DC petrol generator for charging RV LiFePO4 battery

[Stever73]

Hi all,
my RV is gas-free, it relies on a 8s 300Ah LiFePO4 battery for all the utilities like induction cooktop, air con, lights and so on, except for the heating and water that run on diesel.
I was able to install 700Wp solar panels on the roof and that’s enough in summertime when the sun shines, but winter and cloudy days are a different scenario and the battery lasts for 3 days.

Looking for a quick way to put some power in the battery whet it runs out, I found these chinese DC petrol generator that can output around 3Kwh and I was wondering if anyone has had a chance to test them out and what are the advantages/disadvantages.

Here’s a link to see what I’m talking about on Aliexpress.
WSEPO WSE3000FA 3KW Silent AutoStart/Stop Autochoke/Throttle Smart Gasoline DC Extender Generator

 

[SamDeleted]

there's nothing better than a Honda , I'd go for quality secondhand over brand new rubbish anyday of the week

 

[Stever73]

there's nothing better than a Honda , I'd go for quality secondhand over brand new rubbish anyday of the week

Honda doesn’t make any DC generator. I know they’re good, but they’re AC inverter generator.

 

[Hedges]

The Honda or other typical generator of course will need a battery charger to convert AC to regulated DC.
This DC generator, need to regulate or cut off as soon as battery voltage reaches target. Lead-acid would be more forgiving that Lithium. We prefer not to rely on BMS disconnecting for regulation, should be backup protection only.

Would be nice for an RV to do "combined heat and power", capture the 2/3 of energy wasted as heat. Of course that is extra weight and mass, typically done for off-grid homes. I wonder if exhaust pipe could do heat exchanger to water. (avoid heat exchanger directly to inside air, because an exhaust leak would be carbon monoxide hazard. Be careful with generator placement and where exhaust blows. Even vented outside it can get pushed back to the home.)

The latest Honda would have far cleaner exhaust than unknown Chinese models. Some also have carbon monoxide detectors. Dirty generators of course can be used, but keeping the exhaust away from living space is important.

 

[Hedges]

You could mount a 24V alternator on your RV engine. Do you ever drive it during these times? Large engine, likely less efficient at making 3kW than a small one. But convenient and safe.

 

[pollenface]

I've had a cheap chinese 1kva genny for a few years, I start it every couple of months to keep it fresh, I just run a 20a battery charger from it and it gets me by in times of need.

 

[Stever73]

I've had a cheap chinese 1kva genny for a few years, I start it every couple of months to keep it fresh, I just run a 20a battery charger from it and it gets me by in times of need.

Hi, I guess it’s an AC generator since you’re using a battery charger, not a DC generator.

 

[Stever73]

You could mount a 24V alternator on your RV engine. Do you ever drive it during these times? Large engine, likely less efficient at making 3kW than a small one. But convenient and safe.

Everything can be done of course, fitting a second alternator would be a tricky but not impossible job. Anyway a ”normal” alternator isn’t engineered to run at 100% power for all time. In addition, a completely empty LiFePO battery can draw a huge amount of current and an alternator without a DC/DC current limiter would blow up quickly. So between powerful alternator, DC DC and the works it would be more expensive and less efficient.
There are marine alternators specifically engineered to recharge lithium but they’re way too expensive, around 3K. The Chinese gen I’ve posted is around 500USD ?

…
This DC generator, need to regulate or cut off as soon as battery voltage reaches target. Lead-acid would be more forgiving that Lithium. We prefer not to rely on BMS disconnecting for regulation, should be backup protection only.
…

The generator I’ve posted will start automatically at 24V and stop at 28V, perfect for 8s LiFePO4

 

[DThames]

Everything can be done of course, fitting a second alternator would be a tricky but not impossible job. Anyway a ”normal” alternator isn’t engineered to run at 100% power for all time. In addition, a completely empty LiFePO battery can draw a huge amount of current and an alternator without a DC/DC current limiter would blow up quickly. So between powerful alternator, DC DC and the works it would be more expensive and less efficient.
There are marine alternators specifically engineered to recharge lithium but they’re way too expensive, around 3K. The Chinese gen I’ve posted is around 500USD ?


The generator I’ve posted will start automatically at 24V and stop at 28V, perfect for 8s LiFePO4

Others have said this but I will repeat it......depending on the size of your battery, the battery load might be more than your power source can handle. The battery could effectively stall the generator or burn it up, if there was not some type of current regulator between the battery and the generator. It might be built in. You should ask, "What limits the current that goes into the battery while charging?"

 

[Stever73]

…
"What limits the current that goes into the battery while charging?"

The generator output is regulated, the limit is 100A, it won’t produce more than that.

 

[Deveak]

Products - Smart alternator regulator

This might help, haven’t tried it but I’ve been eyeballing it. Looks like they updated it to cover lithium. That’s about 180 bucks with 25 dollar shipping to the US.

Most smart regulators are marine stuff and falls under the B.O.A.T. category. Bust out another thousand.

 

[Nobodybusiness]

Hi all,
my RV is gas-free, it relies on a 8s 300Ah LiFePO4 battery for all the utilities like induction cooktop, air con, lights and so on, except for the heating and water that run on diesel.
I was able to install 700Wp solar panels on the roof and that’s enough in summertime when the sun shines, but winter and cloudy days are a different scenario and the battery lasts for 3 days.

Looking for a quick way to put some power in the battery whet it runs out, I found these chinese DC petrol generator that can output around 3Kwh and I was wondering if anyone has had a chance to test them out and what are the advantages/disadvantages.

Here’s a link to see what I’m talking about on Aliexpress.
WSEPO WSE3000FA 3KW Silent AutoStart/Stop Autochoke/Throttle Smart Gasoline DC Extender Generator

I have this one.

alphagen dcx3000 - Google Search

It’s a telecom generator so selectable 36/48v but only generates about 53v max.

Works better than nothing and quiet.