PLEASE NOTE: Messing about with batteries/cells
Most cells contain hazardous materials and injury and/or damage can
from mishandling them.
Cells that are shorted,
charged or otherwise maltreated can pose an explosion/burn/chemical or
other hazard. It is entirely up to you to do research and
provide the appropriate precautions to prevent damage and/or
You have been warned!
Acknowledgments: The information contained herein is from a
many different sources ranging from personal experience to
data sheets, the experience of others, various articles, and the
experience of some individuals that have long dealt with manufacturing
products that use NiCd (and other types of) cells. In this latter
group, I'd like to thank Robert Barth, DL1SDX, for his valuable
Additionally, see the disclaimer at the
of this page.
The emphasis on this page has, over time, shifted from the use
of NiCds to NiMH cells. This has to do with the fact the NiMH
cells have more than twice the energy capacity of the same-sized NiCd
cells and have achieved a high level of market penetration due not only
to the higher capacity of the NiMH
cells, but the fact that there is a preference toward the use of NiMH
cells as they are far less hazardous in their disposal than NiCds
contain the toxic, heavy metal Cadmium.
About Rechargeable Cells:
There are instances where Alkaline cells have distinct advantages over NiMH cells:
Rechargeable cells are quite economical: Even if abused, they generally cost less to operate on a per-hour basis than non-rechargeable "primary" types like Alkaline cells. They do not, however, usually have the energy density (the amount of energy with respect to their volume) of Alkaline cells. What this means, in plain English, is that a rechargeable AA cell cannot store as much energy as an Alkaline AA cell. This means that you will need more rechargeable cells to run the piece of equipment as long as an Alkaline cells would.
Or do you?
Alkaline cells - A comparison to NiMH and
"Resistance is NOT futile... it's E/I!"
While alkaline cells generally more energy per-cell than
types (NiMH or NiCd) this energy may not be accessible to the
using that cell - particularly if it is a device that draws a lot of
current. One good example of this is a Digital Camera.
Digital cameras are notorious for seeming to have appallingly short battery life: A brand new set of batteries, in some cameras, may only allow one or two dozen pictures to be taken before they are "dead." A NiCd or NiMH battery, on the other hand, may last several times as long - even if that NiCd you used is rated to have about half of the amp-hour capacity of Alkaline, why did it seem to last longer?
Internal resistance is the culprit. When fresh, the internal resistance of a good-quality AA alkaline cell is on the order of 0.15 ohms per cell, increasing to 0.3 ohms per cell when the it is 50% discharged. If your camera uses a battery of 4 cells, that means that the total resistance of new cells (excluding resistance of battery contacts and wiring) is about 0.6 ohms, rising to 1.2 ohms when the battery is 50% discharged. Not only this, the "nominal" voltage of an alkaline cell is 1.2 volts when it is at this 50% discharge point - a voltage that is comparable to NiCd and NiMH chemistries.
Note: There are some newer types of Alkaline cells specifically designed for "High-Drain" electronic devices. While these cells do not necessarily have more capacity, they do generally maintain a lower resistance than standard alkaline cells and thus, the appliance may be able to utilize more of the cell's capacity. For more information on these newer types of cells, visit one of the manufacturers' web sites. Furthermore, more-recent digital cameras have been better-designed to handle the characteristics of alkaline batteries, enabling more usable operational life to be extracted from them.
If the digital camera consumes, say, 800 milliamps (a reasonable amount when a flash is charging, a backlit display is operating, etc.) then cell resistance alone will dictate a voltage drop of 0.48 volts for a battery with new cells, and 0.96 volts or so for cells that are 50% discharged. Again, this does not take into account other resistive losses - such as contacts and internal wiring - some of which can be significant!
For new cells in a 4 cell battery, this voltage will (optimistically - assuming a nominal 1.5 volt unloaded output) amount to about 5.5 volts under these conditions, dropping to about 4 volts when the cells are 50% discharged - a voltage that may be inadequate for operation of the camera.
There is yet another problem: Often, cameras contain switching-type voltage converters. While these are efficient in their energy conversion, they attempt, by their nature, to maintain a constant power output over a varying input voltage. What this means is that, as the battery voltage drops, the current consumption will increase as the voltage converter attempts to maintain the constant voltage output - exacerbating the problem of already-low voltage. This problem can get worse when the camera's load changes because of a charging flash, a backlit display being illuminated, or the camera's CPU pulling more current when processing the image and saving it to memory.
