DIY power system build thread resurrected

Started by RonnyRonin, June 26, 2021, 11:36:08 PM

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Or the "keep me accountable" guilt thread.

Having some portable power infrastructure has been on the to-do list for a long time; I thought I had this covered when I started finding Goal zero Yetis really cheap, but it turns out I wanted the roughly $1000 in craigslist profit more than I wanted a couple lithium power banks. Looking at my ledger it looks like I let four Yetis and a GZ 100w solar panel come and go and leave me without power again.

Finally I started haunting CL until I found a good deal on some ZAMP solar panels and a charge controller; x2 115W panels and a 30Amp controller for (I think) $150ish. Problem is they have languished in my garage for probably a year at this point without having any way to really use them, so I've decided it's time to build a DIY Goal Zero Yeti style power bank (I despise the name "solar generator" that gets tossed around so much). I just started buying parts today, so I figure it would be a good time to start a build thread to keep me on task and ask questions of the gang.

First off, what do I want to power?

1) Area lighting
2) Incidental electronics charging (cell phones, laptops, AA/18650 batteries)
3) Mobile ham radio (80W?)
4) Charging cordless power tool batteries (18V Ryobi lithium)
5) Refrigerator
6) maybe climate control (a stretch, but I haven't explored low power swamp cooler options yet). At a minimum a few fans.

My main scenario is simply a power outage at my apartment, after that car camping/road trips, or on the extreme side powering a mobile BOL basecamp. I do not have the radio or the refrigerator yet, but I'm exploring small 12v options (like ARBs and Dometics) or on the extreme end a converted chest freezer like is popular with offgrid folks.

So what is the plan? So far I'm going the popular direction of using the Ridgid tool boxes for the container:

Lots of DIY people seem to be using the middle box for their entire setup, batteries and all. I think I want a bit more capacity than most of these projects so I am leaning toward using the bottom rolling box for multiple batteries and putting the charge controller/fuse box/outlets in either the medium or small box. I already use Ridgid boxes for a lot of my important tools, bug out gear, and electronics (as does some of my local friends) so this would integrate nicely into our system and I already have a few empty ones around (shout out to whichever ZS member turned me on to these, I have at least 7 now).

I am also going to start quite small; I have basically one wiring project under my belt and it went horribly. So far the parts I have ordered are:

1) 3.0 dual USB outlet with voltmeter

2) 12v car accessory outlet

3) dual anderson powerpole outlet

4) 6 way fuse box

Tomorrow I'm going to check my local hardware stores for wire and sundry connectors to start putting it all together. For now I will probably mount everything to a small sheet of plywood to test before I start drilling holes in my Ridgid box, once that is done I will source a small crappy battery locally to work some bugs out before I make a final decision on what batteries and how many to get for the real deal.

At the moment I think I will use the powerpole outlet as my input from the solar panels; I have two panels so I can just throw some extension cables on them and plug them in separately.


I already have a few inexpensive inverters laying around, I will probably throw one in but I really don't plan to use it for much of anything if I can help it.

I haven't done a ton of research on fridges but a lot of people seem to say the dual fuel fridges are far less efficient and also more finnicky than the pure 12v ones; I plan on having lots of propane around for cooking and heat so that was my original plan as well. Apparently it is the difference between a compressor fridge and an absorption fridge? I'm still a little fuzzy on the details. I've seen people buy just the compressor and cooling plates and convert dorm fridges or small chest freezers; I've considered whether a premium cooler (pelican, yeti, etc.) would create a good host for a home made one.

For AC I'd probably only consider a ghetto 12v swamp cooler as I'm just assuming a 120v AC unit would be far to power hungry. While I'd never run an electric heater directly off this one of the diesel heating options I'm considering does need a tiny amount of power just to run the thermostat, blower fan, and fuel pump.


Quote from: woodsghost post_id=2754745 time=1613998758 user_id=71854
Ok. At this point I would sit down and do some math on what you plan to run on this because that will determine the amp load on the system and that in turn will determine the wire sizes and fuses you want on there.


6 gauge?

