Sparky, The Electric Vehicle (EV)

Electric Vehicle Project: Charger

Jan-Mar 2007: In the test run debrief I mentioned that the charger quit after just 2 minutes. What a bummer! So is that it? I get one ride and that's it? At first we thought it was the charger, so I packed it up and sent it back to the distributor.

The charger is a Zivan NG-3. It is made in Italy and designed to be a "smart" charger. Mine came to me by way of Electric Conversions in Scaramento, CA. NOTE: This is NOT the same company as Electric Vehicles of America. Electric Conversions set up the charger for the specific battery pack (mine is 20 Trojan T-125 batteries). I returned the charger to these folks and they found nothing wrong with it. I got it back the day after Thanksgiving 2006 and tried it again, got the same results. It would start charging normally and then quit after 2 minutes.

At this point I started examining my system for some kind of fault. I checked the cable connections, double and triple checked the polarity of the batteries, and checked for ground faults. No obvious problems were found. I decided to see if I could charge each battery individually. I actually charged them in pairs using a +12V deep cycle charger (available at your local Wal-Mart). This took over a week's time since I could only do 1 pair a day. Each pair charge up fine, no errors were recorded by the charger.

What now? I had some rather interesting discussions with the folks at Electric Conversions. I must say their customer service is somewnat lacking. The lead tech (manager?) there said he had spent enough time on this problem (and had lost enough money on the deal) and that I should just send the charger back. Oy! He did give me some ideas for trouble shooting like checking the incoming AC mains. I set up a test where I could monitor the AC voltage peaks during a charge cycle. Mine measured from 238 to 242 VAC with no dropouts. The problem was not in the AC power.

To me this problem looked like the charger was detecting an over current condition and shutting down. I decided to measure the current by placing a power resistor in line with the charging cable. To my surprise, the charger held up for a longer period (4 minutes). I had used a .02 ohm resistor and measured 19.45 amps at start up. This got me to thinking that the problem had to do with the load the charger was seeing. I checked my charging cables and found them to be just fine. I even tried using automotive jumper cables. No luck. I finally added a second resistor and lo and behold it worked! I had a total of .04 ohms in line.

My success was fleeting. The next round of charging failed after 5 minutes. I kept trying the same set up and each time the charger would last longer and longer between failures. Eventually, it would work. I learned by observing the current measurements that with each failed cycle the batteries drew less current with each trial. So my guess is that the batteries were partially charging and requiring less current the next time around. Eventually I would get to a point where it would work. The magic number seems to be 19 amps. The current draw needs to drop below 19 amps before a specified time otherwise the charger shuts down.

Electric Conversions was not interested in this information (I have tons of current vs time readings). I figured perhaps they could adjust my charger to not be so sensitive and allow for, say 20 amps. But no luck there. I decided to limit the current myself and I increased my resistance to .1 ohms. I am now using a 100 watt power resistor mounted on a heat sink. I have it inline with the positive leg of the charging cable.

Charging is now repeatable and dependable.