Overkill Solar BMS as a Current limiter

[dma]

Hi,
would it be possible to use the Max charge current option in the Overkill (4s) BMS as a current limiter instead of installing a DC/DC charger?
My battery now pulls up do 100A from the alternator, which is not desirable.
I was wandering if limiting the current to 40A in the bms would be a solution, or that installing a dc/dc charger is the only (good) sloution.

Best regards,

Dick Martens

 

[Dzl]

Hi,
would it be possible to use the Max charge current option in the Overkill (4s) BMS as a current limiter instead of installing a DC/DC charger?
I was wandering if limiting the current to 40A in the bms would be a solution

No, unfortunately the BMS cannot do what you hope, it does not limit current, it can only switch off if the current limit is exceeded. Or at least that is my understanding.

or that installing a dc/dc charger is the only (good) sloution.

Its the simplest option I am aware of for charging LFP from the vehicles starting system. There are other solutions (like an external regulator, but they are most costly and more advanced).

Here are the companies I am aware of that make a DC-DC charger for charging LFP from the vehicle charging system:
Victron
Red Arc
Sterling Power
Kisae
Renogy
CTEK

 

[Steve_S]

(1) A small clarification on BMS' {they do not charge cells} | DIY Solar Power Forum (diysolarforum.com)

 

[Mike Jordan]

No, unfortunately the BMS cannot do what you hope, it does not limit current, it can only switch off if the current limit is exceeded. Or at least that is my understanding.


Its the simplest option I am aware of for charging LFP from the vehicles starting system. There are other solutions (like an external regulator, but they are most costly and more advanced).

Here are the companies I am aware of that make a DC-DC charger for charging LFP from the vehicle charging system:
Victron
Red Arc
Sterling Power
Kisae
Renogy
CTEK

I am not sure this would be a very good use scenario for a BMS. As in, I do not think I would do it myself.

And there is probably a good reason everyone is not doing it. Like, current limit is a once in a while emergency type protection parameter. Not an all day everyday planed operation. So the BMS is probably not designed as a high duty cycle current limiter. But for better understanding, how is switching current off, when the current limit is exceeded, different from, limiting current?

If current is switched off... it is very limited in my mind

 

[HRTKD]

With the current OFF, you're not charging your battery. If the battery NEEDS to be charged because it is at 30% state of charge, you're screwed.

A DC-DC charger that will allow only a set current is the way to go.

 

[Dzl]

I am not sure this would be a very good use scenario for a BMS. As in, I do not think I would do it myself.

And there is probably a good reason everyone is not doing it. Like, current limit is a once in a while emergency type protection parameter. Not an all day everyday planed operation. So the BMS is probably not designed as a high duty cycle current limiter. But for better understanding, how is switching current off, when the current limit is exceeded, different from, limiting current?

While the BMS does have a current limit (noun) has no ability to limit current (verb) to some number of amps. It can only switch off when a threshold is exceeded, like a fuse/breaker. OP is looking for a way to "turn down the tap," a BMS switching on/off would not do this.

If current is switched off... it is very limited in my mind

touché

 

[willo]

Yup, get a proper DC-DC charger. They aren't very cheap, but they are worth protecting your battery investment.