Sanyo Eneloop batteries and charger: Work for Texas Instruments 84 calc?

Anyone have this system?

I really don't use a LOT of batteries but the idea of throwing them away bothers me as we have no way to recycle them here locally

I'm wondering if they would work ok in graphing calculator?

Sorry to post here but didn't know where else to put it. Also, is there any diff between a cheap $13 Kodak NiMH charger and more expensive $40 one?

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me
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I've been using Eneloops, and similar "ultra-low discharge" NiMH batteries from other vendors, in both digital cameras and in the AA-cell pack for a portable amateur radio.

They work quite well - they hold their charge quite well for many months (much better than older-generation NiMHs).

Very probably - this is a relatively low-current-drain application and you should get many hours of use out of a single charge.

The least-expensive chargers are probably simple fixed-current slow-chargers, operating at around a ten-hour charge rate... they take somewhere between 12 and 16 hours to load up fully-discharged cells. Such chargers do work, but they stand a fairly good change of overcharging the batteries if you don't know just how far discharged they were when you started. Over time, too much overcharging can reduce the cells' capacities and shorten their lifetime (although this isn't a really serious problem at such low charge rates).

More expensive chargers will often run at a higher charging current (faster charging) and have a sophisticated temperature-and-voltage sensing circuit to detect the cells' full-charge state and turn off the charge current. This is both better for the batteries (less overcharging) and more convenient (a good charger can restore fully-discharged batteries to full charge in a couple of hours).

--
Dave Platt                                    AE6EO
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Reply to
Dave Platt

If you don't use a lot of batteries, there's nothing wrong with using disposables. You may never recoup the cost of the rechargeable batteries and the recharger.

In my opinion, you should not use rechargeable cells in a calculator (unless you always carry a backup pair), simply because they might drop dead when you need them most. Nicad and NiMH cells are particularly bad in this regard, because they have a flat discharge curve, followed by an abrupt voltage dive, the worst-possible characteristics for any kind of battery, especially rechargeables.

Rechargeables make the most sense for medium- to heavy-drain applications, such as flashlights, motorized toys, and electronic flashes. Calculators are light-drain, and probably not worth the trouble.

Reply to
William Sommerwerck

I use Sanyo Eneloop AA batteries (as well as other brands of low self-discharge NiMH batteries) in several devices, including a police scanner, AA cell flashlight, cordless mouse, remote controls, etc. I'll never go back to regular NiMH batteries, or alkaline for that matter. I always have four or so fully charged ready to go.

BTW, I've used a Maha MH-C401FS charger for over two years. About $35. I don't recommend cheap chargers for the reasons given by another poster.

Reply to
UCLAN

OK thanks

I was really unsure of the cheap vs expensive charger!

Reply to
me

I have Eneloops, Ray-O-Vac "Hybrid", and Duracell Low-Self-Discharge batteries, and love them all. My children (and the rest of my family, including me...) go through a lot of batteries, so I sprang for the best charger (Just an opinion, there are other very good ones out there) - the Ansmann Energy 16 (Paid $119 at Amazon.com) If you're just interested in charging just AA's and AAA's, I think the LaCrosse BC-900 is a much better choice (tells you actual maH accumulated charge!) for much less ($40 at Amazon, free shipping) and comes with 4 each (total 8) AA and AAA batteries, plus other accessories. It has features even my Ansmann does not, like user-selectable charge rates, and a test mode with actual battery capacity readout on a digital display. I haven't used one, but the reviews seem to indicate that people are very happy with it.

If you don't want to spend the extra money on a good charger, I would recommend you have extra batteries on hand, so you can switch them out when one set is dead in your device(s), and charge only completely dead batteries for only the time recommended by your charger for your capacity batteries. As long as you're diligent in taking them off charge when they are done, and are not trying to charge only "partially dead" batteries, you should be o.k. Regardless of how they are charged, LSD batteries beat the pants off "conventional" Nimh and Nicads - I use 'em in nearly everything. Circuit City has been closing these out (eneloop) real cheap, like $6.00 for 4 AAs or AAAs - I cleaned my store out - I can't imagine why they don't intend to stock these any more. I don't think they marketed them properly in the stores to explain to people what their advantages are.

snipped-for-privacy@privacy.net wrote in message news: snipped-for-privacy@4ax.com...

