Blown cell !

Dedicated to the conversion sold by the now defunct Electric Car Company

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genawin
Posts: 66
Joined: Wed Apr 11, 2007 5:39 am
Location: north somerset

Blown cell !

Postby genawin » Mon Mar 04, 2013 5:04 pm

O dear just had to tow the Mrs back after she reported smoke everywhere and a very strong smell
Are the fumes from the electrolite anything to worry about ? Blimey what a stink !
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So i'm hoping Grumpy or Matt might have a spare cell ? ,Grumpy is it true that charge master ended up with enough kit to do another 50 conversions except for BMS's , That was the message i got from Anthony , i approached them by email twice over the spares availability but didn't get a response.
These cells are 280 x 183 x 71 prior to 2010 but where can we get this size now ?

Grumpy-b
Posts: 991
Joined: Sat Dec 01, 2007 12:06 pm

Re: Blown cell !

Postby Grumpy-b » Tue Mar 05, 2013 6:04 pm

Oh dear thats not nice.
I do have spares.
I hope tht the BMS hasnt been damaged.
No ECC disnt have enough spares for 50 vehicles. There are some parts, varying hugely in numbers. Loads of Vacuum pumps, probably 50 odd, but only a handfull of motors, and a few of most other parts, lots of steel work though.
I can get up to 10 bms from the board manufacturer, who still has some stock, and are cleared by ECC to sell them to me.

WHat I have seen in others that have burn like this , is that they have taken out the cells each side, the heat being so intense that they can be melted together. Thankfully its on the pack that is the easiest to remove.
Your problem now is that the BMS will continue to try and balance the cells. So it will take down the pack. WHat you need to do is to shut down the BMS connection to the cells, this needs to be done before any work is carried out and needs to be reversed when reconnected. The order of dis and re connection is important.

IMPORTANT HANDLE WITH CARE!!!
SWITCH OFF THE DIP SWITCHES BEFORE REMOVING CON3
ALWAYS SWITCH OFF IN THE ORDER SET OUT BELOW

DIP4:
8 OFF
7 OFF
6 OFF
5 OFF
4 OFF
3 OFF
2 OFF
1 OFF
9 OFF
10 OFF
11 OFF
12 OFF

DIP3:
10 OFF
9 OFF
8 OFF
7 OFF
6 OFF
5 OFF
4 OFF
3 OFF
2 OFF
1 OFF
11 OFF
12 OFF

DIP2:
9 OFF
8 OFF
7 OFF
6 OFF
5 OFF
4 OFF
3 OFF
2 OFF
1 OFF
10 OFF
11 OFF
12 OFF

Re connect by reversing the order.
WIth this done the BMS will cease to monitoir the voltages.

PM me if you need to talk
Grumpy-b

genawin
Posts: 66
Joined: Wed Apr 11, 2007 5:39 am
Location: north somerset

Re: Blown cell !

Postby genawin » Tue Mar 05, 2013 7:33 pm

That's great , the cells either side appear to be ok , just 2 days ago i checked the balance of the cells and it was 0.1 down but the rest of the pack were very close.
What would a replacement cost through you , would there be a choice of new or used ?
The switching sequence has been ignored be me at least 8 times already so would you expect that the damage is already done - how would i know - all seems ok except the obvious single cell ?
Would you rather i pm you or are you happy this way ?

Regards Mart.

Grumpy-b
Posts: 991
Joined: Sat Dec 01, 2007 12:06 pm

Re: Blown cell !

Postby Grumpy-b » Tue Mar 05, 2013 8:40 pm

From what I have seen of the ECC battery remains, there is quite a number that have failed. I have over 100 that are duff, all sorts of reasons, no one clear cause.The quality does seem to vary, even neighbouring serial numbers seem to vary a lot in quality. And some batches seem more likely to fail than others. Some faults can be down to misuse but a lot like internal shorting will be down to manufacturing faults.
CALB are supposed to be much better in consistency, and the latest ones being more automated in production are seemingly of a completely different scale in terms of quality and consistency of capacity.

Grumpy-b

mattcarr
Posts: 389
Joined: Sat May 12, 2007 2:27 pm
Location: Hampshire

Re: Blown cell !

