On Fri, 26 Feb 2016 03:31:22 -0800, wrote:

On Friday, February 26, 2016 at 10:59:10 AM UTC, David wrote:
This first post is a place holder in part, so that I don't forget to
ask the question, as I usually do once I get involved in stuff during
the day.

The Motor Home has mains powered habitation air conditioning - that is
an ELectrolux slug on the roof.

So for it to work you need to be on a site with mains electricity.

There is also the issue of the power surge on start-up compared to the
power demand on normal running.

What I would like to be able to do:

(1) Run the A/C whilst driving - that would I assume involve an
inverter which could take power through the 12V electrics buffered by
the habitation batteries (unless the demand needs a direct connection
to the alternator charging circuit instead of via the charge controller
which charges the habitation batteries). This also allows starting the
engine, firing up A/C and then stopping the engine and letting the A/C
run on using the habitation batteries.

(2) Run the A/C when away from mains power - using a small Honda
generator which might be able to meet most of the demand apart from
start-up. I am envisaging perhaps the generator pushing power into the
system whilst the A/C takes power out so that the use of habitation
battery charge is slowed. This probably equates to running a UPS (that
is, power in to UPS for charging, power always out of UPS for running
the device) and using a small generator to keep feeding some power into
the UPS during a power cut. The generator may not fully meet the power
demand but it slows the rate of discharge.

This does seem to demand a lot of inefficiency, though, potentially
with the generator input being converted from 240V to 12V then back
again. It would be nicer if the battery 12V power could be used to
boost the 240V input from the generator so that most of the power comes
directly in at 240V.


Bottom line is that one way may require blending two 240V inputs into a
single output, with obvious (I think) requirements to lock the wave
forms of the 240V together.

If I can manage ASCII art:

12V - 240V - Blender - A/C 240V -----------^

I think this is probably not realistic because you would have to
prevent back flow which is why there are so many issues with combining
power inputs connected to the grid. Then again, it is only like
combining a solar panel and mains (but that does allow back flow into
the grid).

I need to dig out the handbook for the A/C to check all the power
demands,
but meanwhile does this sound in any way feasible?

I know (2) could be met by just buying a bigger generator, but I bought
the little Honda because I could just shoehorn it into the available
storage and anything bigger is too tall/wide to fit anywhere usable.

Cheers


Dave R


--
Windows 8.1 on PCSpecialist box

Non starter. Aircon requires an immense amount of energy that you are
just not going to get out of the 12V system or a battery.

You possibly could add an aircon compressor to the engine if there is
space for one and all the other components of course (many engines just
substitute an idler pulley instead of the compressor if the aircon
option isn't chosen) but it would be hugely expensive.

Probably better all round to open the window when driving and sit
outside in a deckchair when camped without leccy hookup.

Philip

There is already cab aircon which is fine for driving along and can also
cool the interior of the MH unless it is really hot - keeps the cab cool
but the interior of a MH has a lot more volume than a van cab or a car.

Also does not solve the 240V issue as you would have to run the engine all
the time even when you are on a powered site.

Also not good to cool the van when you are out at the beach - which seems
to be one of the favourite reported usages.

Cheers


Dave R



--
Windows 8.1 on PCSpecialist box