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DIY Off-Grid Solar Power

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181–190 of 234 posts

Re: DIY Off-Grid Solar Power

#181

Earlier quoted context omitted.

Hypothetically, for the lithium batteries, what if you made a big stainless steel vacuum wall insulated enclosure? Or just a metal box with r-60 value of foam around it? The amount of heat needing to be generated can then be calculated based on the average temp over a longer period of time, and those batteries I don't imagine have to be "warm" exactly.

What about summer? Those batteries also need to stay cool...

They do not need to stay that cool at all. When used for solar, the C rate for charging usually never exceeds .2C for overpaneled systems. And usually never goes beyond .5C for discharge. So the heat generated is very small. Now when I am pushing 30-100C rates with a lithium polymer, cooling is an issue. this is why nissan leaf cells were recalled. The battery size was too small for the application, and they overheated which caused significant degradation rates. This is not an issue for solar. Just keep them at room temperature and they are fine.

Re: DIY Off-Grid Solar Power

#182

Earlier quoted context omitted.

I would love to have found that magical car battery that doesn't die after 5 years or so. But the real comedy is that my EV is required to have one of them independent of all the lithium batteries, and if it discharges/fails, it's a whole fan dance to get into the car.

>> it's a whole fan dance to get into the car. I've never jumped a full EV, but I have had to jump a couple hybrids after their 12v batteries ran flat. Can you not get to the 12v battery using a mechanical key? Any 12v jumpstart kit should provide enough voltage to activate the solenoid and get everything online.

The mechanical key on my EV, a Mustang Mach E, is a blank. but here's the fan dance to get into the car on a dead battery...

https://youtu.be/AKK_Vt1m5TA

Re: DIY Off-Grid Solar Power

#183

Marketing. I would take everything on this website with a grain of salt. Take it from someone who has actually built an off-grid system, one that is relied upon for 24/7/365 living rather than mere vacation cottage. For example: OP re lead-acid battery options: "Heavy, cheap, easy to use and they work! Typically will last about 3-5 years. Slower charge rates than lithium, much heavier, and they cost way more in the l…

Will Prowse here. Are you kidding me? Those lead acids are kept at a high state of charge and not deeply discharged. Sure some expensive FLA can last much longer, but they are garbage. The coulombic efficiency is horrible. The internal resistance is awful. If I sold lead acid batteries, I would make way more money. You have no clue what you are talking about. And yes, when used for solar and deeply discharged, your l…

Over the years, I've generally made the observation that those who really slam lead acid for energy storage use seem to have been nowhere near a modern lead acid datasheet from the last 20 years, and that seems to be the case here as well. They also tend to make assorted arguments in the context of off-grid power that don't reflect the realities of off-grid power systems in annual use.

The mid-range Trojan Solar Premium line (my office runs an older version of this, the T105-RE and I'm five years of daily cycling in with what seem to be entirely healthy batteries still) datasheet [0] shows a 3500 cycle life at 30% DoD, which is 10 years of daily cycling use. However, depending on loads, panels, and how you use the place, you'll typically see far shallower cycles in the spring/summer/fall, and then some deeper cycles in the winter months. So you can average it out - a single 80% discharge isn't going to have a huge impact on longevity, just don't do it all day, every day. If you've got enough panel area to recover a low battery bank in a good day or so of sun (generally recommended for off-grid), you'll have enough panel area to ride through daytime loads most of the year without really bothering the battery pack either.

The Solar Industrial line [1] is rated 3500 cycles at 50% DoD daily cycling, and about 6250 at 30% DoD. Good luck finding them, though.

They also, as has been discussed elsewhere here, don't need heating in the winter to be able to charge safely. I generally don't like charging lithium below about 45F, and even that would be a low C-rate. Not having to heat lead makes winter an awful lot easier.

As far as the rest of your claims... they mostly don't matter for a typical off-grid power system, which is the general context of this thread.

Coulombic efficiency for lead varies rather significantly depending on where in the state of charge, and it's not really reasonable to discuss "average" numbers for lead. Once you're full, up in absorb, the CE is quite poor, as it's gassing, but that's also required to mix the electrolyte and prevent stratification, so it's still doing something useful. However, the times when it matters - cold, dark winter months, if you're running partial state of charge cycling (which the modern carbon additives allow without the problems of hard sulfation), the CE during charging is quite good - near 100%, as long as you're below gassing. So when CE matters, when you're power limited, it's perfectly reasonable, and when it doesn't matter, when you have a surplus of power, it's poor. I don't particularly mind that.

As far as internal resistance goes, it's certainly far worse than lithium, but at typical off-grid C/20, C/8 type rates, it just doesn't matter that much. Nobody is asking deep cycle off grid lead to deliver starting amps for a tractor, and it won't do it, because it's a substantially different internal design than a starting battery (which have far lower internal resistance - go measure one sometime, it's pretty impressive just how low IR on a warm car battery is).

And my 48V/225Ah bank ran me $1400 about 5 years ago, and is about halfway through service life, or perhaps a bit less than half. To do that on a lithium chemistry would be quite a bit more expensive.

Plus, flooded lead acid lacks the energy density to do anything terribly exciting, as long as you give hydrogen generated from charging an "up and out" path. I consider this a feature for stationary storage.

And they're almost entirely recyclable (and actively recycled). It's a quite circular economy in the lead acid battery space.

Different chemistries have their places. For a somewhat overpaneled off-grid system in daily use, lead acid is still an absolutely reasonable chemistry (as quite a few people here are still observing).

