Monday, 8 September 2014

Dead Cell & Powerlab 8 Purchase

So after removing the safety LVC on Wednesday, I drove the car apparently normally on Thursday and Friday and then took the car off road for a couple of weeks whilst I had a break from work and investigated the issue, when I did finally find the time to investigate I reinstated the LVC and separated just the front battery box and sure enough after another test drive my suspicions were confirmed the fault was either in the LVC loom or a faulty LVC/HVC board or a dead cell, either way I would need to get the box out and investigate.

So a while later I had the box on the bench with the lid off and the issue was immediately apparent one of the cells in the offending parallel block had a severe burn mark on the balance lead plug, so as it turned out it was a dead cell after all and the LVC was just doing its job as it should do.
Just before I had taken my holiday I had ordered a Revolectrix Powerlab 8 battery tester and so I was able to test the apparently dead cell on this doing a discharge and graph, Now I have done over a hundred of these tests and they normally take around 15 minutes to do a 20A discharge and graph test, this faulty cell crapped out in around thirty seconds, it began and looked normal but as soon as the load was applied and the discharge began proper cell 4 bombed and dropped straight below 3.0V activating the cut out.

So lesson learned I now know that if the EV’s throttle appears to cut out intermittently under load this is most probably a dead cell rearing its head and at least I have the option of laying off the throttle and limping home to investigate the fault rather than breaking down on the road side as I did before the safeties were implemented.

Once the faulty 5S cell pack was replaced with one of the ones I had opted not to use before (The best of the worst from my last battery rebuild which Steve had said looked fine anyhow) I rebalanced the cars whole Traction Pack to 3.8v (Probably unnecessary) and then charged using the EMW on-board charger and top balanced to 4.2v since then I have been driving the EV without any issues all the LVC/HVC is reinstated and things are back to normal, unfortunately due to other demands I did not get any of the “Treats” I had planned even started!

Still there is always tomorrow.

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