Re: NiMh vs NiCd batteries

I invented a method of recharging heart pacer batteries, similer to the way tooth brush batteries are recharged now. I did this while at TRW and TRW gave me permission to patent the idea on my own. The problem was that it cost to much to get a patent.

The reason I did not follow up on it was that, I discovered on investigation, the Charging of the nicad batteries in heart pacers was not the reason the batteries had to be replaced. It seemed that NI Cad batteries just do not last longer than 5 years.

Dr. Joe Schulman (We had been technicians at Litton together many years before) had discovered that the reason that the NIcad batteries did not last that long was because of impurities. If the battery could be produced with out impurities they would last a lot longer if not forever.

We used sintered anode NICads for satelites and they were produced in special ways to make them as pure as possible.

Last I heard of JOe was that he was working on a Balistic Galvonmeter at UCLA. . . I DO NOT FOLLOW MANY OF THESE NEWS GROUPS To answere me address mail to snipped-for-privacy@aol.com

NiCad batteries need to be cycled full charge and full drain. A pacer would not be a good application for this.

investigation,

I recharge mine in a Ni-Cd slow charger. Because of Ni-Mh's better capacity, I must let them charge for several days. I would not charge them in a fast charger period. Fast chargers (less than 4 hours) are hard on batteries. Mi-Mh in a fast Ni-Cd charger may even be worse.

Here is some comparison info:

Ni-Mh:

*More capacity *low shelf life (they need recharged after setting 6-8 weeks. cold storage will improve this significantly) *does not require conditioning (run down before full charge often, though it may be helpful to "exercise" them now and then) *withstands lots of recharge cycles but not as many as Ni-Cd. *Much less toxic to the environment *more sensitive to overcharge

Ni-Cd:

*Less capacity *requires conditioning every so often to get maximum capacity *better temperature and shelf life performance *Lots of recharge cycles *toxic to the environment

On Tue, 05 Aug 2003 21:36:34 GMT, "Gym Bob" Gave us:

No. GANGED NiCad batteries that do not have watchdog charging circuits on them need such handling. If circuits are in place to insure proper charging of a multi-cell battery pack... all is fine.

Memory effect is NOT an effect of an individual cell, it only happens to multi-cell ganged battery packs that are not modern enough to have charge monitoring and management circuitry in the pack..

DO you have a reference for this? I've never seen this as a requirement. The old "memory" is simply an ol' wive's tale, both for NiCd and NiMH. The real problem is reverse charging caused my draining a battery such that a weak-sister-cell goes negative. This is certain death to any NiCd or NiMH cell. Other than this, there is no significant "memory effect" anymore.

On Tue, 05 Aug 2003 21:35:31 GMT, "Gym Bob" Gave us:

NiCad batteries do NOT have a memory effect.

Older, Series connected NiCad battery PACKS do.

The individual cells themselves do not.

In a sense, your statement is correct, because we should not be calling individual cells batteries as we do with single cell types. They are cells, not batteries. A battery is by definition a ganged cell structured item. An AAA, AA, C, and D cell are not batteries, even though that is the accepted lay person's term for them. So yes, NiCad batteries have a memory effect, IF it is an array that includes cells in series.

Parallel cell packs, and single cells do not sport a memory effect... at all.

Just to add my experience...

Modern NiCds are very close here.

MiMH batteries have about 2-3x the self discharge. This isn't always badness.

I don't believe this is necessary for NiCds wither. Perhpaps thirty years ago. Old habits die hard.

Agreed. ...at least for modern batteries.

Absolutely! Nickel is about as benign as dirt. Cadmium is about as toxic as Mercury. OTOH, recycling batteries works.

Only if the charger is dumb. NiCds are also very sensitive to over-charging. They're *easy* to toast. However, the chargers are different. MiMH batteries must use temperatur to sense terminal charge. NiCds often used the negative dI/dT. Even though the charge/discharge profiles are very similar, this will

*kill* a NiMH.

Modern ones are very competitive.

Don't believe it.

Sure.

Perhaps. That was the issue. I don't believe it's settled though.