Reply to
Haywire1

better

batteries,

I would recommend the MAHA (Powerex) MH-C9000, which I _have_ used and am very enthusiastic about.

I don't understand this business about "low self-discharge" NiMH batteries, as I'ven never noticed any particular problem with them.

Reply to
William Sommerwerck

In order to have a lower self discharge rate, they have to have a higher internal resistance. This lowers the effective charging rate, and the output current.

I'm using Recyko+ battries sold by GPT out of Hong Kong. They are the same batteries as one of them (there are only three companies that make them), but I don't know which.

In order to get them to work, I have to charge them an awfully long time with the chargers that have a fixed rate. For example the one that came with the AAA batteries should charge them in 12 hours, I leave them on at least 24 to get a useful charge. I also have one that times the charge for 7 hours and I have to charge them twice.

With a normal NimH battery of the same capacity, the charger would charge it completely in 7 hours.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM
Reply to
Geoffrey S. Mendelson

OK

Well I just don't want to spend a ton of money cause I only have a "few" devices that use AA or AAA right now and am afraid the payback would be too long if spending much money for charger and the cells

Reply to
me

Agreed. The degree of control and information it provides is wonderful.

My own experiences are otherwise. "Traditional" NiMH batteries I have used, would tend to lose a substantial fraction of their charge within a few weeks, and would be nearly "flat" after three months of storage.

The problem seems to be worse with the higher-capacity cells... a 2600 or 2700 mAh classic-NiMH cell would lose charge at a faster rate (both absolute and percent-per-day) than an 1800 or 2000 mAh cell of the same brand.

This isn't an absolute rule, though. I had a set of Lenmar "NoMEM Pro" 2000 mAh cells which lost almost a third of their charge after sitting around for only a week!

In certain applications - e.g. in the camera or flash unit of a very busy photographer - the high-capacity "classic" NiMH cells may be the best choice. It doesn't matter very much if they lose 2% of their charge per day, if you're going to be running 'em down within a week anyhow.

For low-rate or standby applications, the new ultra-low-discharge cells are wonderful. I keep two sets of six in my ham-radio "go-kit" for my spare dual-band handheld radio... each set will run the radio through two 8-hour shifts of typical operation, and giving the a brief topping-up charge every six months seems to be all that's required.

--
Dave Platt                                    AE6EO
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Reply to
Dave Platt

There *is* no problem with them. I use several brands, including Sanyo Eneloop. Low self-discharge NiMH batteries have made regular NiMH batteries obsolete, IMO. [Except for in heavily used high current applications, only because the capacity of low-discharge NiMH batteries is not yet as high as regular NiMH batteries.]

Reply to
UCLAN

That is a fault with your charger more than a fault of the batteries. I can charge LSD NiMH batteries in a few hours in my Maha charger.

Reply to
UCLAN

That's about right, if not pretty good. The discharge rate that Motorola once claimed in an ancient phone manual I once had was 30% per week.

In effect what they have done is traded off how long a charge lasts versus hom huch that charge is. Unless you have the guts of a battery hidden in a black hole, there is only so much room in the case.

That depends upon what power level you run the radio. I found that out in the mid 1990's with the Ray-O-Vac rechargable alkelines. Everything I had as except flashlights only worked for one or two charges before they could not put out enough current to be of any use.

There were just some places that 1 watt would not open the local repeaters even with an better quality rubber duck than the one that came with the HT. Switching to higher power drew too much current. :-(

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM
Reply to
Geoffrey S. Mendelson

Sure, I can charge then in a few hours with a better charger too. But the cheaper fixed current ones won't. The one that takes 24 hours is the one that came with them. :-(

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM
Reply to
Geoffrey S. Mendelson

You've been lucky. I deal with a lot of 2-way radio handhelds that sit idle for months at a time. The early NiMH batteries would self-drain to unuseability in less that a month. At wurk, we replaced them all (at least the ones we could find) after a year with newer technology NiMH batteries like the Eneloops and such.

Reply to
nobody >

There could be a number of things going in here.

