Imiev repair - precharge resistor

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mark_hetho
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Real Name: Mark Hetherington
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Re: Imiev repair - precharge resistor

Post by mark_hetho » Wed, 19 Dec 2018, 05:24

Best commute to work I've had in a while this morning!

Also I have a pretty good handle on how I'd go about replacing the cells, after seeing the way the pack goes together.

tonyw
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Re: Imiev repair - precharge resistor

Post by tonyw » Fri, 21 Dec 2018, 05:47

As a matter of interest, how would you go about disconnecting banks of cells before removing them? As a retired electrical engineer, the thought of handling 360 V DC appalls me. Nightmare stuff. I'd rather handle 415 V 3-ph mains.

How many cells in a bank? Is there a single nut on a post at each end? Can you get a metal spanner onto the nut without shorting it to something else? Do you have to bend a fat busbar out of the way to remove the bank? None of these questions is answered in any of the videos I've seen.

I am now driving an i-MiEV at last and I want to upgrade the battery when it gets older - as in Chris' upgrade thread. But I'll need to be a lot more confident of the job.
cheers

tony


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brendon_m
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Re: Imiev repair - precharge resistor

Post by brendon_m » Fri, 21 Dec 2018, 06:18

Yes there are bus bars, but you can mostly just unbolt both ends and pull them off with a jiggle.
In terms of the voltage, the plug you pull out to isolate the pack is in the middle of the pack so you're actually working at half the voltage which while I wouldn't recommend licking, you can touch and not explode.
Its DC, if you touch it you get brought to its potential and that's it, assuming the voltage isn't high enough to conduct current to ground/your resistance is low because you decided to dismantle the pack while having a hot soapy bath you'll be fine. AC is the one that'll bite you.
That being said, use insulated tools, keep you're bare fingies away and don't make love to the pack because you "just can't help being aroused by the power"

mark_hetho
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Re: Imiev repair - precharge resistor

Post by mark_hetho » Fri, 21 Dec 2018, 06:52

We wanted to remove one bus bar that was in the way of where we were working. However one end of it was quite close to another bus bar, so we tried to carefully loosen the bolt, but found we were burring it.

However if one was removing all the bus bars, you can start from the more accessible ones on the outside of the pack, and remove each module as you go to get better access to the next one. As noted, the pack is already spit in the middle from the removal of the service plug, and by the contactors at the "outer" terminals. There are some other fairly accessible bus bars that can be remove to further lower the total voltage you are playing with, but even a single module will give you trouble if you give it a dead short. Taking a bit of care it shouldn't be a problem though, as to get above 50V you need to reach between physically more distant parts of the pack, and most of the live parts of the pack are covered or tucked away to some degree. The pack is also isolated from ground by the casing, so it's hard to accidentally complete a circuit that way.

There are ten 8 cell modules, and two 4 cell modules.

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