Rechargeable Batteries with LEDs

UnknownVT

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NiMH rechargeables - although are the current state of the art high capacity/drain batteries -
often do not work well with LEDs because of their lower voltage of 1.2V compared to the 1.5V of standard alkalines.

But how do the Rechargeable Alkalines such as the RayoVac work out in LEDs?

They appear to be rated at the standard 1.5V and and said not to self-discharge, so are good for long term use/storage.

They are advertized at 100 charge/recharge cycles - so would seem to work out more economically than disposables.

They are available in the standard AAA, AA, C and D cells

http://www.rayovac.com/products/recharge/rec_alk.shtml

Any comments?
 

Rebus

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They work great! The secret is
to not let them discharge to far.
I try to recharge mine before they
get below 1.25 volts. This allows them
to recharge back to a full 1.5v and
last for more charging cycles.
If you discharge too far they WILL NOT
come back to 1.5v!

-Rebus
 

FalconFX

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Yep... You can pretty much fry a NiMH to nil and it'll charge back up, but drop a rechargeable alkaline to below 1.0V and it's "meet the trash" time...

And careful about the 100x charge cycles, because I believe they only apply to the newer generation of Rayovacs. The older generation ones (with the older labels) go **** up in 8-10 charges, no matter what happens...
 

UnknownVT

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Neat! thanks for the replies -

so how do you know when to recharge them
(without carrying around a volt-meter
tongue.gif
)?
 

FalconFX

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If you're a frequent user, like I am, it would never hurt to charge them after a day's worth of use... If, for example, I use a mimim$g with a BB500 at 30min a day, then I'd charge it after 2-3 days... Anything heavier than 2 hours of use and you'd want to charge it right afterwards... The farther you keep it from that 1.0V, the better it will keep it's 100+ cycle...

BTW, the reason why NiMHs don't work well with LEDs doesn't necessarily have to do with the lower voltage, but with the higher current NiMHs give out. Thus, you can fry an LS by direct driving it with NiMHs, even though it has a lower voltage rating...
 

UnknownVT

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I do realize to be safe one could charge each day - but then surely the battery would last only 100 days' usage?

So is there any indication, other than keeping track of one's usage time -
like the LED being perceptibly dimmer -
or is that likely to be too late?

thanks
 

Jonathan

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NiMH cells should not be a problem in any flashlight that _regulates_ the current to the LED.

They have the dual issue of low internal resistance and lower voltage. If your flashlight requires the higher voltage to meet the Vf requirements of the LEDs (say a 2AA cell direct drive LS), then the NiMH cells might not provide the necessary drive voltage. On the other hand, if Vf isn't a problem (say three AA cells in series direct driving an LS), then the low internal resistance of the NiMH cells means that you can easily smoke the LED.

If you are using a boost converter, such as the BB500, then using a pair of AA NiMH cells should work fine. My experience is with other boost driven LEDs, which actually prefer the AA NiMH cells because of the low internal resistance.

With respect to when to charge them, I simply carry a spare set of batteries, and swap and charge when the LED drops out of regulation...of course this presumes a regulated design.

-Jon
 

FalconFX

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You can tell if the LEDs are dimmer that it's time to charge... You don't want to run it to the point where the LEDs barely emit any light anymore... Essentially, what I'm trying to say is if you start noticing a dramatic change in the brightness (say an Arc-LS going into moon mode, or a KL1 flickering in brightness), it's time to charge it up...

And also, keep in mind that the 100 charge that's advertised is for the cycle of an almost dead battery back to full, so if you charge a battery when it's only half empty, you're not going to waste a full charge on it...

IE: 3000mah for a AA battery. 100 charges get you 300,000ma... Essentially, you can charge as frequently as you'd like for that duration of 300Kma... Obviously, it'd make absolutely no sense if I put the battery into the charger, took it out every 2 seconds and put it back in, and after 100 rotations, the battery's toast...

It's an accumulation... The further you drain the battery, the less likely it's going to hold a charge next time you put it into a charger. So to prolong the battery life and charge cycle, you want to keep it fresh and charged up...
 

MY

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I have gone through about 50 rechargable alkalines during the past few years. They all leaked before the time they would not hold a charge. I basically threw them all away and strictly use NiMH. Maybe the newer ones don't leak as much?
 

FalconFX

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The newer ones are a lot better. When I stored my old D sized rechargeable alkalines, they'd start rusting and leaking... The newer ones do much better in storage, and seem to hold their charge better. At the very least, I can get much more than the usual 8-10 charges I'd get from the old ones with the newer ones (~100 charges)...
 

Whistler

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I use AccuCell rechargeable Alkalines. Quite good. They only tend to leak when they are abused by discharging them quite far... I only had 2 batteries who finally leaked (out of ?). As mentioned before, for regulated LED flashlights no really need for them. Keep in mind that you will need a special charger, so it's getting a bit expensive.
 

UnknownVT

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Originally posted by FalconFX:
IE: 3000mah for a AA battery. 100 charges get you 300,000ma... Essentially, you can charge as frequently as you'd like for that duration of 300Kma... Obviously, it'd make absolutely no sense if I put the battery into the charger, took it out every 2 seconds and put it back in, and after 100 rotations, the battery's toast...

It's an accumulation... The further you drain the battery, the less likely it's going to hold a charge next time you put it into a charger. So to prolong the battery life and charge cycle, you want to keep it fresh and charged up...
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Cool! Many thanks for the explanation FalconFX - much appreciated.

So it would be safe and prudent to charge (top up) Recharageable Alkalines often, even on a daily basis - without any danger of prematurely "using up" its charge cycle life.

Unlike Ni-Cads where one is advised not to top up due to Ni-Cads' notorious reputation of "charge memory".

Thanks.
 

UnknownVT

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Many digital cameras are supplied with proprietary
Li-ion (Lithium-ion) rechargeable batteries - that seem to have good capacity and good low temperature usage(?).

Why don't we see Li-ion rechargeables in standard battery sizes like AA -
is it another case of the native voltage being too high?
 

highlandsun

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The main reason is because the average consumer is stupid, would probably buy a LiIon AA, put it into a device designed for a 1.5V alkaline battery, destroy it, and then sue the battery company. A fully charged LiIon cell is 2.5x higher voltage than an alkaline, and that's enough to fry any gear that wasn't designed for it.

Second, LiIon batteries are much more volatile/temperamental than other battery chemistries. If you mistreat them they don't just fail quietly, they tend to explode violently. The LiIon batteries in use today all have on-board charge control circuits to make sure they can't be driven into abusive conditions.

That said, I've got a set of AA LiIons that I ordered from a battery manufacturer in Hong Kong. They work very well with LEDs. There's nothing stopping an *educated* consumer from using whatever battery you wish.
 
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