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Small Cabin Forum / Off-Grid Living / Low Voltage disconnect, Adjustment?
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# Posted: 16 May 2022 13:14

Usually when I get to the cabin the solar controller read 13.7, I believe. Windynation setup I have had for going on 4 years. Was up there since Friday, sunny skies. I have 3 led lights and charge only my iPad and hearing aids. Yes, I am old and deaf.
This morning as I was leaving. The controller gave me a low voltage warning. Went off when the controller read 12.5. I have since learned this is a factory setting and is adjustable.
My question is? Is it advisable to lower this setting? And to what?
This has never occurred before. The only thing new is the rechargeable hearing aids and I did not think that had a huge draw.
Any suggestions? Anything I left out?

# Posted: 16 May 2022 14:18 - Edited by: paulz

What type of batteries? Lithium sounds like?

# Posted: 16 May 2022 14:25

Amazon says I bought them in 2019.
Universal Power Group 12V 100Ah Solar Wind AGM SLA DEEP Cycle VRLA Battery 12V

# Posted: 16 May 2022 16:52

12.0V resting (no draw) is roughly %50 state of charge on an AGM battery.

A low voltage alarm of 12.1V is probably pretty good as that should keep you above %50 (especially if you are measuring with a load).

However, a battery monitor is really required for a good system. Relying on voltage is not a good idea as loads can affect the voltage.

# Posted: 16 May 2022 21:49 - Edited by: gcrank1

Well, 1st off, maybe discon all the connections starting with the load side, then solar to scc, then the bats from the scc and each other. Clean all connections up and reassemble. You may just have corrosion/poor cons somewhere.
Fwiw, with lead acid (after I learned) I preferred to only draw down the top 30% of my bat bank amp hrs., only occasionally to 50%, IF I wanted to get long life from them. You have low watts/amps draw with only those few items. Your overnight usage/discharge should be no where near taking the bat to alarm and you have typically not been discharging to that point (a very moderate alarm point-good for bat life).
Sounds like it has in the worked well in the past so.....what has changed?
The batteries are now older, maybe one is failing and pulling down the other one?
Id discon them (Assuming parallel), let rest a while and check the voltage of each to determine if one drops low, indicating it wont hold.
Even better would be a load test of each.
If one looks to be better hook it back up to solar and it should charge better, then take the other one home to put on a charger to see if you can save it.
Now, for consideration, those 2 100ah bats only have, when new, 100ah between them to 50%dod, if you try to stay in the top 30% you only have 60ah. Uggg.
Just one 12v 100ah LFP battery would equal both agm's at 50%dod or 3 agm's at 30%dod.
I was going to have to replace all my 4 agm's this year at substantial cost, that went a long way to buying the LFP.

# Posted: 17 May 2022 07:38

LVDC is a prety poor way to set your system to shut off. What happens is of you put a load on the batteries the voltage sags and can make the disconnect alarm go off. I wouldnt even use this for daily or even weekend use. When it comes in handy is if your inverter dosnt have a timed off function and you leave the inverter on by accident and leave. It can save your batteries in that situation.

My LVDC is set to about 11.9v, with FLA batteries.

# Posted: 17 May 2022 14:24

Agree with Brett. My laptop charger pulls 2amps btw, enough to knock the battery voltage reading down a bit in use.

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