You mention the higher resistance of the low-self-discharge cells. Frankly I'm sceptical that this, by itself, could be great enough or have enough effect on the battery to reduce the charging efficiency by as much as you have observed. The low-self-discharge cells seem to be able to discharge at rates of C/2 or even C/1 without their terminal voltage dropping by very much, which means that the internal losses aren't very high.

It's possible that the cheap charger you got with the batteries, simply isn't very good - it may not be delivering as much current into the batteries as it was supposed to. Possibly its internal current regulator is poorly designed... if it consists only of a series resistor hooked to a poorly-regulated DC voltage, then modest variations in the DC supply voltage (from its internal transformer) or in the battery's terminal voltage during charging could make a big difference in the amount of current that the charger actually delivers to the battery. You might be charging at a C/20 rate rather than a C/10 rate. If the charger design was originally created for lower-capacity cells, and wasn't revised when the capacities were increased, it wouldn't be surprising if it's slow.

Another factor is something that I understand is true about NiMH cells in general (not just the low-self-discharge type): charge acceptance is quite poor at low charge rates. There seems to be a significant "overhead cost" to charging... a fairly high fraction of the first

50-100 mA or so that you push into an AA cell just turns into heat, rather than recharging the electrochemistry. Your charger may be using such a low current rate that it's not actually making much headway against this issue.

My impression is that a lot of the cheap/inexpensive "overnight" chargers were originally designed for NiCd cells, and have been re-branded as dual-chemistry (NiCd/NiMH) chargers without significant change. Since NiMH cells typically have around twice as much capacity as NiCd cells of the same size, it's not surprising that the charging takes a long time.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
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Reply to
Dave Platt

Yup. I understand that it's an issue of the specific metal alloy and structure that they use to create the hydride. Alloy structures which bind the hydrogen more firmly have a lower self-discharge rate, but less capacity per volume, and vice versa.

Changes in the plate separators also seem to be part of what they've done to reduce the self-discharga rate.

Putting the guts in a black hole seems impractical... you just can't get enough of the stored energy back out in Hawking radiation when you really need it :-)

In general, alkalines seem to be a poor choice for high-discharge applications. Digicam owners have discovered this independently... most digital cameras will "kill" alkalines quite quickly. I believe I've read that the rechargeable alkalines were even worse in this regard... their ESR rose significantly after a few charge/discharge cycles. So, I don't find your experience at all surprising.

I've found the low-discharge NiMH cells to work quite well in my HT even at high power.

Somebody over in one of the rec.radio.amateur newsgroups (I think it was Roy but it might have been Cecil) posted an interesting point about high-current usage recently. He noted that NiMH cells have a reputation as being worse than NiCd, when high discharge currents are required... presumably due to higher internal resistance.

His point was true that the comparison works out this way *only* if you're doing the comparison on the basis of discharge rates in terms of the battery's total capacity... say, how much energy is lost from the battery at a C/2 or C/5 discharge rate. Measured in this way, NiMH cells do come up looking rather worse than NiCd.

In many situations, though, this isn't the right question to ask. The better question to ask is how much of the battery's total energy is wasted, at a specific discharge rate measured in amperes (e.g. running a given radio at high power, or taking photos with a digital camera).

When compared on this basis, modern NiMH cells come out looking about the same as NiCd in terms of loss.

The reason for the difference, of course, is that the NiMH cells have a much higher capacity (2x or so) than the corresponding NiCd cells. They'd look worse in the first sort of comparison, even if their internal resistance was identical with that of a NiCd, because they were being tested at a higher absolute current level.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
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Reply to
Dave Platt

Like, wow, man. Trippy.

Reply to
William Sommerwerck

I've heard this as well. Specifically, at "low" charge rates (which which would actually be on the "high" side for nicads), NiMH cells are less likely to enter the negative delta-V region that indicates end of charge.

Having grown up with nicads, I'm reluctant to charge faster than 0.1C, but it appears that 0.3C and even 0.5C is acceptable with good-quality NiMH cells.

Reply to
William Sommerwerck

Alkalines were traditionally well-suited for high-drain applications. But the Ray-O-Vac rechargeables had significantly higher internal resistance and didn't handle high drain very well.

Reply to
William Sommerwerck

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