Rechargable battery question.

[Boomyal]

Can you mix the use of Ni-MH batteries of different mAh values. Example, I have a device (LED light) that uses 3 AAA batts. I have two pairs of AAA Ni-MH batts. One pair is 900 mAh and the other is 750 mAh. Obviously I cannot select three of them with identical ratings. <br /><br />So d'ya think it is alright to mix them?

 

[18rabbit]

Re: Rechargable battery question.

You can but your trolling motor will run down your starting battery.<br />

 

[Bob_VT]

Re: Rechargable battery question.

bad info sorry deleted

 

[ZmOz]

Re: Rechargable battery question.

NO, you absolutely CANNOT mix them! The package every battery comes in says not to mix battery types and sizes for a reason. When the 750mah batteries are dead the 900mah batteries still have 150mah left. The leftover 150mah will reverse charge the now dead 750mah's and then you can throw them away.

 

[Reel Poor]

Re: Rechargable battery question.

Read this Boom. You'll have to add the htp://<br /><br />ask.metafilter.com/mefi/30954

 

[Boomyal]

Re: Rechargable battery question.

Well, I guess that answers that! You'd think that the Manufactures would put notes on their products, warning not to mix (at least) different rated batteries. <br /><br />I'll refrain!<br /><br />Thanks all!

 

[18rabbit]

Re: Rechargable battery question.

There’s something that happens when you mix a/hrs of batts where the smaller of the batts goes to 0v and actually flips over, i.e. it reverses polarity. It’s something I read about, don’t know much more than that, except it is possible but impractical to flip the battery back and have it useful again. Don’t know how that is done.<br /><br />From what I read, the same thing can happen with the lead acid batts in your car or boat if taken to 0v but in that case it is usually just one of the 2v cells that reverses polarity. But that’s all it takes to ruin the whole 12v batt.

 

[ZmOz]

Re: Rechargable battery question.

Originally posted by 18R:<br /> There’s something that happens when you mix a/hrs of batts where the smaller of the batts goes to 0v and actually flips over, i.e. it reverses polarity. It’s something I read about, don’t know much more than that, except it is possible but impractical to flip the battery back and have it useful again. Don’t know how that is done.

It can be undone by simply recharging the battery again, with a dumb charger that will just force current into the battery no matter what. It usually doesn't work though, and even if it does the capacity is way less than it was, so it will just happen again.<br /><br />This is a very common problem in nicd or nimh packs...causing their death as often as anything else. It's almost always blamed on "memory" though. More expensive battery packs in demanding applications are matched to within a few mAh of each other to try and keep this from happening. Even batteries from the same manufacturer of the same rated capacity can vary by a few hundred mAh. I have about 40 Duracell 1800mah AA batteries that my battery analyzer shows range from 1200mah to 1900mah. I have them arranged in groups of 4 with their capacities matched as close as possible, since most things I have use 4 batteries.