I'm getting a 72v3000w80amp controller from nbpower Im new to this so wanted to know if the bms in the battery have to match the output of the controller or should it be higher or doesn't it matter either way I know it has to be a 72v battery but I don't understand the bms part thank you
Bms
- Thread starter Mr k
- Start date
First, the BMS should be no more capable than the cells.
What can your cells handle?
Next, assuming the cells can handle it, the BMS should be more capable than the controller will ever require, worst case current possible under any conditions.
What could your controller ever draw, worst case?
If the cells can't handle what the controller would draw, then the controller should be either tuned down to less than what the cells can handle, or it should be replaced with one that draws less than what the cells can handle, or the cells should be replaced with ones that can supply more than the controller will ever require.
Let's say your cells can only supply 60A. the BMS should be rated or programmed for less than that, so it protects the cells against overcurrent. Then the controller would also need to be rated or programmed for less than that, so it doesn't stress the BMS (it shouldn't be able to stress the cells because the BMS would shut off output and turn off the system when the controller exceeds the limit).
It is better if the cells can handle much more than the controller would need, because as the cells age they will be less and less capable, so you should get ones more capable by some large margin (say, 25% or more) to allow for aging losses. Meaning, if you needed 100A out of the cells, get ones capable of 125A. Then as they age then for some time they will still be able to supply what the controller needs, without sagging much in voltage (so they still deliver as many watts as you need; W = V x A).
What can your cells handle?
Next, assuming the cells can handle it, the BMS should be more capable than the controller will ever require, worst case current possible under any conditions.
What could your controller ever draw, worst case?
If the cells can't handle what the controller would draw, then the controller should be either tuned down to less than what the cells can handle, or it should be replaced with one that draws less than what the cells can handle, or the cells should be replaced with ones that can supply more than the controller will ever require.
Let's say your cells can only supply 60A. the BMS should be rated or programmed for less than that, so it protects the cells against overcurrent. Then the controller would also need to be rated or programmed for less than that, so it doesn't stress the BMS (it shouldn't be able to stress the cells because the BMS would shut off output and turn off the system when the controller exceeds the limit).
It is better if the cells can handle much more than the controller would need, because as the cells age they will be less and less capable, so you should get ones more capable by some large margin (say, 25% or more) to allow for aging losses. Meaning, if you needed 100A out of the cells, get ones capable of 125A. Then as they age then for some time they will still be able to supply what the controller needs, without sagging much in voltage (so they still deliver as many watts as you need; W = V x A).
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