Postby mattcarr » Wed Mar 06, 2013 9:48 pm

Hi Mart,

Sorry to hear about your car. Do you have any idea what might have caused this particular cell to fail? Bad connection - had the car been used excessivly priot to this happening? I've PM'd you about the cells.

Grumpy, I am surprised that you have got so many duff cells - what in your mind constitues a duff cell? You mention the CALB cells. I see that the one in the same size is rated at 180ah compaired to the Thundersky's 160ah. Do you know if the BMS can be modified to work with the CALB cells as they have got a much lower maximum cell voltage. I have to say that if I was to replace the pack in my car I would try to see if I could get a higher capacity pack in there - either voltage wise ( number of cells ) or same number of higher capacity cells.

Matt

mattcarr
Posts: 389
Joined: Sat May 12, 2007 2:27 pm
Location: Hampshire

Re: Blown cell !

Postby mattcarr » Wed Mar 06, 2013 10:14 pm

Grumpy,

I know that when I had my coupler changed ECC advised the garage doing the work to disconnect the 12 volt battery as this rendered the car safe to work on. Could this be the same for if anyone wanted to work on the battery pack? Disconnec the 12v battery. Change out the cells in the main traction pack, and then connect up the 12v battery when all was done? Or should they still go through the motion of completely disabling the BMS as well?

Matt

Grumpy-b
Posts: 991
Joined: Sat Dec 01, 2007 12:06 pm

Re: Blown cell !

Postby Grumpy-b » Thu Mar 07, 2013 11:35 am

The duff cells vary, from badly swelled (both over charged and over loaded in terms of power extraction will do this) Burned like Genawins, to no obvious signs of damage but really low capacity.
I have just replaced 3 in a pack of 25, that knocked the range down to about 6 miles before the car went to cut back.Under load these went down to well under 2.8v while the rest were lingering at about 3.1v. A small number of poor cells really hit the range, bad cells not only have a poor capacity but hit high voltage very quickly. This can cause the BMS to shut off the charge or cut back the charge, resulting in the rest of the pack getting less charge than they need.
Once they are drained down to 0v they can be difficult to revive. Needing very small initial current to encourage them back to life.
Turning off the 12v wont stop any spikes that can be caused by plugging and unplugging the BMS or cells. Its that that can damage the BMS. Its really no big deal to turn them off in the right sequence. It probably takes about 2 minutes. Good value for money if it saves the BMS from getting damaged. But thats my view, I just hate it when an avoidable cost is forced to be dealt with.
disconneting the 12v is appropriate for dealing with the motor, as the Curtis can not do anything without 12, none of the contactors can ever be live and no power can be passed through the motor cables. So that was the right thing to do.
Grumpy-b

genawin
Posts: 66
Joined: Wed Apr 11, 2007 5:39 am
Location: north somerset

Re: Blown cell !

Postby genawin » Thu Mar 07, 2013 5:02 pm

I assume the BMS will detect the first cell to hit the upper limit and cuts back the charger, if so do you know what that voltage is and is it staged ?

Grumpy-b
Posts: 991
Joined: Sat Dec 01, 2007 12:06 pm

Re: Blown cell !

Postby Grumpy-b » Thu Mar 07, 2013 5:14 pm

Sorry dont know how it calculates the cut back but cells much over 4.15 cause things to turn off. I will see if I can find out the working rules.
Grumpy-b

mattcarr
Posts: 389
Joined: Sat May 12, 2007 2:27 pm
Location: Hampshire

Re: Blown cell !

Postby mattcarr » Thu Mar 07, 2013 9:11 pm

I have to say I have been sad enough to watch a few charge cycles with the laptop connected and monitoring the BMS output. I have got a couple of cells that do start to climb in voltage first towards the end of the charge and the BMS will enable the bleed resistor on them and this stops them in their tracks for a while and gives the others chance to catch up. I then see that the voltages will all come in line together fairly well. and as the overall pack voltage rises then the charger output is then cutback. I have measured the charger output and it does seem to ramp back quite quickly until it seems to go in to a very low power mode until the BMS tells it to turn off.


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