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OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
1,781
Interesting research. My 10,000 cells (81kwh so far) are under a corner of the house with cinder block and concrete on 4 sides. Its the 5th and 6th sides I think about.

* 5th side (top) - is corrugated roofing metal against drywall. I suspect the metal may melt? and/or heat may ignite the plasterboard? - don't know.
* 6th side (facing out to the room). This videos are interesting in that I have about 6 ft of open area with nothing to burn.... but then there are the exposed next row 2 x 4's supporting the floor of the house above. I suspect the cells could 'blast out' (like exploding fire crackers) and set fire to these based on vids I've seen.

I didn't go to such extreme testing as @Wolf but I did test each and every cell and I'm comfortable with the cell qualities as all are legitimate/known cells and were at least 85% original spec capacity and most were 95% or better with reasonable IR. Nothing 'odd' about the cells.

The powerwall is
* operating under continuous, detailed monitoring...
- Batrium cell level, battery level -> shunt-trip
- Midnite Classic battery voltage -> battery load on/off
- Custom web page/data storage for trend alerts and POP-UP alerts of anything amiss on main computer that I spend most of my life in front of :)
* individual cell fused,
* circuit breaker'ed & shunt-tripped,
* operating in a modest voltage range (almost 0 chance of overcharge/undercharge) ,
* operating in mild ambient (cannot get hot or cold),
* operating under modest charge/discharge amps (<200mah per cell).
* almost no balance required - e.g. all are 'healthy cells'.
* physically secure from any kind of 'something crashing into the cells'.

As such I'm comfortable that the risk of it catching fire is very low for the time being - next several years - and I'm willing to defend this decision. However, the things I wonder about is aging & dendrites

Aging?.
* I presume that as long as the packs operate modestly (as outlined above) with no significant self-discharge / balance needed, then they can age gracefully till at least 60%? original capacity? Does capacity exhaustion lead to fire somehow (other than dendrites)?
* Does capacity reduction lead to dendrites?

Dendrites?
* Does the formation of dendrites short the cell and cell level fusing mitigate fire - or does it cause combustion in addition to shorting. So even if you're fused and the cell level fuse works - you still have a fire?
* Does capacity exhaustion = higher and higher dendrite formation / risk?

Future
* I'm considering all-metal, all 6 sides enclosures for next year - just not sure what I need to do yet - e.g. how thick must the metal be etc.
* I'd like to determine an evaluation process of when a pack must be pulled / replaced before it happens so I have an objective criteria to follow and not be swayed by an emotional - let's let it run a bit longer!.
 
Last edited:

Wolf

Active member
Joined
Sep 25, 2018
Messages
1,608
@OffGridInTheCity I think @Generic in his posts https://secondlifestorage.com/index...sting-18650s-for-1-600-cycles.6868/post-75850 has in a way proven that by the time the cells are exhausted we will know just by the capacity reduction of our batteries/packs will become degraded to the point of non usable. Some small temperature increases were noted but nothing dangerous even with the "cheap" chinese cells. I think we will know when it's time to "bury" our longtime friends and send them to the recycler in the sky. Maybe by the time our cells/packs/batteries give up the ghost there will be a better recycling program in place. Given though @Generic's tests with 2000 cycles + I think we may be able to hang on to our friends for quite some time. Without a fire.
Kinda like our laptop batteries just don't have the umph anymore so we know it is time.
Wolf
 
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