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New 48v 200ah 10kwh battery troubleshooting

There is the Big Hint as to what is happening. Clearly, when you turn on the water pump the Start Surge is too much for the BMS' to cope with resulting in an overload trip. The pump you have is NOT a Soft-Start pump so it will start with a very large surge (typical 2X the rating for that moment) and this can be made worse, the deeper the well is, the more force is required to push the water up & out.

You did not specific WHICH Inverter Model you have: (BTW, this info should have all been provided up front. Help yourself by being MORE Informative.

MS4448PAE​

Output Power4,400W
Peak Watts8,500W

MS4348PE​

Output Power4,300W
Peak Watts7,500W

A Typical soft-start pump will start off at 500W stage up in 150/200 increments over a few seconds which puts no strain on inverters. There IS a reason the lights dim for a second when the pump kicks on.

Looking at the links you posted, it does not appear that they carry Soft-Start pumps and one thing jumped out Right Away. If anything THAT IS A RED ALERT ! There is also no info on Amps / Watts draw on that pump on their site... 1.5HP does not translate into Amps/Watts.
The Meritsun Packs says it can handle 300A surge @ 48V so that should be 14,400W.



View attachment 24657

Motor probably draws 1.5 to 2 kW running.
Staring surge has been 5x running for smaller motors I've tested (window A/C), haven't tested a large induction motor yet.

Is this the battery?


"300A for 1 second" would be 15 kW.

What is the surge current for your inverter? Not listed here:


But Steve_S found 8500W. That is probably insufficient to start the motor easily, so could be struggling for an extended time. Good old lead acid kept up with it. Do you have a way to measure battery voltage and AC voltage over a few seconds, like oscilloscope or a logging DMM that can store dozens of measurements per second?

Maybe a large capacitor paralleled with battery would provide the necessary current. Try 10,000W for 1 second, 1V drop. That would be 50V, 200 farad. (rated higher voltage than peak charging voltage, of course.) Maybe smaller couple of farads like Maast suggests, but I've observed 150 millisecond starting times for motors with grid behind them. I think yours is taking longer.

A different inverter with twice the rating would likely work, but that costs more. What would be ideal is a pump that starts gradually, like 3-phase with VFD, but that's expensive and I haven't found small 3-phase well pumps. Other applications like my 2-horse pool pump are readily available; that one slowly ramps up to speed over several seconds.
Hi unfortunately I do not have a oscilloscope or a logging DMM that can store dozens of measurements per second. The peak watts of the inverter is def 8500 watts as stated on the attachedment I postdated above. I was also suggested a VFD drive by others but def expensive. In regards to a larger inverter, that will help because it will be able to more efficiently manage the surge of the pump load? And if thats the case then technically my inverter is the issue or to large of a well pump. Steve mentioned the 300 amps surge for my Meritsun battery which is correct,. This implies if I am not mistaken that with this well pump load I am maxing out my inverter specifically and its is lagging at the pumps initiall start up causing the high amps to exceed the batteries 300 amp surge time frame of i believe 1 second. Is this sound about right, sorry have patience i am not as knowledgeable. Sounds like thr capacitor modification would be the cheapest easiest option. Please post more information if possible.
 
Hi unfortunately I do not have a oscilloscope or a logging DMM that can store dozens of measurements per second. The peak watts of the inverter is def 8500 watts as stated on the attachedment I postdated above. I was also suggested a VFD drive by others but def expensive. In regards to a larger inverter, that will help because it will be able to more efficiently manage the surge of the pump load? And if thats the case then technically my inverter is the issue or to large of a well pump. Steve mentioned the 300 amps surge for my Meritsun battery which is correct,. This implies if I am not mistaken that with this well pump load I am maxing out my inverter specifically and its is lagging at the pumps initiall start up causing the high amps to exceed the batteries 300 amp surge time frame of i believe 1 second. Is this sound about right, sorry have patience i am not as knowledgeable. Sounds like thr capacitor modification would be the cheapest easiest option. Please post more information if possible.

Look into the details of your pump control first. It apparently has a motor starting capacitor, which may have degraded since new, or perhaps could be replaced with a different value to make starting easier. This will be a conventional electrolytic in the microfarad range and 300VAC range, fairly inexpensive. It provides a phase shift to start motor more easily.

If you could reconnect the old lead-acid battery and measure starting current or time in some fashion, then you could see how that changes with different capacitors. If the motor was accessible you could probably record its hum with a cell phone, but being a well pump it is out of earshot. Does the inverter hum during startup?

Then, or in addition, you can consider a supercap to help supply additional current that lithium battery can't, so it performs more like the lead acid battery for one second.
 
Hi,

i am not saying that all bms do this but mine does and apparently so does his. if your bms is able to handle the surge then you must have a high amp rating

I was more concerned with the "you have to apply voltage with a resistor first" part. I would want a BMS to reconnect once the overload is cleared, without user intervention. It would be preferable that the BMS was sized so that inverter would be the device in charge of overload protection.

Thinking about it, probably would be good that it required a manual BMS restart, in case the overload was caused by an inverter fault.

So many things to consider with LFP, that I never thought about with LA or Ni-Fe. I relied on a fuse in case of gross overload/dead short.

dRdoS7
 
this is the starting capacitor in my well control box. I looked up online and most people say you can increase a starting capacitor up to 20%. Not sure in terms of capacitors what to base the increase off of. Please give suggestions on farad ratings based off this one I posted. Thanks
 
The rating that matters here is the µF one. So in your case it's a 120 µF cap which means you can put a 140-150 µF one by your 20 % rule ;)
 
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