted
cell and battery pack.
It is our
opinion that Ni-CD batteries can be safely stored for “up to” 2 years
in a cool environment in a discharged state. We do not use
battery cells on our shelves more than a few months old for our own
manufacturing purposes. After that you
can begin to see reductions in actual performance verses
specification sheet performance.
Wet / Gel cell
or dry cell lead acid cells can safely be stored off of the floor in
a cool ,environment. These cells must be stored fully charged
and they must be checked and recharged between every 30 to 60 day
companies manufacture battery assemblies, a few companies
manufacture simple battery charger units and 3 (I can think of)
manufacture a system they refer to as an analyzer \ conditioner.
Two of those companies were in a long term legal
battle over the charger system and it is not an accurate system even
for an analyzer conditioner. It appears to work fine in the
fast food industry, if you consider burning up the insulator fine.
ourselves, we are aware of three companies that develop battery and
battery charger systems for one particular market ( video) and that
is their only market. Their systems are sophisticated smart
chargers and battery packs for that particular industry.
Cadex, Christie and PAG are the only companies we are aware of that
develop battery management analyzer systems and we sell all these chargers.
Engineering specification sheets call for a battery cell not to be
discharged below 1.0 Volts per cell, otherwise they could damage the
cell as discussed above. When we design a system charger we add
another safety feature to warn the person responsible for battery
packs of a video shooter, or person in their service discharging
their packs below a particular voltage. This safety is
incorporated in the following manner.
Engineering specification sheets list a fully charged battery pack at
1.25V per cell. In general purpose layman’s terms we reference
as 1.2V per cell and yes, all Ni-CD battery cells are at 1.2V per
cell fully charged.
All “ smart” systems have some type of chip inside the unit.
Some use a very simple and basic chip, some use very sophisticated
chips. Cadex, Christie, PAG and ourselves use a
co-processor along with a very extensive line of highly sophisticated
chips. These chips can be programmed with very simple routines
to very complex routines. The cost of the chip is the same in a
“non-expensive” and an “ expensive unit. The expense is in
writing the detailed software routines so the company or user has all
or non of the available “ bells and whistles”.
High End refers
to a high quality battery cell . Also press negative cells have
more internal resistance than sintered on sinter or pasted.
Any battery cell manufacture would be glad to mail you a product
manual, but these do not tell you what I just have and they will not
take the time to do this for individuals.
As for cell
assembler’s, most do not intend to educate the user, or the customer
in any way. The job is to sell what they have and education
could cost them a sale.
Remember: (Short recap then on to the rest of the
Point of information:
All rechargeable battery packs have an “internal resistance”.
This causes the battery pack or cell to discharge while on the shelf.
A nickel cadmium battery cell or pack will loose 3% of its total
charged capacity per day while sitting on the shelf.
“As a Rule of
Thumb” A Alkaline battery cell can re-energize, but is
rechargeable battery pack is continually discharged to zero it will
be ruined and even if occasionally discharged to zero will stand a
high probability of un-repairable damage.
battery is consistently discharged to a rate less than 1.0V per cell
you can create unbalanced cells in the battery pack or if discharged
very low, reverse discharge situation. With unbalanced cells,
the battery pack will only charge to the weaker of all the cells in
that pack. Our Battery Management Analyzer Chargers are designed to
correct this problem if it is not too severe.
From our point
of view, the length of time between use and discharge of a Ni-CD and
recharge is not relevant. The Ni-CD pack can be stored for up
to 2 years in a discharged state. If a Ni-CD is stored for a
long period of time it will build back a percentage of its “ stamina” with proper
charge, use, and discharge.
Reverse discharge means that the cells current is attempting to
move in the correct negative to positive polarity and a number of the
cells are attempting to move in the incorrect positive to negative
is only 10% of the problem it was 10 years ago and can be kept at a
minimum with proper maintenance of the battery pack as listed if
articles already faxed or e-mailed to you.
Memory effect is
the chemical reaction of the insulator between the negative and
positive plates changing from a liquid or gel consistency to a
crystallization build up thus not allowing the chemical reaction
between the plates that will
generate energy. The more crystal build up the less chemical
reaction and the less the energy output. This would be accurate
and not allow for misleading thoughts or understanding. Some
assemblers and manufacturers would have a field day on my company
with our shared customer market if I were quoted that way on “ Memory
Trickle (overnight) chargers
increase this problem.
person or company telling you that there is such a thing as memory
is simply promoting low end cells or does not know batteries.
