Low battery shutdown relay..?

[Smith]

I have a general question about low voltage shutdown relays..

I currently live off grid, and use 4 group 31 batteries ( 31-5T, CCA-950, CA-1170) ..
Set up for 24 volts..
With a Giandel, 24v, 2000 watt pure sine wave inverter. And a "all powers", 20a, solar power controller..

The system works fine, but if I run anything overnight, it will drain my batteries down, well past 50%..

Anyone have a recommendation or experience in "low voltage shutdown relays".. ?

Or is there another solution to my problem..?

Thanks,
Vp

 

[pollenface]

I programmed an mppt to disconnect the load (via a 200a relay) at a desired voltage (25.2v) I didn't have any reliability with cheap programmable voltage sensing relays.

 

[chrisski]

Victron Battery Monitor has an option for a relay. I don’t use the relay, but my first time I used my RV overnight, I realized low voltage was not the best way to determine a cutoff because of voltage sag. We plugged a crockpot in that drew 1000 watts, and my low voltage alarm started beeping. I shut off the crockpot and the voltage went up.

The less amp hours in a battery bank, the higher this sag will be. I think a battery bank with a high discharge rate will have less sag then a battery with a low discharge rate. LIthium batteries would be have less drastic voltage sag on high load items then my flooded lead acid batteries.

 

[Smith]

I programmed an mppt load low voltage disconnect/recovery to power a relay that shuts off the load at a certain point. I didn't have any reliability with cheap programmable voltage sensing relays.

Can you explain how you did that..?


Thanks..

 

[Smith]

Victron Battery Monitor has an option for a relay. I don’t use the relay, but my first time I used my RV overnight, I realized low voltage was not the best way to determine a cutoff because of voltage sag. We plugged a crockpot in that drew 1000 watts, and my low voltage alarm started beeping. I shut off the crockpot and the voltage went up.

The less amp hours in a battery bank, the higher this sag will be. I think a battery bank with a high discharge rate will have less sag then a battery with a low discharge rate. LIthium batteries would be have less drastic voltage sag on high load items then my flooded lead acid batteries.

I can't throw away my lead acid batteries and buy lithium...

Thanks..

 

[chrisski]

I can't throw away my lead acid batteries and buy lithium..

What I was really trying to say, is if you are going to power a relay for shutoff, state of charge determined by a battery monitor tracking amp hour usage is a better cutoff than voltage.

 

[pollenface]

Can you explain how you did that..?


Thanks..

I have Epever mppts, using the remote monitor (MT50) which plugs into the comm port you can make adjustments to all charging and discharging parameters.

 

[Smith]

I have Epever mppts, using the remote monitor (MT50) which plugs into the comm port you can make adjustments to all charging and discharging parameters.

I can adjust my parameters on my mttp controller too, but it doesn't interface in btwn my batteries and my inverter..

Unless I'm missing something, like another module or relay, that can be added to my system..?

Thx

 

[Smith]

What I was really trying to say, is if you are going to power a relay for shutoff, state of charge determined by a battery monitor tracking amp hour usage is a better cutoff than voltage.

Sounds like o would need a module, that interfaces with my mttp controller..
That would sit in btwn my batteries and inverter..?

Thx

 

[pollenface]

I can adjust my parameters on my mttp controller too, but it doesn't interface in btwn my batteries and my inverter..

Unless I'm missing something, like another module or relay, that can be added to my system..?

Thx

A relay, plain old simple fat relay, like a 200a jobbie, the mppt controls the relay and the relay disconnects the inverter

 

[Smith]

A relay, plain old simple fat relay, like a 200a jobbie, the mppt controls the relay and the relay disconnects the inverter

You have a controller like this..?

 

[pollenface]

No I have the 4210AN and 2210AN

 

[Smith]

I can't throw away my lead acid batteries and buy lithium...

Thanks..

Victron Battery Monitor has an option for a relay. I don’t use the relay, but my first time I used my RV overnight, I realized low voltage was not the best way to determine a cutoff because of voltage sag. We plugged a crockpot in that drew 1000 watts, and my low voltage alarm started beeping. I shut off the crockpot and the voltage went up.

The less amp hours in a battery bank, the higher this sag will be. I think a battery bank with a high discharge rate will have less sag then a battery with a low discharge rate. LIthium batteries would be have less drastic voltage sag on high load items then my flooded lead acid batteries.

I understand what you mean now..

Thx..

 

[Texas-Mark]

I found some (used but not abused) low voltage cutoff modules on ebay for like $15. While these are for 12v, there probably is a 24v version. The cutoff is adjustable with a multi-turn pot. It has a low voltage relay, but I have that wired in parallel with the inverter's power switch. Works great. Model number on this one is Sure Power Industries 130512.