I am looking for a replacement battery for a cordless power tool.

The original is 12V 1.4Ah, I can get the same, or, 12V 2Ah and even 12V 3Ah.

Now, I understand "Ah" refers to the storage capacity of the battery, e.g. it will last longer on the same current draw, and take longer to charge fully.

However, does that mean that if the tool in question asks the battery for lots of current, the battery may be able to provide more (e.g. 3A instead of 1.4A max) ? This could damage the tool if the wiring / motor hasn't been designed to take the higher current

Thanks in advance.

 

No it will be fine m8.

 

Cheers

 

the current that the tool takes is a function of the voltage and the resistance of the windings in the motor greg - V=IR and all that. so that doesn't change. it just means that a higher Ah battery will be able to supply that current for longer so you're onto a winner

i think it's always nice to give the question asker a reason for the answer so that they understand it and can either agree or not, rather than a simple yes or no

 

Thanks nick, that makes perfect sense, I was wondering however, if an increase in load (it's a drill driver) would result in an increase in amps being drawn, possibly up to more than the windings, etc... can take.

For a given trigger position (speed), surely driving a screw into cotton will draw less current than the same driven in a harder material - hence my thinking along the lines of the battery will be able to provide (flow) more current... Am I making sense.

I now realise why I shouldn't have partied so much when I was studying electronics

 

that all sounds plausible, and i am now not convinced that i am right and telling the whole story but at least there's a discussion going and maybe someone can tell us more (kev KSA-cossie?)

 

Nick's first explanation was spot on.
Whilst the larger capacity battery "may" have the potential to supply more current when under a heavier load, that is only a reflection of shortcomings in the lower capacity battery which may cause the terminal voltage to drop when loaded heavily, whereas the larger one would probably hold up better.
The current that the drill will draw at it's design voltage is independent of the battery capacity and will be fine on the larger one.

 

This is starting to make sense Thanks everyone.

 

You could quite easily fook the drill on the 1.4 ah battery,as stated above just means you get a longer supply of power from the bigger battery.1.4 2.1 or 3 ah can still overcook the field coil.

 

That does make sense. I suspect that if I shorted the terminals of the 1.4ah battery I would see quite a bit more than 1.4Amps for a very short period of time
I would be very surprised if the battery had any kind of built-in current regulation