Low Voltage Disconnect?

[OffGridMikey]

Q: I was just wondering what people do for low voltage disconnects with small (~200W) solar systems?

I've got a low cost 30amp PWM charge controller and I'm looking to get a 20-25amp MPPT on order. Both seem to have a low amp fused load side but it has a LVD feature directly on the controller...but the fuse ratings in those controllers are <=25 amps...

Right now I've redone my electrical prints to come off the battery directly to my Blue Sea 5026 fuse panel but in doing so I loose the LVD feature on the load side. I say this because I may run a DC-AC inverter in the future that could draw as much as 40 amps.

Can I use the Load Side output to operate a relay (MCR like) that can handle the higher amperage?
This way if I loose the load side from the controller on low voltage it will also kill all loads going to my fuse panel through the relay rather than risk draining the batteries to zero if one of my hunting buddies leaves the cabin power breaker on?

[Sunking]

Most inverters have auto shut down on low voltage to prevent killing the battery.

[OffGridMikey]

Ok but..

Most inverters have auto shut down on low voltage to prevent killing the battery.

Good to know. And if one of the dumb asses leaves all the lights on (34.4 watts @ 12VDC) on would a LVD help or should I just count on the solar panels to do their jobs? With 200W and MPPT I could get a solid 14-16 amps for 4-5 hours
3 amps @ 24 hours = 72 Amp-Hours out and 15 amps @ 5 hours = 75 in not counting losses... What would something like this do to my batteries?

I know... I know... the old saying 'You can't fix stupid!' is ringing in my ears.

[inetdog]

Good to know. And if one of the dumb asses leaves all the lights on (34.4 watts @ 12VDC) on would a LVD help or should I just count on the solar panels to do their jobs? With 200W and MPPT I could get a solid 14-16 amps for 4-5 hours
3 amps @ 24 hours = 72 Amp-Hours out and 15 amps @ 5 hours = 75 in not counting losses... What would something like this do to my batteries?

I know... I know... the old saying 'You can't fix stupid!' is ringing in my ears.

If your inverter has a programmable LVD setting, and you do not have any direct DC loads, you will be fine. And there will not be an override button for your friends to tape down. But if you regularly go down to 50% or below, that by itself will cost you battery life. But you want to be able to go that low to ride through cloudy days.
4-5 solar hours equivalent? Not in the winter. That is what you have to design for. Use PVWatts to check on what is real for your area.

[Naptown]

If your inverter has a programmable LVD setting, and you do not have any direct DC loads, you will be fine. And there will not be an override button for your friends to tape down. But if you regularly go down to 50% or below, that by itself will cost you battery life. But you want to be able to go that low to ride through cloudy days.
4-5 solar hours equivalent? Not in the winter. That is what you have to design for. Use PVWatts to check on what is real for your area.

In red is the operative phrase. Most inverters disconnect at too low of a state of discharge (generally 10.5V) If you can program it higher great.
Mostly however a separate LVD disconnect is preferred Take a look at the Rogue LVD's they are programmable. Keep in mind that you can set it a bit lower than the desired disconnect voltage as the battery will recover after a rest some. However 10.5V is too low to maintain battery cycles for any length of time.

[OffGridMikey]

All current loads are 12VDC.

If your inverter has a programmable LVD setting, and you do not have any direct DC loads.

That is my concern, in order to keep wattage low my cabin is wired for only 12vdc now. All direct LED lighting inside and out with low watt consumption products. In fact I have no AC right now and was looking at the inverter to run <200W AC products occasionally.

This is a 10x15' shed converted into a hunting cabin on some remote property. It's about as off the grid as you can get.

[Naptown]

Then look at the rogue 12V lvd It is good for 15A has a fuse and programmable disconnect voltages.