Low Voltage Cutoff Question

[DenverGuy]

I have a simple 12V system with a 100W PV and two 100Ah AGM batteries.
I am under the impression that I shouldn't ever let the batteries drop below 12.2 volts - 50%.
I see that the charge controller (Windy Nation P30L) was set to shutdown at 10.7V. If it hits that, wouldn't it be too late?
Shouldn't it be set to 12.2 or 12.3 volts?

I just bought an Epever MPPT 30A controller that I will install tonight. What settings should I change from the default? I know the battery type is one. Is an AGM considered flooded?
Thanks.

 

[RCinFLA]

If you drawing more than 25 amps per battery you will not prevent AGM battery dropping below 12.2v under load.

Battery voltage will come back up after load is removed.

 

[time2roll]

I see that the charge controller (Windy Nation P30L) was set to shutdown at 10.7V. If it hits that, wouldn't it be too late?

Is that the load terminals? Otherwise it does not make sense. Try not to use the load terminals.

No, AGM is not same as flooded. AGM probably a little lower boost voltage and no equalization.

 

[Substrate]

10.7v for lead-acid is the canonical "dead man" backstop. 10.7v is considered zero capacity for lead acid, and taking it further is very harmful. So yes, one should set their LVD a bit higher.

Depending on your surge load and peukert, you *could* get away with 10.7 if your load causes it to get near the lvd temporarily. Under light loads with very little peukert - yeah, 10.7 is the dead-man switch just to help prevent immediate battery degradation.

This is a common mistake for those starting out and relying solely on their inverter's lvd, which is usually 10.7 / 11.7v or so. Sure it will prevent immediate damage by going that low and having your inverters lvd activate. But hitting that backstop - essentially taking your lead-acid battery to zero capacity really cuts into the cycle life. Better to use a higher lvd as you have mentioned.

 

[DenverGuy]

Thanks.