I have been a long time reader, but never had a question (hence why I never registered) until now. I have a degree in EE, so electrical concepts/math are second nature to me, but solar is something that just isn't taught in school . I am hoping you guys can help answer what will probably seem like basic knowledge to some of you veterans!
My brother in law lives in upstate NY and wanted to supplement his propane generator with a small solar system for just his well pump. Even though he has a 500 gallon propane tank, there are times during the winter when rationing propane is appropriate when the power is out. Since water is essential to living, he wanted to focus on providing solar power for that first.
He purchased the following:
6: 100 watt, 12 volt solar panels (currently wired in parallel)
1: 60 amp cMPPT charge controller
4: AGM 12 volt, 100 AH batteries (currently wired in parallel)
1: 3000 watt continuous/12,000 watt peak low-frequency split-phase inverter (12 volt input)
His well pump is 1/2 HP, 220 volt. I don't have the make/model yet, but I have seen specs online where units of this type surge 35 amps on start (@220) and drop to 9 amp continuous.
I already realize he should change the way the system is configured to take advantage of the MPPT charge controller, but I want to focus on figuring out why it is not working properly first.
Now the bad news. When the pump starts, the inverter immediately goes into fault mode.
I gave him my volt meter and had him check everything, so I know its wired correctly.
I've checked all his wire gauges/lengths vs current draw/voltage drops and it all seems within spec.
Let's do a little math and you guys tell me if I am correct.
Surge watts for this pump would be 220 x 35 = 7,700
Since the input voltage to the inverter is 12 volts, the inrush current would be 7,700 / 12 = 642 amps
- Are those assumptions correct so far?
- Regular car batteries have CCA (cold cranking amps) specs that would apply to this situation, but does this apply for AGM batteries for solar systems?
- Is the inrush current exceeding what these batteries can supply and that is why it is failing? If so, can he swap the inverter to one that supports 48 volt input, wire the 4 batteries in series, which would drop the current from 642 amps to 160 amps?
- If all he is using the inverter for is the 220vac well pump, does he really need split phase?
Thanks in advance and I apologize if these are noob questions!!
My brother in law lives in upstate NY and wanted to supplement his propane generator with a small solar system for just his well pump. Even though he has a 500 gallon propane tank, there are times during the winter when rationing propane is appropriate when the power is out. Since water is essential to living, he wanted to focus on providing solar power for that first.
He purchased the following:
6: 100 watt, 12 volt solar panels (currently wired in parallel)
1: 60 amp cMPPT charge controller
4: AGM 12 volt, 100 AH batteries (currently wired in parallel)
1: 3000 watt continuous/12,000 watt peak low-frequency split-phase inverter (12 volt input)
His well pump is 1/2 HP, 220 volt. I don't have the make/model yet, but I have seen specs online where units of this type surge 35 amps on start (@220) and drop to 9 amp continuous.
I already realize he should change the way the system is configured to take advantage of the MPPT charge controller, but I want to focus on figuring out why it is not working properly first.
Now the bad news. When the pump starts, the inverter immediately goes into fault mode.
I gave him my volt meter and had him check everything, so I know its wired correctly.
I've checked all his wire gauges/lengths vs current draw/voltage drops and it all seems within spec.
Let's do a little math and you guys tell me if I am correct.
Surge watts for this pump would be 220 x 35 = 7,700
Since the input voltage to the inverter is 12 volts, the inrush current would be 7,700 / 12 = 642 amps
- Are those assumptions correct so far?
- Regular car batteries have CCA (cold cranking amps) specs that would apply to this situation, but does this apply for AGM batteries for solar systems?
- Is the inrush current exceeding what these batteries can supply and that is why it is failing? If so, can he swap the inverter to one that supports 48 volt input, wire the 4 batteries in series, which would drop the current from 642 amps to 160 amps?
- If all he is using the inverter for is the 220vac well pump, does he really need split phase?
Thanks in advance and I apologize if these are noob questions!!
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