Jim Burrow
Solar Enthusiast
- Joined
- Jun 27, 2020
- Messages
- 516
I have got a question or puzzle if you will. I bought two 12v 220ah AGM (lead-acid) batteries yesterday because I am a poor boy and can’t afford to go Lithium at this time. – The batteries are connected in series for 24v
My 2424lv (MTTP controller/inverter) option 29 (low voltage cutoff) is set to 21.0v, but in option 05, I have AGM battery type selected.
Here is the issue, running a test load of 900 watts, my 2424lv controller reached 22.3v or and of course the buzzer goes off as it is getting close to my battery cutoff voltage point.
But at the same time as the MTTP (2424lv) display is reading 22.3v, the voltage at the battery posts is reading 23.9 volts. – I do not have a cheap meter!
With respect to my house, the most it would draw in the evening is around 500 watts to 600 watts. The 900 watts above is just for testing and what I happen to have available at the time.
So, it seems to me that I should lower my battery low voltage cutoff point to the minimum for my controller which is 20.0 volts.
The question is, to set the low voltage cutoff point, should I go by the voltage reading at the battery posts which is showing (23.9v) or what the MTTP controller is reading of 22.3v? Hence, lower the cutoff point down to the minimum of 20.0v – note that there are no datasheets for these batteries, I looked all over the internet.
I may have to change option #5 to User-defined (presently set to AGM) and control the battery voltage levels manually.
What’s everyone’s opinion on this issue? Note PV basically no power due to no sun and the Utility to the MTTP is turned off for this testing.
My 2424lv (MTTP controller/inverter) option 29 (low voltage cutoff) is set to 21.0v, but in option 05, I have AGM battery type selected.
Here is the issue, running a test load of 900 watts, my 2424lv controller reached 22.3v or and of course the buzzer goes off as it is getting close to my battery cutoff voltage point.
But at the same time as the MTTP (2424lv) display is reading 22.3v, the voltage at the battery posts is reading 23.9 volts. – I do not have a cheap meter!
With respect to my house, the most it would draw in the evening is around 500 watts to 600 watts. The 900 watts above is just for testing and what I happen to have available at the time.
So, it seems to me that I should lower my battery low voltage cutoff point to the minimum for my controller which is 20.0 volts.
The question is, to set the low voltage cutoff point, should I go by the voltage reading at the battery posts which is showing (23.9v) or what the MTTP controller is reading of 22.3v? Hence, lower the cutoff point down to the minimum of 20.0v – note that there are no datasheets for these batteries, I looked all over the internet.
I may have to change option #5 to User-defined (presently set to AGM) and control the battery voltage levels manually.
What’s everyone’s opinion on this issue? Note PV basically no power due to no sun and the Utility to the MTTP is turned off for this testing.