Low Voltage Cutoff Help

[arborist.boi]

Hi folks,

I am running into some issues with my DIY battery bank and my Victron multiplus. I built two 304 AH 12V batteries with two overkill solar bms units. I have a victron multiplus 2000w inverter charge. I have the batteries in parallel. When I draw a large load (approximately 1500 watts) it only takes a few minutes before my system is shut off and a restart occurs due to low voltage. I am wondering if there is something I am missing here. Please let me know if you need any other information to help me with this.

 

[RCinFLA]

From your description of two battery and batteries in parallel I take that to mean you have a 12vdc 2000 watt inverter.

That takes a lot of DC current (175 amps) from a 12v battery. Your battery cables and/or breaker, and/or connections have too much resistance causing too much DC voltage drop at inverter DC input when you put a heavy load on inverter. This causes a low voltage cutoff on inverter.

The greater the voltage drop to inverter, the more current the inverter has to draw to make same AC output power. Also, inverter efficiency drops at lower input DC voltage. It is a compounding downward spiral.

Most common issue is using too small a gauge battery cables. For a 12v system better to use fuse and not a breaker, as high current breakers have about 4 milliohms of series resistance compared to less than 1 milliohm for a fuse.

 

[Rocketman]

I have the same issue only smaller in my MotorHome. As I run my Multiplus 12/3000 with a larger load the voltage drops at the Multiplus. I found several connections that were getting mildly hot.

I have rewired a few areas to shorten and improve the current flows. It has helped a bit.


What size of cables do you have? And what fuses and other items in the current path?

Good Luck