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Off grid fridge project in west africa
#11
yes 1W consumption is about 1kwh in 6 weeks, I guess I should have thought about that... though quite ironic that the bms killed the battery...
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#12
(01-16-2019, 01:13 PM)babish Wrote: though quite ironic that the bms killed the battery...

If there's no LVD that's just expected behaviour - the WM4 has a wide operating voltage so will continue to function down to around 8 volts. 

I would not have expected over discharge to have caused the physical damage you have described, however over charge would.
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#13
could anyone tell me the exact consumption of the WM4?
Also is it wise to try to apply some charge to the battery to see what happens?
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#14
Not if they have balooned Sad

Pics of the damage?
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#15
(01-17-2019, 11:50 AM)babish Wrote: could anyone tell me the exact consumption of the WM4?
Also is it wise to try to apply some charge to the battery to see what happens?

It rather depends on how its configured and what its connected to or driving - but likely less than 20mA with no outputs being driven, so minimal but not negligible.

Dont try charging visibly damaged cells.

Are you sure they weren't left connected to a charger (that wasnt configured correctly ?)
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#16
(01-17-2019, 12:48 PM)Dala Wrote: Not if they have balooned Sad

Pics of the damage?


not that easy to see the slight curvature on the pictures, but they have expanded

(01-17-2019, 01:48 PM)Sean Wrote:
(01-17-2019, 11:50 AM)babish Wrote: could anyone tell me the exact consumption of the WM4?
Also is it wise to try to apply some charge to the battery to see what happens?

It rather depends on how its configured and what its connected to or driving - but likely less than 20mA with no outputs being driven, so minimal but not negligible.

Dont try charging visibly damaged cells.

Are you sure they weren't left connected to a charger (that wasnt configured correctly ?)

no outputs driven and yes I am sure there was no other loads connected;
my mistake was also to not have rewired the bms power connection after the shunt, then I would have seen its consumption when everything else was disconnected.
here is the voltage per cell:
1 0.4
2 0.28
3 0.43
4 0.46
5 0.4
6 0.6
7 0.64
8 0.09
9 0.09
10 1
11 1.1
12 1.03
13 1.14
14 0.7
15 1.31
16 1.63

is there any point trying to remove the lowest voltage cells (also the most visually damaged) and charge them under low voltage and current to see what happen?
or there is no hope anyway as those cells are not supposed to go below 2.5V? (https://files.ev-power.eu/inc/_doc/attac...040AHA.pdf)
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#17
Just charge them and try it. Most likely they're still fine with some degradation of power in some cells more than others. That means it won't keep a good balance if you try to charge it to the max. So reduce your usable voltage range and you'll be ok.
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#18
You could try recharging them gently but have a read of the "over discharge" part here:
http://nordkyndesign.com/lithium-battery...egradation
(the article seems conservatively/strong on the safety side written)
You don't have any reversed voltage cells but some issues from dissolved copper might come out later.
Maybe try charging them gently, maybe 1A at first until you get to about 3V per cell.
Probably should plan towards replacement later.
Running off solar, DIY & electronics fan :-)
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#19
at what voltage should I charge them? should I try a lower voltage first, eg 12 or 24V?
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#20
Voltage across the packs probably won't make that big of a deal. So you could charge them either 12V or 24V setup. Or even individually in parallel.

The key here is to charge slowly, with low amps per cell. Redpacket says 1A, I might even would go a little lower to 500mA if possible (per cell). If the charger will output 5A, then have 10 in parallel. The slower the charge current, the more gentle the recovery and less likely any damage will occur.
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