Either way, they should not be in the battery business.
Nickel Metal Hydride:
Nickel Metal Hydride cells are Great for cordless
and cellular telephones as well as very small portable devices.
They have made there way into the broadcast market and we will sell
It is my opinion, generally speaking, that nickel
metal hydride cells will give you
50% more run time per density
50% less charge discharge cycles for the amperage
Cost 50% more per density
Cost 50% more for the charge discharge cycles given
and cell amp hours
Do not hold up well under constant high current
demand situations or heavy use.
For Broadcast: Also have less weight and do not
assist in the balance of your camera lens / battery to your
As for broadcast or heavy use devices you should
simply compare the comparable manufacturers nickel metal hydride
and nickel cadmium cell specifications sheets as well as your cost.
Conversion to Nickel Metal Hydride from Nickel Cadmium:
Some companies encourage you to convert your nickel cadmium
battery pack to nickel metal hydride.
We will do
this conversion IF you are using a Cadex, PAG, or Rathbone Energy analyzer:
Nickel cadmium: To get the best performance from
your nickel cadmium cells they should be charged with a primary
charge routine of Negative Delta V backed up by voltage and then
Nickel Metal Hydride: To get the best performance
from your nickel metal hydride cells they should be charged using
charge technique of DT/dt.
It is possible to charge a nickel metal hydride
cell on a nickel cadmium charger that is designed to use a
negative delta V charge circuit. BUT, you will NOT get the
proper performance from your nickel metal hydride cells.
The consideration for the different circuitry in
the battery packs themselves.
Negatives of Lithium Ion Batteries
contacts for information on Lead Acid:
Dennis Sharpe of MK Battery is a very good authority on wheel chair
batteries and they are a very good company.
Jack Verdin of
Schauer Electronics is also a very good authority on wheelchair
batteries and chargers. He is a remarkably bright person and
always ready to share his knowledge.
I will note that
wet cell and dry cell lead acid is different from Ni-CD in that when
a product is being driven by a Ni-CD or Ni-MH product that the discharge rate
is consistent from a fully charged to almost discharged state. Lead
acid characteristics are different on this point as the discharge
current of lead acid is more heavily produced from full charge and
the discharge current reduces as the lead acid battery becomes more
discharged. That is why it is very important to have a voltage
regulation system on a product driven by a lead acid type battery.
batteries to a voltage cut off between .8V & 1.0V per cell.
rates create more heat than a bad charger. Once we get past the
old problem of MEMORY, we find that today’s battery problems
are not memory so much as they are unbalanced cells, reverse
discharge cells within the battery pack, and the use of trickle
deteriorates the insulator between the plates of metal inside the
cell, thus creating the shorted cell.
This is why
press negative cells,( 500 - 700 charge - discharge cycles ) do not
hold up as well as sinter on sinter cells / paste cell ( 900 - 1200 charge -
discharge cycles ) do in heavy or long duration discharge
different capacity cells. It is better on your battery NOT to
mix new and older cells because you will develop an Unbalanced
Management Analyzer Systems are so much more efficient than the so called “
smart chargers “. A smart charger can tell you that a battery
is ready when it reaches its full voltage and still possibly be below
the correct capacity level. A Battery Management Analyzer System will not tell
you that a battery is ready until it is at 100 % of it’s full
facilities for any chemical type of battery cells and packs. We
are aware of 2 battery recycle companies in the USA that meet
every requirement if the EPA.
We work with:
John A. Patterson or
P. O. Box 720
Ellwood City, PA 16117
John did an
article with a production company (we supply battery packs and
chargers for) on recycling batteries and the environment and it was
aired on the Discovery Channel. He may not remember me, but We
were the battery assembler that Discovery had contacted for another
article on recycling.
Lithium Primary Cells:
battery cells are a very good choice for many products except that
they are a throw away type cell which is not environmentally
conscious. The user can help by searching out a battery recycle
chemistry is designed for use with low or medium current drain
applications. This chemistry is designed to “re-energize”
itself over a short period of time. A fully charged alkaline
cell would give off 100% of its capacity on the first use. When
the power drain is disengaged the alkaline cell will begin to
re-energize up to a % of the original charge capacity.
