Ian Hynes wrote:
>
> PICers,
>
> I have this battery power supply that has a 12V gel battery in series
> with a 6V gel battery. The idea was to have a 12V & and 18V rail.
> (Could've been done better but i'm stuck with it for now.) OK, I'm
> sick of clipping the charger terminals onto each battery separately so
> I figured a clever(?) way to switch the batteries in series when
> on-load and in-parallel for charging whilst disconnecting the load
> device. Used a 4PDT switch. Seems to work too, at least the switching
> side of it.
>
> But how to charge a 6 volter & a 12 volter from the same source? What


An easier way is to use a 18v source, (+ allow for
overhead) and leave the batteries in series.
You can put a parallel resistor across each battery
and this will not affect the initial charging much
but works well for the topping off stage and trickle
charging, to make sure both are equally and fully
charged. Like a 60 ohm resistor across the 6v
battery and a 120 ohm resistor across the 12v battery.

Obviously these stay with the charger, and you need
three terminals from the charger.
I've used this system before with 2x 12v batteries,
(24v total) and it works great. I've also seen similar
systems on old industrial chargers.
-Roman

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