rechargeable battery experts info please

happyhero

Hi I have 3 kids and they have loads of things that take batteries and they nearly all take AA batteries. After buying throw aways for ages and spending a fortune it seems to me that it would be better to buy rechargeables bearing in mind that for example the UNIROSS 2500Ah ones say they will last longer per charge than Alkalines and can be charged approximatly 1000 times.

I am tempted to change all my AA Alkalines to rechargables.

I have looked on ebay as I was looking at getting quite a few (4 would be a joke with my 3, I need to look at about 20 plus or more) There are loads of different types available.

What I would like to know is are they mostly all the same assuming like for like "Amperehours" of course or do they vary quite a lot, ie should I stick with Uniross? Buying loads means there will be a significant price difference.

What does the "Ah" actually mean, ie will a higher Ah last longer (I have seen 2700Ah ones but not Uniross).

Also I see Uniross do different types, is there a certain type that is preferable, if so why are they better?

Basically what do you guys recommend I should do?

Any help appreciated.

chatta

I had two kids and was glad my dad bought me my first batteries and charger. Sorry can only tell you it saved me fortune even if I had bought them myself. Buy as meany as you can afford at least 20 as you say, and be very organised in rotating them in charger so you always have fresh ones. Technically I cant answer your questions but it saved me money I know. And you help the enviroment by not throwing away loads of batteries.

Little_John

The number of mAh the better, consider it the fuel tank the bigger the number the more fuel you can get in it and the further you go or the longer the batteries last.

I have always used Uniross rechargables and they have been brilliant but they have been pretty much the only companies making rechageables Duracel have started and I expect energiser will do them too. the largest capacity available in AA is 2700mAh but it seems you can only buy them with a charger at the moment the next highest is 2500mAh
There are loads of chargers that only do AA or AAA batteries with really quick 15 minute charges, if you plan buying the larger C and D cells then get one of the chargers that will charge them unfortunatly they are usually slower.

A tip when using the batteries keep them in sets, if you have somthing that uses 4 batteries keep those 4 batteries together use them and charge them together so you dont end up with partial charges batteries and dead batteries a mix will reduce the life of them and wont last long as only half of them are at full capacity. I have 5 sets for an old digi camera each set has a number on them so they cant be mixed.

ollyk

happyhero wrote:

Hi I have 3 kids and they have loads of things that take batteries and they nearly all take AA batteries. After buying throw aways for ages and spending a fortune it seems to me that it would be better to buy rechargeables bearing in mind that for example the UNIROSS 2500Ah ones say they will last longer per charge than Alkalines and can be charged approximatly 1000 times.

I am tempted to change all my AA Alkalines to rechargables.

I have looked on ebay as I was looking at getting quite a few (4 would be a joke with my 3, I need to look at about 20 plus or more) There are loads of different types available.

What I would like to know is are they mostly all the same assuming like for like "Amperehours" of course or do they vary quite a lot, ie should I stick with Uniross? Buying loads means there will be a significant price difference.

What does the "Ah" actually mean, ie will a higher Ah last longer (I have seen 2700Ah ones but not Uniross).

Also I see Uniross do different types, is there a certain type that is preferable, if so why are they better?

Basically what do you guys recommend I should do?

Any help appreciated.

Ok I first recomend buying a decent charger, so look around and don't be afraid to pay a little extra. personally I don't like fast chargers, they may be great for occasional 'emergency use but not for every charge.
As for rechargeables, I have been buying NiMh batteries from Maplins as they sometimes have BOGOF. Saying that this place has some very cheap batteries - I haven't tried yet so can't vouch!
always go for the highest mAh (milli-Amp Hour) rating you can justify. A 2700mAhr battery will allow you to draw 2.7 Amps for 1 hour or 270mA for 10 hours.
Just bear in mind that a rechargeable cannot deliver quite as much power as alkaline, being lower in voltage but I don't think you will notice the difference LOL! rechargeables will however perform much better in temporary high drain applications.
regarding mixing batteries no batteries should ever be mixed, keep 2.7Ahr batteries with likewise and 2.5Ahr with likewise also. I prefer not to mix makes either.

ffym

Ah is short for Ampere/hour or how many amps a battery can give for an hour, it is the measure of power output from a battery given that the voltage is fixed. Simplistically, the higher the Ah the more power the battery can provide. AA cells are nominally 1.5 volts, so an AA cell rated at 2500mAh can give you 1.5 x 2.500= 3.75 Watts of power, an AA cell rated at 800mAh can give you 1.5 x 0.8 = 1.2 Watts of power - you don't really need to know this!!! For kids toys etc bigger is better.
There are two main types of domestic rechargable batteries, Nicd (Nicads) and Nimh (Nickel metal hydrids) I recommend you buy NiMH not NiCd. NiMH batteries generally are less fussy about when you recharge them and should last longer - they are more expensive initially but should work out cheaper in the long run.
Uniross are by far the commonest make in high street shops and I have found them fine. Have a look around for special offers in shops like Argos or Maplin, you can normally buy battery / charger packages. (Maplin have an offer currently with a free charger whan you buy batteries see here:http://www.maplin.co.uk/Module.aspx?TabID=1&DOY=2m7&ModuleNo=-155&criteria=Batteries%20and%20Chargers

John_3:16

When getting a charger go for one that discharges before a re charge. Also get one with a cut off in when the batteries are ready. So many batteries are wasted because of overcharge.

hobo28

What sort of devices will these be powering?

