High Amperage BMS Reccomendation

I am currently working on an electric motorcycle project. The project consists of a 20s10p battery pack with a total voltage of 72 and a continuous discharge of 200A. The largest, high quality BMSs I could find for a 20s system were 150A. Looking a continuous discharge of 200A and a controller that will support up to 500A I'm trying to find a solution to use the BMSs during charge and discharging. I wanted to ask if I can connect multiple BMSs in parallel to possible double the maximum current? I have heard both sides of the story for using the BMSs for discharging and I will include a small section of what I have learned. I want to see if anyone has any recommendations or ideas for my setup. Any and all help is appreciated

BMS During Dishcarge:
-Balances cells during discharge and charge
-Allows shut down based on individual parallel groups rather than the battery as a whole

No BMS During Discharge:
-Allows the option for regenerative breaking (haven't been able to find a high amp model that will support that)
-ESC can limit current from the battery preventing over draw

Use a BMS with teh features you want *except* for it's discharge rating, and bypass it's output FETs. Instead, use the signal that would've turned those on and off, and drive a contactor instead, so the contactor does the battery cutoff.

Then you can also use the contactor for keyswitch/safety control, too.

You can also use the charge port's control line to shutoff the contactor during regen braking if the risk of overcharge is worse than the risk of braking power loss at a critical moment. (generally I'd rather momentarily overcharge the pack than lose braking at any time).

This one?
https://www.aliexpress.com/item/Smart-Display-300A-200A-150A-100A-70A-Lithium-Battery-Protection-Board-Balance-BMS-Coulomb-Meter-Li/32826820690.html?spm=a2g0s.9042311.0.0.10df4c4dwfsBx2

you could split the battery into two 72V packs, each with their own BMS? which would cut the high amperage requirement in half

Who said you can't use regen with a typical china BMS?

I have tried about 20 Different models from Ebay,Aliexpress and Bestech, and you can do regen on all of them.

Also 72V 500A Controller continuous?

At such high discharge currents I wouldn't waste any more energy on heating mosfets. I would connect the battery to the controller with an High amp fuse and power only the controllers Ignition wire from a weak 20S 25A or so BMS.

You would just need a sort of relay switch connected to the BMS, since you need to switch the B+ to ignition.

Or another way would be to only connect the 12V DC-DC converter to the BMS, and then power the controller with 12V. Which at least works on Kelly Controllers, you will have to check with the Controller you are going to use.

Baron said:

you could split the battery into two 72V packs, each with their own BMS? which would cut the high amperage requirement in half

Click to expand...

And as soon as one cuts out for any reason, the other suddenly is supplying the whole current, and POOF.....

If you are willing to optimise the system for 16S you could use this product: https://www.energusps.com/shop/product/tiny-bms-s516-150a-750a-36
Discharge/Charge/Regen current 750A if used with external relays, current sensor and mounted on a heatsink.

Any BMS could be used at any current level, regen, charge, discharge, etc., as long as external relays (contactors) are used. That's what I pointed out previously.

Sorry for the late replay, I haven't had access to a computer that would let me log in. The BMS I have access to is the link on the bottom. According to the company's very spotty customer service they said it would not support regen braking. Is there a way to test this without hurting the bms because the customer service rep did not seem very confident in their answer?

Would you be able to provide a simple diagram for the wiring setup you are suggesting with using the contactor as a cut out? I believe I understand what you are saying but won't I still need to run the discharging current through the BMS in order for it to be able to sense the discharging current and send the signal to the contactor?

I'm pretty much looking for the most reliable solution with these parts. Here is a link to the motor I will be using as well. The pack will be a custom build of the LG HG2 batteries in a 20s10p configuration.

http://www.evdrives.com/product_p/mot-me0907.htm
http://kellycontroller.com/kls7275d24v-72v500asinusoidal-brushless-motor-controller-p-1338.html
http://www.batterysupports.com/72v-84v-20s-150a-20x-36v-lithium-ion-liion-lipo-battery-bms-p-296.html

jktobin1 I would like to ask you some questions.
1)

The project consists of a 20s10p battery pack

Click to expand...

What cells are you using?
2)

continuous discharge of 200A

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Desired peak current is? For how long, your estimation?
3)

Balances cells during discharge and charge

Click to expand...

Why would you balance during discharge?
4)

No BMS During Discharge:
-Allows the option for regenerative breaking

Click to expand...

How much current do you think you get at regen?

jktobin1 said:

The BMS I have access to is the link on the bottom. According to the company's very spotty customer service they said it would not support regen braking. Is there a way to test this without hurting the bms because the customer service rep did not seem very confident in their answer?

Click to expand...

I bought a 12S BMS off those guys, but it was years ago. From memory, there is a common negative, but a separate charge and discharge port. This means that regen "isn't supported" because all energy will be coming back in from the "wrong" port. This can mean one of two things:

1. You can safely regen energy into there, but if regen over-voltages the cells, you're on your own.
2. You can't safely regen - reversing energy flow will blow the board.

My one was NOT damaged by charging through the discharge port. But remember this was nearly 7 years ago, they could have changed their designs since then.

For $99+shipping, I wouldn't recommend trying it out. I'd ask them whether "not supported" means that it won't protect the battery, or the BMS itself will be damaged.

amberwolf said:

Any BMS could be used at any current level, regen, charge, discharge, etc., as long as external relays (contactors) are used. That's what I pointed out previously.

Click to expand...

Just curious how to connect BMS with this setup as I cannot find BMS match with my desire.
Any diagram would be appreciate.

If you are willing to spend the money, you could use the BMS24T from Chargery. It supports up to 24S, and up to however much current you want I believe. It uses 1 or 2 external contactors (relay) to control charging/discharging. So for 500A, you would just need a contactor that can support 500A, they sell them up to 600A.

Take a look at the manual on their website to see if it's what you want.

http://www.chargery.com/BMS24.asp