This cell is
designed this way by the use of particular chemical makeup’s that
interact between themselves with no outside assistance.
They are not a
rechargeable battery cell, but do energize themselves each time they
Of course, the re-energize process and end result are directly related to the amount
of available capacity per each use. This is why an alkaline
battery will last so long, as re-energize is relevant to available
Zinc models come in standard to heavy duty and are not designed
to re-energize themselves at all. The heavy duty carbon zinc
batteries are designed for high discharge applications like toy
products and halogen flashlights or flashlights that are kept on for
extremely long duration’s with no turn off points.
battery cell would have no opportunity to re-energize and thus the
heavy duty carbon zinc models are more cost effective in high drain
applications, but still should be recycled for their material content
and preserve nature for our future Family's.
Lithium cells for 9V applications can come in two forms, coin cell
A lithium coin
cell is designed for very long term low drain rate.
cylindrical cell is designed for a very heavy high discharge rate.
Each has an application and this is directly related to which of the
two cells is used for the 9.0V batter pack.
A 9.0V lithium
battery pack built with a coin cell would be appropriate for monitors
where a 9.0V lithium batter pack built with cylindrical cells
would be more appropriate for a high discharge alarm.
There is also a
difference in the cost of the manufactured product. Ultralife
manufacturers a very good product and of course we sell Ultralife
Cadmium 9 Volt Battery:
There is also a third alternative 9.0V batter pack and it two needs
some clarification. The third is a nickel cadmium battery pack.
Remember, 9.0V battery pack is really a style of battery.
Depending on the chemical make up and the manufacturing technique,
they will range from 7.2V to 8.4V and the capacity will range from 80
to 120 mAH.
Nickel cadmium 9.0V battery packs will actually be either (7.2V 84mAH
or 100mAH) or (8.4V 100mAH or 120mAH).
Like all other
chemical type 9.0V battery packs, these to are assembled using either
coin cells or cylindrical cells.
The preferred choice nickel cadmium battery pack for TENS unit will
be a unit that is 8.4V110mAH. You do not usually find the
8.4V110mAH 9.0V battery pack on the retail consumer shelf. What
you do find on the consumer shelf will show you the voltage of that
cell, but, will NOT usually show you the milliamp Per Hour Readings
which are almost always 7.2V84mAH. A significant difference in
performance with a very insignificant difference in cost.
That is because
in retail the nickel cadmium rechargeable battery cells and packs the
consumer is supplied with are almost always the least expensive
battery cell possible allowing for the highest possible amount of
margin for the reseller. The reseller usually supplies the
smallest capacity possible of each particular cell. Most
retailers are not aware of any difference and Consumer USA is
certainly not aware of any options. Battery cell manufacturers
have enjoyed this situation for as long as the technology has been
exposed to the consumer. Consumers and
most resellers have not been educated on what they should expect from
their battery cell or pack product.
Systems, Inc.,is capable to
manufacture very good quality wall “smart” chargers for rechargeable
9V battery packs and we can also manufacture multi-port 9.0V battery
management chargers for medical service centers or TENS rental
facilities and manufacturers.
The only real
draw back to rechargeable battery packs is that neither the medical
manufacturer, reseller or consumer has ever been educated on or had
access to information on the use and care of rechargeable
battery packs. They are the most cost effective if the proper
unit is purchased and used properly as suggested in our information
on the proper use and care of rechargeable battery packs.
Technical Information Quoted from other authorities in the field of
battery cells, analyzers, and Chargrs: (Including Memory,
Heat, Trickle Chargers, Alternate Charging Methods)
The below paragraphs were pulled or borrowed from various technical
manuals or magazine articles to enhance what we have to say or
reference on rechargeable battery cells and packs.
“memory effect” myth about Ni-CD batteries has been pretty well
debunked. Turns out that a memory effect can only be
demonstrated under very carefully controlled lab conditions, where
the cell is slightly discharged hundreds of
times to exactly the same discharge point.
Otherwise it does
The most damage done to Ni-CD cells by the memory effect is when
users attempt to fully discharge the cells to avoid the mythical
effect, and then drive it into reverse polarity, damaging the cells.
