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DIY Off-Grid Solar Power

mobile-solarpower.com

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Re: DIY Off-Grid Solar Power

#201

Post by Syonyk »

Scoundreller wrote: post #137
Syonyk wrote: post #39

Earlier quoted context omitted.

The problem with holes in the ground for storage of things like batteries is that... they're holes in the ground. The ground, as a general guideline, actively dislikes holes in it and strives to fill them in whatever way possible. Liquid rolling in, soil creep, debris blowing past and building up, it doesn't matter - given a long enough time, a hole in the ground won't exist anymore. You can build a hole that will ho…

> actually, inverter limited - if I added some 48VDC loads I know it’s only lighting as a load, but I’ve heard standard LED light bulbs will happily run as low as 36VDC, as they chop the voltage down to that level anyway. It makes me wonder how many “120VAC” devices with switch mode power supplies could be plugged into 48VDC without any thought at all. And not just electronics like a laptop or non-plasma flatscreen,…

Most modern switch mode power supplies will run on DC, but you really, really want to jack the input DC up high unless you're a fan of replacing bridge rectifier diodes and other input wiring.

Active power factor correction circuitry will have a fit, but... eh, whatever. It's DC now, nobody cares!

A 120VRMS AC signal peaks around 170V, and most (not all, but most...) switch mode power supplies are auto ranging, so they'll tolerate from about 100VRMS to about 250VRMS - which is near 400V peak. If you can get 300+VDC into them, they'll be quite happy, but the boost converters to do that are a pain to find, and by the time you build one, you may as well just get a 120VAC inverter and call it good.

The main thing to be concerned about, and the reason to jack the input voltages about as high as you can, is that almost every switch mode power supply has a full bridge rectifier on the input side. From an AC input source, each diode has a 50% duty cycle. Put DC on it, now two diodes are at 100% duty cycle, two are at 0% duty cycle. How much overhead was there in the system? Well... you'll find out! However, a system capable of running and not overloading the diodes at 50% duty cycle at ~100VAC should be totally fine in terms of diode heating at 300VDC - just, perhaps not at 100VDC.

Re: DIY Off-Grid Solar Power

#202

Post by jacquesm »

Solar2 wrote: post #177
AYBABTME wrote: post #163

Earlier quoted context omitted.

Mate, I've been following you for a while and have a generally positive opinion of you. I think you're not going to have a good experience coming here with your guns out. I watch all your videos, but wouldn't I be a fool if I just absorbed what you say as gospel? You don't do this yourself, don't you? I'm happy for you and your success and I'm very happy there are people out there like you changing their life outcome…

No of course not, I just see people on this site stating to use recycled NMC cells that are capable of burning down their house with one wrong move, then saying my videos are dangerous. I cover safety all the time, more so than any other channel I know. I do not understand why people are saying these things. I work very hard to make my videos, and people here on this site who do not understand batteries are trying to…

Instead of being 'seriously upset' you could ask yourself if posting this kind of stuff:

https://www.mobile-solarpower.com/diy-beginner-friendly-sola...

Is going to bolster your reputation as safety conscious or harm it, besides your general attitude in this thread. You are quite clearly advising people to copy this design, you make money of them doing so. Even a one-off should be better designed, let alone something intended for duplication.

I had you down as well meaning but a bit out of your depth at times, let's just say that that didn't improve based on the interaction here and your various comments.

Re: DIY Off-Grid Solar Power

#203

Post by naikrovek »

zoba wrote: 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…

> Temperatures below freezing are bad for batteries.

bad for lithium batteries. even then, it is only bad if you charge or discharge them in freezing temps. lead-acid handle cold just fine.

Re: DIY Off-Grid Solar Power

#204

Post by aliswe »

sandworm101 wrote: post #132

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…

It would have helped to do a more benevolent analysis/interpretation here. For example, you mentioned yourself that lead batteries need checking, change of fluids, etc, most of which noone does.

Re: DIY Off-Grid Solar Power

#205

Post by jacquesm »

aliswe wrote: post #204
sandworm101 wrote: post #132

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…

It would have helped to do a more benevolent analysis/interpretation here. For example, you mentioned yourself that lead batteries need checking, change of fluids, etc, most of which noone does.

Everybody whose house power depends on their batteries will do this religiously. It's a five minute job every month and a half our job every year.

Re: DIY Off-Grid Solar Power

#206

Post by Scoundreller »

Syonyk wrote: post #201
Scoundreller wrote: post #137

Earlier quoted context omitted.

> actually, inverter limited - if I added some 48VDC loads I know it’s only lighting as a load, but I’ve heard standard LED light bulbs will happily run as low as 36VDC, as they chop the voltage down to that level anyway. It makes me wonder how many “120VAC” devices with switch mode power supplies could be plugged into 48VDC without any thought at all. And not just electronics like a laptop or non-plasma flatscreen,…

Most modern switch mode power supplies will run on DC, but you really, really want to jack the input DC up high unless you're a fan of replacing bridge rectifier diodes and other input wiring. Active power factor correction circuitry will have a fit, but... eh, whatever. It's DC now, nobody cares! A 120VRMS AC signal peaks around 170V, and most (not all, but most ...) switch mode power supplies are auto ranging, so t…

I never considered the diode duty cycles. If nameplate was 120-240VAC (my TV says 120 but the p/s PCB inside says 100-240…) I’d like to think each would have the overhead to handle under 100VDC, but maybe I’m underestimating the impact of higher current. Edit: you’re right that the “hot” ones will run twice as hot with their 0.6V or whatever drop.

