samben7
1 µW
probably a very dumb question but if my battery is rated at 50A BMS should i get a controller that is also rated 50A or should it be higher/ can it be lower?
Any help appreciated, thank you
Any help appreciated, thank you
Controller amps match battery amps?
- Thread starter samben7
- Start date
Good question.
Controller max amp rating should be lower than the battery max amp rating. Rule of thumb lower by at least 30%, so in your case, a 35A controller (if your battery specs can be believed, see below).
Reasons:
How do you know your battery can actually deliver 50A?
endless-sphere.com
Controller max amp rating should be lower than the battery max amp rating. Rule of thumb lower by at least 30%, so in your case, a 35A controller (if your battery specs can be believed, see below).
Reasons:
- Amp draw too close to battery max will overly strain the battery and also possibly trip the BMS.
- Rampant over inflation of battery capabilities by battery vendors (battery may not actually be able to reliably deliver 50A).
- Batteries degrade over time and with use. Next year (month?) the battery might not be able to deliver its full 50A rating.
How do you know your battery can actually deliver 50A?
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endless-sphere.com
"Always"*** use a battery that is more capable than you need by as much as you can afford and fit, both in capacity and current capability.
That way it will not be stressed even as it ages, and will still have the capacity to do the job you need it to even as that capacity drops over the years.
Note that the BMS rating doesn't mean the battery is actually capable of that current for more than a few seconds. You would need to know which cells are in it, in what configuration, and check the spec sheet for those cells to see how much continuous current they are actually designed for, then multiply by the number in parallel. In a good pack that number will be higher than the BMS is capable of, but in many packs, especially cheap ones, it is not.
***if it's a system you don't intend to use much or for long, then it doesn't matter if the battery degrades from usage, as long as it isn't damaged (which could potentially lead to a fire).
That way it will not be stressed even as it ages, and will still have the capacity to do the job you need it to even as that capacity drops over the years.
Note that the BMS rating doesn't mean the battery is actually capable of that current for more than a few seconds. You would need to know which cells are in it, in what configuration, and check the spec sheet for those cells to see how much continuous current they are actually designed for, then multiply by the number in parallel. In a good pack that number will be higher than the BMS is capable of, but in many packs, especially cheap ones, it is not.
***if it's a system you don't intend to use much or for long, then it doesn't matter if the battery degrades from usage, as long as it isn't damaged (which could potentially lead to a fire).
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