Solar Generator Build

wvengineer
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Solar Generator Build Sept 4, 2020 14:33:14 GMT

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Post by wvengineer on Sept 4, 2020 14:33:14 GMT

I am thinking about a project for the winter. I want to build a portable solar generator. It would be a mobile setup where solar panels feed into a battery bank. The batteries are hooked up to an inverter to produce AC power. This is very high level planning at this point.

So far, I would take a rolling toolbox and put in 12 AGM deep cycle batteries, each rated for 12V and 12 AH.

I would have an inverter for 1,500W or 2,000W.

On the outside of the tool box, I would have AC outlets, readouts, Car power ports, USB ports, and Anderson power poles. Power input would be from both solar panels and a AC charger. Unit would have an inboard charge controller for the solar panels.

I am just starting to price it all out. So far I am looking at about $700 not including the solar panels. I have not really done much research to maximize pricing yet.

Questions that I have.
1. Inverter. Pure sine ware or modified? Is the pure wave really worth the extra cost?
2. 12V or 24V base battery system? 24 means less current through the wires, but I would need a buck converter for the 12V accessory ports.
3. Is it worth looking at wiring the batteries in 36V or 48V? The inverters look to be quite a bit more expensive.
4. Do I size wire based on continuous current loading of the inverter or the peak output?
5. Running power from the batteries to the inverter. Let's say it is running 12V to a 1500W inverter. Can I run 14 gauge wire (15A) from each battery to the inverter, or do I need to size it for the 100+Amps the whole system will be pulling?
6. When charging, as long as everything is wired in parallel, can I hook the charger (solar controller or external AC) to a central bus and charge everything together?
7. Is battery balancing needed with multiple AGM batteries like it is with capacitors and Li-Ion batteries?

Tool Box: www.lowes.com/pd/CRAFTSMAN-VERSASTACK-System-20-in-Red-Plastic-Wheeled-Lockable-Tool-Box/1000578397
Batteries: www.amazon.com/dp/B00K99CJKQ/
Full pricing so far: Solar Generator.xlsx (15.69 KB)

Last Edit: Sept 4, 2020 14:35:03 GMT by wvengineer

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the light works
Demi-God

Posts: 38,742

Solar Generator Build Sept 4, 2020 15:15:03 GMT

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Post by the light works on Sept 4, 2020 15:15:03 GMT

I think they now have an all-in-one solar module that will do all the electrical conversions in one box. as for true/modified sine - that really depends on what electronics you will be using. motors don't care, and if you want a built in music system, you can always use a car music system straight off the 12V system.
run the big wire from batteries to inverter. this is a performance issue even before it becomes a safety issue. undersized wire will cause low voltage issues. something the fire department found when our mechanic wired inverters to run cell phone and radio chargers on #12 wire. (you know, because installing an inverter is so much easier than buying a 12V cell phone, and radio charger)

addendum: pretty much anything electronic can be gotten with a power supply that will run directly off the DC system.

Last Edit: Sept 4, 2020 15:16:27 GMT by the light works

wvengineer
Evil Senior Member

Just this guy, you know...

Posts: 2,678

Solar Generator Build Sept 4, 2020 19:43:34 GMT

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Post by wvengineer on Sept 4, 2020 19:43:34 GMT

In theory, if you are running a 1500W inverter off of 12 batteries in parallel, each running 12V, it is pulling 10.4 amps from each battery. Even is you oversize and use 12 gauge wire (20A) from the inverter to each individual battery, the wire should be able to support the current draw. At least in theory.

What is real world application like? Will a device pull from all batteries evenly, or will it vary as they are used?

"In the beginning, the universe was created. This has made a lot of people very angry and has been widely regarded as a bad move." -- Douglas Adams.

the light works
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Posts: 38,742

Solar Generator Build Sept 5, 2020 0:18:55 GMT

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Post by the light works on Sept 5, 2020 0:18:55 GMT

Sept 4, 2020 19:43:34 GMT wvengineer said:

In theory, if you are running a 1500W inverter off of 12 batteries in parallel, each running 12V, it is pulling 10.4 amps from each battery. Even is you oversize and use 12 gauge wire (20A) from the inverter to each individual battery, the wire should be able to support the current draw. At least in theory.

What is real world application like? Will a device pull from all batteries evenly, or will it vary as they are used?

standard parallel battery connection is to connect all the batteries in parallel, and then connect the battery set to the inverter. otherwise, you have to have a 12 position busbar on the inverter.

and I am told you want all the batteries to be the same model and age, or they will develop what is essentially a convection current in the battery bank and drain themselves. no, I haven't tested it.

GTCGreg
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Solar Generator Build Sept 5, 2020 3:45:04 GMT

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Post by GTCGreg on Sept 5, 2020 3:45:04 GMT

First question I have is why are you using such tiny batteries? You would be better off using one or two 100AH AGM batteries rather than a dozen 12AH. Probably wouldn't cost that much more and you wouldn't have to worry about bussing them. Use the heaviest wire you can handle between the batteries and inverter. I'd recommend at least 0 gauge automotive battery or welder cable. Even a 1 or 2 volt drop on a 12 volt system can be critical. I'd also stick with 12 Volts. 1500-2000 Watt modified sine 12 Volt inverters are relatively cheap and easy to come by. 24 or higher voltage inverters will cost twice as much for the same wattage and your choices are limited.

If you do go with multiple batteries, you don't need to worry about balancing AGM's if they are in parallel so long as they are the same type and AH capacity. Wiring them in series can be a little trickier. Another reason to stick with 12 volts.

If you're looking for a source of 12 Volt high amperage wire, connectors, switches and circuit breakers, check out waytekwire.com. They have a pretty good selection and their prices are reasonable. Or maybe I should say as reasonable as everyone else's.

Sounds like an interesting project. Keep us updated on how it's going.

Last Edit: Sept 5, 2020 3:59:38 GMT by GTCGreg

the light works
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Solar Generator Build Sept 5, 2020 12:29:07 GMT

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Post by the light works on Sept 5, 2020 12:29:07 GMT

Sept 5, 2020 3:45:04 GMT GTCGreg said:

First question I have is why are you using such tiny batteries? You would be better off using one or two 100AH AGM batteries rather than a dozen 12AH. Probably wouldn't cost that much more and you wouldn't have to worry about bussing them. Use the heaviest wire you can handle between the batteries and inverter. I'd recommend at least 0 gauge automotive battery or welder cable. Even a 1 or 2 volt drop on a 12 volt system can be critical. I'd also stick with 12 Volts. 1500-2000 Watt modified sine 12 Volt inverters are relatively cheap and easy to come by. 24 or higher voltage inverters will cost twice as much for the same wattage and your choices are limited.

If you do go with multiple batteries, you don't need to worry about balancing AGM's if they are in parallel so long as they are the same type and AH capacity. Wiring them in series can be a little trickier. Another reason to stick with 12 volts.

If you're looking for a source of 12 Volt high amperage wire, connectors, switches and circuit breakers, check out waytekwire.com. They have a pretty good selection and their prices are reasonable. Or maybe I should say as reasonable as everyone else's.

Sounds like an interesting project. Keep us updated on how it's going.

and as I said, our mechanic wired the inverters in our conflagration response engines on small gauge wire, and hey went into low voltage shutdown just trying to charge a cell phone.