Off grid solar system design help?

[Cord]

We have a off grid cabin and I'd like to use a solar panel to power some low voltage lights. My thinking is to buy some 400 watt, 40 volt solar panels and use them to charge some semi truck batteries. I can get these batteries super cheap used. Because the batteries would not be matched, I was thinking there's be one solar panel and controller per battery. I'm guessing two setups would be enough to power the led lights. I only want to power lighting, any other power demands would be on the generator. Does anybody have experience with a system like this? I want to confirm my approach before buying any parts. These are the panels I was considering: Solar panels

 

[Skagit]

We live off grid and our house is run off 120w (x6) solar panels. I wouldn't do a split system like you're describing... If you have a source for used group 31 batteries then finding a matched set shouldn't be an issue, highway trucks run sets of 3 to 6 depending on the application and they're always replaced in sets.

 

[Cord]

The panels that I was considering makes 40 volts, can this panel be used on 12v batteries that are in parallel?

 

[AndyMA]

You don't want to connect the panels directly to the battery. You connect the panels to a Charge Controller which controls how the batteries are charged. A good charge controller is the Midnght Solar Kid MidNite Solar Products

 

[Grumpycat]

The panels that I was considering makes 40 volts, can this panel be used on 12v batteries that are in parallel?

A solar panel needs a purpose-made inverter/controller to optimally function. Your PV panel does not "make 40 volts", that is just marketing telling you numbers to make you think you understand. The actual voltage for optimal electric production depends on brightness of the sun and temperature. Optimizing the voltage is best for getting the most power and for life of the panel.

400W are super premium panels these days. 315W is the best value. I think your best bet would be to purchase several panels and a matching off-grid inverter which is designed for battery storage. The same inverter will charge your batteries and provide 120VAC and probably 240VAC too, all day and night if you have enough battery.

 

[LittleBill21]

if your sole purpose is lighting and low voltage, you can skip an inverter. just need panels and a solar controller.

 

[Williy]

You need batteries that are the same voltage and amps buy your solar panels in 3's and the panels usually are 30 volts, 7 to 8 amps and they don't produce like the panel says 400 watts don't expect they will produce 400 watts maybe about 250 to 300 watts would be more realistic. Midnite solar makes very good products. Your solar panels you want in groups of 3 so you can set up your controller. You would
also need a dc circuit breaker box that you will hook
up all you solar panels and can shut them off if need be. Think its a state law?? Check this web site out:

DIY OFF GRID SOLAR SYSTEM

DIY OFF GRID SOLAR SYSTEM: Day by day the price of the solar panel falls gradually. But still, installation of a complete off-grid solar system is costly. So I write this instructable to get all the components of your solar system separately and assemble it all by yourself. C…

www.instructables.com

willy

 

[Grumpycat]

if your sole purpose is lighting and low voltage, you can skip an inverter. just need panels and a solar controller.

You do not understand electricity. You think everything is explained by “voltage”.

Solar panels are silicon solid state devices and being such are current devices. A proper PV inverter is constantly searching for the optimal voltage to transfer energy from the panel.

Download a PV panel data sheet. The open circuit voltage is commonly around 40. But the maximum power voltage is around 34 and will vary several volts depending on how bright the sun and temperature.

So one spends $300-$500 for a premium 400W panel and you recommend skipping the inverter or battery controller?

This isn’t a particularly good data sheet, but ine I found quickly.

https://documents.unboundsolar.com/media/9434325__black_mono_perc_1621295931.pdf?_ga=2.46697447.1325783907.1622500938-1744675150.1622500938

With no more knowledge than demonstrated the O.P. should plan on spending money to get a working package rather than buy the most expensive PV panel, the cheapest battery, and pray to find a means to put them together. This is $2616

https://documents.unboundsolar.com/media/9434325__black_mono_perc_1621295931.pdf?_ga=2.46697447.1325783907.1622500938-1744675150.1622500938

 

[LittleBill21]

You do not understand electricity. You think everything is explained by “voltage”.

Solar panels are silicon solid state devices and being such are current devices. A proper PV inverter is constantly searching for the optimal voltage to transfer energy from the panel.

Download a PV panel data sheet. The open circuit voltage is commonly around 40. But the maximum power voltage is around 34 and will vary several volts depending on how bright the sun and temperature.

So one spends $300-$500 for a premium 400W panel and you recommend skipping the inverter or battery controller?

This isn’t a particularly good data sheet, but ine I found quickly.

https://documents.unboundsolar.com/media/9434325__black_mono_perc_1621295931.pdf?_ga=2.46697447.1325783907.1622500938-1744675150.1622500938

With no more knowledge than demonstrated the O.P. should plan on spending money to get a working package rather than buy the most expensive PV panel, the cheapest battery, and pray to find a means to put them together. This is $2616

https://documents.unboundsolar.com/media/9434325__black_mono_perc_1621295931.pdf?_ga=2.46697447.1325783907.1622500938-1744675150.1622500938

LOL

Dude... he said he needed low voltage lighting. that's all he said, that tells me he's looking at some form of 12v lighting like an rv setup. he needs a solar panel and a solar controller, to charge the battery, the 12v lights will have their own buck/boost controller, or are old school and just a regular bulb, use all the fancy words you want but at the end of the day, he needs a battery a panel and a controller and a light and he's done. if he actually provide more then 2 words for what he wanted, maybe we could give him a better design.

I don't care what panel he's quoted, if he knows nothing about solar, then he knows nothing about solar panels, so why should I base my comments off that.

LOL maybe you should look at what he quoted. he's looking at 65 dollar used panels, and used truck battery's, yea i think he wants to go cheap...... most controllers can easily handle a 40v OC panel with ease. so yea, he doesn't need a inverter, can always add one down the road if need be

 

[ning]

We have a off grid cabin and I'd like to use a solar panel to power some low voltage lights. My thinking is to buy some 400 watt, 40 volt solar panels and use them to charge some semi truck batteries. I can get these batteries super cheap used. Because the batteries would not be matched, I was thinking there's be one solar panel and controller per battery. I'm guessing two setups would be enough to power the led lights. I only want to power lighting, any other power demands would be on the generator. Does anybody have experience with a system like this? I want to confirm my approach before buying any parts. These are the panels I was considering: Solar panels

These panels look like they've been through an intense hail storm or were damaged by some other means.

*If* they work at all, they're going to be missing a lot of cells and certainly will never come anywhere near 400W.