[cricketo]

Yeah, at such currents you definitely need a BMS that supports external contactors for switching load/charger. Orion, Zeva, Batrium can do that. Batrium definitely can scale up to 20 cells. With Zeva you could use multiple cell monitors, like three 8-cell ones, or two 12-cell ones. Orion also supports wiring multiple units in series for larger strings.

If you're feeling adventurous, you could try Chargery BMS24T. There are very serious concerns over quality of their products though.

 

[cricketo]

Is it possible to estimate the discharge amps without running the vehicle first ?

I think I answered my own question - The primary fuse in the car is 300amps, I can't exceed that.

I believe Leaf modules are only rated for 240A continuous, though they certainly can peak more. Make sure your controller limits the current to the motor correctly, and ideally it should also be configured for maximum draw from the battery pack. I don't know if this Curtis can be setup like that though.

 

[cricketo]

Would this bms work and support the discharge side ? https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/192702426670

It may work... Noname Chinese vendors are known to overstate the specs, and often they don't use correct parts (such as MOSFETs). If you happen to order that board, double check if those MOSFETs are indeed rated for 300A (which I actually doubt, more likely that's peak).

Here is a good thread about various BMSes :

https://endless-sphere.com/forums/viewtopic.php?f=14&t=88676

 

[cricketo]

I suspect that we are all talking at cross purposes

I would NOT expect any BMS to actually try and control discharge current - you have got a controller and some contactors to do that

A BMS will monitor some cells and MAY do some cell/cell balancing

But it will NOT shut off the charger - it will instead instruct the charger to shut off

At the discharge side most do nothing - but IF it does do anything it will instruct the controller to cut back or off

The BMS needs to handle the balancing current - a piddly small amount

You are mistaken. Many BMSes intended for use in high current applications have specific port(s) for connecting charge/discharge contactors. Here is a wiring diagram for Zeva BMS16, with two separate contactors clearly visible :

http://www.zeva.com.au/Products/images_lge/BMS16v2_Example.jpg

 

[cricketo]

I don't think that diagram proves what you think it proves...

The discharge current is not under the control of the BMS normally. The controller throttles that and keeps it within limits. This diagram shows the BMS controlling the main contactor (to open it if a cell is low) and a charge contactor (to prevent overcharging). Neither of those are concerned with discharge amperage. The only reason it has a shunt is for state of charge calculation, probably. That's all my Zeva does with the current sensor.

Sent from my SM-N960U using Tapatalk

You are technically correct here, you just misunderstood what I was saying. The question of current is only relevant to the way BMS may be switching load/charger on/off. Many low current BMSes do that by means of on-board MOSFETs. Since it is impractical to use solid state devices as switches in high current applications, BMSes meant for high current applications rely on contactors, while providing control interfaces for those contactors.

I still insist you were mistaken in your previous comment regarding shutting off charger by means of communication. Some BMS/Charger combos indeed do that, such as Chargery BMS. Zeva, as I've referenced above, has no means of instructing the charger or controller to switch themselves off should any of the cells be pushed beyond their operational parameters. Instead Zeva will kill the load/charger via contactor should it detect any cell has approached a charge/discharge threshold.

 

[cricketo]

That is EXACTLY what I said
The BMS does NOT control the current in either situation but it does effectively tell the charger or the controller to STOP

Except you said

But it will NOT shut off the charger - it will instead instruct the charger to shut off

Which I explained it often can't do, as there there may be no integration between the BMS and the charger.


I also responded to jbman thinking that was your comment. Sorry jbman