Solar power advice?

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(Dennis Lanigan) #1

I’m looking at purchasing a solar kit pretty soon. Any advice on what I should get? Or not get?

I’m looking to get the Renogy 100 watt kit. I’ll likely get the pwm charge controller and upgrade to mppt later. Any reason I shouldn’t get this kit? Any advice on batteries?

I’m in northern NM if that’s helpful at all.


Without knowing your usage it’s difficult to be much help. I’d recommendusing grid tie panels through a good mppt charge controller. SolarEpic makes a $200 40amp mppt that’s really nice and grid tie panels can be found on craigslist for $0.50/watt. Trojan T105re batteries are the best I’ve found and I recommend using multiple small, cheap inverters over one big expensive one.

(Dennis Lanigan) #3

I’m looking for an off grid system as I’ll be off grid in a month or so.

I’d like to power my phone, old laptop, sewing machine (.7 amps), and maybe some led lights. The big need is the sewing machine. I’m considering going to a treadle…but I need to find a heavy duty sewing machine first.


I recommended off grid panels because they’re much cheaper than 12v ones. I assumed you were doing an off grid setup.
A good mppt controller will step the voltage down to charge a 12v battery and get the maximum juice out of the panels.

The charge controller I recommended is overkill but they’re down to $170 now. With this you’d get the most out of your panels, would have room to upgrade, and it’s way less likely to burn up like the sub $150 cheapie ones seem to do frequently.

Even if you ran the laptop (65w?), the sewing machine(85w), and 50 watts of light, simultaneously, you won’t need much inverter. Some electric motors don’t like modified sine wave power though so you may want to look for a 400w pure sine inverter. The extra wattage is for extra headroom and to account for a possible higher startup wattage on the sewing machine. I used to run a lathe that only pulled 600 watts but it took a 2500w pure sine inverter to start it and run it wihout the motor getting really hot.

If you calculate how many hours a day you want to run things and when, we can figure out exactly what size battery bank and panels you’d need.

(Andrew) #5

We have 2 Renogy 100W panels. We also have an extra Renogy PWM charge controller. If we upgrade to MPPT as planned, we’ll have 2 extras. I don’t know if there’s a way to do a swippity swappity, but if there’s a way to avoid another PWM charge controller in the world, I’d consider it.

(Andrew) #6

We use this inverter. Works for most of what we throw at it. The only thing is kinda balks at is the DeWalt 20V Max battery charger, but that thing is a bit of a power hog. The only thing I don’t like about it is the cooling fan stays on whenever the AC switch is on. But the DC (USB) still works when AC is off, so it’s often off.

(Dennis Lanigan) #7


I basically would like the capacity to sew on a project for eight to ten hours a day for two to three days in a row. I’m sewing my tent on the grid, but would like to see if I can sew my other projects (anorak, mukluks, duffel bags) off grid. I could do that by candlelight or one led bulb if need be. I use my laptop about once a month for a couple hours at a time, but would like the capacity to use it for at least for four hours at a stretch. I use my old smartphone a lot so it dies almost twice a day. I’ll likely get an anker power core for back up on the phone.

Max/peak electical use:

  1. Sewing machine. 8 hours, day/night.
  2. Laptop. 4 hours, night.
  3. Smarphone/battery back up. 12 hours, day and night.
  4. 1 to 3 led bulbs. Two to four hours at night.

(Dennis Lanigan) #8

I’ll check in around mid-September when I start ordering stuff and ask if you want to send a pwm controller down. Thanks.

(Andrew) #9

We have 2 basic 12v Energizer deep-cycle marine batteries (135ah?)from Sam’s Club. With that setup, phones and LED lights cause a trivial drain on the batteries when used for days at a time.

Our setup sometimes gets uses for 4+ hours of laptop (45W peak) and 5+ hours of satellite internet. On sunny days, we basically have unlimited power and don’t think about it. As soon as the clouds roll in, we basically only have one day of capacity. Also, working during the day with full load still charges the batteries at full 14V (or whatever).

It sounds like the sewing machine probably draws roughly the same amount of power as the satellite internet, but it may be a bit higher.

If you can plan your electricity use around weather and daylight, you could probably get away with a setup like ours. If you need to work through periods of darkness without worrying about power, you’ll need more batteries.

(Dennis Lanigan) #10

I decided to start small for now. Very small. I got an Anker 20 watt foldable solar panel and will get a backup battery soon. (I’m just going to sew at a friend’s house for now.)

I like the panel. Charges my phone really quickly in the NM sun. The huge drawback is the panel can’t get wet.


I went an entire winter in Hesperus, CO with a 15 watt panel. It kept a car battery charged up and I ran a little 400 watt inverter off of it to run the laptop, guitar amp, and a few led lights.

Can you encapsulate your panel? I was planning to encapsulate some scrap solar cells in supersap clr natural epoxy on my trike.

(Andrew) #12

Getting close to the end of solar at node one. On November 25, the sun barely creeps above the spruce trees. That’s with a few hundred yards of clear space to the south (the river).

It has been interesting to see that there is some advantage to charging 5V (USB) devices with 12V panels. 12.1V doesn’t really charge the 12V bank, but does have enough overhead to keep small USB gadgets going.


I accidentally bought a 3a boost converter and I needed a buck converter to step 24v down to 5v to run a raspberry pi that will control the new cnc machine that I’m building. The boost converter I got will take something like 3-22 volts in and convert it to 5-24 volts out. The first thing I thought of when I realized that I got the wrong one was putting it on a small solar panel to boost the voltage up enough to put everything in can into a car battery. Just an idea if you’re in a pinch and need to charge a 12v battery. Most panels can be series connected to make more volts in low light conditions too, if your charge controller could handle it.

Here’s the boost converter I got:

🔋 Battery Bank for solar and generator