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I didn't find any answer to this simple question, but please correct me if so, and feel free to edit this to be readable or more general (I'm not good at these technical terms in English).

I want to divert power from just a part of a series of batteries, to get different output voltage. Since I've been told since forever that you should not mix good batteries with bad etc. I wonder if it's a bad idea because of an uneven power load?

The object in this matter is a 48V forklift, with a battery pack consisting of 24 cells, 2-volt each.

Is it in anyway a bad idea to, let's say, connect a cable to battery number six to get a 12V current, with a 10 amp load?

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  • \$\begingroup\$ That probably depends if they are loaded as 12V batteries or in series as one 48V battery. \$\endgroup\$
    – PlasmaHH
    Mar 25, 2015 at 13:44
  • \$\begingroup\$ They are all charged in series using a 48V charger, but I want to install some stuff that requires 12V, like a car stereo and an some additional headlights \$\endgroup\$ Mar 25, 2015 at 13:45
  • \$\begingroup\$ A car stereo on a forklift? you must have some lonely nights there... ^^ \$\endgroup\$
    – PlasmaHH
    Mar 25, 2015 at 13:55
  • \$\begingroup\$ Haha, and too mych spare time ;) \$\endgroup\$ Mar 25, 2015 at 13:59

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The problems start once the battery you are tapping has gone flat.

The other batteries in the circuit may still have enough charge to push current the wrong way through the discharged battery, causing overheating, off-gasing and other damage.

Then when you come to recharge it, you have the opposite problem: in order to put current into the discharged battery, you also have to put it through the fully charged batteries.

The best solution for this is either an entirely separate battery or a suitably-rated (at least 60V on the input) buck converter.

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  • \$\begingroup\$ Thank you very much for a great explaination! A converter would be much easier I guess, otherwise I have to use two chargers everytime. I'll check it out. Thanks again! \$\endgroup\$ Mar 25, 2015 at 13:54

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