In other words, the cells may be, say, only 50% discharged, but the
equipment (the digital camera, in our example) may simply be unable to
use the energy that is still available. If this is the case
probably get plenty of life out of those same batteries if you put them
in a small flashlight or portable FM radio, or TV remote control.
other words - don't throw them away just yet!
Several years ago, a friend of mine (also a fellow amateur radio operator) was issued, by his employer, a "talkback" pager - one of those pagers that can send as well as receive messages - and he noticed something that seemed odd at first: It had both an Alkaline and and a NiCd cell in it.
He quickly realized why this was done: While the Alkaline cell had the energy capacity, it was the NiCd that had the current-loading capacity: The transmitter drew enough current when operating that it would easily overtax the Alkaline cell, especially near the Alkaline's end-of-life when it's resistance was higher.
NiMh and NiCd cells and internal resistance:
NiCd and NiMh cells, on the other hand, typically have a much lower
internal resistance over their charge life and this resistance (which
varies depending on
of charge, temperature, age, condition of the cell, the cell's internal
chemistry and its construction) is typically lower than that of an
cell - even when the NiCd or NiMH cell is significantly
According to info from a well-known manufacturer, a relatively new AA NiMH cell typically has about 0.17 ohms per cell when fully charged (as opposed to 0.15 ohms for a "fresh" Alkaline AA cell) and this rises to about 0.18 ohms at the "100% discharge" point. A typical AA Alkaline cell, on the other hand, can reasonably have over an ohm of internal resistance at 80% discharge - and this value skyrockets as the battery is discharged further. From what information that I have been able to find, a typical NiCd seems to have about half the internal resistance of the same-sized NiMH and is one of the factors that explains its suitability in very high current situations.
What this means is that while an alkaline cell may be able to run
digital camera (our equipment example) only until the cell is at its
charge level, a NiCd or NiMH battery can probably output the required
and voltage until it is at or below its 15% charge level. The
lower intrinsic resistance also means that they are more likely to be
to tolerate impulse loads (i.e. additional current drawn by the flash
for example) without causing the camera to shut down due to low
Comment: At the current level of technology, NiCd
cells are preferred over NiMH cells for certain applications, most
notably those requiring very high current consumption such as in
battery-powered tools, etc. In these applications, the high
current drawn by the tool would over stress a typical NiMH cell and
likely result in shorter operational and useful life than a NiCd cell.
Treating your cells properly -
It can be tricky to determine exactly when you have fully-charged a NiMH or NiCd cell. Often, the cell is overcharged slightly, at which point your charger can say "Oh yeah, it's charged already..." One "safe" way to charge either a NiCd or NiMH cell is via the "slow" charge. Typically, this is done at about 1/10th to 1/50 C. What is "C"? That is the capacity of the cell in amp-hours.
For example, say that you have a 1 amp-hour cell. In that case 1/10th "C" would therefore be 1/10th of an amp, or 0.1 amps (100 milliamps.) This charge rate is maintained for 12-14 hours for a "dead" cell and at the end of this period, you may expect it to be fully charged.
Because charging a cell isn't 100% efficient, you must put in
approximately 120-140% of the energy into
cell (hence the 12-14 hours part) of its capacity rating when "slow"
charging it. In the
above, this would work out to be approximately 1.4 amp hours (that is,
0.1 amps for 14 hours.) It is recommended by several
battery manufacturers that when doing a "slow" charge that the charge
be terminated after 120% of the cell's capacity has been input by the
charge cycle. After the 120%-140% of energy has been
inputted to the cell, it is recommended that the charge current cease
"Quick" Charging and "Fast" Charging:
"Quick" charging often refers to a means by which the cell is fully
recharged in about 4 hours, implying a "C/3" charge rate. At this
rate, one would typically dump 120-150% (or even more!) of the cell's
that cell (assuming that it had been fully discharged, of course) and
then switch to a "Maintenance" charge afterwords.
"Fast" charging, on the other hand, usually refers to a method of
charging a cell within
an hour, implying charge rate of greater the "C."
"Quick" and "Fast" charging requires careful, constant attention to
of the cell(s) being charged. At these higher rates (which could
be 2C or higher) the cell will heat up and, if care is not taken, be
A good high-rate charger (of either the "quick" or "fast") has means of
monitoring the temperature of the
and the voltage, and possibly how much energy has been already dumped
in - not to mention a "fail safe" timer that will unconditionally
terminate the charge after a certain amount of time.
