Thursday, 22 May 2014

“Dooms Day” EV Style (or how to incinerate 1/3 of your traction pack)

Tuesday 25th February, Left for work as normal in the EV after a normal charge the night before, got to my daughter school and dropped her off as I was leaving I got a call from my partner “you have my car keys!) Shit I thought, now I will be pushing my range to get home and back to work and home again, my EV only has 40 mile range and my round trip to work is 22 miles, my daughter school is around 2/3rds the way to my work and I and I had not pushed the charge to the max the night before as I was not anticipating any extra journeys.

Oh well I thought, better get the keys back to the missus and worry about this later (BIG MISTAKE NUMBER ONE), drove home and back to work no probs, left for home that evening and got nearly home before the car began to judder and slow, shit I thought, oh well it’s another tow (third time I have run a cell flat or the low voltage cut-off in the Soliton has kicked in I am not really sure) anyway towed the car home (only a few hundred yards) and put it on charge as normal (BIG MISTAKE NUMBER TWO, Steve has already advised me that following a run flat you should always check your cells for problems!)

Came out a couple of hours later expecting the car to be nearly charged (after all I had done extra mileage and was expecting a longer charge time this evening, possibly double my normal 2 hour charge) it was still far from charged, strange I thought Oh well I will give it more time (BIG MISTAKE NUMBER THREE) and went back in for another hour or two, I was not unduly worried as the charger throttles back the duty cycle when it nears the max voltage for the entire pack.

When I came out to switch off I realised that I was in BIG TROUBLE, there was an all pervading smell that told me something was not right, I checked the voltage in the charger and it was still far from max and still at around 70% duty, SHIT! SHIT! SHIT! Cut the power and checked the front battery box as this is the only one I can get easy access to by flipping the bonnet up.

Extremely strong chemical smell coming from under the bonnet obviously from the LIPO batteries, got my widget and checked voltages on this third of the pack and to my horror 2 banks were not reporting anything DEAD and the other two were severely overcharged at 4.4v per cell! FUCK! FUCK! FUCK! MAJOR PROBLEM, called Steve for rapid advice, he told me to watch it closely and whilst I was on the phone to him doing exactly that the smoke began! Just a whiff at first “It’s smoking Steve what the fuck do I do” Steve advised tipping a shitload of water on it.

As I was fetching the first watering can (luckily we have a load of water butts around our garden with thousands of litres) the venting began!

I am talking Lithium steam train at full tilt! I spent the next 2 hours tipping water on the burning battery until it finally gave up venting around 1:00 AM in the morning.

Went to bed with doom and gloom in my heart (oddly satisfied that I had at least prevented the whole car going up in flames!)

Spent the next weekend decontaminating the car and the area of my garden it had vented in.
Spent the weekend after that stripping the burned battery box out of the car and recovering whatever I could (not a lot) all 36 5S cells in this box were torched, the fire had ripped through the box end to end taking everything with it bar the Ali box which survived remarkably intact and the buss-bars however these will need servicing with new banana plugs (sockets seem ok) the plugs are supposed to spin freely some do not anymore and therefore will need replacing.

Also all the batteries in the rest of the car (the other 2/3rds) were also all severely overcharged to around 4.4v per cell, and after speaking with Steve it appears I will have to breakdown the entire pack test everything, rebalance all cells that are good, discard any bad cells and reassemble.

Basically a shit load of work!

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