Only using fridge to make ice...?

[rruff]

...with 30lbs of LFP Ive now got an energy surplus

That's a 100Ah battery? That's about what I'm looking at *not* needing to get 4 days of no-sun refrigeration capacity... and that's minimal use (no new beers added!). Freezing ice packs or adding an extra 100Ah LFP battery, what will it be? It appears those batteries aren't getting any cheaper. Still near $1,000.

 

[dreadlocks]

if all I have is water in there yeah, but ive also got all the other food thats mostly water.. and if a few pouds of it are frozen, like a big slab of bacon or two then all that changes.. its not so cut and dry, its also colder at night so if your cooling in the day w/extra solar when its heat loss rate is highest, and then coasting at night or overcast when heatrate loss is the lowest your also throwing all your calculations off.

yeah just a single 100AH battery, with 650W of solar backing it.. charges up in ~2.5h, chances of going 4 days w/out 2.5h of sun are much smaller than going 4 days w/out 8h+ of sun.. especially when its not summer solstice and the light is hard to get through the canopy and days are shorter.. I keep a small genset for dire emergencies, it gets really hard in PNW to get any sunlight.. but if yeh only hadda burn gas for 2.5h every 4 days the idea of it becomes far less offensive than running it for a full day solid when its tapped out.. its also not just idling the whole time wasting more energy than its storing.. putting energy into and pulling it out of LFP is like >98% efficient.

When you calculate weight of my LFP (30#) and my Solar Panels (80#) and my Genset (40#) they are roughly the same as a pair of GC2 FLA's alone (150# total).. not only does it perform so much better and go indefinitely in any conditions, I can spread its weight out on my trailer so its not all on the tongue.. but as they say, you gotta pay to play.. and saving weight is never cheap.

 

[rruff]

yeah just a single 100AH battery, with 650W of solar backing it

That's a lot of solar! I can't put panels on the roof because they wouldn't survive. I can probably get ~150W on the hood and the rest would have to be portable. I got some Chinese cells I can solder into a pack to get ~120Ah. Besides refrigeration the main power draw will be laptops... especially if we play games at night! If the video cards are cranking, figure about 150Wx2 but only for a couple hrs. Still that's 600W-hrs. But also something we can easily *not* do if necessary.

I might rethink the panels on the roof... put some angle up to protect them. The problem even if that works is that I won't *always* be parked in the sun, so I'm back to portable.

It's an interesting problem, managing your personal mobile power system! Can't cover every contingency... and when I'm out there, history has shown that I don't care if I have to do without something for awhile.

 

[shade]

I have several HDPE Nalgene bottles that get used to fill space, provide thermal mass. The rectangular ones pack easier than typical outdoor recreational round ones. You see them sometimes at outdoor stores but the larger ones are usually considered lab ware. They come in lots of sizes up to 64 ounces and they even make 5, 10 and 20L monster carboys if you want to fill lots of space.

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View attachment 570713

I use 1L Platypus bottles in the role. Under filling them allows the bottles to easily conform and take up minimal space. With the cupholder inserts removed, they fit in my truck's front bin well. A little floppy, but manageable, with no waste involved.

 

[john61ct]

Yes, willingness to compromise is the key to affordably and sustainably living off grid.

The "modern conveniences" so many first-worlders take for granted are usually unnecessary, best thought of as "nice to have".

And we all have our priorities to be balanced, as well as resources available. Even refrigeration is optional for me, but internet access, only for a few weeks at a time, and playing music maybe a couple days.

Stuff like a dishwasher using electricity to dry clothes, I find unacceptable even living S&B

 

[dreadlocks]

yeah it is a ton of solar but LFP can take it, a pair of panasonic HIT 325W panels.. one is fixed on roof w/angle iron protection and the other is stored inside for portable use, I need to fabricate up a hanging system to drape it off the outside vertically, was going to use my rear gate but found a better spot on the side, its just the side 6in from my fence so I gotta wait til later this year when I pull it out of the back to work on it.

Combination of fixed and portable is very nice on a trailer, I get full charge while driving and have even refilled the batteries and cooked a meal in a crockpot tied down on an overcast day.. most of the the time im parked in a shady spot but it does usually get a lil bit of sun on top in the summer, enough that both panels see full output for an hour or so and its full by noon after using 60AH overnight.. in fall-spring its almost all up to the portable panel unless I'm in the desert w/nothing casting shade for 100s of miles.. at worst case just the 325W portable alone and a few hours of sunlight can push me off from bringing out the generator for quite a while.. its not usually until we're taking long trips in October we have an issue, winter/spring I'll tend to venture into the southwest deserts and solar is back on the table despite the short days..

I don't see need of severe energy savings most of the time anymore, even just using LFP as a buffer to get me through the day I dont mind running genset for an hour or so daily, total runtime is equal to a lead bank big enough to go 4 days.. and with a 60AH day diet, thats like a 480AH lead bank to match my usage and generator runtime in worst case w/little solar assistance.. so >300lbs of lead equivalent in engine runtime metric.. thats an order of magnitude in weight savings.