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Car Battery problem : 1st/last cell issue ?
#11
No insults intended

 Imagine that the cells are plastic bags of water and the connections are straws . the larger the straw , better the connection.
 With letting a small volume thru the straw , there isn't any problem , all the bags drain somewhat equal.
Resistance of the cell is adding to the restrictions to the straw opening or outlet
When you pull out more than " the natural flow" the first bag will empty quicker because of the other bags are still doing " the natural flow"
Natural flow = below 1C rate .   1C / number of cells in a series   LTO 6s, 12v , 10ah = 1.66ah draw , this is where I have noticed cell imbalance is does not occur much. Unfortunately a costly compromise.
 
All the water in the center of set has to flow thru the first straw, so it is better to put the smaller cells in the center of the pack.
So they empty at the same time.
 This helps but if you do not have any , you need a voltage equalizer solution to make all the cells the same voltage.

So to avoid cell imbalance , try not to stress the cell above 1C rate , charge or discharge. Cell imbalance is a lot less under 1C , it is geometrically less. In the real world, you still need a bms or voltage equalizer , because of it is progressive each cycle.  

Your connections are copper , that's good . How many cells are in parallel ? Most people connect on one end only, It
 should be from the center or both ends of the parallel sub pack.

What type of cell chemistry are you using ?



https://www.aliexpress.com/item/QNBBM-6S...autifyAB=0
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#12
(03-03-2019, 05:51 PM)Jim Jr. Wrote: No insults intended

 Imagine that the cells are plastic bags of water and the connections are straws . the larger the straw , better the connection.
 With letting a small volume thru the straw , there isn't any problem , all the bags drain somewhat equal.
Resistance of the cell is adding to the restrictions to the straw opening or outlet
When you pull out more than " the natural flow" the first bag will empty quicker because of the other bags are still doing " the natural flow"
Natural flow = below 1C rate .   1C / number of cells in a series   LTO 6s, 12v , 10ah = 1.66ah draw , this is where I have noticed cell imbalance is does not occur much. Unfortunately a costly compromise.
 
All the water in the center of set has to flow thru the first straw, so it is better to put the smaller cells in the center of the pack.
So they empty at the same time.
 This helps but if you do not have any , you need a voltage equalizer solution to make all the cells the same voltage.

So to avoid cell imbalance , try not to stress the cell above 1C rate , charge or discharge. Cell imbalance is a lot less under 1C , it is geometrically less. In the real world, you still need a bms or voltage equalizer , because of it is progressive each cycle.  

Your connections are copper , that's good . How many cells are in parallel ? Most people connect on one end only, It
 should be from the center or both ends of the parallel sub pack.

What type of cell chemistry are you using ?



https://www.aliexpress.com/item/QNBBM-6S...autifyAB=0
I tried 3 times to read- its very difficult to understand. (ROTFL)

Jim, i am professional in electronics. You can talk facts with me.
As long as the batteries are in series, i do not see why the cell get a different load (in amp-hours (Ah)) deopending on their position.

Car usage load is somewhat - ourageous, sometimes. Cannot change that.
Capacity and parameters of BMS/Balancer are unknown.
Chemistry unknown. Must be something actual in use, in far-east suplliers.
0,8kWp in Test
4 kWh battery target
Ultra low cost
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#13
How many cells ?
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#14
(03-08-2019, 01:47 PM)Jim Jr. Wrote: How many cells ?
Its Car batteries, several 100, i guess.

Latest news, problem is possibly solved.
Details only on PM, not in public. (sorry, protection of my "customer").

Thanks to all who helped thinking for effort and ideas. Great Team here !!!! Smile Smile Smile Smile Smile Smile Smile
0,8kWp in Test
4 kWh battery target
Ultra low cost
Reply


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