BMS Separate Port wired as Common Port?

[John Frum]

(+)---------------------------------------------------------------------
   battery         charge_source   load
   breaker_shunt   breaker_shunt   breaker_shunt
(-)---------------------------------------------------------------------

 

[Jake]

Okay, now that we’ve figured out the real use of the C- charge port when the BMS detects a cell overly discharged and turns off the load but allows the battery to be charged! It brings up another Question... Most of the Separate Port BMS only allow 8 amps of charge current? What happens when My Victron Controller sends 8.1+ amps to the batteries? Does the BMS regulate it down to less than 8.1 amps? ... or does it shut down the charging? ... or does it just burn-up ? the BMS ?
Not sure if I want to test it out....?

 

[John Frum]

Okay, now that we’ve figured out the real use of the C- charge port when the BMS detects a cell overly discharged and turns off the load but allows the battery to be charged! It brings up another Question... Most of the Separate Port BMS only allow 8 amps of charge current? What happens when My Victron Controller sends 8.1+ amps to the batteries? Does the BMS regulate it down to less than 8.1 amps? ... or does it shut down the charging? ... or does it just burn-up ? the BMS ?
Not sure if I want to test it out....?

The charger should trigger the over-current protection which will open the circuit.
It won't throttle it.
Would be cool if it could though.

 

[MisterSandals]

The charger should trigger the over-current protection which will open the circuit.

I do no think you mean charger do you?
I believe the BMS would fry if it receives more than 8 amps.
The BMS’s “over current protection” as you call it, from my understanding, is based on any of the cells’ voltage exceeding a certain voltage ( detected thru the loom).

 

[John Frum]

I do no think you mean charger do you?
I believe the BMS would fry if it receives more than 8 amps.
The BMS’s “over current protection” as you call it, from my understanding, is based on any of the cells’ voltage exceeding a certain voltage ( detected thru the loom).

It should have over current and over voltage protection.
The over charge current protection on the charge port is just like on the discharge port but in reverse.
FET based.

Oh I get it, not the charger but the current flow.

I don't think the bms will fry unless its majorly over.

 

[Craig]

I want to know is if overcurrent protection is a real problem if your system is properly set up. If your inverter is sucking up max battery power I think you may need a larger battery or smaller inverter

 

[dashdrum]

Sounds like the moral of this story is that if you have a separate port BMS you should have the load and the charger hooked to their respective ports. If you have one wire that carries both load and charge, use a combined BMS.

 

[Bhupinder]

Could someone please share Separate Port BMS connection diagram with SCC?
My SCC requires Batteries to be connected before PV Panels else it burns up internal fuses.
Going by the separate port BMS design below, looks like negative connection from SCC output should terminate in C- port on the BMS.


If that's the case, how is SCC supposed to power up because C- ain't going to provide any reverse current to do that - Right?
Could some share their schematic of connection between the two modules to elaborate this.

 

[BiduleOhm]

It's correct, the SCC should go between battery positive and C-.

If that's the case, how is SCC supposed to power up because C- ain't going to provide any reverse current to do that - Right?

It will as mosfets all have an internal diode

 

[Jake]

I used a Separate Port BMS for my latest configuration, but I’m wiring it as if it’s a Combined Port BMS so that if the BMS detects low voltage it shuts off the Neg Main current lead but allows the C- Charging port connected to charge the Low Cell! This also allows the Victron battery % charge indication to continue operating properly.

6.3KWH Battery Bank with 500 watts of solar panels... yes I know that’s a bit to much Battery power but I never (rarely) charge the batteries to Absorption. I’ve never run out of power ?.

 

[BiduleOhm]

I used a Separate Port BMS for my latest configuration, but I’m wiring it as if it’s a Combined Port BMS so that if the BMS detects low voltage it shuts off the Neg Main current lead but allows the C- Charging port connected to charge the Low Cell! This also allows the Victron battery % charge indication to continue operating properly.

That's a bad idea. Please use a common port BMS if you want one, don't use a separate port wired as a common port.

 

[Jake]

Don’t worry... I have a set of SSR that control when the main is shut off and the Charge (C-) is turned on. Have tested it in the shop a dozen times. The SSR also acts as a diode so the main power out is turned off....

 

[BiduleOhm]

Not sure ofthe configuration of your system but if you tested it and it works for you then it's ok

 

[Jake]

Thanks BiduleeOhm... I’m an old Engineer (Electronic-Electorial) that has been interested in Solar Power for over 45 years. Love trying new things! Almost 80 now...?. I’m in Canada ?? now even though I’m an American? Got in because Wife is Canadian. Presently I’m in Quarantine for my 14 days... tomorrow I finish!
I had a small Problem making my Coulomb meter read correctly before installing the SSRelay! Guess everyone out there might have the same problem when working they need to keep the % of charge working correctly? Or maybe Not?
Isn't really hard to figure what I did...