Charger - Mark I

The charger is at a point where I can put it in the car. I etched a circuit board to hold the smaller components.


The larger ones - inductors, capacitors, and rectifiers - are mounted wherever they could be fit.


A computer power supply is used to drive the control circuitry.

It has a wooden enclosure sized to fit on the left front fender.


I know it ain't pretty, but it's working.

Charger - First Steps

The parts for the charger arrived a few days ago. I have let the magic smoke out of some of them, but I made some progress.

The diode I chose (STTH6004W) comes in a DO-247 package. While it is rated to 60A, the terminal legs are rather small, and did not last long when soldered to 14ga stranded wire.

I lost some IGBTs when I thought the varistor across would protect them. Or the fuses would help, but nope - IGBT goes bang!

However I can push 10A through a string of 4 batteries.

Charger - The Beginning

What to do about charging the batteries? As I am using 12V lead-acid, I could buy a commercial charger for each one. I have one of the Samlex 1215A chargers and it is a solid piece of work. They run about $120, and as I plan to have 20 batteries, that's about $2400. A benefit of this approach (example here) is that each battery is charged individually to the correct voltage for as long or short a time as necessary. And with good whole pack (high voltage) chargers running over $2000, the costs of this plan seem reasonable.
Reasonable even more so because I do not know how many batteries I will have in the end. As I understand it, the whole pack chargers are programmed at the factory with the charge parameters (voltage and current) for your pack. So if I decide I want to up it to 23 batteries, I would need to send the charger back (from Africa) to be reprogrammed. On the other hand, if I switch to lithium, I would need a new charging system anyway. (Though it may be possible to sell a bunch of 12V chargers....)
Searching around for ideas and information, I came across this thread started by Simon Rafferty, where he shares his design for a programmable buck charger. (There is now a thread about a 10kW 60A DIY charger!) I could understand it, and I figured I could risk a few hundred dollars in parts to learn whether or not I could build one. So today I ordered parts from digikey.com, coilws.com, allelectronics.com, and from a few ebay sellers.
I already have Atmel ATmegas for control and LCDs for display. It's the power components with which I am not familiar, primarily the inductors but also the IGBTs.
Waiting for parts....