DIY power system build thread

[RonnyRonin]

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.

[woodsghost]

https://m.youtube.com/watch?v=0C7gFREl7h8

This is a good place to learn from, and a good source of inexpensive batteries which will house enough power for you to do what you want to do.

https://powerwerx.com/dc-power-products

The link is good but a bit pricey. You can get all the tools and connectors and wires you need. I've found for my smaller power box I just built I mostly sourced stuff from Autozone. But a powerpole tool and connectors are something you might want to get from powerwerx. You can get them other places too.

Harbor Freight had a small inverter on clearance for $17. For your needs I might go get one of the bigger ones if they are still on clearance as a starter inverter. But there is better quality out there and eventually you will probably want one of the better ones.

Most of what you want can be rigged up directly with 12v options and so I'd get more powerpole connectors to drill into your box.

Running AC will need to use an inverter. I don't know of any 12v AC units.

I would consider a multifuel fridge which can run off 12v or propane.

More important than "what you want to run" is:

What are the volts of the things you want to run?

What are the amps of the things you want to run?

What are the run times you intend to use?

That will give you the total watts your system will need to be able to handle. That can help us size your system and recommend fuses and wire sizes.

Also, I imagine you will want to use this in the winter? I would get a battery blanket too.

[Blast]

Hopefully your project will be the kick in the ass I need to assemble mine. I have all the parts, just not the motivation.
-Blast

[ZMace]

Following closely. Do you feel the pressure to complete it yet?

[boskone]

Running AC will need to use an inverter. I don't know of any 12v AC units.

They do exist. No experience with them, however.

[woodsghost]

Running AC will need to use an inverter. I don't know of any 12v AC units.

They do exist. No experience with them, however.

Thanks! I just did a search on them and they are more pricy than I'm willing to deal with. Also I have no experience.

I wonder if you could pull one out of an old RV/trailer someone is getting rid of?

[boskone]

Running AC will need to use an inverter. I don't know of any 12v AC units.

They do exist. No experience with them, however.

Thanks! I just did a search on them and they are more pricy than I'm willing to deal with. Also I have no experience.

I wonder if you could pull one out of an old RV/trailer someone is getting rid of?

Seems like most RV HVACs are 110V. There are a few, but I couldn't turn up many.

At a guess, until people started wanting to run solar frequently it wasn't useful (profitable) to design 12v units.

[eugene]

Most of the rv type that you see on the roof are evaporative coolers and not a compressor type like you find in your home. They don't cool as well.

I'm trying to find a powerpole hack which has a spring loaded cover like how a trailer plug works. Something where I can yank the cable out and it springs shut.

[RonnyRonin]

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.

[woodsghost]

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.

Otherwise, if you get the wire and fuses first, you can work from there to determine what load you can safely handle without catching things on fire.

You want to know the amps and volts of everything you want to run, and the total amps and volts of everything you want to run at once.

Amps * Volts = Watts. So if you pull 20v out (my computer is listed as 19.5v) and it pulls 1.7 amps, I multiply 20*2 and get 40 watts. But I have a 12v system, so I say 40w /12v = 3.3 amps. So I'll plan, for safety sake, to pull 3.5 amps out of that system and I'll need wires which can handle that load. I also round things off to account for inefficiency in the system and to build in safety margin.

Also, because my inverter is a modified sine wave inverter, it is very clear that it can damage computers and medical equipment but can be used to charge batteries. I don't expect to draw electricity directly from the battery box because it is 12v and the computer need is 19.5v, so I need the inverter to get up to 110v, then the computer only draws 19.5v and charges the battery.

And let's say you do the math and realize you want to pull 800w an hour out of the system. Well, you have a 12v system, so 800w / 12v = 66.67 Amps. So you would want wire which can handle over 67 amps, which is ....



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.

[MPMalloy]

Hey all: From those who also rent, how do you DIY your systems?

[woodsghost]

Hey all: From those who also rent, how do you DIY your systems?

Hey MP, I currently rent an apartment, and it depends on your needs, but right now I have a Harbor Freight 400w inverter (not to be used with a CPAP or any other medical equipment, just an FYI, I don't know what all you have), a 15AH SLA battery, and a Harbor Freight ammo box. Some zip ties and drilling some holes and I have about 84 watts (12v * 7a - efficiency losses) of power I can throw at a problem. Total cost has been $54? Maybe a little more?

I need some protectors for the battery or I can run it dead. A multi-meter for $10 helps, but is a little on the cheap side. I should have splurged and got a better one. Probably a digital one.

From there you can scale up to whatever your needs are, and I've linked to a guy who builds batteries. You can build lithium batteries for less than the coast of a SLA battery, so that is pretty incredible.

You can buy little 9AH SLA batteries online for about $13 each (beware shipping costs), and that would be a good and cheap way to do things too, but you would want to run a block of them.

And MP, if you go the route I have gone and you don't have solar panels and a charge controller I would get an AC battery charger and make sure it desulfates batteries. And make sure it is a "charger," not a "maintainer." (Obviously this means you can only recharge when the grid is up, which sucks, but for me this is where I'm at for now)

My good charger I got at AutoZone and cost me $30.

