Thursday, 22 May 2014

Back on the road at last.

It has been a long couple of months but at last my EV is back up and running, this time with and HVC/LVC harness in place!
LVC is already wired in line with the throttle albeit to only the 2 rear battery boxes I will be wiring the 3rd and final (for now) battery box in tonight which will give me a proper low voltage cut out at 3.0v on the nose on any of the cells in any of the 3 battery boxes, basically if any of the cells hits 3.0v the throttle is cut, I have not tested this in place as yet but I have tested the board on the bench with a variable PSU as a test cell and sure enough the LVC “Sig” line drops to 0v when the cell pin goes below 3.0v.
Once the HVC/LVC loom is complete (Tonight) I will be wiring the HVC side of it into the BMS pin on the charger in an attempt to get the HVC working as well although this would only cut out as a last ditch safety measure as it cuts at 4.4v not 4.2v.
So I still need to upgrade the firmware on my charger to allow a CV cut out of 4.2v (currently limited to 3.99v) and also to put in some physical isolation of the chargers case from the chassis of the car, this is because when the charger is plugged in and running the chassis has some voltage on it, I would not call it live but I think the stray voltage might be either leakage from the bridge rectifier, or possibly inducted from the large toroid.
I also need to investigate a low voltage safety in the charger software as according to Steve the charger should error if it detects an abnormally low voltage and cause you to check to see if any dead cells are present, charging dead cells could result in a thermal runaway event (Yeah don’t I know it!)
And to top this lot I still need to implement the fuel gauge and the heater/demister.

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