Fully Automated Charger for Renault Car - Design and Implementation

The Renault electric car of the late Marcos developed a serious malfunction in its battery charger system to the point that it was ruining its lead-acid batteries.
I was asked to determine if the charger system could be repaired locally.
After thorough examination, I recommended that all the components be removed, and adopt a completely different design with a more advanced set of features.

The new charger was a thyristor-fired system, enabling it to achieve high levels of electrical efficiency.
Firing was achieved at the secondary side of a completely isolated two-winding step-down transformer specifically designed for this purpose. The thyristor current ratings at the secondary were higher compared to what it would have been at the primary. This approach, however, provided better safety for all concerned.

It is plugged to any 230-volt wall outlet and left there, unattended and indefinitely.
Once plugged it checks its charge condition, and from there, ramp up to 100% charge according to a predetermined algorithm.
If fully discharged, it shifts to "fast charge" until just prior to its liberation of "gases".
It reduces the charging current and taper it off beyond "float voltage" up to 100% charge.
At 100% charge, it shifts charging conditions to "float charge", where it stays for a while.
After 2 minutes at "float", it checks whether it is still fully charged.
If it is not fully charged, it resumes charging to 100% and go back to "float" again.
If it is fully charge, it goes back again to "float".
In this way, no human intervention is required.

All the work was performed by a staff of five, who learned the technology on the job, under direction.
All materials used were locally available.
Only solidstate components were transistors, TTLs and analog ICs, no microprocessors.
Total cost came up to about $1,500 including nine heavy duty 12-volt lead-acid batteries capable of delivering 200 amperes.