In other words: Don't quick-charge unless your charger have a
to monitor all of these parameters (the first two, anyway) closely.
Note that the faster you charge the cell, the less-efficient the
charging becomes as more and more energy is lost in heat. This
should be kept in mind if you have a limited power budget - say,
charging from a solar panel. If you can afford the time, you are
better-off "slow charging" in that case - if your absolute power is
As the name implies, this happens when you continue to dump energy into the cell - even after it is fully charged. When this happens, the energy has to go somewhere. The most obvious effect is heat. If you are "Slow" charging cells and they become even slightly warm, they are already overcharged!
Likewise, while heat is a normal by-product of "quick charging" a cell, when the energy is no longer being chemically converted (as in the charging process) the cell will suddenly start to warm up even more: One of the indications of full/overcharge is a sudden rise in cell temperature.
If charging persists even after "full charge" is reached, not only is heat produced, but gases can be generated as well. Small amounts of these grasses are normal, and may be reabsorbed into the cell's chemistry. If gas production is too high, pressure will build up and safety vents built into all types of cells will allow the excess gas to escape. Because this gas is derived from the cell's electrolyte, venting implies that some of the cell's capacity has just escaped into the air. If one particular cell vents more material than another, then it can become the "weakest link." As you will read below, this is bad.
Another effect may be present when the cell is in a continuous state of "slight" overcharge. Normally, when charging, the grasses that are produces (one of which is oxygen) are re-absorbed by the cell's chemistry. Oxygen, however, is an extremely corrosive element and may contribute (along with the elevated temperature) to breakdown of portions of the cell's internal structure - including the plastic (usually polypropylene) separator. When this separator starts to fail, self-discharge can greatly accelerate. All of this can happen even if out gassing has not occurred.
In the case of NiMH cells (where the self-discharge rate is rather
- especially as the cell ages) it may be desirous to leave it on a
"maintenance" (or "trickle") charge for very long periods of
time. Recent recommendations by some battery manufacturers
"C/300" current for this while other manufacturers recommend a charging
rate as high as C/40. Following the C/300 example, our
amp-hour cell above, this would be about 3.33 milliamps. I have
seen any specific recommendations for such a maintenance charge for
NiCd cells, but I would expect that the same C/300 rate would be
It should go without saying that charging a "dead"
battery at the maintenance charge rate may take weeks to
A "Floaty-Thingie" - A simple device to maintain NiMH
charge during periods of non-use.
When cells go wrong
One of the best-known properties of NiCd cells is this thing that people refer to as "Memory."
It is most unfortunate that this trait is not only misunderstood, but it is usually mis-identified and it is not "Memory" at all, but an effect of cell reversal. There is also a phenomenon occasionally referred to as "lazy cell" syndrome. (More on these later.)
One of the first places that the so-called "memory effect" was first noticed and quantified was when NiCd cells were first used in communications satellites. These satellites rely on solar panels for their power, but the Sun is eclipsed by the Earth at times and it is during these periods that the satellite must operate from battery power alone. These eclipses were typically of very similar duration, which means that during the "eclipse season" the battery is run down by about the same amount, time after time.
The "memory" was noticed when, after several eclipses, the battery voltage would relatively quickly drop to the voltage attained during the latter part of the eclipse - and typically stay there.
It was also noted that this "memory" effect could be reversed simply by charging the battery and then discharging it to a different point for several cycles. This was done by clever management using multiple battery strings onboard the satellite and preventing a battery string from being discharged to the same point repeatedly. Little (or no) permanent damage was actually done to the cells by this "memory" effect - the result was (more or less) a temporary reduction in the cells' capacity until they were conditioned appropriately.
In typical use by those who use NiCd-operated devices, it is unusual
to discharge the battery to precisely the same point
Usually, the amount of discharge is somewhat random - and just one or
variations from a precise cycle will "erase" the memory effect.
the very few documented cases of "terrestrial memory"
been in pager service where, regular as clockwork, the batteries would
be run down during the day and recharged overnight. This was a
time ago - back in the days when pagers were those half-brick sized
that only VIPs and doctors wore - and batteries only lasted a day or
It has been reported that NiMH cells can also exhibit this same
"memory" effect - but remember that it is atypical to expose a cell to
very precisely repeated discharges of equal depth time after
time: Most people just don't use their battery-operated devices
This is very common - I have several devices (like a cordless phone) made by some very reputable companies that suggest that one should completely discharge the battery occasionally to avoid the "memory" effect.
