Rotating rechargeable batteries in radios that use three

Factual Questions
1

I’m a pretty logical/mathematical person, but this is driving me a bit nuts.

I have two radios that I use frequently in the bathroom and the kitchen to listen to NPR. One takes three AAA’s; the other takes three AA’s. The charger can charge two at a time or four at a time but not three at a time. It does seem to accept a combination of AA’s and AAA’s charging together — but I’m not sure if that’s actually a good idea, especially if it’s three and one rather than two and two.

I would like to have spares already charged so I can just swap them out without waiting several hours in between; at the same time, though, I don’t want to have more spares than I really need. For one thing, that is a more expensive initial outlay for batteries. But also, unless I engage in some sort of labelling and numbering system (which I will do if I have to), having a bunch of extra charged spares increases the chance that one or more of them will lose their juice before they get used.

I’m not at the store to verify this at the moment, but I believe they are sold in packs of two, four, or eight.

Thoughts, suggestions?

2

Get more radios.

3

Get a better battery charger that supports independent charging. I can’t help you with the battery count thing. I use Sanyo eneloop batteries exclusively and they come in multiples of 4 only, up to 16 packs. Pick up an 8 pack of each. You must have something that uses a pair of AA/AAA batteries, right? The low self-discharge of the eneloops make them suitable for remote controls, flashlights, etc. that aren’t really suitable for standard NiMH batteries.

4

Buy two led flashlights. One using AAA cells and the other using AA cells. I have some O-light S15 batons running on AA cell and it’s a nice light.

5

smart chargers will support single battery charging. you can get them with an LCD display showing each cell. these chargers will also discharge the battery before charging, if you select that function, to exercise the battery.

labeling the batteries is good to figure what might be happening.

get a battery tester, about $7, that tests a battery under load (a resistor). match battery levels that you put in the radio.

6

But those wouldn’t get used up as fast as the ones in the radios because I don’t often use flashlights.

7

Well, you’re either going to have to get a better charger or deal with a sacrificial battery in a set of four. It’s really that simple.

8

A sacrificial battery would be fine. But how would that work? Is it okay for the charger, and the other batteries, if they are charged when exhausted, along with a battery that keeps getting charged over and over, but is never discharged?

ETA: That charger you linked to looks very nice, but too pricey.

9

I’d just number your four rechargeable batteries 1 through 4, charge all 4, then run 1,2,3 in the charger. Then recharge the 3 batteries, and then put 2,3,4 in the radio. Recharge, then put 3,4,1 in. Then 4,1,2, and finally 1,2,3 again.

Just rotate the batteries so all batteries get charged/discharged the same.

If you get the Sanyo Eneloops mentioned up thread, they’re good for thousands of charging cycles, so it’s unlikely you’ll actually wear them out even if you don’t rotate the batteries, and they’re Low Self Discharge batteries, so the spare battery won’t lose its charge while out of the rotation either.

10

I’m not really sure what affect pair-charging NiMH batteries has on individual cells, but I can’t think of any possible consequences to the charger. Contrary to bump, I would maintain one battery as the designated goat, behind the idea that batteries used in series should be maintained at the same charge level as much as possible. I admit this is instinct, not fact.

What charger are you using? What batteries?

I’m going to assume, based on the pair-charging requirement, that you have a non-regulated battery charger. You should never leave any batteries in a non-regulated charger as it will drastically reduce their useful life. If you have low self-discharge batteries, you can charge up the secondary set and pull them from the charger. If you have standard NiMH batteries, charging them and pulling them will mean the batteries will be nearly dead by the time you need them. Maintaining standard NiMH batteries in a state of full charge with a non-regulated charger is self defeating. The best you can do is charge and replace them on a schedule.

In any case, a regulated charger will increase the useful life of any batteries it charges versus non-regulated, so beware of false economy.

11

It’s just the standard type charger they sell at Wal-Mart IIRC. Same with the batteries: the cheapest they sell (Ray-o-vac I think). Spending much more would start to tempt me toward just buying a big package of non-rechargeables.

So: under a rotation system, each battery would have three cycles of being used in the radio until exhausted, then charged up, followed by one cycle of being charged twice?

What if I kept a total supply of nine AAs and nine AAAs, just getting rid of (or maybe setting aside for potential future needs) extras I had to purchase to get to nine each? Then I have three in the radio, and can charge the other six by doing four and then two. I save the six in the fridge, and when they run out, I take three from the fridge to replace them and set the three exhausted ones aside, near the charger. When these next three run out of juice, I replace them with the three remaining in the fridge. I now have six exhausted batteries ready to be charged, and I start the cycle again.

