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Recharging 4 12V batteries in parallel

  1. Oct 13, 2008 #1
    I have 4 lead-acid batteries in parallel that I need to recharge. The batteries are Genesis NP7-12FR batteries rated at 12V, 7.0Ah. I need to create a circuit so that when I plug it into a 120VAC wall socket the batteries are charged. I was thinking of using a DC power supply but have no idea what size to use. Any help would be appreciated.
  2. jcsd
  3. Oct 13, 2008 #2
    I would suggest a good 13.8 V (well stabilised) supply possibly with current limit. They would probably charge at something like 2 Amps (guessing really) each initially so that is 8 A x 13.8 V = 110 Watts. Ham radio stores will have lots of 13.8 Volt PSUs used for running radio transceivers. Steering diodes in series with low value resistors (for current monitoring - 0.1 - 0.25 Ohm...measure the voltage across them) in series with each battery would be a better arrangement but may not be very convenient if the batteries are connected as a parallel pack in normal use.. The diodes will drop 0.7 V so you will need 14.4 Volts. The resistors will act as current limiters.
  4. Oct 13, 2008 #3


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    Welcome to PF uchacker11.

    I'm guessing that you have a UPS. If so you might want to consider constant charging.
    From the Genesis spec sheet (http://www.tnrbatteries.com/ennp72.html):
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