All I can say is DO NOT DO THAT!!!
Why would they say that, then? Generally, the manufacturer of the device does not also make the batteries as well - and certainly, the person who wrote the manual didn't know any better.
For the more conspiratorial-minded of you out there, perhaps it is simply a plot to sell more batteries?
(About my cordless phone? I simply put it back on the charger when I'm done. This telephone was made in 1995 and not only am I still using the original battery pack, I have yet to have ever run it down during a telephone call - even ones that last well over 3 hours!)
"What is this thing (mis)called 'Memory' then?"
Abused NiCd cells will typically exhibit a loss of capacity and/or
inability to take or retain a charge, and it this
that is too-often misidentified as "memory." But,
is not "memory."
What is going on, then? There are two things that might be happening. Let's talk about cell reversal first:
Good quality battery packs are made from individual cells that have been matched in terms of resistance and capacity. This is important in terms of maximizing battery life. Here's why:
A battery typically consists of cells wired in series for higher
Ideally, all cells will run down at exactly the same
This is not usually the case, however, especially as the cells
Temperature also has a large impact on cell longevity. A cell
is operating at a higher temperature will generally have a shorter
lifetime than one that is cooler. An effect of this can be noted
in a large battery pack (such as that on a cordless drill) in which a
number of cells are grouped together. Often, the cell(s) in
the "middle" of the pack die first as these are surrounded by
other cells: Not only can these "inner" cells not get rid of
their own heat
as easily as those cells on the "outside" layer of the pack, but they
also exposed to heat from the cells that surround them! How
important is heat to the life of a cell? One oft-quoted statistic
(that I've not verified personally with NiCd cells) is that for every
ten degrees F of temperature rise above 80 degrees F, the usable
lifetime of the cell will be halved! Even if these numbers aren't
correct, cells that are warmer will die sooner!
Inevitably, one or more cells will run down sooner than the rest and its voltage will drop. Because the other cells still have some charge, current is still flowing through the cell and the voltage will not only drop to zero, but it can go below zero and effectively start to "charge" backwards.
The effect of this is a very quick death to a NiCd cell! Why?
It comes down to chemistry. When a NiCd cell is
a strange thing happens: Conductive metallic "hairs" (often
begin to form - and they "grow" from one electrode to another.
this dendrite forms a short across the cell - one that can have a range
of resistance from high to low, depending on the severity of the
Note: NiMH cells do not seem to exhibit this
growth" problem, but cell reversal tends to cause gasses to be
generated. If these gasses are produced as too high a rate, they
cannot be reabsorbed internally and pressure will build within the
cell, causing outgassing and resulting in a permanent loss of cell
Once this dendrite has formed in the NiCd cell it is permanent and cannot be "dissolved" by charging the cell correctly. Furthermore, this dendrite can form a leakage path that can cause the cell to run down by itself - the rate at which can vary depending on the resistance of the dendrite. The effect can range from a cell that just doesn't "hold a charge as long as it used to" to, in extreme cases, the dendrite may be big enough that the cell won't even seem to take a charge at all (except, maybe, on a "quick charger.")
Perhaps the worst thing about the dendrites is that they represent an amount of electrolyte that can no longer be used to contribute to the charge capacity of the cell. What this means is that not only is the cell likely to run itself down more quickly because of charge leakage due to the dendrite, but even if it is fully charged to begin with it will be the first in the battery to run down and go into reversal - again - and will be prone to forming even more, bigger, and better dendrites! (In other words: A vicious little circle...)
You may have heard about a technique for "restoring" NiCds often referred to as "Zapping." As the name implies, one dumps a brief surge of energy into the cell and, almost as if by magic, the cell is "restored" to operating condition.
Well, not quite!
The surge of energy should be limited - often, a "zapper" consists of a very large capacitor (50,000 to 200,000 microfarads) charged to 50-100 volts, the source voltage disconnected, and the energy of this capacitor is dumped into a cell via a very heavy switch or a beefy SCR. This "one shot" short burst prevents too much energy from being dissipated by the cell and blowing it (and the person doing the "zapping") up. Another method uses a lower voltage - but much higher current - say, from a large power supply: The obvious disadvantage of this latter method is that it is not "self limiting" (as is the one-shot nature of the capacitor discharge) and one can easily "pop" a cell either by burning open internal conductors or cause the cell to rupture due to sudden buildup of heat and gasses. Needless to say, neither situation (especially the latter) is particularly desirable.
