The low-voltage cutout is more of a feature than an inconvenience. Since the
original SLAs had a higher voltage rating, the old, used, lower rated ones
will likely only give a short duration of running time before the cutoff
level is reached.
You may be able to modify the controller to operate in a different range of
voltages, but the way circuits are made today it could be unlikely.

Curtis is another manufacturer of a lot of bike/scooter mobility
controllers, and may be a source of useful specs and other technical info
wrt the controller and motor.

BTW, discharging lead-acid batteries into an over-discharged state will
generally cause damage that will significantly decrease the useful life of
the batteries.
That might not be an issue with the old used batteries, run 'em till they
die, but generally all batteries are damaged by over-discharging them.

If the controller is also the charging circuit, there would be an issue of
trying to charge an 18V pack with 24V.

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


"George Herold" wrote in message
...
Hi guys, I scored an electric scooter on trash day. (A Schwinn zone
5)
Of course the SLA batteries were toast. (2 X 12V @10A-hr.) But I’ve
got two old power wheels from when the kids were younger. (What, me
throw something out?) 4 x 6V @12 A-hr. I charged up the old
batteries but found one of those was dead also. (It refused to have
any charge pushed into it.) So I figured with three I’d have 18V
which should be enough. And it is, it runs fine. (maybe 10mph on a
flat.)
Now here’s the problem. There’s an electronic speed control (hidden
somewhere.. I haven’t found it yet.) And there must be a low voltage
cutout in the controller. So when the current draw drops the battery
voltage below some point the controller cuts out.
So I’d like to find out first where the speed control is hidden. And
then I’m hoping I can hack it and drop the voltage cut-out.
I’ve done a few web searches, but I mostly find sites where they want
to sell me something... nothing useful. Any hints on finding
schematics for something like this would be appreciated.

As a side note: I took apart the thumb throttle control on the handle
bar and discovered only a pot. The sad news is that it looked like a
little trim pot... I guess those last a bit longer than their 200
rotations spec.

Thanks
George H.