[Duncan]

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'm using Volt modules and a Volt main fuse - I believe it is about 330 amps

However my controller is set to 1200 amps and my battery current reaches that value as I accelerate

So far I have nor blown the "Main Fuse"

Tesla use a pyrotechnic main fuse that can blow immediately you exceed that current but the wire type main fuses will take quite a while (seconds) to blow even with a 400% overload

 

[Duncan]

Are you using a bms on the discharge side ?

No
No BMS at all

I use a Batt Bridge and charge using a BRUSA charger - no BMS

 

[Duncan]

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

 

[Duncan]

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

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