Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

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mattcarr
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby mattcarr » Sat Nov 12, 2011 4:37 pm

so in total you drew 88 ah from them - that seems pretty good for a 100 ah cell.

Grumpy-b
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby Grumpy-b » Sat Nov 12, 2011 5:28 pm

Good amperage but not with voltage going down to 4+ volts. Even at 5+ V the berlingo would have long since come to a halt. Usable for something but doubtful they would be musch use in a Berlingo. I have loads that anyone can have that would do similar to this, but they are no good as a traction battery in a Berlingo, unless you want to get about 10 to 15 miles range. One battery like this will bring the fail safe power limiting on at about 35%, 2 cells like this would do it at 40%. I recently had 3 poor cells and the light/ limiting came on at about 50%.
Poor cells also for some reason also exhibit higher initial charged volatges, then drop like a stone when they get under 6 volts.

Grumpy-b

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EV_dub
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby EV_dub » Sat Nov 12, 2011 6:03 pm

Grumpy-b wrote:Looks like one duff cell in each to me. Thats a similar result to a failing cell.

Grumpy-b


Its normal for Ni-cad cells to react like that. They will maintain a gradual decline in voltage and then suddenly drop. This is called the "knee" characteristic

I know the minimum load voltage for the berlingo is 130v (5 volts per batt) but I dont know what the minimum idle voltage has to be to stop the controller cutting out.?

Just some quick figures of the top of my head: berlingo capacity: 16kwh, usual mileage range about 50 miles =320wh per mile .

so assuming the system will stay switched on with (5.5v) 143v you can run these batts for 2.5hrs x which gives 83ah so 83ah giving 13.5kwh = to 42miles???

I am going to cycle these a few time to get them working, apparently this can also help to wake them up.

I am listening to you Grumpy-b, you seem to have the most experience with these batts.
1993 Veedub Golf, 156v, 1200A, 150ah's

Grumpy-b
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby Grumpy-b » Sun Nov 13, 2011 4:44 pm

The attached spreadsheet shows two sets of berlingo batteries, the 4 box and the front 6 box. Each vertical column shows each separate 6v cell Voltage as each 5% charge is used, the % being shown on the last line.All of these voltages were taken within about 2 mins of the vehicle being in use and under load. The far right show where the cells are that are obviously failing, by their low volatge. This number of poor cells meant that a vehicle failure was occuring at about 35% charge. With two cells down the voltage drops considerably when under load, which pulls the whole system down which is obviously having to work harder to make up the required power from the remaining cells in the string.

Grumpy-b
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batt fail aug11.xls
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ChrisB
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby ChrisB » Sun Nov 13, 2011 9:47 pm

Been out of the loop on this chat :oops:

EV_dub wrote:
With Nicads, initially there is a huge number of very tiny crystals on the surface of the positive plate, but due to a gradual change in the nickel oxide/hydroxide crystal structure, (usualy from under discharging, "memory effect") these are gradually replaced by much larger crystals. This Reduces the surface area of plate to the electrolyte.
Reconditioning shrinks the crystals on the surface of the plates and dissolve any dendrites that may have formed
However this process wont achieve much if the batteries porous separators have been seriously damaged by
dendrite growth.


Must admit I didnt think we sufferd from this with our wet nicads :? certainly I've not really seen any sign of it in my berlingo, yes dry nicads I've had loads of trouble, although I've found "flashing" a 1.2v dry nicad with a 12v car battery appears to restore them when nothing else will 8)

Certainly with the berlingo saft units theres nothing really you can do once you get an internal failure on a cell :cry:

ChrisB
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EV_dub
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby EV_dub » Sun Nov 13, 2011 10:22 pm

On the Berlingo, Does anyone know the minimum voltage at idle (no load) before the controller switches out?
1993 Veedub Golf, 156v, 1200A, 150ah's

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EV_dub
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby EV_dub » Sun Nov 13, 2011 10:34 pm

ChrisB wrote:Been out of the loop on this chat :oops:

EV_dub wrote:
With Nicads, initially there is a huge number of very tiny crystals on the surface of the positive plate, but due to a gradual change in the nickel oxide/hydroxide crystal structure, (usualy from under discharging, "memory effect") these are gradually replaced by much larger crystals. This Reduces the surface area of plate to the electrolyte.
Reconditioning shrinks the crystals on the surface of the plates and dissolve any dendrites that may have formed
However this process wont achieve much if the batteries porous separators have been seriously damaged by
dendrite growth.


Must admit I didnt think we sufferd from this with our wet nicads :? certainly I've not really seen any sign of it in my berlingo, yes dry nicads I've had loads of trouble, although I've found "flashing" a 1.2v dry nicad with a 12v car battery appears to restore them when nothing else will 8)

Certainly with the berlingo saft units theres nothing really you can do once you get an internal failure on a cell :cry:

ChrisB

All nicads suffer from the memory effect, (Crystal build up) when the batteries are not discharged deep enough regulary. NiMh don't suffer from this problem as much.
1993 Veedub Golf, 156v, 1200A, 150ah's

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ChrisB
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby ChrisB » Thu Nov 17, 2011 8:50 pm

EV_dub wrote:On the Berlingo, Does anyone know the minimum voltage at idle (no load) before the controller switches out?


Not quite sure what you mean :? the controller never really "switches out" it puts on a caution recharge soon light, this happens normally underload and from memory its about 136v or there abouts, but thats under load remember.

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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby ChrisB » Thu Nov 17, 2011 8:52 pm

EV_dub wrote:
ChrisB wrote:Been out of the loop on this chat :oops:

EV_dub wrote:
With Nicads, initially there is a huge number of very tiny crystals on the surface of the positive plate, but due to a gradual change in the nickel oxide/hydroxide crystal structure, (usualy from under discharging, "memory effect") these are gradually replaced by much larger crystals. This Reduces the surface area of plate to the electrolyte.
Reconditioning shrinks the crystals on the surface of the plates and dissolve any dendrites that may have formed
However this process wont achieve much if the batteries porous separators have been seriously damaged by
dendrite growth.


Must admit I didnt think we sufferd from this with our wet nicads :? certainly I've not really seen any sign of it in my berlingo, yes dry nicads I've had loads of trouble, although I've found "flashing" a 1.2v dry nicad with a 12v car battery appears to restore them when nothing else will 8)

Certainly with the berlingo saft units theres nothing really you can do once you get an internal failure on a cell :cry:

ChrisB

All nicads suffer from the memory effect, (Crystal build up) when the batteries are not discharged deep enough regulary. NiMh don't suffer from this problem as much.


Must admit I've never noticed any issues from under discharging the safts, unlike I've had with dry Nicads.

ChrisB
I reject reality and substitute my own !!!!!!


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