12 volt charger mods.

I am using 2 x 'off the shelf' 230v to 12 volt 25A switch mode power supplies for my 12 volt system. One is powered from 0 to +300v and the other from 0v to -300v respectively.

As a consequence 2 modifications were required.

1. The feedback circuit needed changing to increase the adjustable output to 13.8V. This was done by tracing the voltage divider circuit and adding the required resistor in parallel with an existing resistor.

2. The 20 ohm bleed resistor needed removing in order for it not to discharge the battery while the vehicle is not being driven.

The image below shows the modifications. (zoom in for detail)

The completed power supplies have been installed into the Variable Speed Drive where some of the AC filter components have been removed. The device between the power supplies is a 50A circuit breaker that will be used for the 12V protection. The Power supplies will be wired in parallel.

The maximum 12V power requirement for the vehicle is just under 50A. After replacing the bulbs with LEDs this will be reduced significantly.