[0]: https://www.trojanbattery.com/pdf/datasheets/SPRE_06_415_DS.... [1]: https://www.trojanbattery.com/pdf/datasheets/SIND_06_610_DS....

Re: DIY Off-Grid Solar Power

#184
post #179

Earlier quoted context omitted.

Tell that to my 12 year-old battery bank powering my family house (solar with diesel backup charge). It is a pack of deep cycle lead-acids that have served me very well. Of course they are watched and maintained regularly, and rarely ever dip below 75%. The only use case I've ever seen for lithium off-grid is for people who want to squeeze their entire rig into a closet or basement corner. And nobody ever talks about…

See, exactly proves my point. DOD is only 25%. If you do not cycle them much, you can make a lead acid last for years no problem. If you are doing 100% DOD, and do not with to deal with maintenance, and wish to have high coulombic efficiency, lithium is far better. Volumetric density is a side benefit of lithium. We use it for coulombic efficiency, low voltage sag, high cycle life (much higher than lead acid, regardl…

Solar2 == willprowseiv? Brand new account responding as such, at least.

Which production lithium ion recycling companies are "dominating the space" and actually recycling more than test quantities of cells? Apparently I've missed that in the past few years - links to them?

Re: DIY Off-Grid Solar Power

#185
post #2

Will Prose seems like a really great person. If you’re interested in what you see on this site, check out his YouTube channel: https://youtube.com/c/WillProwse

> Will Prose seems like a really great person.

My opinion of him after his attempts to interact in this thread (turn "show dead" on - a bunch of his more arrogant/abrasive posts have been killed, and it looks like he's posting as Solar2 as well) is now far, far lower than it was.

Re: DIY Off-Grid Solar Power

#186
post #8

I recently set up my own off grid solar system in a tiny cabin that I designed and had built. I used the Solar Controller+Inverter Combos recommended on this site (Growatt) but ultimately switched to ones by Renogy. The Growatt one I purchased has a wifi adapter and app - wifi requirement was a deal breaker when remote. The renogy one has a Bluetooth adapter and app, plus feels better designed (though actually I thin…

Have you considered a small backup generator? If it exists I would go with one that is propane powered. Propane goes to -50° before freezing so unless you live in Alaska, you have quite some margin here.

Re: DIY Off-Grid Solar Power

#187
post #102

Earlier quoted context omitted.

Yep. Unless you've got running water or a high cliffside for wind, the best off-the-grid heat source for cold climates is an acre of woods and an axe. Insulation, too. A lot of sheds and cabins (and single-family homes) could do with more. Saves on cooling bills in the summer, too.

I live on 25 ha of forest, have an axe and saw, and heat with wood. Let me tell you: you want to use the saw for everything but splitting. Axes are fine for burly cavemen. Anyway, in a cold climates like mine an acre would not be enough to keep you warm because trees grow slow when it's winter six months out of twelve. It takes a lot of wood to keep you warm, and one tree gives surprisingly little wood. After a handf…

You could try coppiced trees: https://www.lowtechmagazine.com/2020/09/how-to-make-biomass-...

They grow faster since they already have a root structure, the size is consistent and the wood is generally straigter (the japanese have a similar technique for extremely straight cedar logs)

Re: DIY Off-Grid Solar Power

#188

Earlier quoted context omitted.

I've driven something like 60,000 off-road miles since I bought my first truck in 2005. For overlanding, all you really need is a one big, high quality battery. The Odyssey PC2150 series are great batteries. Not cheap, but fantastic. It's very difficult to kill one. Also, you'd be surprised how little energy you actually use out there. A quality fridge-freezer like an Engel or ARB can be run for days before it will d…

Out of curiosity how far off grid do you go in your truck. That is, how far by distance and time are you away from the grid and stores? I know little about this stuff but am interested and would appreciate any helpful resources or videos you know of for a newbie. I’m interested from an overlanding / camping perspective but also a bug out vehicle perspective.

This guy has a pretty awesome channel and you can probably rabbit hole from there: https://www.youtube.com/watch?v=50wQBUX-Lbs

It is an interesting feeling when you are truly bugging out or off the grid, almost a primal kind of thing, because instances where self reliance is the only thing left is becoming less and less of an occurrence. If you ever go camping in the wilderness by yourself and set in for the night alone, you probably know the feeling!

Re: DIY Off-Grid Solar Power

#189

Just a (hopefully amusing) piece of anecdata: we have a squaredrop trailer, with a set of solar panels to power/charge the 12v marine battery and a pair of Jackery power banks. Most of our camping is done in the eastern woodlands: WV, PA, VA, etc. There is so much tree cover all the time. Some days, even though it's mostly or fully sunny, we're almost always at the end of some disused fire road on the wrong side of a…

Why not use the engine of the trailer to (also) charge the batteries while driving? My campervan does that.

Re: DIY Off-Grid Solar Power

#190

Together with my girlfriend I’m planning a trip. Driving from the Netherlands to South Africa and back with an EV. We want to charge the car with solar panels we bring with us. See our website for more details: www.4x4electric.com Challenge for now: how to charge the car with ~60m2 of flexible solar panels. We need a threephase offgrid solar system, but did not find a suitable solution yet. Any ideas?

Leuk idee!

Perhaps it makes sense to have a chat with Solar Team Eindhoven/Twente/Delft? Or have a chat with the people at Lightyear. They have a lot of former teammembers.

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