Help with BMS for battery

Hello All,

I need some help, should the BMS match the battery amps or the Motor draw?

My 13s8p battery is about 80 amps, but if the 65161motor can draw 200 amps shouldn’t the BMS be able to handle the draw at peak current? Should the BMS

80 or 200amps

Product Spec: 65161 Motor

Voltage range: 6-20S (25.2-84V)

Max Spin Speed(RPM): 16380.

KV(RPM/V): 120KV/100KV.

Max Power:6000W,rated power 3000W.

Peak current: 200A.

Thank you very much for your help Mike

You mean you battery is 80 Ampere hours? Or you can draw max 80 Ampere from it ?

Hi! To begin with, do not confuse the pulse peak currents to the motor and the discharge current from the battery. These are different currents. To be calm, your battery should give out a current of 100 amperes without any problems. I weigh 95 kg when overclocked on a flipsky 65161, I can reach up to 90 amps, with intensive overclocking! But on the wing we ride at 40-50 amps. This is at speeds up to 35 km.h. I still have all BMS Chinese 200 amps working. There is a rule, with Chinese BMS, buy with double stock! 200 definitely! You can have 300.The price difference is not big! Good luck!

It’s a simple yet complicated question since it depends on how hard you are wanting to push your parts for longer durations.

If you have a 10A cell in 13s8p then it’s good for 3.8kW at least in short term (if it’s a branded cell…)

For an efoil that power level is needed only for starts, some seconds and therefore you can use a bms specified for the same power and current. But @Anatoly has a good point, the bms’s we use (low price, dedicated to diy or rc market) often wildly exaggerate their specs and what fails in these systems is normally the bms or esc. It’s recommended to get a good bms and overspec it, or use the bms for charge and balance only.

If you’re planning on using your battery in a boat or setting efoil speed records then the battery and bms speced at 3.8kW will likely overheat.

I use this bms on some builds:

It’s been working flawlessly so far and you can monitor each cell and shut on/off from your phone.

The confusing thing witth LLT bms is that they have a hundered variations that can do roughly the same thing. When i bought my first i emailed them and described what i needed, then got a recommendation. They were good to deal with.

I would stay away from Daly bms and Ant bms, have had issues with both brands and seen a lot of others having issues to.

Thank you everyone for you help.
If i got this correct the bms can be a higher amperage then the battery without causing a problem with the VESC?

How much amps the 65161 really draws is also defined by a lot of other factors, such as your body weight, size and type of propellor, size of board, etc…
The really important question is what your batteries can handle without damage, as you’re planning on running 8 cells in parallel. If you don’t plan to use high amp cells, than this will be your limiting factor.
So to be honest, a real answer to your question is only possible if you give more details about your planned build!

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Yes, you can choose any bms that can take your max amount of current without overheating.

bms does not control current, they only have an on/off protection which shouldn’t be activated during riding. bms shutdown can kill your esc if it happens at higher power - it’s meant to be the final protection layer for your battery (as well as help with balancing)

the esc does the current control and also should shutdown itself when battery reaches too low voltage.

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