Are the temp sensors killing cells?

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antiscab
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Are the temp sensors killing cells?

I have noticed after pulling apart my 9th vectrix battery an above average failure rate on the cells attached to temp sensors

I have no theories as to why this may be, but after 9 batteries I'm getting past the statistical anomoly stage

has anyone else noticed this?

BigTony
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Re: Are the temp sensors killing cells?

I agree, I have done 3 batterys now, and there are certanly a large number of them dead with a temp sensor. I just think it applies to all center pac cells..I still havent found a dead cell in an end position..

MEroller
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Re: Are the temp sensors killing cells?

That sort of sounds like it was the other way round: Vectrix possibly placed the temperature sensors in the battery areas that are most prone to overheating?

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Mik
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Re: Are the temp sensors killing cells?

I did not find this effect in the "Vectux" battery. See http://visforvoltage.org/forum/5052-uneven-distribution-weak-vectrix-cells-within-battery-pack-why

However, I analysed the battery before any cells were dead, and you have counted dead cells. That might be part of the explanation, but I doubt it.

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There might be a way to differentiate between effects due to cell location and effects due to temp sensors:

In the 8-cell modules there is no centre cell. You can therefore compare the failure rate of those cells located next to temp sensors with the failure rates of the cells with temp sensors in the 8-cell modules. That would be easier than the more detailed analysis suggested below.
.

Did you keep records? It would help to see the data to get a feeling for possible explanations.

I think that if the "centrality" of a cell is causing failures (due to higher temperatures or whatever), then I would expect a normal distribution of cell failures, with the peak of the Bell curve over the middle of a module and the tails towards the ends of the module.

If the temp sensor was somehow to blame for failures, then I would expect an even distribution over the module, except for a spike at the temp sensor cell position.

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antiscab
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Re: Are the temp sensors killing cells?

Did you keep records? It would help to see the data to get a feeling for possible explanations.

regrettably no, I didn't keep detailed records.
I just marked the cells that were bad, but not if they had a temp sensor attached

Matt

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2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
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Galago
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Re: Are the temp sensors killing cells?
Did you keep records? It would help to see the data to get a feeling for possible explanations.

regrettably no, I didn't keep detailed records.
I just marked the cells that were bad, but not if they had a temp sensor attached

Matt

Just out of curiosity, do you remember if any of the drilled and tapped bolt-heads
ever snapped off during pack dis-assembly or re-assembly?

antiscab
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Re: Are the temp sensors killing cells?
Just out of curiosity, do you remember if any of the drilled and tapped bolt-heads
ever snapped off during pack dis-assembly or re-assembly?

I have only every snapped one bolt off, but it was a normal one

the reason that one snapped was as a result of being over torqued

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
conversion

ofx210p
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Re: Are the temp sensors killing cells?

I've done the same thing and over torqued one, they snap remarkably easily. I had the guys at work easy out the remains of it and i fitted a new bolt.

I'd love to replace all the bolts to be honest as they seem really soft !

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