Charging LiFePO4 With an External Generator Through an Inverter

[Timothy]

I have three SOK 270AH LiFePO4 batteries and a Victron inverter along with solar. I am getting ready to do some boondocking. I want to buy an external generator that I would plug into my system through the shore power connector and use that to charge my batteries as needed. In my mind, the power from the generator should be essentially like shore power from a pedestal. If I turn on the inverter, I expect the inverter will direct power to the batteries to charge them and also manage the process along with the BMS system. But, I read in an article you should not charge your batteries through an inverter.

Am I wrong to take this approach? Should I instead buy a compatible battery charger, connect it to the generator, and then connect the charger to the batteries? Much more convoluted IMHO.

I appreciate the help.

Thanks

[TucsonJim]

I have three SOK 270AH LiFePO4 batteries and a Victron inverter along with solar. I am getting ready to do some boondocking. I want to buy an external generator that I would plug into my system through the shore power connector and use that to charge my batteries as needed. In my mind, the power from the generator should be essentially like shore power from a pedestal. If I turn on the inverter, I expect the inverter will direct power to the batteries to charge them and also manage the process along with the BMS system. But, I read in an article you should not charge your batteries through an inverter.

Am I wrong to take this approach? Should I instead buy a compatible battery charger, connect it to the generator, and then connect the charger to the batteries? Much more convoluted IMHO.

I appreciate the help.

Thanks

You may be fine, but let's clarify.

Inverter: Uses 12V DC battery power to create 120 volts AC power
Converter: Uses 120V AC shore power to create 12V DC power to charge the batteries and provide power for items like lights.

If you are using a generator to plug into the shore power outlet, it's no different than plugging into a shore power pedestal. The Converter/charger (not inverter) will charge the batteries just fine. But it gets a little more complicated. Unless your converter is dedicated to charging lithium batteries like yours, they will not achieve 100% state of charge. But they will charge up to 85-90% which may be just fine.

What you never want to do is turn on an inverter if it is wired such that it provides power to the converter. That doesn't work.

EDIT: I missed that it was a Victron Inverter. If it's a Multiplus, you'll be fine running the generator through the shore power connection. The Multiplus is an inverter/charger and will charge the batteries.

Jim

[acoleman43]

Timothy I agree with Jim. Which Victron Inverter do you have and how is it connected to the trailer electrical system?

[Timothy]

acoleman43, I have a MultiPlus-II 2X 120V, 3000VA 12-Volt Pure Sine Wave Inverter and 120 amp Battery Charger. as for how it is connected, I have a Victron Lynx Distributor, Smart Shunt, MPPT solar charger (don't recall the size at the moment), and 1200 watts of solar on the roof. I also have the Cerbo. I think I am forgetting something. But, I think that's the basic set up.

[Timothy]

My next order of business is to try and size the generator. Frankly, a big consideration will be weight. I am looking at something with about 3700 watts continuous power because that is the maximum weight I think my son and I can handle without a crane. Not sure it will be able to get me to a full charge on the batteries, but at least keep me going. My issue is I am working on the road so if we boondock (and we will soon), I have to have a backup source of power if it isn't sunny enough to run the solar.

[acoleman43]

acoleman43, I have a MultiPlus-II 2X 120V, 3000VA 12-Volt Pure Sine Wave Inverter and 120 amp Battery Charger. as for how it is connected, I have a Victron Lynx Distributor, Smart Shunt, MPPT solar charger (don't recall the size at the moment), and 1200 watts of solar on the roof. I also have the Cerbo. I think I am forgetting something. But, I think that's the basic set up.

The Multiplus II is an Inverter/Charger (I'm assuming the 120A charger you are referring to is the Multiplus II). If you have shore power running through the Multiplus II then to your main distribution panel (it looks like that is your setup), a generator connected to shore power will charge your batteries through the Multiplus II just like shore power would charge the batteries.

A generator is a great backup. We also have 1200W of solar, just over 10KWH of batteries, and still needed a generator to top off batteries when we were back east. Cloud cover 24 hours a day or under trees does not charge the batteries. We have a 3600W generator which we would have to run about 2-3 hours every other day to keep batteries where I wanted them. Without the generator we would have been in trouble.

[Timothy]

acoleman43, Thanks for the feedback. Then the generator I am looking at sounds like a good choice.

[steveluannj]

2 2000W generators and a parallel kit is also worth considering. They are easier to move around, you can use 1 when you don't need full capacity, and if one fails, you are not totally out of luck.