AA vs AAA question

[aruna1]

Hi
what are the difference between AA 1800mAh NiMH battery and AAA 1800mAh NiMH battery other than the size difference?

I'm currently using 12V 1500mAh NiMH battery pack (made by connecting 10 AA batteries).I wonder can I replace it with 10 AAA NiMH batteries with 1800mAh? it will reduce weight considerably
are there any drawbacks?
thanks

[rbtying]

Maximum current out of a AAA will be less (higher internal resistance), but I'm wondering - where'd you find an 1800mAh AAA?  The usual consideration is that AAA cells tend to have a capacity of around 650mAh, thus AA would have more capacity. 

If you want weight reduction, go lithium - power per weight is the highest.  Most likely the 11.1v ( 3 cell ) would work for you, but 14.8v (4 cell) is also a possibility.

[aruna1]

Maximum current out of a AAA will be less (higher internal resistance), but I'm wondering - where'd you find an 1800mAh AAA?  The usual consideration is that AAA cells tend to have a capacity of around 650mAh, thus AA would have more capacity. 

If you want weight reduction, go lithium - power per weight is the highest.  Most likely the 11.1v ( 3 cell ) would work for you, but 14.8v (4 cell) is also a possibility.

hi there are plenty of 1800mAh AAA in ebay.for example
http://cgi.ebay.com/2x-AAA-1800mAh-1-2V-NiMH-Recharge-Rechargeable-Battery-/370464128272?pt=US_Batteries&hash=item564161fd10

I dont like Lipo because they are expensive,need special care and tends to caught fire.

so what you are saying is 1800mAh AA is better than 1800mAh AAA?

[Soeren]

Hi,

hi there are plenty of 1800mAh AAA in ebay.for example

so what you are saying is 1800mAh AA is better than 1800mAh AAA?

There is no such thing as a 1800 mAh NiMH presently. Anyone telling you otherwise is lying through their teeths.
But don't take my word for it, buy them, measure them and be disappointed if you like.
The best brands in public trade achieve around 900 mAh presently.
The page you linked to claim double that capacity - a bit of scepticism is required here.

[aruna1]

Hi,

hi there are plenty of 1800mAh AAA in ebay.for example

so what you are saying is 1800mAh AA is better than 1800mAh AAA?

There is no such thing as a 1800 mAh NiMH presently. Anyone telling you otherwise is lying through their teeths.
But don't take my word for it, buy them, measure them and be disappointed if you like.
The best brands in public trade achieve around 900 mAh presently.
The page you linked to claim double that capacity - a bit of scepticism is required here.

oh i see thanks soeren

[Daanii]

If you look closely at the eBay page you linked to, they are saying that two AAA batteries give 1800 mAh. So they are claiming the 900 mAh per battery that Soeren mentioned. Not 1800 per battery.

It is pretty deceptive the way they do that.

[rbtying]

900mAh per AAA cell is much more reasonable.

Lithium only catches fire if you a) are careless b) set it on fire or c) don't use an appropriate charger.  Cheap balancing chargers are only $20.00 or so, and I've gotten nice 3000mAh 2s Lithium Polymer packs off DealExtreme for less than $15.00.  All rechargeable batteries need "special care": if you treat NiMH's badly, they can catch fire, as well. 

[Soeren]

Hi,

If you look closely at the eBay page you linked to, they are saying that two AAA batteries give 1800 mAh. So they are claiming the 900 mAh per battery that Soeren mentioned. Not 1800 per battery.

It is pretty deceptive the way they do that.

Where do you see that?
I cannot find anything saying that, but the photo of the cell says 1800mAh.

[Daanii]

Where do you see that?

It says "2x AAA." And the picture of one battery then says "x 2." I think they would argue that they are selling an 1800 mAh battery pack, made up of two batteries.

Myself, I would agree with you that is lying. But eBay and similar websites often let this kind of thing slide. As you say, skepticism is required. 

[klims]

I bought some AAA rated at 1600mAh a while back and as Soeren said it I was completely let down. Tested them and the best cell only showed around 650mAh.

Maybe try Lithium Ion? Still dangerous when they short circuit but don't really catch on fire. Not as great a discharge rate as Lithium Polymer though. From memory it is about 2C for a cheap Li-Ion.