Gauranga108
New Member
- Joined
- Oct 5, 2020
- Messages
- 51
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 Power 4,400W Peak Watts 8,500W
MS4348PE
Output Power 4,300W Peak Watts 7,500W
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
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.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?
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"300A for 1 second" would be 15 kW.
What is the surge current for your inverter? Not listed here:
4400W 48VDC Pure Sine Inverter Charger MS-PAE | Magnum Dimensions
www.magnum-dimensions.com
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.