OT: Rechargeable Batteries

[Fredxxx]

I should have read all the other posts first!

[Theo Markettos]

Just been looking at bike lights, and lots of them seem set up to take 3x AAAs or a 18650 lithium ion cell. 3.7v lithium ion would fit voltage-wise - charged is about 4v. You can get 3.7V 4Ah lithium cells, and you can also put them in parallel for more capacity.

It seems there's such a thing as a 'protected cell' that has a PCB that disconnects the battery if it's overcharged/discharged.

Theo

[Graham.]

Either that, or technology I am unaware of.

There used to me a craze for recharging zinc-carbon cells with "dirty dc"

It does work up to a point, but I wouldn't recommend doing it.

[Jeremy Nicoll - news posts]

The latter then. I bought quite a few of the cells a few years ago, and found them great (mainly) for some devices that wouldn't work with NiCd or NiMH cells. But - as some reports suggest - some of the RAM cells don't last anything like as long as they're meant to... but they still easily last long enough to have been better value for money than ordinary non-chargeable alkaline cells.

Someone in the USA had quite a stock of the cells... and a couple of years ago I bought all his remaining stock - which sounds grander than it really was - it netted me just over 24 more cells.

I label each of the cells individually and keep track of each one's usage. I use them mainly in an old wireless keyboard (maybe modern ones would work with NiCds?) and wireless mice (which might also work with NiCds but as they work with the RAM cells, I use them)...

Last time I looked there were still places selling bundles of typically 4 cells with a charger, which is no use for a new customer - they'll need more than 4 cells, and no use for existing customers - who don't need umpteen chargers.

I'll be quite sad when the cells finally all die.

[Dave Plowman (News)]

Well, the beauty of ordinary rechargeables is they'll generally do better than 500 cycles. And not many things these days won't run off a nominal

1.2v rather than 1.5v. Did use to be a problem with things like Walkmans where the peak audio power output was battery voltage dependant - but I'd hope not now.

[Roland Perry]

In message , at 15:57:54 on Sun, 25 Jan 2015, Vortex11 remarked:

I used to deploy AA/AAA versions of those almost exclusively, rather than NiCads. But only available in the USA at the time (this was before online shopping).

They came with a special charger, but have a finite number of charge cycles, which is perhaps why they don't seem to be around any more.

[Ian Jackson]

In message , Graham. writes

Back in the 60s, when transistor radios were still a relative novelty, I. made up one of the many popular kits. It was battery-only (a large PP9) - but as it still had loads of room inside, I fitted a small mains-to-9V power supply.

In order to allow the radio to be occasionally used on battery by simply unplugging the mains connector, and to keep the battery topped up, I added a couple of diodes and a resistor to allow the battery to steal a couple of mA of charging current from the 9V. Obviously, this was 'clean', well-smoothed DC, but despite this, the battery lasted for years - in fact I don't recall it ever being replaced.

I've since done similar with a couple of off-the-shelf FM mains/battery radios. These were OK on rechargeables (of course), but there was no provision for charging them in situ. As the batteries were meant to be charged, I think a set the charging current a little higher.

[meow2222]

Its a long time since I did that. PP9s are ancient history now.

NT

[polygonum]

Far from it, if you allow the alkaline version. This afternoon I had to locate the PP9s for a Cat5 tester/identifier. And our upstairs smoke alarm uses one alkaline and one alkaline-or-old-fashioned PP9.

[Windmill]

Smoke detectors.

[Windmill]

Battery manufacturers used to claim that there was an explosion hazard if you tried to recharge non-rechargeables, but I used to know someone who eked out a barely-satisfactory living repairing "collectable" toys. He regularly recharged zinc/carbon cells, maybe including alkalines, because he frequently had to test and/or demonstrate battery-powered toys. Said he never had a problem, but maybe he was careful to check for temperature rise.

[Ian Jackson]

Indeed I also thought they would be long gone, but apparently not!

Surprisingly, they're not too expensive (around £5.50).

[Ian Jackson]

It'll be a pretty large smoke detector!

>

[Martin Brown]

I suspect a DAB radio draws just enough current to ensure that if it does work at all on rechargeables you won't be able to read the LCD display. That is the problem I have with my landline phone which requires a battery backup for its internal clock and caller display - it must use secondary cells or it is invisible!

Higher current motors tend to do OK since the low internal resistance of NiMH or NiCad compensates for the lower open circuit voltage but at modest currents and voltage sensitive parts the result is not good.

Only way to find out is to try it but my guess would be 1-2 hours running time if you are lucky on a good day with a trailing wind. Eneloops have about the highest output voltage to start with but I really would not invest in rechargeable batteries for it!

Battery powered DAB radios are fit only for landfill!

[charles]

I have two, totally different models, from Pure. They run very happily on batteries.

[meow2222]

Could you be confusing PP9 with PP3? My smoke alarm & cat tester both take PP3, and I've never seen a smoke alarm big enough to fit a PP9 in. Nor can I think of any reason either would need a PP9.

NT

[meow2222]

I reckon they're so historyt hat some have forgotten what they even are

NT

[polygonum]

Yes I am indeed - and, stupidly enough, always have! Especially as today we talked about their 9V-ness.

[meow2222]

Do you reckon that would work on my 1930s Zinc carbons? Maybe not, as they're marked best before 1942.

NT

[Chris French]

In message , charles writes

And ditto, the two different ones i have mentioned elsewhere in the thread that run fine on NiMH cells. I get probably about roughly 10 hours or so on my Phillips one with 4 x AA cells.