Sorry we don’t have references with us on this. There was an
article in the past years in QST (a ham radio magazine, published by
the (American Radio Relay League) about this, and a few years back
there was an item in QST Technical Correspondence from a battery
engineer at Goul explaining that memory effect in Ni-CD's does not
The myth is
quite popular though. We have seen ads for fancy microprocessor
controlled Ni-CD charges that carefully do a deep discharge before
Every so often, The Subject that Won’t Die returns to life. One
of these is the “memory” effect that Ni-CD cells are supposed to be
subject to. It turns out that there isn’t such a thing except
in very rare cases.
From Nickel-Cadmium Battery Application Handbook, Second Edition
22.214.171.124 Memory effects
effects on discharge voltage levels at any point during the discharge
period, or an apparent reduction in capacity to a predetermined
discharge voltage cutoff point, are developed in the battery system
from repetitive use patterns. If the battery is discharged to
random depths of discharge, and overcharged for random amounts of
overcharge time, and subjected to various duty cycles, these
temporary effects will not manifest themselves. The following
paragraphs will discuss the factors and causes of these temporary
subjected to a repetitive depth of discharge under certain cycling
conditions may exhibit an apparent temporary loss of capacity.
This phenomenon, sometimes referred to as
“memory”, was first noticed
in a satellite where the cell received a very precise
charge/discharge regime using only a small portion of the available
capacity over and over again. If the cell experiences such a
series of repeated partial charge and discharge cycles of exact
magnitudes, the cell may become so conditioned that it will deliver
to the normal end-of-discharge voltage only slightly more capacity
than has been required of it during these preceding repetitive
cycles. Thus, if the discharge cycles are short, the cell
capacity may be temporarily shortened to coincide with the discharge
capacity previously experienced during the repetitive discharge
cycle. The complete discharge voltage profile of a “Memorized”
cell may appear as portrayed in Figure 7-3. This is more likely
to occur when the overcharge coefficient is small, the rate of
discharge is high, and/or the temperature is elevated. This
effect is also more significant when the cutoff voltage is above 1.0
volt at the C rate.
If the cell is
subjected to a deep discharge and then recharged, this “memory” is
erased and nearly all of the original cell discharge energy is
It must be
emphasized that the “memory” effect does not manifest itself when the
battery is discharged to random depths of discharge or overcharged
for random amounts of overcharge time as is typically the case in
Compare this explanation with their third edition (1986):
4.5.3 Voltage Depression (This would apply to trickle
The effects of
elevated charge temperature on the immediate cycle capacity of the
cell have been discussed in Section 3.2.1 and 126.96.36.199. Cells
exposed to overcharge for very extended periods of time, particularly
at elevated cell temperatures, may develop an additional shortcoming
called VOLTAGE DEPRESSION. This phenomenon is one in
which the cell voltage is depressed approximately 150 mV below the
normally expected values which were calculated on Figure 4.19.
This depression affects Eo and is independent of discharge rate.
This depression effect initially appears on the discharge voltage
curve near the end of discharge. With extension of the
overcharge time (non-discharge) of the cell, this depression
progresses slowly toward the mid-point and beyond. Accompanying
this effect of depression in the voltage dimension of the curve is an
actual slight increase in the capacity dimension as illustrated in
Figure 4.21. This depressed voltage effect is an electrically
reversible condition and disappears when the cell is completely
discharged and charged (sometimes called conditioning). It thus
appears only on the discharge following a very extended overcharge.
It will reappear if the extended overcharge is repeated.
which causes this depressed voltage is continuous overcharging of the
active material of the electrode. The effect is erased by
discharging and recharging that portion of the active material which
has experienced the extensive overcharge. For this reason the
depressed voltage effect in the discharged portion of the curve is
erased by the very act of observing it, when the discharge is carried
beyond the first knee of the depressed curve. Complete
discharge, and subsequent full charge, essentially restores the curve
to its normal form.
reversibility of this effect is probably the very characteristic that
gives rise to the misnomer MEMORY. When cells are subjected to
continuous charge/overcharge, with only modest discharges (repetitive
or otherwise), the reversibility of the effect actually prevents the
voltage depression from occurring in that portion of the electrode
active material which is cycled. The voltage depression
phenomenon is, however, not erased from that portion of the electrode
material which has been subjected to continuous overcharge but NOT
discharged. In this situation, whenever the cell is discharged
deeper than recent previous discharges and reaches the beginning of
the previously uncycled material, the voltage may decrease 150 mV per
cell. This misleads the observer into believing that the
discharge is at the knee of the normal discharge curve and
erroneously concluding that the cell remembers and, thus, delivers
only the amount of capacity previously repetitively used.
