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I understand the thundersky spec sheet says to charge to a max voltage of 4,0 v, but I read that many here are only charging to 3,6 or 3,8 v, in order to increase battery life, and seeing as there is only little energy in charging to a higher voltage.

I have now got a good offering on thundersky cells, but I have to choose the right number of cells, and the most important thing is not to go above my controller's max voltage. I have e-mailed the manufacturer, and the cut off voltage is at 140 v, above which the controller will not operate. The controller shut off somtimes with the previous 120-v (60 cells) lead-acid pack when fully charged and regenerating downhills, and I want to avoid controller shut-off during driving, of course. I am also told the controller might get damaged with voltages above 150 v. I was going to use 32 cells to be on the safe side, but maybe I can get as many as 36 if I only charge to 3,8 v?

Does anyone has experience in regeneration voltage for thundersky cells? And suggestion of what voltage to go for?

also anyone can recommend a good charger for these? I would appreciate to be able to set a lot of parameters myself.
 

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Your voltage resting will be about 3.35-3.38V so the first time you hit the throttle that's the voltage the controller will see, NOT 3.2V. Do your math with 3.38V.

And yes when you are charging the voltage will increase very slightly until it is nearly charged. At that point it will rise rapidly in comparison. That voltage should be less than the Max V on the data sheet.

Calb says Max charge is 3.6V. 3.5V works nicely so I've been told.
 

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I understand the thundersky spec sheet says to charge to a max voltage of 4,0 v, but I read that many here are only charging to 3,6 or 3,8 v, in order to increase battery life, and seeing as there is only little energy in charging to a higher voltage.
the consensus on TS seems to be that setting the average cell max to 3.65 is plenty to use most of you capacity, and avoid possible overcharge on slightly imbalanced cells. The nominal cell count for 120v is 38; which would give 38*3.65= 138.7v just after full charge... and would settle to closer to 38*3.4= 129v after just a little use and drop to 38*3.2= 121.6 v under 'normal' loads.


The controller shut off somtimes with the previous 120-v (60 cells) lead-acid pack when fully charged and regenerating downhills, and I want to avoid controller shut-off during driving, of course.
Your regen system HAS to be smart enough not to attempt to overcharge the batteries or you will fry them for sure.
 

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Discussion Starter #4
Ok, thanks a lot for the help! seems like I will use 38 batteries, and charge to 3,65 v/cell- then I will stay within limits. 40 cells might be too many.

As the controller will cut power at 140 v, max regen voltage is 140/38=3,68, which should not damage the batteries. This also speaks for using 38 cells and not 36, since 140/36=3,89, far higher, and might overcharge an imbalanced cell... I can of course limit the regen current to prevent voltage form rising too high.
 
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