Rechargeable AA Batteries

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alec

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The ones I have for Digi cameras and HH GPS seem to be quite poor. They have Ni-MH on them.

After charge, they are only 1.5 volts instead of the 1.6 volts on the alkaline throw aways.

Is there a better rechargeable I can buy ?

Thanks in advance.
 
1.5v is pretty good - my NiMHs are quoted as 1.2v. Fully charged with meter gives 1.33v

Are there variations of these?

Rechargable Alkalines are 1.5v but don't last that long, but if you need the voltage then they are perhaps the only way.
 
Any single cell battery is rated at 1.2v although they may read higher when new or fully recharged if of that type.
 
?

My Revorac Rechargable Alkaline AA has a 1.5v charger; has 1.5v written on it and gives over 1.5v when fully charged, unlike my NiCads and NiMHs. Non-reachargable AA's are 1.5v

Don't understand your comments. Please clarify.
 
I have tried all manner of rechargables over the years for HH GPS and have never managed to get the battery indicator to 100%.

I have now reverted to alkaline disposables they seem to last a lot longer.
 
As already stated NimH and NiCad batteries are nominally 1.2 volts while alkaline disposable are 1.5 volts however it is not as simple as that.
An alakline starts at 1.5 volts and under load declines to about 1 vollt in a near linear manner, when they are usually considered flat. A simple voltmeter on the device serves well as a battery indicaotor.

Ni Cad and Ni Mh batteries have a far better discharge curve in that they will hold to 1.2 volts until very near the discharge state. This means that a voltmeter as a "fuel gauge" of battery indication is not very good although still used but it also explains why a 1.2 volt battery will work well in place of a 1.5 volt battery. ( it emulates a half flat Alkaline)
When not connected to anything the 1.5 volt alakaline will measure 1.5 volts until nearly dead but will be quite low under load when near the end of life.The Ni cad NiMh will measure possibly up to 1.3 volts no load when fully charged but will settle to a little over 1.2 under load.
So fit your Ni Mh or Ni Cad batteries ignore the voltmeter fuel guage and carry spares cos when your camera or GPS stop working that is when the batteries are flat. If your camera or GPS are really fussy and switch off too early the rechargeables may be dead or the device has a cut off too high. In the latter case you will have to use Alkaline. Regards and happy Christmas olewill
 
Olewill - many thanks - I have puzzled the behaviour of my various battery types over the years and scratched my head with all the inconsistences.
I'm a lot clearer now

regards
happy christmas
stephen
 
Could I just echo thanks, Olewill, for such a straightforward and clear explanation. From experience, from reading previous postings and from numerous discussions with others I have come to the same conclusion but you put it most succinctly and helpfully.
 
Thanks for that. That explains why my bike lights got slowly dimmer as the battery went flat when using ordinary batteries. They go more or less from on to off when rechargeables go flat. So much so that I used to carry spares. Who needs Google with posters like Will.
 
Re: Rechargeable ordinary alkaline AA Batteries

And with a special battery recharger at about 25 pounds you can recharge ordinary alkaine batteries around a dozen times. [ However you should recharge the batteries before they are flat. I keep my Worldspace radio, which uses four D cells going, living aboard most of the summer, by having eight cells, and swapping the 'in use' cells with those just rechcharged] The ordinary alkaline AA seems to have a higher basic capacity than the genuine rechargables and are somewhat cheaper. I am not a battery technican. Just 'careful'.
 
I use these with a uniross fast charger and they definitely last longer than Duracell Ultra etc. The only word of warning is they are very slighly larger in diameter than standard AA cells and some devices can be a tight fit.
 
I use a lot of NiMh AA cells in photographic equipment. For heavy current drain devices like digital cameras, flashguns and portable GPSs or VHFs used frequently they are the best choice. Modern NiMh cells deliver at least twice the capacity of standard alkaline Duracells or Energisers. The voltage is irrelevant - what matters for high power consumption equipment is the ability to deliver current.

One minor snag is that 'battery meters' on equipment often are set to read alkalines, and thus show NiMhs as only half full even when freshly charged. It's an illusion. Test things out by putting a set of new alkalines into your GPS and running it non-stip till it dies. Then do the same with a freshly charged set of NiMhs - it will probably run two to three times as long.

Look for ones that are over 2,000 mAh (milli-amp hours - a measure of how much power they can store) capacity - currently I'm buying 2,700 mAh cells to replace three year old 1,800 mah cells (that have probably now been recharged several hundred times and are still working, though getting less efficient). They only cost about twice as much as Energisers, and last for years and hundreds of recharges. Unfortunately supermarkets only seem to sell really poor-capacity rechargeables - not surprising given the profit margin on standard batteries. Buy your NiMhs from a specialist supplier and look for high numbers on the side - at least 2,000 for AA size.

However, if you only use an item of equipment rarely, (eg emergency torches, a spare handheld GPS or VHF in a grab bag, etc) use alkalines. This is because alkalines keep their power for years, whilst rechargeable NiMh cells (although rechargeable hundreds of times), self-discharge - ie steadily lose stored power even if unused. They are typically down to half power after about three months storage - though even that is still as good as a brand new Energiser. But you don't want to turn on your emergency grab bag VHF once in your liferaft and find that you hadn't charged the battery for 12 months and it was nearly flat.

Also rechargeables are pointless for ultra-low consumption devices such as clocks, etc., as they will self-discharge long before the clock's power needs runs the battery down.
 
Suggestion on rechargeable batteries. Most chargers seem take pairs of cells in series. So when you buy the batteries number them in pairs. That way you can avoid recharging a partially discharged battery with a completely flat one. Which tends to overcharge the partially flat one whereupon it gets very hot.

No idea what you do with devices that take odd numbers of batteries though...
 
I agree use the highest current capability rechargeables. Understand that most rechargeables self discharge quite quickly. The exception seems to be my Kodak camera which has a lithium iron battery and seems to good for 6 months without recharge
 
Proof of the pudding is in the eating.
My digital camera used to eat up Duracells instead of pudding at an extraordinary rate.
I bought myself a charger from Energizer that came with 4 NiMH batteries of 2500mAh and it made a world of difference. As somebody else has already suggested, I have marked mine in pairs (nail polish) so that the same two are always used together.
Charger is very well made and the kit more than paid for itself in the first two weeks.
Conclusion: proof of the pudding. Never mind what the meter says, what is important is how long the batteries last.
 
The secret with using rechargeables is to always carry a set of spares, maybe even two sets, as they die very quickly.
I have rechargeables in all my AAA & AA powered devices. I cycle the batteries between devices that are not used often or have low drain and ones that are recharged often.
 
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