# Could you use an inverter generator as a battery charger?

#### zirconx

Joined Mar 10, 2010
154
I'm interested in being able to recharge 12v batteries when camping off the grid. Most generators I've looked at do have a 12v output, but they are limited to around 10A.

I did find some gas powered 12v chargers, but they are very expensive (like $2000). I was thinking about an inverter generator such as this Generac or the popular Honda. Aren't these just 12v alternators/generators driving an inverter? Do you think I could tap the 12v output and use it to charge a battery directly? Or worse case, maybe drive a DC-to-DC charger with it? #### drjohsmith Joined Dec 13, 2021 397 I'm interested in being able to recharge 12v batteries when camping off the grid. Most generators I've looked at do have a 12v output, but they are limited to around 10A. I did find some gas powered 12v chargers, but they are very expensive (like$2000).

I was thinking about an inverter generator such as this Generac or the popular Honda. Aren't these just 12v alternators/generators driving an inverter? Do you think I could tap the 12v output and use it to charge a battery directly?

Or worse case, maybe drive a DC-to-DC charger with it?
The generators you show, look like they are "mains" , 240 or 110 V
they will not have "12v" inside, they go streight to the mains voltage,

Batteries can not be "just connected" to a voltage to charge,
you need to use a controler circuit, a battery charger,

Is there not a mains to the batteries you want to use charger around ?

#### Alec_t

Joined Sep 17, 2013
12,815
A 12V battery needs around 14.5V to charge it fully, so neither a 110VAC output nor a 12VDC output would be suitable for direct connection to a '12V' battery. As said above, a charger/controller would be needed too.

#### zirconx

Joined Mar 10, 2010
154
The generators you show, look like they are "mains" , 240 or 110 V
Are you sure? I thought inverter generators used an inverter. And therefore are probably fed with DC?.....

Ok I just did some googling, which I should have done before posting. I learned that an inverter generator still uses a shaft driven generator that creates AC, which gets rectified and fed to an inverter. Ok so it doesn't generate DC directly, but perhaps the rectified DC could be used to power a DC-to-DC charger.

...Batteries can not be "just connected" to a voltage to charge,
you need to use a controler circuit, a battery charger,

Is there not a mains to the batteries you want to use charger around ?
No, when we are camping in a remote area for example, there are no mains available.

Yes I agree one option is to just use a regular 120v-to-12v battery charger plugged into the generator. I was wondering if a step could be skipped, and just use the DC directly and more efficiently.

#### debe

Joined Sep 21, 2010
1,294
The 12V DC charger socket on inverter gen is generaly around 10A or less. They are not regulated at all & will go as high as 15V or more as the battery reaches full charge, so need to be monitored. Its far better to use a mains charger thats regulated on a generator to charge a battery. I use a 30A regulated mains charger on my Inverter gen.

#### debe

Joined Sep 21, 2010
1,294
This is the circuit of a couple of typical inverter generators. As you can see the 12V DC charge is very basic & not regulated at all.

#### drjohsmith

Joined Dec 13, 2021
397
Are you sure? I thought inverter generators used an inverter. And therefore are probably fed with DC?.....

Ok I just did some googling, which I should have done before posting. I learned that an inverter generator still uses a shaft driven generator that creates AC, which gets rectified and fed to an inverter. Ok so it doesn't generate DC directly, but perhaps the rectified DC could be used to power a DC-to-DC charger.

No, when we are camping in a remote area for example, there are no mains available.

Yes I agree one option is to just use a regular 120v-to-12v battery charger plugged into the generator. I was wondering if a step could be skipped, and just use the DC directly and more efficiently.
I was referring to the "mains" from the generator, not provided on site,

The 12V out of these generators, is akin to the 12V socket in some older cars,
it has no regulation, at most a fuse,

If you have a generator,
just plug in a mains from the generator battery charger.

#### bassbindevil

Joined Jan 23, 2014
422
If it's unregulated full-wave unfiltered, that's the same as millions of old-school unregulated car battery chargers out there (though those often have selenium rectifiers which add some series resistance). I expect that name brand generators like Honda deliberately designed that output for battery charging, but with new stuff from China who knows. Connect it through an ammeter (if possible) and monitor the battery voltage, and you may well find that charging current drops off before it reaches 15V. Occasional overcharging is desirable with lead-acid batteries to equalize the cells.