Instead, the phenomenon is actually related only to extended
overcharging and incomplete discharging, not repetitive shallow
cycling. This is because that portion of the
material which has experienced overcharge and not been discharged for
an extended period of time slowly shifts to a more inaccessible form.
voltage effect can of course cause loss of useful capacity in those
application cases where a high cutoff voltage prevents complete
discharge of the minimum capacity cell in the battery. If
voltage depression has occurred, complete discharge requires
continuation down through the depressed knee to that voltage level
which keeps all the electrode material active...
By the way, when
these guys talk about overcharge, they talk about charging at C/10
for weeks or months.
Using a standard
16 hour charger for a day or two do not excite them. In this
case, the only problem they see would be the elevated temperature
that the cells would be subjected to.
temperature... that’s another problem. I talked to four
applications engineers at Gates and each one stressed that
temperature is the killer. They say that each 10 degree C over
the life of the cell reduces cell life by one half.
THAT’S THE BIG THING.
GE found that while there may be some very infrequent cases of a true
“memory”, the vast majority of problems seen with this type of cell
were due to improper selection of the cell for a given application
(improper choice of cell for expected discharge characteristics),
and, more importantly, improper charging of the cells. Ni-CD
cells, in contrast to lead-acid types, are *not* suitable for
constant “trickle charging” (unless some provision is made for
sensing cell voltage/temp, or *very* low current is used), which is a
mode seen very often in consumer applications.
charging characteristics will do more than anything else to degrade
overall cell performance.
To quote from one technical reference which discusses the subject (Varta
“Sealed Ni-CD-Batteries Product Range and Technical Handbook”, 1987,
of Sealed Ni-CD Batteries”) :“...Electrical stress and charging
methods have a vital impact on service life...The best way to ensure
long service life and trouble-free operation is to follow the
charging instructions carefully. Sealed Ni-CD batteries may be
stored for years regardless of the charge state they are in.”
, Inc., states an
opinion that when Ni-CD cells are stored for long periods of time
they must then go through an exercise routine in order to tone or
build the cell strength just as a person would do to build or tone
their body muscle.
And, from the aforementioned GE note (General Electric Technical
Flash TMF 8517):
“To the well-informed, however,
`memory’ is a term applied to a
specific phenomenon encountered very infrequently in field
applications...GE has not verified true memory in any field
applications, with the single exception of the satellite application
noted above. Lack of empirical evidence notwithstanding, memory
is still blamed regularly for poor battery performance that is caused
by a number of simple, correctible application problems.”
Gould Inc., Portable Battery Division, had this to say:
“A nickel-cadmium cell which has been charged for an extended period
of time exhibits a reduced operating voltage on subsequent discharge.
The characteristic [has been referred to as] `voltage depression’,
`memory’, or `stepped discharge voltage.’”
Thus, while there is a possibility of a true “memory” in Ni-CD's, it
is *extremely* rare, as it manifests itself only under some very
specific and unlikely conditions, one being that the cell is
repeatedly discharged to the same level, *within no more than 2-3%*
(which is what happened in GE’s one example - the cells in the
satellite assembly were being discharged under very precise computer
It may have been overstating the
case slightly to say that there is
“no” memory effect possible, but done so in the interests of
simplicity. It is also far, far closer to the truth than the
current level of understanding, which has people actually wasting
discharge cycles for no good reason.
characteristics of a Ni-CD cell are very basic in nature.
During charge, only current and cell temperature are critical.
Discharge may occur at any current rate until the cell terminal
voltage falls below 1.1 volts, but the cell temperature rise must not
cause the cell electrolyte to boil (gas). When connected in a pack, the
pack must be unloaded when the individual cell voltage falls to 1.1
volts to prevent reverse charging of the lowest voltage cell in the
discharge cells at an excessive high rate where gassing becomes a
problem, with the exception of toy electric cars (these are “toys”
for men). Cells designed for this application
usually have larger than average plate area and large connecting tabs
to support the higher peak current. Cell temperature is kept
below the critical value by selecting the cell capacity such that the
cell will dissipate its charge before gassing occurs.
