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dasPil #1
#1
dasKonzept: dasPil #1    -> learning attempt with weakest kept cells

4s24p - 96 cells - 48 Ah
avg 2000 mAh (min: 1958 mAh / max: 2044 mAh)
16.4 V - 4x 4.1 V -> 0.78 kWh
3x 2.5 mm² copper twisted busbar (3x AWG 14?)
2A glass fuses on positive poles, fuse wire at negative poles




soldering one side completed, time consuming process, duty 100 W solder pen
wise doing it in open air

How big fuse suggested as circuit protection/breaker?

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#2
The fuse depends on the max amps per cell you want to operate at.
People typically go with 0.5 to 1A max per cell in parallel.
So you have 24p = 24 x 0.5A = 12A nominal operating current.
Ie you might get a 15 or 20A breaker.
Running off solar, DIY & electronics fan :-)
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#3
(08-08-2019, 05:14 PM)ben teker Wrote: dasKonzept: dasPil #1    -> learning attempt with weakest kept cells

backside - busbars


assembly & soldering finished, initial measuring pack/battery = 16.67 V


BMS connected, cell unbalance 11 mV, battery not charged so far
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#4
Since you as many other turn the question the wrong way around regarding fuses.....

What was the testing current ? Thats the max current per cell... But since you allready choose cell level fuse at 2a your max current per cell should be 0.5 a att the Main fuse. This is therefore 12a.

You dont want to swap out 96 fuses... Only 1.
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#5
(08-08-2019, 05:14 PM)ben teker Wrote: dasKonzept: dasPil #1    -> learning attempt with weakest kept cells

Goal of use:
- medium capacity battery setup for solar-powered (dis)charging next +2000 harvested 18650 cells  Tongue

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#6
It's hard to judge from the tiny resolution picture, but it looks like your clamp is causing some shading on your PV panel. Due to the way solar panels work, that bit of shade will cause the power output of the whole array to drop by 10%~20%, and it might cause that spot to overheat. Try to mount it without causing any shades on the PV cells.
While at it, angling it to make it face the sun will get you much more power. In the summer you'll want it _almost_ flat, facing south. In the winter 45deg or steeper, again facing south.

Also, that is a PWM charger, and they can be very inefficient. Some say that a MPPT based system can potentially pump as much as 30% more power.

12V is fine for a tiny low power system, but if you're going for 2000+ cells for your main system, you'll want to step up to 48V, or at the least 24V.
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#7
changed scheme

skipped PWM control, BMS seems to perform the same functionality
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#8
(08-08-2019, 05:14 PM)ben teker Wrote: dasKonzept: dasPil #1    -> learning attempt with weakest kept cells

one cell up-levelling
continuously in time cell 2 stays between 30 and 50 mV behind so it does in low and upper voltages. From first day of battery use till today ten days later the same deltas.

Give it a small push, loading individually cell 2 till value of other cells. Watch the delta the upcoming days. Seems no self-discharging cell.
before:


after action:
  
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