What is supposed to happen in this process is that enough energy applied to "fuse" (or blow away) the dendrite that is shorting (or "almost" shorting) the cell. Once this low-resistance path is removed, the cell can be charged again.
It should be kept in mind that such a "repaired" cell, although it
may be more
able to take a charge than before, will still have reduced capacity
when used in a battery, is still very prone to discharging early and
into reversal - again.
Remember: The material that formed the dendrite no longer contributes to the charge capacity of the cell - even after you "zap" it. Furthermore, the cell contains a separator material that will often be damaged by dendrite growth and "zapping" - something that further contributes to self-discharge.
If you do this technique, make sure that you have completely disconnected the cell/battery from the appliance being operated to prevent the voltage surge from the "zapping" process from damaging it. Finally, while you may get some additional use out of a battery as a result of "zapping" - I personally consider that "zapping" a cell may simply be buying me enough time to get a replacement ordered and on its way.
Note: It should go without saying that this "zapping" procedure can be hazardous: Not only are potentially dangerous voltages and currents involved, but there is a chance that the cell may explode and/or leak hazardous material. Finally, this procedure can be done only on an individual cell, and not the entire pack at once: That is, you must be able to access and test each cell you plan to "zap" individually.
Getting the most out of your NiCd/NiMH cells:
I reiterate: For reasons unknown to me, some manufacturers of battery-operated equipment recommend that you "condition" NiCd battery packs by running them completely down, and then charging them again. I guess that the claim is to prevent a "memory" condition from occurring - but it is already known that to cause this "memory" the cell would have to be precisely depleted to exactly the same charge state repeatedly: This just doesn't happen with most people's usage of equipment.
Why do they make this recommendation, then? The cynical side of me says that they are just trying to sell more batteries or devices: By recommending you go through some steps that are guaranteed to shorten battery life, they can increase sales! The other side of me would guess that the person writing these instructions is just poorly informed or just doesn't know any better.
Here are a few things you can do to prevent premature failure of NiCd battery packs:
There is an effect that is often noticed with new cells of many types: Reduced capacity. A brand new NiCd (and possibly NiMH) cell may not have its full rated capacity when it is brand new - it may take a few (half dozen or dozen) charge/discharge cycles in order to get the full cell capacity. What can you do about this?
The table below shows the approximate amount of time that it takes to lose 10% of the cell's current charge capacity at different temperatures.
A - Storage or use of this type of cell at 60C violates the manufacturers recommendation for consumer-type cells and one may expect poor lifetime. It is not recommended that any cell be exposed to such high temperatures for an extended period of time.
B - The self-discharge rate of LiIon cells varies widely according to its chemistry and manufacturer. Information on self-discharge rate at temperatures other than 20C was not available at the time of writing but, as in the case of other types of cells, it increases dramatically with increasing temperature and the age (and past use) of the cell.
The differences in using NiCd and NiMH cells:
At first glance, it would seem that NiMH cells are just "better" versions of NiCd cells as they have the following advantages:
In practical terms, a NiMH cell may actually outlast a NiCd
in terms of charge cycles even though they supposedly have fewer
charge/recharge cycles. Why? A lot of NiCd cells
"die" due to cell reversal (see above) and the resultant
NiMH cells do not readily form dendrite shorts when they go into
Damage to a NiMH cell may still occur, though: Cell reversal
gases to form in the electrolyte and it is possible that pressure will
build up and the cell will vent. The resultant loss of gas means
a loss of electrolyte material and a subsequent loss of capacity.
Even without loads, all cells slowly lose their charge over time as
the cell's chemistry slowly changes. In all cases, the rate of
self-discharge increases dramatically as temperature also increases.
The chart to the right compares various cell chemistries and their
approximate rates of self-discharge showing how long one can expect to
lose 10% of the cell's present capacity. Please note that these
rates are typical published specifications by various manufacturers
and, in the case of rechargeable cells, represent the sort of
performance that may be expected from new cells. In
general, independent testing has shown that the manufacturers'
specifications concerning self-discharge are more-or-less in line with
what is actually observed. Also, reduction of self-discharge is
one of those parameters on which the manufacturers are continually
As can be seen, the clear winners are the non-rechargeable
types. The two cheapest are the alkaline and Zinc Chloride (the
"heavy duty") types and these do a respectable job of retaining their
capacity over time. Ahead of the pack are the non-rechargeable
Lithium types (The Lithium-Iron Disulfite and the Lithium Manganese
Oxide) and these two chemistries also perform better than the others
even when they are very cold.
