Charge 2 x 12v in parallel, draw in series as 24v

Discussion in 'General Electronics Chat' started by Roblaw84, Jan 28, 2015.

  1. Roblaw84

    Thread Starter New Member

    Jan 28, 2015
    I was wondering whether it would be possible to have 2 x 12v batteries which are charged in parallel, but then the power is drawn in series to give 24v? I have sketched this using diodes and on paper it works but will diode actually work correctly in this manor?

    To give some background, Its for running a 24v diesel heater, in a campervan with 12v circuits and charging.

  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Welcome to the forum.
    Let's see your sketch, or at least a link to it ;)
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    While you may possibly get this to work the results may be poor to very poor. The reason being ia the charge phase is best done by monitoring the voltage of the battery. With two in parallel you never see either batteries voltage correctly.

    Either get a 24V charger and leave them in series, or get two 12V chargers and disconnectof ro charging. </two cents>

    (Others may have done this and have better comments.)
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    It takes a DPDT switch or relay to do the switching (cannot be done with just diodes).

    Two lead-acid batteries of the same capacity and manufacturer (not other chemistries) can be charged in parallel.
  5. crutschow


    Mar 14, 2008
    Two identical lead-acid batteries charge okay in parallel since, even if one battery would charge up slightly before the other, the rise in its voltage from being charged, diverts the current to the other, which has a lower voltage from not being fully charged.

    But, as Mike noted, you can't do the series to parallel conversion just with diodes.
  6. bwilliams60

    Active Member

    Nov 18, 2012
  7. Roblaw84

    Thread Starter New Member

    Jan 28, 2015
    Thanks for you help everyone.