At some point I'll get solar panels and a charge controller. And bigger batteries.

And in case it is not obvious to anyone reading this, only do this with deep cycle batteries. If going the lead route, get SLA batteries.

And be aware of how cold weather affects batteries. Whatever you intend to get, look up the cold weather performance and maintenance needed.

[MPMalloy]

Hey all: From those who also rent, how do you DIY your systems?

Hey MP, I currently rent an apartment, and it depends on your needs, but right now I have a Harbor Freight 400w inverter (not to be used with a CPAP or any other medical equipment, just an FYI, I don't know what all you have), a 15AH SLA battery, and a Harbor Freight ammo box. Some zip ties and drilling some holes and I have about 84 watts (12v * 7a - efficiency losses) of power I can throw at a problem. Total cost has been $54? Maybe a little more?

I need some protectors for the battery or I can run it dead. A multi-meter for $10 helps, but is a little on the cheap side. I should have splurged and got a better one. Probably a digital one.

From there you can scale up to whatever your needs are, and I've linked to a guy who builds batteries. You can build lithium batteries for less than the coast of a SLA battery, so that is pretty incredible.

You can buy little 9AH SLA batteries online for about $13 each (beware shipping costs), and that would be a good and cheap way to do things too, but you would want to run a block of them.

And MP, if you go the route I have gone and you don't have solar panels and a charge controller I would get an AC battery charger and make sure it desulfates batteries. And make sure it is a "charger," not a "maintainer." (Obviously this means you can only recharge when the grid is up, which sucks, but for me this is where I'm at for now)

My good charger I got at AutoZone and cost me $30.

At some point I'll get solar panels and a charge controller. And bigger batteries.

And in case it is not obvious to anyone reading this, only do this with deep cycle batteries. If going the lead route, get SLA batteries.

And be aware of how cold weather affects batteries. Whatever you intend to get, look up the cold weather performance and maintenance needed.

Got it

[RonnyRonin]

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?

[CrossCut]

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?

75 watt Yaesu FT-2900, should be comparable:

Supply voltage:13.8 V DC ±15 %, negative ground

Current Consumption (typical):
Rx: less than 0.7 A, less than 0.3 A (squelched)
Tx: 15 A (75 W) / 9 A (30 W) / 5 A (10 W) / 4 A (5 W)

No regulator required so long as the voltage is between ~12-15 volts.

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).

[sheddi]

I'm mostly a spectator on this thread, it looks very interesting!

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.

There's a useful worldwide GIS that the European Union put on-line that estimates how suitable your location is for solar power (and how many watt-hours of output per day you might expect to get from your panels). The off-grid tool also lets you experiment with different battery pack sizes and loads.

https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html

Just to illustrate, I looked at 100w of solar in mid-Manhattan and is forecasts 200 watt-hours daily in January and 400 watt-hours daily in July.

Plug your numbers in and see what you get.

------

This is probably a dreadful idea, but somewhere here I've got a 3KVA APC UPS that I bought used for a £tens some years ago. It's small enough to use a 48v (12v x 4) battery pack (bigger ones use, I think, 192v packs, 12v x 16). It has an external Powerpole connector for additional bateries. And it will cold start (you can force it to swithh on even without AC present). It occurred to me that if I hacked it about to allow 48v solar charging of the batteries I would have a basic grid-linked hybrid power system. While the grid is up the load is powered by the grid, if it fails the UPS kicks over to battery and the solar would keep them charged.

[RonnyRonin]

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.

[boskone]

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.

Have you checked it's inrush/starting current? E.g. it may operate at 1.3A, but for a fraction of second might need several times that.

There are mitigations (you can find some soft-start links people left), but it's still something to factor in.

[CrossCut]

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.

Was wondering what space/mounting options for more panels were available when you mentioned living in an apartment. I was thinking more like a small balcony on a 3rd floor apartment, but obviously not if it has a wood stove.

Have to admit when I saw your list of items to power and the size of the battery box it looked like an expensive failure waiting to happen. Looking up the specs on some of the options available now has changed my mind. The advances in offgrid power have come a long way in the last 20 years when I built my first system - T-105 FLA batteries at 120 pounds for the smallest 12v system, only 50% depth of discharge if you wanted them to last very long, and panels costing 4-5 dollars per watt. Just your "At a minimum a few fans" comment for cooling, I was thinking about 10 watts for a little 6" fan and almost half a kilowatt-hour per day to run two of them constantly, then I found one that size that uses <2 watts... A portable frig (with more capacity than say a lunchbox) that runs off 1.3 A / 15 watts for only 8 hours a day boggles my mind lol.

[sheddi]

A portable frig (with more capacity than say a lunchbox) that runs off 1.3 A / 15 watts for only 8 hours a day boggles my mind lol.

Not portable, but I've got one of these (or sometrhing very similar) in my kitchen.
https://www.currys.co.uk/gbuk/household ... 9-pdt.html

Under standard test conditions it's rated at 113 kWh/yr, which is an average of ~13 watts.