In essence, the
toy car runs continuously with a nearly zero series load resistance
allowing the cell temperature to rise near critical just as cell
discharge is reached.
brief notes will further amplify an understanding of Ni-CD cell
1. Ni-CD's are
very easily damaged due to gas pressure caused by over-charging at
high charge rates. Unfortunately, Ni-CD's do not have a
positive indicator for indicating the state of charge.
It is up to the
user to estimate the relative charge state. Typically, the
charge rate is calculated at C/10 where C equals cell capacity and
the 10 represents hours for charging. At C/10, a nominal or
normal charge would occur. A fast charge can be accomplished,
cell design permitting, by changing the ratio, i.e., 5C/2.
temperature does rise at the completion of the charge cycle,
particularly at high charge current values, and can be used as a
charge completion indicator. At the moment of temperature rise,
the charge current must be reduced immediately to prevent excessive
gas pressure build-up. Some chargers monitor the cell
temperature and reduce the charge current to a small sustaining
value. For 500mAHcells, the sustaining value is typically
between 10-25mAH, or just enough current to compensate for the
chemical change ( internal current leakage).
charging of Ni-CD's, Ni-MH, Li-ON is most preferred as it is more efficient than a
steady-state current value. Steady state current creates gas
bubble formation on the plates of the cell, while pulse current tends
to create fewer gas bubbles allowing the charge to be more uniform
across the plate area. The charge uniformity is enabled by gas
bubbles being moved around due to current pulsation’s. Bubble
movement allows more plate area to be exposed during charge.
Pulse charging also creates less of a temperature rise. The
charge rate still has to be calculated as a function of C/10 during
each charge pulse to determine total charge time (The accumulated
charge is equal to the sum of the charge area under the pulse curve).
4. Older Ni-CD cells would not accept high charge rates above C/10 an
would develop electrolyte seal leakage at attempted higher charge
rates. A leaky seal, in any case, means the eventual loss of
the cell. Newer cells, as used in most handheld radio
applications seem to tolerate high charge rates without developing
cell leakage as long as the temperature is controlled (kept low).
5. In the event corrosion around the seal of a cell
develops, the corrosion can be removed. Wipe the corroded area
with a vinegar soaked cotton swab. Use an ample amount of
liquid and dry the cell with a tissue. Keeping the cell clean
allows it to be used until it fails completely. Take note that
weeping cells can cause corrosion problems if they are not
inspected and cleaned regularly.
6. Discharge of a Ni-CD is critical only if the cell is under a load.
When loaded, the cell voltage should not be allowed to
drop below 1.1 volts which is just over the edge of the discharge end
of the curve. Allowing the cell to drop to 1.0 volt or less while
under load may cause permanent plate/electrolyte damage.
The result would
be a loss of cell capacity. Of course, a loss also takes place
naturally with age which limits the number of charge-discharge cycles
the cell is capable of supporting before it is exhausted.
cells may be stored almost indefinitely and allowed to discharge to
whatever cell terminal voltage the cell can maintain on its own.
When putting a
previously stored cell into use, charge the cell, at least the first
cycle, at C/10 for 12-14 hours. Shelf life of a cell is usually
a function of how fast nickel whiskers (crystallization) develop
internally that can short the cell. Two methods have been
proposed as a way of extending cell life when whisker formation is of
a) Cycle the use
of the cell/pack periodically. It is believed that the rate of
formation is reduced when cells are charged and discharged
b) Allow the
cell to sit on the shelf as long as needed and if a whisker short
should occur, blast it away with a high current pulse from a
capacitor or other source. It has been
observed that once whisker growth/shorting begins, it can not be
permanently stopped. It is like a mold or fungus.
8. It has been
observed that the terminal voltage across a charged Ni-CD cell will
increase as the cell ages. Using this
observation, the life expectancy of a cell can be evaluated and
monitored. As an example, a new/fresh cell will exhibit a
terminal voltage of 1.25 volts while an old cell will exhibit, say,
1.5 volts. It is believed that the cell dehydrates with age and
the rising voltage is a function of the increase in cell impedance.
Many hints and
kinks have been published regarding the nature and care of Ni-CD's
and all point to the fact that Ni-CD's require user TLC to obtain
long cell life. The bottom line is that the user must pay
attention to how the cell is being treated.
Thursday, 18. September 2008 04:49:53 PM
Copyright Rathbone Energy
, Inc. 1990