All I could think about was the (potential) improvements on capacitor lifespan since they won’t have to smoothen, but wasn’t sure if their electrolyte could still heat/dry if it was actually the connection to power that makes them hot.

Thinking further, an internal fuse might blow with the (expectedly) larger current draw at 48V.

And yeah on input wiring, you’re pulling more current at 48V.

Re: DIY Off-Grid Solar Power

#207

Post by mlac »

sandworm101 wrote: post #145
mlac wrote: post #142

Earlier quoted context omitted.

This is a really good point, but my car batteries last between 3-5 years. Maybe I’m doing something wrong.

What actually happened to your car battery to cause you to replace it? Did you do anything to fix it? Did you ever maintain it? Did you replace the fluid? Or did you just drive your car every day and then replaced the battery when the mechanic told you it was broken? It is normally cheaper to replace a standard car battery than attempt to maintain and fix it (100-200$) but in an off-grid situation many thousands of d…

It wasn’t about the mechanic telling me, it was about the car not starting anymore and the battery not taking any charge.

And that’s why I asked - I honestly don’t know what steps are recommended to maintain a car battery (or if given the price it is worth the work).

Thanks for the links - I’ll look later

Re: DIY Off-Grid Solar Power

#208

Post by lazide »

WalterBright wrote: post #200
lazide wrote: post #130

Earlier quoted context omitted.

You’d still need backup heat production (heat pump, or wood burning, or fossil fuel, or electrical off batteries) for the inevitable month long ‘gray and cold’ stretches, or you’re gonna freeze. Single purpose but not reliably there heat capture methods add cost and maintenance. It’s often more cost effective to have a general purpose method that while not as efficient in one case is generally more overall (cost) eff…

Passive solar heating should be very maintenance free. It's the point of it. Sure, a backup plan is a good idea. But it doesn't have to be very good or very efficient, as it will be rarely used.

Pretty sure you don’t live in Central Europe or areas like northern Michigan?

There are weeks with zero direct sun, just low cloud cover, scattered snow, and cold cold cold.

I was in Michigan once when Lake Superior froze over, shore to shore.

Unless the place is so well insulated you can keep it warm purely with body heat, you need supplemental heating in climates like this. The sun is not always shining.

Re: DIY Off-Grid Solar Power

#209

Post by Syonyk »

Scoundreller wrote: post #206
Syonyk wrote: post #201

Earlier quoted context omitted.

Most modern switch mode power supplies will run on DC, but you really, really want to jack the input DC up high unless you're a fan of replacing bridge rectifier diodes and other input wiring. Active power factor correction circuitry will have a fit, but... eh, whatever. It's DC now, nobody cares! A 120VRMS AC signal peaks around 170V, and most (not all, but most ...) switch mode power supplies are auto ranging, so t…

I never considered the diode duty cycles. If nameplate was 120-240VAC (my TV says 120 but the p/s PCB inside says 100-240…) I’d like to think each would have the overhead to handle under 100VDC, but maybe I’m underestimating the impact of higher current. Edit: you’re right that the “hot” ones will run twice as hot with their 0.6V or whatever drop. All I could think about was the (potential) improvements on capacitor…

Welcome to the world of powering AC equipment on DC. It can be done, surprisingly often.

But as soon as you've got some stuff that requires an inverter, you may as well just light the inverter up for everything. I've got the equipment to do a separate, lithium-backed "DC rail" in my office that would be around 40V, and then buck it down for various devices, run my routers direct on it, and... I've never gotten around to doing it, because until literally everything is on that, I'd still have to run the inverter for things like system sleep (I sleep most of my computers overnight). I'm fiddling watts around and it's just not worth it unless I can actually shut the inverter down entirely. Unfortunately, boosting up to 300VDC isn't cheap or easy.

I've wondered if you could run some of that stuff straight off solar during good sun, but I've never really wanted to subject my computers to that sort of abuse.

Re: DIY Off-Grid Solar Power

#210

Post by sandworm101 »

hasbot wrote: post #171
sandworm101 wrote: post #132

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…

"And, at a given price point, they can charge faster than lithium too." Please elaborate; I have no idea what you're talking about here. My deep-cycle RV batteries are nearly dead and I'm going to spend the $$$ to replace them w/ a lithium battery partially because of lithium's faster charging. At peak solar season, I only get about 3 to 4 hours of good sunlight on my forested property so I need batteries that charge…

Because for the price of one lithium battery you can buy five lead-acids, wire them in parralel, and charge at 5x the rate.
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