Victron battery Isolator for charging 2 different battery banks?

hwse · Feb 9, 2023

The diode based isolator will cause you charging problems which is why I have one for a paper weight I will give away. I switched to the ArgoFET 300-3 which sells for less than $150 and solves most of your problems. This will allow you to charge all batteries together but let you isolate them for discharge.

hwse · Feb 9, 2023

roly1 said:
Does that controller have a sense wire or get it through the charge circuit? Why can’t it bypass the isolator? As long as the controller is powered from that battery. Thats how I planned to do it.
And dedicated small AC/DC dock charger.
Which is where boat spends most of its time.

I had a diode isolator and thought that it would work just as you describe but it did not turn out that way. The voltage drop is due to resistance, so it is not a constant 0.7v. It is a max of 0.7v at the rated current. If I sensed the LFP, the AGM got too high of a voltage because it got much lower current. That also left me vulnerable to a BMS disconnect causing problems. If I sensed the AGM, the LFP got a much lower voltage than planned because of the much higher current on that side. It also caused the isolator to get very warm.
I switched to the ArgoFET 200 and solved all of those problems. I sense the input terminal to the isolator.

Marinepower · Mar 8, 2024

hwse said:
I had a diode isolator and thought that it would work just as you describe but it did not turn out that way. The voltage drop is due to resistance, so it is not a constant 0.7v. It is a max of 0.7v at the rated current. If I sensed the LFP, the AGM got too high of a voltage because it got much lower current. That also left me vulnerable to a BMS disconnect causing problems. If I sensed the AGM, the LFP got a much lower voltage than planned because of the much higher current on that side. It also caused the isolator to get very warm.
I switched to the ArgoFET 200 and solved all of those problems. I sense the input terminal to the isolator.

Hi Hwse,

sorry i know this is an old thread.

I also have an argofet to separate a AGM start battery and a LFP bank (and to allow for a 'dump load' should the LFP disconnect).

I note you put your sense wire on the input side of the Argofet. I put mine on postive terminal of the LFP.

Just curious why volt sense on the input of the Argofet? What voltage does that input terminal see if the LFP disconnects? I may be doing this wrong, so I would like to understand how to make it better....

MP

hwse · Mar 10, 2024

Marinepower said:
Hi Hwse,

sorry i know this is an old thread.

I also have an argofet to separate a AGM start battery and a LFP bank (and to allow for a 'dump load' should the LFP disconnect).

I note you put your sense wire on the input side of the Argofet. I put mine on postive terminal of the LFP.

Just curious why volt sense on the input of the Argofet? What voltage does that input terminal see if the LFP disconnects? I may be doing this wrong, so I would like to understand how to make it better....

MP

I connect to the input of the ArgoFET so that I do not need to worry about the voltage sensing being affected by the ArgoFET or any BMS dropout. The only downside I can see to this arrangement is that I might get a bit lower voltage than desired at the battery due to voltage drop in the cable from the ArgoFET to the battery. In my case, that is all 2/0 wire, so the drop is minimal, and the drop decreases as the current is reduced as you near full charge, so I do not see it as a significant issue.

Victron battery Isolator for charging 2 different battery banks?

hwse

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