Monday, 11 November 2013

My first EV breakdown!

Ok so even EV’s are prone to human stupidity! And I surprise myself at just how daft I can be sometimes, Last Thursday after leaving work I got back to a dead EV! A quick check and I spotted the culprit, I had left the sidelights on and drained the 12v LIFEPO flat, Damn!

Checked the Voltage it was way low < 2v.
“In my infinite stupidity” I thought that I may be able to use the 12V PSU to feed current from the good Traction Pack to the 12v block by defeating the contactor! (“WHAT ARE YOU MAD!”)

Yes I realise now that this was infinitely stupid thing to do as there is obviously a limit to the current the PSU can take after all its not a battery charger but a PSU, luckily I realised my mistake when the PSU turned into a nice electric heater for a couple of minutes and I disconnected it before I blew that up!

However whilst I was attempting to defeat the contactor using my battery cable, I inadvertently (in the dark) used the wrong +ve from the twin pack rather than the one from the single pack, which would be at 155v not 220v this promptly blew the 40A fuse I had on my battery connection lead and took out the contactor at the same time, SHIT! (I am guessing that current tried to flow back into the 3rd pack?)

After checking with Steve my friendly local EV expert it appears that my thinking was not entirely wrong here and Steve replied with
“Hmm the PSU SHOULD be able to charge the 12v pack OK – I’m guessing you mean that you shorted across the contactor so as to bring full input voltage to the PSU? I used to carry a real small 12v pack in the boot with a couple of croc clips – that way, if the 12v voltage dropped below the 9v required to operate the contactor I could touch the terminals with the little pack and supply enough power to close the contactor, at which point the PSU would kick in and recharge the 12v system.

However, this is only safe if the 12v pack doesn’t go below 8 or 9v.
That will be why the PSU started to creak then as I mentioned my 12v block was sat at less than 2v for several hours killing it dead me thinks, I have since tried to charge it but I think it has given up the ghost.

So I switched the 12v battery over to the lead acid that came with the car, same small size and it is quite a good Yuasa the original from the car so that should do for now, can't afford another LIFEPO at the mo.
After driving the car home on Friday lunchtime I felt sure the lead acid was working well and gave it a good charge to make sure.

So to summarise this week I have blown a 12V £100 LIFEPO due to leaving the lights on! I blew my 12v battery charger trying to recover said 12v LIFEPO £70, and I thought I had also blown my contactor  although after my long range test drive this weekend amazingly the contactor sprang back into life and is now working normally, following my stupid mistake last week when I blew a 40A fuse I have since swapped it for a 30A and charged successfully without blowing that fuse, so I will stick with 30A on that one.

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