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Old 10-12-2011, 01:54 PM   #1
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KyDan's Avatar
Join Date: Mar 2008
Location: Louisville, KY
Posts: 9,916
Charging batteries with a portable generator

I have 2 12v batteries in parallel. Nothing exotic or deep cycle.
I just take
the battery box top off one and clip on a 25 Amp charger.
Then I start my Honda EU2000i and turn on the charger. After an hour
that charger will be starting to slack off amps. At that time
I plug in the trailer to the generator so my power center/converter
is also online.
This is how I do it. I am not telling you to use a charger and onboard
power center at the same time but that's what I do if I'm in a hurry.

(Actually each charger is working less when both are online but the total
amps into the batteries is more.)

When charging via generator and RV power cord there are things you need to make sure are
Turn off your electric water heater and make sure your refrigerator
is on LP only. Also some dometic fridges have a condensation switch
that turns on a little heater that warms the metal strip between
the fresh food and freezer doors. IT RUNS ON DC!!! Sheesh, what were
they thinking?!? You want THAT thing off anytime you are on battery
or generator. Who cares about a little condensation, we're trying
to go as long as possible while staying off the grid!

I have an LED bulb in the bathroom and one over the sofa. We also
have a thin-lite fluorescent over our table. We use these exclusively
when on battery. Other incandescent fixtures we pull out one bulb
and only use them briefly when needed.

Doing this we are able to go 5 nights using our maxxair fan on low
each night and watching an hour or so of TV using a little
cigarette socket inverter.
We normally watch at least one DVD movie and will pump most of a
full tank of water. This June we stayed in Shenandoah NP 5 nights
and the day we left our water pump still sounded peppy.
I did not use my generator at all that trip.

Last fall we spent 5 nights in Cumberland Gap NP and it was down in
the low 30s at night. We ran our LP furnace a couple times a night
and needed a charge on the 4th morning. 2 hours using the dual charge
method seemed to give me a pretty good boost. I ran it during
breakfast and we could hear others in the neighborhood doing the

I used to have one of those little 2 cycle gennys. It was so loud!
I often wondered if there wasn't some way to put a good muffler
on it but never tried anything. I think a box full of some sort
of foam baffles set in front of the exhaust would help but you
have to consider fire danger if you have it too close. Also the
2 cycle exhaust has some oil mist in it so the foam baffles might
become coated and even more prone to combustion.
I dreamed of getting a small car type muffler and some flex pipe
and jury rigging something but gave it to my son instead.
I really think it could be done for not a lot of buck$.

My lovely wife talked me into getting a Honda 2000 and it's pretty
quiet but if I could go back in time I'd get the 1000. It's a little
bit cheaper and a little bit quieter and a little bit lighter. I was hoping the
2000 would run my roof AC but it only will start the compressor
on a cool day at low altitude. The 2000 will run the microwave but
we can do without that on the few occasions we're boondocking.

As far as charging trailer batteries while on the road--
Most trucks today have 100 amp alternators. You don't want it running
full blast at 100 amps very long or it will over heat but I don't
think you'd need to upgrade it to get some boost to your batteries.
You do need to run large wire from engine battery to trailer battery.
The wires in your rear bumper plug just aren't usually large enough to
get much charge in the trailer batteries.
I think just running large wire from truck battery to trailer
batteries would make a difference. Just my opinion.
Once upon a time someone mentioned a 12v to 12v charger they
had seen online. It boosted the voltage and was made specifically
to charge batteries while on the road like a bass boat could
charge his trolling battery on the way to the lake or a golfer
could boost his golf cart while on the way to his golf course.
It was pricey but sounded like it would do the job if you really wanted
to stay off the grid and were going to be moving place to place
every few days.
I don't remember what it was called, sorry.

Hope this helps!
Happy camping!
Dan & Rita D
2017 Nissan Titan 5.6L King cab 4wd
1999 Suzuki Intruder Motorcycle
Blue Ox WD hitch

Camping days 2010-53, 2011-47, 2012-41, 2013-41, 2014-31, 2015-40, 2016-44, 2017-63, 2018-75, 2019-32, 2020-41, 2021-49
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