Growatt SPF 6kW DVM and Cheap Generator

Brett V

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Joined
Apr 5, 2021
Messages
311
I installed a Growatt SPF 6kW DVM over the summer and have been 100% satisfied with it. Although a ground mount of panels is in the budget for next year, right now my only battery charging option if the grid is down long term is a Smarter tools 9500 watt (7500 running watts) generator. These are notorious for making dirty power and I had concerns about it playing nice with the Growatt. It's been a hectic last few months and I've been lazy so the generator had never been tested with the Growatt. A Predator 9kw inverter generator came up for sale on Facebook Marketplace recently and I was going to snag it but thought I should at least test the generator I have.

The test consisted of killing the AC and running the house on batteries for a few hours, bringing the battery level down to about 75% Then I connected the generator and switched over. With my batteries charging at 40 amps, this put a 2000 watt load on the generator. Along with a variable load in the house ranging form 1800 watts to a little over 3000 watts, I saw some voltage fluctuations ranging from 233 to 245 volts across L1 and L2 on the Growatt display. When the well pump kicked on, the generator did its usual grunt and the frequency dropped to 59hz with a voltage sag to 230 volts for a minute. I don't have an easy way to measure the actual total load on the generator but going by the sound of the motor, I was pushing the top end several times. It finally crossed the threshold when my wife decided to use the hair dryer and the the Growatt shut down. Unfortunately I wasn't looking at the display when this happened so I don't know how how bad the output of the generator got.

I think the Inverter generator is a much better machine and wish I could justify it, but this test was done with a lot of unnecessary loads to simulate a worst case scenario and the Growatt was very forgiving of what it was fed. The Harbor Freight inverter generator for sale has only 124 hours on it and at $1700, is a bargain. I'll save that cash for the aforementioned ground mount I have planned for next summer.
 

neilhel

New Member
Joined
Dec 21, 2021
Messages
3
I have the same scenario and was wondering if all power goes to the battery or is some passed through. My concern is generator dirty power getting to sensitive electronics.
 

Brett V

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Joined
Apr 5, 2021
Messages
311
The Growatt thinks it's back on utility power so the generator needs enough capacity to power whatever is on bypass as well as the battery charger. As for this generator, I've used it many times over the years and none of the electronics in my home were adversely affected except for an APC UPS that didn't like the dirty sine wave. I had to replace it with one that had a generator setting so it's expecting the dirty power.
 
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neilhel

New Member
Joined
Dec 21, 2021
Messages
3
The Growatt thinks it's back on utility power so the generator needs enough capacity to power whatever is on bypass as well as the battery charger. As for this generator, I've used it many times over the years and none of the electronics in my home were adversely affected except for an APC UPS that didn't kike the dirty sine wave. I had to replace it with one that had a generator setting so it's expecting the dirty power.
 

neilhel

New Member
Joined
Dec 21, 2021
Messages
3
Thanks. Could you run run a separate charger off of the generator connected straight to the battery while the battery is powering the inverter?
 

Brett V

Solar Addict
Joined
Apr 5, 2021
Messages
311
I think the Inverter generator is a much better machine and wish I could justify it, but this test was done with a lot of unnecessary loads to simulate a worst case scenario and the Growatt was very forgiving of what it was fed. The Harbor Freight inverter generator for sale has only 124 hours on it and at $1700, is a bargain. I'll save that cash for the aforementioned ground mount I have planned for next summer.

So the warden stepped in and said she wanted me to go ahead and get the inverter generator. I've learned over 30+ years to follow instructions.
 
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