winter plans

In April I wrote about using a more limited snowbirding loop to reduce expenses. This has worked so far, and my average monthly spend has been reduced.

I understand there is a Jewish saying something like “God laughs when men make plans” and sometimes reality intrudes. My presence is required/appropiate where my family lives so I will be wintering in northeast Texas.

but first, El Paso

I have V.A. medical appointments (3) in El Paso that require me to be there (as of this writing) between Nov 16th-27th. After that I will continue on to NE Tx.

how NE Tx will be different

insolation

Solar wattage	750
Month	Daily Wh Avg
Jan	1772
Feb	2142
Mar	2824
Apr	3583
May	3978
Jun	4475
Jul	4501
Aug	4048
Sep	3404
Oct	2595
Nov	1989
Dec	1613

That December number is ~24% less than the sun available in El Paso. It’s also less than the 1.76kWh average I’ve used daily over the past 5 years.

I definitely won’t be able to cook from solar power.

temperature

There is about an 80% chance of seeing temps below 20F. I follow mild weather so my rig is not set up for freezing temps. I should probably keep the interior ≥40F to keep the plumbing safe.

Keeping the mattress pad running constantly at level 2/8 for my and Muffin’s comfort would take ~576Wh/day, about a third of total available power. If the battery warmer is maxxed out it will also consume another 384Wh/day, so now we are using 2/3rds of the available solar just to maintain comfortable temps for the batteries and doggo.

shore power

I think I will have to augment with shore power. Luckily, it’s already set up.

12A input

Power comes through a shore power port and into a breaker box with a 12A breaker. I did it this way so I could not trip a 15A breaker from a donor site.

So we have 1,440w to play with.

converter

The “converter” is a DIY rig that uses the 10A MPPT otherwise used for portable panels:
breaker box -> 24v 10A power supply -> MPPT controller -> battery bank

Since shore would be (gentle) supporting battery charging I’ll probably set that MPPT up to hold something like 13.0v. That should let the bank relax at night.

13.0v x 10A is 130w, so let’s call this 150w after losses.

120VAC

There is a single 120vac GFCI outlet fed by the breaker box. I used it during the build to run lights and power tools. I figure this winter it will be running a thermostatically-controlled electric space heater on LO, ~750w. It will be interesting to see if 750w can hold the van interior safely above freezing in <20F weather. I think it will (~75% confident).

total AC demand

This puts my demand on shore power at ~900w when everything is running at once. My extension cord is rated for 10A so I think we’ll be ok. If I need more heating power it will require a heavier cord. We shall see.

water

I’ll have access to water from the garden hose, so I can fill my tank as required.

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