I recently watched this 3 min video by Damian ...http://ashtangapictureproject.com/wp-content/uploads/2014/10/dwipadasirsasana159.jpg
He's building a 20s10p pack for a road vehicle and at first sight it seems quite wrong ... he's hot glueing the cells in a very tight pack , and shrink wrapping them so it's very difficult for the heat to get out ...
I forgot an important point ...he uses new cells which will have a low internal resistance and so will produce less internal heat when charged or discharged ( I don't think the type ofcells he uses ,NCA ,have a particularly low int resistance compared to laptop)
Damian tells us he's never had more than a 15C rise in temp in the center of his pack at 1C discharge .
I did an experiment to see what would happen with (almost) perfectly thermally insulated recycled laptopcells at 1C discharge .. after 10mins the temp had risen 21C ... so we do need to space salvaged cells to get the heat out . I would guess the black holders generally used, allow enough cooling even at high discarge...
Is it all about how new the cells are that determines the amount of this internal heat?
Tesla road vehicles use new cells , but still have the cells spaced far apart ...and use a liquid cooling system ... is that really necessary?
I would bet in most conditions it's not... the thing is tesla cars have to be able to handle all extremes , temperatures in Saudi Arabia can get upto 50C , and someone therewill quick charge , and then go for a drive ... and the comfort zone for cells is only up to 60C.
He's building a 20s10p pack for a road vehicle and at first sight it seems quite wrong ... he's hot glueing the cells in a very tight pack , and shrink wrapping them so it's very difficult for the heat to get out ...
I forgot an important point ...he uses new cells which will have a low internal resistance and so will produce less internal heat when charged or discharged ( I don't think the type ofcells he uses ,NCA ,have a particularly low int resistance compared to laptop)
Damian tells us he's never had more than a 15C rise in temp in the center of his pack at 1C discharge .
I did an experiment to see what would happen with (almost) perfectly thermally insulated recycled laptopcells at 1C discharge .. after 10mins the temp had risen 21C ... so we do need to space salvaged cells to get the heat out . I would guess the black holders generally used, allow enough cooling even at high discarge...
Is it all about how new the cells are that determines the amount of this internal heat?
Tesla road vehicles use new cells , but still have the cells spaced far apart ...and use a liquid cooling system ... is that really necessary?
I would bet in most conditions it's not... the thing is tesla cars have to be able to handle all extremes , temperatures in Saudi Arabia can get upto 50C , and someone therewill quick charge , and then go for a drive ... and the comfort zone for cells is only up to 60C.