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Re: off-grid - battery & winter 12V-generator?

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On 7/30/26 8:11 AM, Richard Smith wrote:
> Somethign you folk from North America will be familiar with.
> 
> There is a 12V light, fridge and occasional inverter to mains-voltage
> system with 12V "leisure" lead-acid battery and photovoltaic (PV)
> charger and charge-regulator.
> 
> For winter when our days are short and sun not bright - would it be an
> efficient solution to have a small gasoline engine running a 12V
> generator eg. from a car?
> Would be efficient to have a small engine which runs full-power for a
> shortish time - something like an hour? - then stops.
> Smallest Honda "GX" engine is 100cc.
> Small engine+12V-generator & battery is much more fuel-efficient than
> running a generator supplying power on-demand?
> Tempting thought is - that would happen when it is dark and *cold* -
> therefore if you coudl recover the waste heat of the generator engine it
> would be welcomed.
> 
> I have no knowledge of this - anyone want to get this going?
> 
> Regards,
> Rich Smith

Over the last 6-7 years the number of brands of self-contained (battery, 
mains charger, solar controller, mains output inverter) "solar 
generators" or "solar power stations" has exploded.  The battery 
chemistry is now exclusively LiFePO4 for both safety over Li ion and 
charge cycle life.  The usual arrangement is to have separate power 
switches for DC output (12 V and USB charging ports) and mains AC output 
so you can optimize the standby draw, and battery life is usually at 
least 80% capacity remaining after 3000 full cycles (so one cycle per 
day is over 8 years).  Portable sizes range from 100 watt-hours to about 
3000 whr depending on what you call portable (3000 whr units are 
ballpark 70-90 lbs), with units past 5000 whr for home backup.  Many 
models allow external expansion batteries for even more storage capacity 
if you don't need more inverter wattage output.  Go to YouTube and 
search for "jasonoid", and pick one of his review videos at random (like 
https://www.youtube.com/watch?v=v5xK62HbILY) to get an overview of 
features and performance.  In the comments he always puts a link to a 
cumulative spreadsheet with all the specs and review results so you can 
get a quick overview of popular brands.  There are several yt channels 
that cover solar generators, I just think he does a thorough, 
knowledgeable, articulate job of it.

The most fuel-efficient way to use a gas generator with a solar 
generator is to only run the generator to charge the solar generator, 
and to match the gas generator rating to the maximum charging power of 
the solar generator so you are charging near the maximum rate the solar 
generator allows and the gas generator is close to it's rating (say 
withing 20% of the max for each).  That way the generator is near full 
throttle for best fuel efficiency and the noisy run time is minimized. 
The solar generator DC charging input for 12 volt charging is limited by 
the current rating of 10 amps on the usual cigarette lighter socket on a 
car and 12V * 10 A is only 120 W so charging even a smallish 500 whr 
solar generator will take nearly 5 hours.  Most larger solar generators 
need at least 30 volts DC input for charging to get faster charging and 
to keep the wire size from getting out of control so the simplest way is 
to use a standard mains output gas generator and charge using the mains 
input on the solar generator.  Again, to keep wire size reasonable the 
usual plan is to wire solar panels in series so the current stays small 
and the voltage goes up so for medium and large solar generators the DC 
input (you can feed this port from either a battery bank or DC generator 
or solar panels) range is usually about 30 V minimum and 60-200 V 
maximum.  Many large generators will accept 12 VDC for charging either 
on the main port or on a separate lower power input but that's mostly 
for historical reasons and probably never used on any solar generator 
larger than 500 whr because waiting 2+ days to charge is just not 
practical :-).

My quick take as someone who started with a 500 whr unit and a small 
solar panel six years ago to make sure I could keep my CPAP running in 
case of a power failure and now has a 2400 watt solar array and 3000 whr 
solar generator that I use to charge my PHEV car and home essentials 
backup if needed.

-- 
Regards,
Carl

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Thread

off-grid - battery & winter 12V-generator? Richard Smith <null@void.com> - 2026-07-30 13:11 +0100
  Re: off-grid - battery & winter 12V-generator? Carl <carl.ijamesXX@YYverizon.net> - 2026-07-30 10:25 -0400
    Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-07-30 14:37 -0400
      Re: off-grid - battery & winter 12V-generator? Carl <carl.ijamesXX@YYverizon.net> - 2026-07-30 16:17 -0400
        Re: off-grid - battery & winter 12V-generator? Richard Smith <null@void.com> - 2026-07-30 21:33 +0100
          Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-07-30 19:12 -0400
    Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-07-30 15:22 -0400
  Re: off-grid - battery & winter 12V-generator? bp@www.zefox.net - 2026-07-30 15:45 +0000
  Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-07-30 13:56 -0400
    Re: off-grid - battery & winter 12V-generator? Richard Smith <null@void.com> - 2026-07-30 21:49 +0100
      Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-07-31 08:23 -0400
    Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-07-30 22:47 -0400
  Re: off-grid - battery & winter 12V-generator? Bob La Londe <none@none.com99> - 2026-07-31 11:27 -0700
    Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-07-31 16:00 -0400
      Re: off-grid - battery & winter 12V-generator? Bob La Londe <none@none.com99> - 2026-07-31 16:30 -0700
        Re: off-grid - battery & winter 12V-generator? Clare Snyder <clare@snyder.on.ca> - 2026-07-31 22:23 -0400
        Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-07-31 22:46 -0400
          Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-01 09:14 -0400
          Re: off-grid - battery & winter 12V-generator? Bob La Londe <none@none.com99> - 2026-08-01 11:18 -0700
            Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-01 16:07 -0400
            Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-02 21:45 -0400
            Re: off-grid - battery & winter 12V-generator? Richard Smith <null@void.com> - 2026-08-03 21:13 +0100
              Re: off-grid - battery & winter 12V-generator? Bob La Londe <none@none.com99> - 2026-08-03 14:03 -0700
                Re: off-grid - battery & winter 12V-generator? Richard Smith <null@void.com> - 2026-08-04 13:10 +0100
                Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-04 10:04 -0400
                Re: off-grid - battery & winter 12V-generator? Bob La Londe <none@none.com99> - 2026-08-04 13:08 -0700
                Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-04 18:24 -0400
                Re: off-grid - battery & winter 12V-generator? Bob La Londe <none@none.com99> - 2026-08-04 15:47 -0700
                Re: off-grid - battery & winter 12V-generator? Bob La Londe <none@none.com99> - 2026-08-04 16:16 -0700
                Re: off-grid - battery & winter 12V-generator? Bob La Londe <none@none.com99> - 2026-08-04 16:30 -0700
                Re: off-grid - battery & winter 12V-generator? David Billington <djb@invalid.com> - 2026-08-05 00:35 +0100
                Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-04 23:02 -0400
                Re: off-grid - battery & winter 12V-generator? Richard Smith <null@void.com> - 2026-08-05 09:13 +0100
                Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-05 09:32 -0400
                Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-05 10:06 -0400
                Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-05 21:33 -0400
                Re: off-grid - battery & winter 12V-generator? Richard Smith <null@void.com> - 2026-08-06 05:34 +0100
                Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-06 09:39 -0400
              Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-03 18:23 -0400
    Re: off-grid - battery & winter 12V-generator? Richard Smith <null@void.com> - 2026-08-03 19:47 +0100
      Re: off-grid - battery & winter 12V-generator? "Jim Wilkins" <muratlanne@gmail.com> - 2026-08-03 16:10 -0400

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