215: Saturday 12th November 2011

Yesterday I set about changing the output voltages for the Zivan charger. I wanted to try to operate on 8 batteries instead of 10. Since I melted that last battery I have tried to find some batteries good enough to use as dummies just to get a charge into the car. I had been charging with ten and running the drive on 9 batteries. I have a reasonable set of 8 batteries and this is enough to drive my car (just). In the photo below you can see 2 of the screws that need to be removed to take the case off the charger.
The next photo shows the other 2 screws at the other end, then the case comes off, but you do have to prize the mains cable out of the case as the rubber grommet sits in a slot that goes round a corner on the case. I have circled the screws in green. When removing the case take care not to knock the indicator LED and the selector switch for the different charge curves. The selector switch has a screwdriver adapter pushed on it and it pops off quite easily. If you disturb the LED then it may not line up with the window in the case when you put the case back.
I connected the charger to the mains and measured the output at the small Anderson connector and found that it starts at 143.8v for a few seconds then changes to 136.5v as the indicator goes from red to yellow to green flashing. As I have 10 batteries that makes 14.38 volts and 13.65 volts per battery on average. If I multiply these by 8 then I know what the new voltages should be. I calculated them as 115.04 volts initially, then settling to 109.2 volts when the indicator is green flashing. The photo below shows the logic board sticking out of the main board. I have outlined it in green. There is a voltage and current adjustment multi-turn potentiometer on this board. Take extreme care not to touch the heat sinks as some of them will hold a high voltage and give you a shock.
In absolutely tiny writing on the board you can just make out the letters "I" and "v" beside the two potentiometers. The right hand one in the photo was adjusted, but the voltage would not go low enough.
On the main board by the Anderson connector is a resistor labelled "R20". I soldered the equivalent of 2Mohms resistor across this resistor. I turned the power off first! When I powered up and allowed it to settle, the voltage was too low, so using the voltage adjustment pot again I wound it up to exactly 109.2 volts. When I cycled the power off and on again the initial voltage was 115.1 and then it settled to 109.2 volts. This was exactly what I wanted, so after breakfast today I fitted it back on the car. In the photo below I have put a plastic clamp between the crocodile clips on my tester just to stop them touching together.
In this photo you can see the tester showing the final voltage after I had completed the adjustments. Unfortunately, despite my efforts, the charger was then stuck in a reset cycle as it was still seeing a high resistance load from the batteries, so it was continuously starting and resetting. I shall try rotating some batteries round again to see if I can get it to charge properly. I had this problem before I started and since I spoke to the supplier on the phone they confirmed it is caused by a high resistance in the battery pack.
The next problem is that the new lower voltages mean that the contactors are not in the correct voltage range as they are meant to be 120v, but now operating at 96v. I was getting a problem with the reverse contactor not releasing some times. I am concerned now that this will be too much of a stretch to try and run like this. I desperately need some more batteries. I shall persevere and see how it goes.


  1. .. maybe, You should give yourself a little kick and change to LiFePos.........
    Ok, there are The costs on the one side,
    but there is such a gain in weight and
    efficience, if You can afford it, you wont
    regret it........
    The rest of the car seems to work fine,
    so,you only need good batteries....

  2. Thanks for the advice. The cost is a problem and you are right, the rest of the system is fine, just the batteries. I could probably find enough money to go to 60Ah on Lithium, but even that is a stretch and won't give me much range. Maybe I could then ad another bank of 60Ah later (same spec) and then another some other time in the future. What is your experience?

  3. Hmmm......
    It is no relal problem, adding some cells later, but you have to cable them like a ladder,
    so that always two or three cells are parallel.
    But the other thing ist not to overload the cells when they are too small.You should not take more than 4C from the cells for about 30sec. and so, 60Ah is too small.As you cant cange the gear, i think, your car easily takes 400-500A at starting, so you will not be on the safe side with cells below 120Ah. the bigger the better, Your Car needs 180-200Ah Cells!
    Dont start with smaller ones, as the car can carry the lead acid batteries, so weight will not be the problem.
    And: no matter what J.R. tells, I would recommend some reliable BMS to be warned at
    low Voltage of every single cell.

  4. Hi vehikelfranz, can you contact my email directly (jameskillick@blueyonder.co.uk). I may have the funding for 100Ah Lithium batteries now. I checked the spec for Thundersky LYP100 and they can handle up to 2000A for 15 seconds in one minute and 300 Amps continuous, that is more than I need. I agree, the spec on 60Ah was borderline and I would have drive carefully to save the batteries. With 100Ah I can drive fairly normal without major concerns. I am developing a battery monitoring system that will show the voltage on bar graphs with a friend as a commercial venture with many different modules including display processor, module voltage capture boards. Currently this will have a 320 x 240 white on blue screen and will be programmed to show 40 battery voltages on 40 bargraphs, so it gives an instant indication if one too high or low. Where did you get your Lithium batteries from?

    Thanks.... James

  5. Hi James,
    I tried to contact You, but the mail came back.
    Either Your mailserver is full, or there is another problem......
    I will retry.