Edit to add:
On the topic of poertable power, I've also got a little compressor coolbox - a Waeco (now Dometic) Coolfun CK-40 - that I can run from an inverter. The current model is rated at 82 kWh/yr.

I would note, though, that the compressor starting current is quite steep; I usually run it from a 1600 watt inverter.

I have tried a 300 watt inverter but that won't start it.

[raptor2]

A portable frig (with more capacity than say a lunchbox) that runs off 1.3 A / 15 watts for only 8 hours a day boggles my mind lol.

Not portable, but I've got one of these (or sometrhing very similar) in my kitchen.
https://www.currys.co.uk/gbuk/household ... 9-pdt.html

Under standard test conditions it's rated at 113 kWh/yr, which is an average of ~13 watts.

One thing to bear in mind with refrigeration especially air cooled units is the ambient air temperature. That has a lot to do with its power consumption. The marine world has for decades been trying to perfect the lowest draw possible for 12/24v refrigeration in the tropics. Even with 4 to 6 inches of closed cell foam insulation a top loading refrigerator at 90F will require a lot more power than the same device at 70F.

[CrossCut]

Not portable, but I've got one of these (or sometrhing very similar) in my kitchen.
https://www.currys.co.uk/gbuk/household ... 9-pdt.html

Under standard test conditions it's rated at 113 kWh/yr, which is an average of ~13 watts.

Or 300 Wh / day, and has auto defrost. Brilliant! (in my best British accent

We originally started with a 120 vac frig/freezer combo when we first moved offgrid, somewhat small by US standards at 14 cubic feet for the frig section, and although "energy star" rated it was still a power hog. Auto defrost never worked quite right on it either, think the inverter power / waveform messed with it's timing circuitry but that's just a guess. Swapped the controller and the heating element, no change. Switched to a similar sized propane (only) model after about a year, uses about 1 lb of propane a day, and freezes items in the frig section if set above the very lowest setting. Added a propane chest freezer later, same fuel consumption, and have confirmed that running it off a 20 pound BBQ sized tank for over two weeks in the summer once (as a test, just to confirm it worked and had all the proper fittings/connectors). Not fully self-sufficient since we need propane, but have an extra 500 gallon tank (80% full) that's shut off/disconnected that I could connect for emergency use if needed, plus a number of 20 pound and two 100 lb tanks. If/when either of my propane frigs die I might have to look at electric refrigeration options again knowing what I know now.

[woodsghost]

Just posting a good video for those who want to make a small apartment box or otherwise have need for a small power box.

In this guy's video description he has lists of parts if you want to buy them, so that is pretty helpful.

The inverter he used for AC power is pretty minimal. Like my own 15AH battery setup, this is pretty minimal and short in duration for what it can do. But he has a well thought out project and good reasons behind everything he did.

https://m.youtube.com/watch?v=g2cLMk3nD3Y

[RonnyRonin]

Have you checked it's inrush/starting current? E.g. it may operate at 1.3A, but for a fraction of second might need several times that.

I already showed my math rounding up by almost a factor of 4 (continuously) for safety margin, for the time being I'm not going to sweat the small math if I can just blow past it.

Was wondering what space/mounting options for more panels were available when you mentioned living in an apartment. I was thinking more like a small balcony on a 3rd floor apartment, but obviously not if it has a wood stove.

Have to admit when I saw your list of items to power and the size of the battery box it looked like an expensive failure waiting to happen. Looking up the specs on some of the options available now has changed my mind. The advances in offgrid power have come a long way in the last 20 years when I built my first system - T-105 FLA batteries at 120 pounds for the smallest 12v system, only 50% depth of discharge if you wanted them to last very long, and panels costing 4-5 dollars per watt. Just your "At a minimum a few fans" comment for cooling, I was thinking about 10 watts for a little 6" fan and almost half a kilowatt-hour per day to run two of them constantly, then I found one that size that uses <2 watts... A portable frig (with more capacity than say a lunchbox) that runs off 1.3 A / 15 watts for only 8 hours a day boggles my mind lol.

I am in a fairly small one bedroom apartment, but luckily I have a detached garage to store larger preps like the solar panels in (batteries will live in the apartment as my garage temp fluctuates too much) and a fairly good sized porch. I do have a fireplace, but my emergency wood stove would either be plumbed as an emergency insert, piped out a window, or heating a tent somewhere else.

For a small primitive swamp cooler in the burning man style I'm seeing numbers around 17 watts, and I'd budgeted 10 watts to run 2 fans, but I will also have smaller USB power banks and smaller solar panels that can be pressed into service for smaller items like this.

For a 7 cu. foot chest freezer fridge conversion I'm seeing about 0.5 kWh/day; and of course in the winter when power outages are more likely this number would go down. I'd say refrigeration is my highest priority and most everything else can be rationed pretty heavily if I can facilitate it. I had kind of assumed I'd need 1000 Wh of capacity but I am still going to put off doing math until I'm further along in the project.