Shortly after I received my electric postal van, the Lester charger died. After several phone call to Lester I was told that the charger was to old to be repaired. I was also informed that Lester could not send me the schematic because the circuit was patented and therefore must be kept a secret (I know the last sentence makes no sense all patents are published and are not secret.).

For a quick fix I built up a board to replace the Lester controller using a simple unijunction transistor to control the SCRs of Lester charger. This gave me manual control of the charger which worked fine except required setting the current several times during a charge.

Recently the unijunction controller died and I decided that there had to be a better way.

I wanted a charger with the flowing requirements:

• Automatic control of current base on battery voltage.
• Manual Override
• Float Mode
• Programmable start and stop times
• To be able to produce a charging report . Which would include the last charge curve and total energy of the charge.

Below are links to the schematic and design documents of the first version of the controller. It currently support only manual mode(phase 1).