How do I correctly set Battery Low Voltage Cut Off?

[sensij]

So are you saying that 24.2 may or may not be 50% SOC? I know my daily usage of the loads I have off grid are nearly close to 3400 Wh's per day. But what was kinda concerning me yesterday was I was seeing that voltage drop faster than I expected. I went from 100% charged and 25.5v's at 4pm down to about 24.8 by 11pm and at 8am the next morning the pump kicking on kicked the inverter off. The voltage on the batteries was about 24.5v, but the surge dropped it. And when the pump went off the voltage returned to 24.5v but the inverter had already kicked itself off due to LBCO set to 24v and not enough delay time.



I'm interested to see what the consensus is on this last statement.

It sounds like you are trying to put too much value on the low voltage disconnect. Voltage is not a good indicator of SOC, as you've seen and for the reasons already described in this thread. Have you gotten comfortable with measuring specific gravity yet? That is something you should figure out, definitely before investing more money in an even more capacity.

The disconnect should probably be thought of as an emergency stop, and set to a value below that which you would ever see in normal usage (and with a delay long enough to ignore normal surges). You can't rely on the LVD to keep your battery healthy, only careful SG measurements and planning/control of your loads will do that for you.

If your loads are so high that you think you'll need to use the LVD to stay above 50% SOC (as determined by specific gravity), you need to cut some loads, or at least shift then to daylight hours when PV can assist.

[Matrix]

It sounds like you are trying to put too much value on the low voltage disconnect. Voltage is not a good indicator of SOC, as you've seen and for the reasons already described in this thread. Have you gotten comfortable with measuring specific gravity yet? That is something you should figure out, definitely before investing more money in an even more capacity.

The disconnect should probably be thought of as an emergency stop, and set to a value below that which you would ever see in normal usage (and with a delay long enough to ignore normal surges). You can't rely on the LVD to keep your battery healthy, only careful SG measurements and planning/control of your loads will do that for you.

If your loads are so high that you think you'll need to use the LVD to stay above 50% SOC (as determined by specific gravity), you need to cut some loads, or at least shift then to daylight hours when PV can assist.

It is all starting to become clear to me. Thanks all for this excellent education.

[fopoku2k2]

I need help configuring my MPP 5048 or MUST PV1800 inverter to achieve the following:

1.0 I want only solar to charge my 48v Nissan leaf batteries
2.0 I want the inverter to only switch on utility when the battery voltage drops down to 48v
3.0 I want the inverter to switch back to battery when solar has charged battery to 57v
4.0 I want grid to be off during 3.0 above