Not a question. However, recycling does work. ...at least for those with a clue.

I believe the memory effect comes from impurities. In any case on Satelites, periodically all the batteries are parreleled and discharged. Or at least they used to be. . . I DO NOT FOLLOW MANY OF THESE NEWS GROUPS To answere me address mail to snipped-for-privacy@aol.com

Never the less they are used in pacers. The ones in pacers I do not beleive are or were recharged. You would have to have an operation about every 5 years to replace the battery. Jo'e garbage (cant think of the word) free batteries were very pure and lasted longer. My idea was to place an induction coil under the bedding and recharge the battery while it was in your body. Now they do that with tooth brushes.

I wonder if Teledyne got the idea from me when I worked there. I did discuss my idea with people there. ?????????? . . I DO NOT FOLLOW MANY OF THESE NEWS GROUPS To answere me address mail to snipped-for-privacy@aol.com

LioN batteries would be much better suited for this application. Longer life, resistant to staying charged, not requiring cycling and higher capacity /smaller size would make them ideal. Is the technology behind or there a medical reason for non-use of them I wonder. Perhaps because of the early ones exploding and blowing airplane cockpits apart? hmmmmmm....

On fast charge they produce heat and gasses. They contain some material that can disapate the gasses up to a certain charge rate. This used to be the 10 hour rate. I understand they have improved them in the past years.

NiCds can *easily* be charged at C now. This has been true for at least 20 years. The charger must be smart though. The C/10 rate was the limit of dumb chargers, and this is a stretch. I wouldn't even keep NiCds at C/20, or floating at all. NiCds do not like to be floated in any way. Applications where float charges are needed (emergency lighting, weed-whackers, and dustbusters) should *not* be using NiCds. SLACs are a far better technology for anything that needs to be float-charged.

I've noticed behavior of high internal resistance with NiMH batteries. Maybe, that's why they aren't seen much in devices where useful voltages must be maintained with heavy loads.

Dave M.

On Wed, 6 Aug 2003 22:26:52 -0400, Keith R. Williams Gave us:

Such systems already exist.

On Thu, 07 Aug 2003 02:44:04 GMT, "Dave M." Gave us:

Ever try shorting one? The internal resistance must not be too low, or it wouldn't be capable of frying larger gauge wires, which it can do.

26 Ga can handle an amp. Most of these cells can do better than that. Sounds pretty meaty to me.

I just replaced the batteries in my wireless mouse. I thought they were nimh but upon closer examination I found they were nicad.

I just put them in yesterday after charging them on my nickel charger and they lasted just one day.

So the question can you use a nimh charger to charge nicad. The answere is no. The nickle charger cuts off after a certain period. At least my two chargers do. That is evidently not enough time or charge to charge a Nicad battery.

The nimh batteries last about a week in the wireless mouse. I keep one set in the charger and the other in the mouse.

. . I DO NOT FOLLOW MANY OF THESE NEWS GROUPS To answere me address mail to snipped-for-privacy@aol.com

Your batteries won't last long being on charge 50% of the time. Take them out when they are charged or the best is to only charge them before their use.

Simply hype, from what I've been able to gather from the battery manufacturers.

YOu mean "multi-battery". Cells (one or more) make a battery.

mAh? You mean mA, surely! You're charging them at less than C/10, so while you may be baking them over the long-haul you won't wake up in an inferno. It's still a horrible thing to do to NiCds or NiMHs. They do *not* like to be baked.

Useless information. We have no idea what batteries you have. One can easily get AA NiCd batteries in this range. Crappy batteries are, well...

Sounds good, but makes little sense. Any decent portable (laptop?) is going to use some serious power. I don't see this being coupled with a "little coil". My laptop's powersupply is

72W. That's going to be tough to do with an open transformer.

On Thu, 7 Aug 2003 20:32:04 -0400, Keith R. Williams Gave us:

Absolutely incorrect. A single cell is a CELL. A plurality of cells (2 OR MORE, dipshit) is what defines a BATTERY.

The fact that it is common practice for people to call single cells batteries does NOT make the moniker correct.