Wouldn’t this work, without having to label anything? It wouldn’t rotate the batteries precisely in the order they are used; but close enough, no?

12

So much for logical/mathematical… Esp. the part about buying a big pack of non-rechargeables.
It ONLY makes ‘sense’ to have a whole other set of batteries if you NEED to swap the batteries and have the radio work right away.

13

don’t keep batteries in the fridge.

14

I have that charger and it is most likely your best bet as it will prolong the life of the batteries + it will allow you to find any weak ones to take out of service - prolonging the life of the batteries you have. So it can be cheaper in the long run.

Trying to figure out which one was bad in a conventional (2 at a time) charger vs which one was still good but appears bad because it was charged alongside a bad battery can be a daunting task.

15

I do! I listen to those radios every day. To have them out of commission for hours (so, basically, a whole day) is not acceptable.

What’s the harm? Energizer sez:

There is no place in this house that is “cool, dry” or “at normal room temperature” consistently in the summer. (We can’t afford the cost of air conditioning rooms when we are not in them.) It gets very hot and humid here. So “not necessary” strikes me as different from “don’t do it”.

16

fridges are not dry. also when a refrigerator chilled battery gets exposed to a humid environment it may condense moisture on your battery.

17

So what if your choice is between “hot and humid” and the fridge? You say hot and humid? This is Missouri, we are talking about triple digit temps at times, with crazy high dew points.

18

Do you have cordless phones that take normal batteries?

We do, so whenever I need freshly charged AAA’s, I just swap the ones that ran out with the ones in a phone. The batteries in our phones last for quite a few years, so it clearly doesn’t overcharge them. The only downside is you can’t jabber on that phone for a while, as it recharges. That only works for AAA’s, so I use a charger for our AA’s.

I keep two boxes: uncharged batteries and charged ones (well, plus a third for batteries to discard). Everyone in the house knows to dump them in one box, take from the other, and I recharge when the available supply is less than the expected demand.

In your case, I’d get 8 batteries.

Charge 3 and install them.
Charge 3 to be ready (but ideally, wait until you think they’re nearly ready to be needed).
Leave 2 uncharged. When the three come out, dump them in with the other two. Use the ready ones. When it’s appropriate, pick 3 random batteries from the uncharged box and charge them, and then dump them in the CHARGED box.

Do the same thing with AAAs and AAs, independently, of course.

Here’s the tricky bit. When the batteries are old enough that you want to try new ones, but not so bad you want to dump them, either get obviously different new batteries, or mark the old ones with a sharpie / magic marker. Don’t mix the new batteries with the old ones, when installing in anything, or when charging.

If your charger has an LED that lights when charging is done, it’s probably an intelligent charger, so you don’t need to worry about leaving the batteries in – but still it’s best to pull them out and put them in the CHARGED box.

You don’t need to worry about one battery having gone through 4 cycles being mixed with one that’s gone through 6 cycles. Chance does a fair job of evening things out, and they don’t need to be perfect. You just don’t want to mix the brand new ones with the stale old ones.

Meanwhile, I’m getting that La Crosse charger (actually, the 1000 one, which shows the capacity when charging is done.) It’ll help me manage the batteries and know when to toss them, and see when I have two old batteries with very different capacities. Also, I’ll try some of those Sanyo batteries. We’re due for more. Thanks for the tip!

Between Wii Fit Balance Board, Wii hand controllers, wireless keyboards and mouses, and regularly used flashlights, we use a fair number of rechargeable batteries on a regular basis.

19

My guess is they’re fine any place they’re not in direct sunlight or experiencing condensation. I’d pick a desk drawer over a fridge, even in Missouri.

20

I meant to mention above: most NiMH & NiCad batteries do best if they’re not left charged. They want to be stored uncharged. That’s why I don’t get way ahead of the demand, and keep just enough in the CHARGED box to handle the likely demand. However, some newer batteries like those Sanyos come charged, and perhaps they’re different in this regard.

While we’re on the subject … I had a set of batteries marked at 2400 mAH. They seemed fine, but eventually got old. When I went to replace them, the best I found (of the same brand, Energizer) were 1200 mAH. Did they just get more honest, or is there a new standard, or did I get crappier batteries? (With the charger, I’d be able to get a clue, though the rating depends on the discharge profile so it’s not totally objective. But it’s better than believing the marketing!)