is there any way to make or buy a 12v battery charge another 12v battery?
If you are prepared to cut the battery you want to charge, yes, otherwise, no, because you need more than 12V to charge a 12V battery.Steve
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how do you mean 'cut'?
Well, its a very sneaky trick, but all 12V batteries are made of 6, 2V cells. They are strapped together by links which may or may not be accessible. If they are, you cut an access into the link, and cut it. Now you have two 6V batteries which you CAN charge from a 12V source. Steve
ah cool could you provide a pic or diagram of where to cut the battery or a link to where i could get some information please thank you :)
You could use the 12V battery to run a DC-to-DC converter to get on the order of 14V, use that to charge the other 12V battery. BUT: There's no free lunch; you'll have to run one battery down to charge the other, and you'll lose some energy in moving it from one to the other.