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Battery Charging

Discussion in 'Photovoltaics' started by Brian Graham, Dec 5, 2007.

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  1. Brian Graham

    Brian Graham Guest

    I have eight 6-volt bats configured for 24 Volts. We've had 3 weeks of
    absolute garbage weather and the DOD is getting to be far too high (about
    70% DOD). I don't have a 24V charger, and I'm planning on moving to a 48V
    configuration in the spring.

    I have three 160W BP panels (24V) that with mppt pull down 17A @24V - when
    the sun shines. But it hasn't for a long time. Did I say that already? ;-)

    Until I get a proper charger which matches the system voltage, I was
    contemplating using my 12VDC charger across a pair of bats while still
    configured as-is. I would expect the power being dumped into the connected
    pair to flow out and equalize into the other bats as well. Of course, at 6A
    and 12V, its going to take a week to put in any appreciable amount of

    Anyone see a problem with the above? Without the sun? With the sun? I'd have
    the inverter offline while charging..

    (I would think that breaking the bank in 1/2 and charging 1 set while the
    other stayed production would result in a very dangerous situation if I
    tried to reconnect a 100% charged bank to say a 0% charged bank. Ie,
    immediate FAST current flow to equalise potential. Ie explosive risk.. You'd
    have to have both sets fully charged to reconnect.)
  2. The power is not going to help the other pair unless you put the charger
    on the other pair.

    I take it you can't/won't buy a proper charger now, so go out and buy a
    matched pair of smart 12v chargers that can put out some significant
    amperage. You currently have 2*220AH in series with with pair to make
    12v. You could put 50amps into that string without worry. You should
    be putting 20amps.

    I recommend a pair of these:
    They have a slightly cheaper model that puts out 1/2 the amps. It
    would probably do fine for you, but the capability per cost is much
    better with the 1093.

  3. Brian Graham

    Brian Graham Guest

    Until I get a proper charger which matches the system voltage, I was
    I'm not so sure about that. If I have 4 bats in series for 24V, and place a
    charger across 1 pair for a week (or whatever), I seriously doubt that I'll
    have 2 bats at 100 and the other 2 at 20% (assuming no solar input or output
    to an inverter). I would have to expect the energy added to be spread across
    all connected batteries.
    I have to say, for a 12V charger, the unit you suggested is NICE! And you're
    right, I don't plan to spend $500 on a 24V Iota charger when I'm planning to
    upgrade to a 48V system in the not-too-distant future.
    Actually, I have 8 Trojan L16H's; 440AH batteries. I have 4 in series to
    make 24V and another set in parallel for a total bank of [email protected] From 80%
    DOD, its going to take a LOT of charging from ANY source to bring it back up
    to snuff. Although, a pair of the chargers you suggested - at 40A DC - would
    recharge the bank in about 17 hours. Not bad at all.

    I think that's just the ticket! Many thanks!
  4. Guest

    That's a hoot coming from the inventor of the ghiosinkronus polar
    orbit. I've added it to your other wisdumb samples at

    But why are you here wasting time trying to convince 99% of the
    posters that *they're* the nitwits? Shouldn't you be doing something
    useful? 1233 empty missives from planet Ghio since you wrote that all
    it needed to triple its solar energy collection was a "parbolic"...

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