I have a 24V (10A capacity) Lead Acid battery charger that was made in 1986,
and would like to replace the control module in it with a module/board
(something) that will handle the cutoff at a safe level.

Any recommendations would be appreciated.

The original circuit is a Lester Compu Time p/n 11625 circuit board (approx
2" x 4") is installed in a Everest Jennings Model 11350 24V/10A wheelchair
battery charger.
A replacement circuit that's much larger than the original board size of ~2"
x 4" would require a larger charger case, or a separate metal box attached
to the original case.

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

I should've realized I'd leave out details since the post was composed
quickly.

The charger consists of a ferro-resonant transformer (third xfmr winding
wound over the xfmr secondary and 2uF AC capacitor), and a full wave
rectifier (2 diodes).

A relay handles the begin/stop-off control (xfmr primary energize/off), and
the charger has no high current components (other than the diodes).

I don't see what takes care of the 24V voltage regulation.

The Lester control board has a small sealed pc-mount pot and 7 ICs, but no
power handling components.. only about a dozen resistors/capacitors/diodes,
and 2 TO-92 transistors.

741
4020
14001 (3)
14040
14093

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.

The relay has a manual button to close the contacts, which is how the
charging cycle is initialized by the user (button is actuated thru front
panel).. this is the only start button (no on-off switch).

The output leads are just two 16 gage conductors.

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

On Sat, 19 Feb 2011 13:13:23 -0500, "Wild_Bill" wrote:

I should've realized I'd leave out details since the post was composed
quickly.

The charger consists of a ferro-resonant transformer (third xfmr winding
wound over the xfmr secondary and 2uF AC capacitor), and a full wave
rectifier (2 diodes).

A relay handles the begin/stop-off control (xfmr primary energize/off), and
the charger has no high current components (other than the diodes).

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 Lester control board has a small sealed pc-mount pot and 7 ICs, but no
power handling components.. only about a dozen resistors/capacitors/diodes,
and 2 TO-92 transistors.

741
4020
14001 (3)
14040
14093

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.

The relay has a manual button to close the contacts, which is how the
charging cycle is initialized by the user (button is actuated thru front
panel).. this is the only start button (no on-off switch).

The output leads are just two 16 gage conductors.

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.

On Feb 20, 3:46*am, "Wild_Bill" wrote:
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.- Hide quoted text -

- Show quoted text -

Get a regular 24 hour mechanical clock timer and use it to power a
relay whose contact is in parallel with the push-on start contact on
the power supply. Set the timer for the minimum possible on time,
usually 15 minutes per day. That will start the power supply once
each day and that should kep the batteries charged just fine. Simple
solutions for simple problems!!!

Wild_Bill wrote:
I should've realized I'd leave out details since the post was composed
quickly.

The charger consists of a ferro-resonant transformer (third xfmr winding
wound over the xfmr secondary and 2uF AC capacitor), and a full wave
rectifier (2 diodes).

A relay handles the begin/stop-off control (xfmr primary energize/off), and
the charger has no high current components (other than the diodes).

I don't see what takes care of the 24V voltage regulation.

that ferroresonant transformer does the voltage regulation- no joke
either. That's what the really weird core or shunts and extra winding with
the capacitor are for.

The solution of using a daily, short duration timer cycle would likely be a
very good maintenance solution for many common batteries.

The forklift battery in this instance is more than a half-cubic yard in
size, weighing about a half-ton, and somewhere in the neighborhood of about
800 Ah capacity.. subjected to outdoor temperatures here in the northest
U.S.

The history of the battery is unknown, but has been able to meet the demand
of occassional lifting, but has recently been subjected to some neglect by
the owner.
As I mentioned previously, the forklift is used only occassionally as a
lift, not for moving heavy loads around with the traction drive.

If the charge can't be automatically/routinely refreshed, it may just become
a scrap battery, which would then need to be replaced with a bank/stack of
automotive or marine batteries, as one possible fairly economical solution.

The heavy duty charger is indoors, and moving the charger to the forklift is
complicated/troublesome, which is why the owner has been neglectful at
keeping the battery charged on a regular schedule.
Once the battery has been charged, a small automatic charger might be able
to prevent further decline of the battery's health from sitting idle without
proper attention.

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


wrote in message
...

Get a regular 24 hour mechanical clock timer and use it to power a
relay whose contact is in parallel with the push-on start contact on
the power supply. Set the timer for the minimum possible on time,
usually 15 minutes per day. That will start the power supply once
each day and that should kep the batteries charged just fine. Simple
solutions for simple problems!!!

Wild_Bill wrote:

If the charge can't be automatically/routinely refreshed, it may just become
a scrap battery, which would then need to be replaced with a bank/stack of
automotive or marine batteries, as one possible fairly economical solution.


Good luck with that. I've seen people try it, and all they did was
ruin a bank of truck batteries.


--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.