Thanks for your comments, Grant. A friend brought me this charger that he
intended to use for maintaining/trickle charging a 24V forklift battery
(approx 1500 lbs battery).

The forklift sits idle for extended periods, and then is needed to be used
just as a lift.. not using the traction motor for moving heavy loads around.
The trouble with this particular charger is that it shuts off and doesn't
restart without manually being restarted.

Since the control circuit is about 25 years old now, I thought it would be
best to replace the controller, to avoid other issues which could arise from
the aged components.

I've seen circuits with a few components and a zener diode that can control
a relay for a charging circuit capable of maintaining lead acid batteries,
but I was more interested in just buying a control circuit to install into
the charger, if someone could recommend a module.

--
Cheers,
WB
..............


"Grant" wrote in message
news
On Sat, 19 Feb 2011 13:13:23 -0500, "Wild_Bill"
I don't see what takes care of the 24V voltage regulation.

The battery does that, think of the charger as a current source.

The power for the circuit appears to be supplied by the to-be-charged
battery voltage.. so it seems that the circuit won't pull in the relay
when
connected to a very low or dead battery.

So it drops out the relay when charge is complete? There's enough logic
to make a comparator (741) and timer stuff with logic to take battery
through
to full charge. Wheel chair battery charging is cyclic, take battery up
to
a voltage, if you are using old flooded cells then start a timer when
voltage
reaches a certain point for a controlled over-charge.

Unsuitable for modern SLA or VRLA batteries due to that timed overcharge.

Maybe you're better off replacing the charger, unless you can reduce the
current for the top-off part of the charge cycle?

Grant.