I have a 12kW Growatt split-phase inverter (SPF-12000T-DVM) powered by 8 6V 390AH batteries (Discover Energy EVL16A-A). I have it set up specifically for backup power so I am not using the solar input. I have solar, but it's connected on the grid side. I have a 100A critical loads panel on the output of the inverter.
On the input of the Growatt I have a switch to go between grid and a generator input. My generator is a 12kW dual-fuel unit that does 8100W running on propane (King Canada KCG-12001GE-DF). The idea is that if I have an outage that lasts more than a few hours I can hook up the generator and power the critical loads and allow the Growatt to charge the batteries some. The load for the circuits on the output is typically between 1500W and 2500W so I figured I had plenty of overhead.
A while back we got our first outage that lasted long enough to warrant use of the generator. It did not go very well. Most of my UPS units hated the generator power, switched to battery power, and shut down. The batteries were charging very slowly, so I tried to increase the charging amps on the Growatt so I could charge them quicker, but that just overloaded the generator. I found that I was able to keep it somewhat stable stable charging at 20A, but some of the UPS units were still unhappy and 20A is below the recommended minimum charge current of the batteries (0.1C * 390AH = 39A).
So it seems to me that the best play would be to decouple the generator and the inverter and simply use the generator to power a charger and charge the batteries while the Growatt is using them. As far as I can tell from searching this forum and other sources, that this would be OK.
However, I have some questions about implementing this.
First, it looks like I need to push between 39A and 97.5A to the batteries, but 48V chargers that can push those amps are extremely hard to find. I found the MEAN WELL DBU-3200-48 charger via this forum and that looks like an attractive option at about $1k CAD. However, if I am pulling 2500W at the same time, the Growatt would effectively be consuming the full output of the charger, and the batteries would not be charging at all, and even at 1500W I would effectively be charging at about 21A.
The next thing I would like to know is where I should hook this up. Between the battery positive and the Growatt I have a Blue Sea battery switch and an Eaton Bussman fuse. On the negative side I have a Victron Smart Shunt. Where should the positive and negative of the charger go? Should I get another switch and fuse and tie together on the load side? The battery side?
On the input of the Growatt I have a switch to go between grid and a generator input. My generator is a 12kW dual-fuel unit that does 8100W running on propane (King Canada KCG-12001GE-DF). The idea is that if I have an outage that lasts more than a few hours I can hook up the generator and power the critical loads and allow the Growatt to charge the batteries some. The load for the circuits on the output is typically between 1500W and 2500W so I figured I had plenty of overhead.
A while back we got our first outage that lasted long enough to warrant use of the generator. It did not go very well. Most of my UPS units hated the generator power, switched to battery power, and shut down. The batteries were charging very slowly, so I tried to increase the charging amps on the Growatt so I could charge them quicker, but that just overloaded the generator. I found that I was able to keep it somewhat stable stable charging at 20A, but some of the UPS units were still unhappy and 20A is below the recommended minimum charge current of the batteries (0.1C * 390AH = 39A).
So it seems to me that the best play would be to decouple the generator and the inverter and simply use the generator to power a charger and charge the batteries while the Growatt is using them. As far as I can tell from searching this forum and other sources, that this would be OK.
However, I have some questions about implementing this.
First, it looks like I need to push between 39A and 97.5A to the batteries, but 48V chargers that can push those amps are extremely hard to find. I found the MEAN WELL DBU-3200-48 charger via this forum and that looks like an attractive option at about $1k CAD. However, if I am pulling 2500W at the same time, the Growatt would effectively be consuming the full output of the charger, and the batteries would not be charging at all, and even at 1500W I would effectively be charging at about 21A.
The next thing I would like to know is where I should hook this up. Between the battery positive and the Growatt I have a Blue Sea battery switch and an Eaton Bussman fuse. On the negative side I have a Victron Smart Shunt. Where should the positive and negative of the charger go? Should I get another switch and fuse and tie together on the load side? The battery side?