Rechargable AA's generally only output 1.2V rather than 1.5V. A new akaline battery initially pumps out slightly more at 1.7V.

The low output has meant that some toys/devices have refused to work. For example, my wireless keyboard will work for a week or so on a fresh charge but after that nothing, my daughter's Pixel Chick refuses to power on even on a full charge and my electric toothbrush spins like its nearly out of juice.

Whilst a difference of 0.3V seems trivial, devices generally need several. So if you need 4 batteries then your voltage using rechargables is 4.8V as opposed to 6V using traditional batteries. thats nearly a whole battery difference!

I'd suggest buying a small pack and testing them out before buying a load of them.

I also found that rechargeables weren't a very good idea for stuff that uses little power such as a remote. You might as well buy cheap batteries which will still lasts ages anyway rather than sticking a set of expensive rechargables in it.

Oh and finally I bought loads and bit by bit they have disappeared. God knows where they have all gone but I had over 20, now I can find about 8 of them!!!!!

happyhero

Hi guys cheers for all the help

hobo28 wrote:

What sort of devices will these be powering?

Rechargable AA's generally only output 1.2V rather than 1.5V. A new akaline battery initially pumps out slightly more at 1.7V.

The low output has meant that some toys/devices have refused to work. For example, my wireless keyboard will work for a week or so on a fresh charge but after that nothing, my daughter's Pixel Chick refuses to power on even on a full charge and my electric toothbrush spins like its nearly out of juice.

Whilst a difference of 0.3V seems trivial, devices generally need several. So if you need 4 batteries then your voltage using rechargables is 4.8V as opposed to 6V using traditional batteries. thats nearly a whole battery difference!

I'd suggest buying a small pack and testing them out before buying a load of them.

I also found that rechargeables weren't a very good idea for stuff that uses little power such as a remote. You might as well buy cheap batteries which will still lasts ages anyway rather than sticking a set of expensive rechargables in it.

Oh and finally I bought loads and bit by bit they have disappeared. God knows where they have all gone but I had over 20, now I can find about 8 of them!!!!!

Going off in a unnecessary direction here, but out of interest why can't they make the rechargeables put out 1.5v, would they have to be bigger. I would pay a little extra if they did make some but were more expensive. I mean they make 24v batteries for drill etc, so why not for example make one that is AA size and gives out 1.7v? I know its not important, I'm just interested why they don't exist.

24_hour_sparks

The pound shop are curently selling 1500mila amp hr type AA batterys, four for a quid, v cheap.

Someone the other day was buying hundreds of them, when i asked why so many he replied that he was going to sell them on ebay.

Andy.

lipidicman

ffym wrote:

Ah is short for Ampere/hour or how many amps a battery can give for an hour, it is the measure of power output from a battery given that the voltage is fixed. Simplistically, the higher the Ah the more power the battery can provide. AA cells are nominally 1.5 volts, so an AA cell rated at 2500mAh can give you 1.5 x 2.500= 3.75 Watts of power, an AA cell rated at 800mAh can give you 1.5 x 0.8 = 1.2 Watts of power - you don't really need to know this!!! For kids toys etc bigger is better.

Sorry but I have to correct this

Ah is short for ampere-hour. Amperes are a measure of charge per unit time so an Ah is a measure of charge

ie 2500mAh=2.5Ah=2.5C/s*3600s=9000C

at 1.5V or 1.5(J/C)
we have
1.5(J/C) * 9000 C = 13500 J

Note the calculation yields an energy value, not a power (energy/time). The number of watts (J/s) delivered will depend on how quickly this energy can be delivered (manufacturers usually assume 5-20 hours). Your value of power cannot be correct as you have a quantity (the Ah value) which uses hours rather than the SI unit, seconds.

If anyone does want to know more have a look at http://en.wikipedia.org/wiki/Ampere-hour
Ain't knowledge great!

happyhero

Are Encore any good, made by Uniross I believe, if they are why are the cheaper than proper branded Uniross, it makes you think cheaper because not as good, maybe Uniross's cheap brand and go flat quicker.

On eBay, Encore always go cheaper than Uniross even though everyone is telling you Uniross make them.

Anyone know about these?