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Author Topic: 48v fork battery connections  (Read 6807 times)
Fionn
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« Reply #30 on: September 30, 2016, 09:52:41 AM »

If outer cells do indeed fail on a more frequent basis then I think temperature variation is probably a more likely explanation in stationary applications. If cells are packed together then those in the middle are likely to be of a consistent temperature whereas those on the outsides of a string have more exposure to environmental air. This could cause differences in how each cell absorbs charge leading to drift in interal resistances over the longer term. This in turn leads to a bit of a snowball effect without balancing.
I've not noticed a particular pattern of failure in series strings myself, but the ones I use are spaced apart to allow for air circulation.
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PV - 2.75kW East, 1.5kW South, 2.5kW West. 3 x Flat Plate Solar Thermal with side arm FPHE on 268L cylinder
baker
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« Reply #31 on: September 30, 2016, 10:46:16 AM »

should I remove the dead call or leave it in
baker
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Fionn
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« Reply #32 on: September 30, 2016, 10:53:10 AM »

Take it out.
One bad cell in a series string eventually ruins the others in the same string - it's contagious  Grin
Seriously, generally often one cell might only charge to say 12.8V when it shoudl be at 13.5V (for sealed batteries for example).
The remaining 3 cells are then overcharged by 0.233V each [( 13.5- 12.8 ) / 3] for 12V batteries in a 48V string for example.
This eventually kills the other cells in the string.
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« Reply #33 on: September 30, 2016, 11:07:05 AM »

fionn
thanks

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baker
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« Reply #34 on: September 30, 2016, 03:57:36 PM »

can the dead call be recovered
 1.9v     no charge
 baker
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eabadger
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« Reply #35 on: September 30, 2016, 05:11:43 PM »

more chance of getting it back by leaving in and removing a good cell from pack, then equalize charge, should get it going.

steve
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1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
Fionn
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« Reply #36 on: September 30, 2016, 06:16:26 PM »

Personally I'd perform any rejuvenation efforts on the bad cell in isolation, less chance of doing damage to others should something go awry.
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baker
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« Reply #37 on: September 30, 2016, 07:27:51 PM »

I have taken out 6 cells the dead cell and the rest weak
and have on repair setting but the first dead cell is not making any bubbles
no movement , facepalm 
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eabadger
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« Reply #38 on: October 01, 2016, 06:08:32 PM »

has it any voltage when rested? it will take a while keep an eye on temp of all in string, any warmer than hand hot turn off and rest.
i also had a go a while back with a power supply 5v 50a had two cells in series and and left with voltage setting at maximum of about 6v, got it off ebay, did work but the desulfator worked best, i never believed them, still dont, but it did work and i now have a second pack up and running.
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1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
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