Which is pretty thick and expensive. This is not to say "I know what you need." I'm just throwing numbers around to illustrate a point. From this I hope you can do the math and size your own system and do it safely.

I've been leaning on my brother a lot for this as he does quite a bit of electrical and we've tried to back in to some of the numbers but it's a lot of guess work at this point since I don't even own the big items like the fridge and the radio yet. My plan at this point is to err on the side of overkill a bit and just work around some of the built in bottle necks. Most of the items will be USB which implies a pretty hard cap on draw; and most of the 12v plug items will be built within the limits of a car outlet so to my understanding that means 10-20 amps per item.

the current plan is to put 12g wire between the fuse box and every individual outlet which should be overkill, and then run double 12g wire anywhere the whole system's power would be running through. I'm hopeful I can do the entire project with one purchase of 50' of 12g wire, and then I only have to buy 12g connectors as well.

Batteries are a big research point I'm probably not going to really dive into until I have everything else straightened out, obviously it will be the biggest expense and I'm quite intimidated by the number of options.

my back of the napkin math says a fridge would be at most 10 amps (and likely more like 5), my usb gizmos are all in the 1-3 amp range, I don't know what my ryobi charger pulls but it has an 8 amp fuse, so less than that. Limiting myself to 4 usb things at once puts me in the 30 amp range at most, and I'm not expecting to be able to run everything at the same time. Radio is the question mark, as I'm reading numbers all over the place, but I'm assuming 20 amps should give me some wiggle room for something in the 80-120 W range. As much left over wire as I expect to have I may just double up the wires to the powerpole outlets just so I don't have to worry about it.

According to my overly optimistic doodle the only place with wiring more than 2 ft should be between the charge controller and the solar panels; which at peak hypothetical maximum never achievable output should be around 10 amps.

Main question for Woodsghost and the hive mind in general: do I need some kind of regulator between the battery and the radio?


Quote from: CrossCut post_id=2754826 time=1614083067 user_id=71020
Do you have, or considering, alternate means of charging the battery bank besides just the 2 solar panels?  Assuming you can get 5 hours of full sun per day, which might take some periodic repositioning of the panels depending, that's about 1 kWh of power on a sunny day.  A 5 A (60 watt) frig with a 50% duty cycle will use about 72% of that solar power alone.  No idea if that duty cycle value is accurate, just adding up some of the power requirements for the 6 items in the first post and it looks to be over what the panels alone can provide (depending on how many hours a day of use).

I could easily add on another 100W panel, and I'm fairly certain more guys in my local MAG will be buying solar soon, so I expect to have some more power available. Later down the road I'll likely buy a small gas/propane generator for backup as well; and I'd very much like to add some thermoelectric plates to go with my primary heat source, which would be my wood stove in an emergency.

While I'm trying to be paranoid and round up heavily, some of the fridges I'm looking at actually list a 1.3 amp draw and a 30% duty cycle, but I assume that is best case scenario of course.
share your tobacco and your kindling, but never your sauna or your woman.


Not much of an update; I did take a stab at wiring everything together but I have stalled out shopping for a battery for the most part. There seems to be a large surplus battery seller in my area so it may come down to showing up and seeing what fits in my boxes the best.

I'm still debating a bit on form factor; whether to perhaps try to cram a smaller battery into the medium box with all of the gizmos (which so far are taking up very little space) or whether to put everything in the smaller box and get some larger, heavier (and cheaper) batteries in the larger rolling box.

I did cheap out and not get the anderson power pole crimper, so I'm hoping everything is fine on that front. My spade bit for my drill is also 1/8" off of what I need for all the plug ins, so I'll fix that before I do any drilling on the box itself.
share your tobacco and your kindling, but never your sauna or your woman.


You can always check some of the videos that Will Prowse (DIY Solar with Will Prowse) on YouTube to see some of the batteries that he recommends.  He's pretty serious about testing batteries and battery packs, including tear downs.  He's also not afraid to call out poor designs or shoddy construction when he comes across it.
Information - it's all a battle for information. You have to know what's happening if you're going to do anything about it. - Tom Clancy, Patriot Games

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