The worst of the bunch is clearly the NiMH cell, which could easily
be found dead after having been left in a vehicle for a month during
the summer (if you have hot summers, that is...) It is certainly
worth repeating that NiMH cells are NOT the proper
choice for your car flashlight, for example, or even for any
item that is left idle for months at a time and is then expected to
work (such as an emergency radio.)
What about putting batteries in the freezer to "keep" them?
For the non-rechargeable types, it can be seen that freezing them will
certainly slow the self-discharge rates, but if you plan to use them
within a year or two, you'll probably not see any real
difference in longevity of those stored in your freezer and those
simply kept at room temperature. What is clear
from this chart is that you should not be storing them
in your attic or garage - or anywhere else that may tend to get
warm: It is preferred that they be stored simply in a cool
location (such as a basement) as compared to a warmer room.
Comment: As mentioned previously, there are
newer types of NiMH cells
(often billed as "ready-to-use") that have significantly lower
self-discharge rates that traditional NiMH cells. It has been
noted that these typically have lower capacities than similar-sized
cells. At this time the self-discharge rate of these types of
cells is unknown.
Replacing NiCds with NiMH cells:
Can you simply drop NiMH cells in place of NiCd ones? It depends. For optimal cell lifetime and performance under ideal conditions, the answer is probably no. For "good" performance (that is, where overall lifetime and charge capacity will probably exceed that of NiCd cells) the answer is likely yes - as long as a few rules are observed:
Alkaline Cell quality:
More recently, very inexpensive cells of various types have been appearing on the market made by companies that may be unfamiliar, or may be "re-branded" with the store's name on them. A number of people have written in saying that, in general, these "cheap" cells have proven to have about the same capacity as their more expensive name-brand counterparts. One interesting side-note, however, is that the reported "dud" rate (cells that were already dead or seemed to have suffered badly from self-discharge) seems slightly higher for these "cheap" cells than the name-brand cells.
Even amongst those
who have experienced this, they generally agree that even with the odd
"dud" the "cheap" cells are still a better bargain than their more
expensive counterparts - if you are able to identify the potential
"duds" before you intend to use them.
planning to store cells in an emergency kit of some sort,
however, I would recommend that you use known-good brand named cells
and relegate the "cheap" cells to everyday use where finding the
occasional bad cell would be only an inconvenience!
What could manufacturers do to prolong NiCd/NiMH cell life?
It somewhat irks me that the appliance manufacturer's recommendation (i.e. to completely discharge a NiCd pack) is precisely the thing that can kill NiCd cells prematurely. What is so terrible about this is the cost of replacement and inconvenience that results: Often, the user will simply throw away the entire appliance. From an environmental perspective this means that devices are disposed of that otherwise have nothing wrong with them, and the Cadmium (a toxic heavy metal) often finds its way (illegally) into public landfills - and maybe into your drinking water.
There are several things that could be done to greatly lengthen cell life of both NiCds and NiMHs:
Again, messing about with batteries/cells
Most cells contain hazardous materials and injury and/or damage can
from mishandling them.
Cells that are shorted,
charged or otherwise maltreated can pose an explosion/burn/chemical or
other hazard. It is entirely up to you to do research and
provide the appropriate precautions to prevent damage and/or
You have been warned!
Do you have any comments or
Send an email.
Please note that the information on this page is believed to be
but there are no warranties, expressed or implied. The author
take responsibility for any damage or injury that might result from
taken (or not taken) as a result of reading this page. Your
may vary. Do not taunt happy fun ball.
pages at this site:
The Floaty-Thingie web
page - This device maintains the charge on NiMH
cells that you may have laying around to keep them (gently) charged - a
useful tool to counteract their tendency to run themselves down during
Operating the FT-817 from Lithium-Ion (Li-Ion) cells- This page is a followup to the one on optimizing power consumption (above) and describes how Lithium-Ion batteries (which have a better energy/weight ratio than either NiCd or NiMH) may be used to power the FT-817.
the FT-817 from other types of cells- This
describes how NiCd, NiMH, and Alkaline cells (to name a few) may (or
not) be used to power the FT-817. (Does not include
cells - see above.)
A few web sites with info about Alkaline, NiCd, NiMH, and Li-Ion cells:
Any comments or questions? Send an email!
This page maintained by Clint Turner, KA7OEI and was last updated on 20101223. (Copyright 2001-2010 by Clint Turner)