My kids ride on Jeep project

[Weldingtutor]

I have come across an old 24 Volt mobility scooter and my plan is to take the running gear out of it and build it into a jeep for kids. The 2x 12 Volt deep cycle lead acid batteries are too old and are no longer holding charge.
I have 2x Volkswagen E-Golf batteries these are 14.4 Volt each I have removed the computer circuit boards on them making them just straight-out batteries.
The plan is to use these two batteries in series to give me the 24 Volt needed to drive the mobility scooter running gear, But I need to step down the voltage from 14.4 Volt to 12 Volt on the individual batteries or 28.8 Volt to 24 Volts off both batteries what is the best way of doing this?
Mobility scooter motor is 24 Volt and 5 Amps. The batteries are 14.4 Volts and **** loads of Amps Sorry; “I do not know the Amp output capacity.”

 

[ZipZapOuch]

It's very unlikely that the designer specified everything so tightly in the 24v mobility scooter that it cannot handle 29v from the lead-acid batteries.

The cold-cranking amps is the maximum amperage that the battery can deliver to a load (depends on the resistance of the load attached to the battery). The motor amperage is the current draw at 24v supply.

Also, make sure the batteries on the scooter are really connected in series. Some are in parallel just to last longer (more range) at 12v.

 

[rjenkinsgb]

I have 2x Volkswagen E-Golf batteries these are 14.4 Volt each I have removed the computer circuit boards on them making them just straight-out batteries.

Those batteries have series-connected lithium cells, four per module (and 3? parallel chains. internally).
That puts the full charge voltage at around 16.8V

A normal "12V" lead-acid battery has a full charge voltage of ~15V on charge, so not much in it.

The voltage itself would not be a problem.

But: You cannot substitute lithium cells/batteries for other types, without also ensuring ALL the correct balance, monitoring and charge voltage control functions are included for safety!

Lithium cells contain equivalent energy to around 1/3rd their weight of TNT - do you want your kids sitting on or near that, if the cells could fail due to lack of proper safety and monitoring circuits?



I cannot find all that much in the way of technical info on those E-Golf batteries, other than mention that the BMS (battery management system) is external. See the link below.

Any series-cell lithium batteries MUST have cell balance (which keeps each cell in the series chain at the same charge state) and absolutely spot-on correct charging voltage control, otherwise the cells can burst or catch fire! They must also have under- and over-voltage protection on a per-cell basis.

The batteries look to have several connectors, which are probably the balance and monitoring points for the BMS?

You mention that you removed the "computer boards" - they were likely part of the cell monitoring, though from what I can see the whole battery set is part of a CAN management network, so not easy to re-use with complex electronics.

Some info on the e-golf batteries here:

E Golf Battery pack - openinverter forum