Building a 24v system - need assistance with diagramming.

[Solar baby]

Hi.

I wanted to ask about a solar set up that I wanted to bring for long term camping.

I would like a 24v system (Gyll 24v from Signature solar)due to [various benefits of 24v] with a Growatt all-in-one inverter, but there were two 12v appliances I would like to run.

I believe Will Prowse's video "$1050 DIY LiFePO4 Version of the EB240 Solar Generator: More capacity for $550 less" is essentially what I would copy, but I wanted to know how I should alter it to include a 24v to 12v dc/dc converter. I was hoping someone would be able to help me.

Thanks.

 

[Diysolar123]

what is your use-case for the 12v appliances? Occasional use? what would the current load be; 100amp inductive, 5amp heater? Would you want a special 12v "on" switch or rather have something wired up at all times so you can just forget about it?

If you want a very high efficiency 12v power supply with lots of protection, consider just using a standrad PC power supply! These supplies provide very stable outputs for 12 and 5v with surprisingly high currents. The platinum supplies are quite efficient even when not supplying much of a load.
This means your 12v/5v power bus comes from a standard commodity item you can find almost anywhere if it breaks!!

For a similiar price you could get also get DC power step down converter, not as efficient (80%ish) but you do not have to use your inverter AC output so no double conversion penalty. This would not be a commodity item, so if it breaks you probably need to hit your favorite online merchant and get another hehe.

24v systems definitely have advantages when it comes to power delivered and wire sizes. However, 12v is more of a common standard and if you do not plan on long cable runs (solar to mppt, battery to inverter), investing in a bit larger cable may make a 12v smaller system more desirable.
Then again, perhaps you do plan on deploying a half dozen 200W solar panels while camping

 

[Solar baby]

If you want a very high efficiency 12v power supply with lots of protection, consider just using a standrad PC power supply! These supplies provide very stable outputs for 12 and 5v with surprisingly high currents. The platinum supplies are quite efficient even when not supplying much of a load.

I have an old 650 bronze power supply I could use, might not be the most efficient but it should work. How would I retrofit the regular PSU modular cables to work with a 12v appliance (or do I need to buy different cables)?

My use case would be one or two 12v lights, a fridge/freezer, and occassionally a diesel heater. I would say 30A max and I suppose it would mostly be a constant load from the fridge.

I plan on being in a car for a few weeks and then long term camping on a property so not yet with the half doesn't solar panels!

 

[Diysolar123]

If you really want to run a fridg/freezer (understandable as it very convenient) even a high efficiency small marine unit is probably going to use 100-200watts. How much power over the course of the day it would use is dependent on environment temp, how often door open, etc.
12v lights can run on 24v system... just run 2 of them in series hehe
if you have not acquired the items yet, consider just getting 24v items if you really want a 24v system.
If you already have the items try and find the power usuage in the manuals. The only item that looks challenging is the fridge/freezer.
Regarding the diesal generator they often have very low power requirements, once again if you have the manual take a look for the current draw. (here comes another "if")... if the generator only need "maybe" 1amp, not worth anything complicated; just get simple buck (down) converter.

 

[Solar baby]

Regarding the diesal generator they often have very low power requirements, once again if you have the manual take a look for the current draw. (here comes another "if")... if the generator only need "maybe" 1amp, not worth anything complicated; just get simple buck (down) converter

The one I was looking at was one of the cheap chinese AIO kits on amazon, I only plan on being on a vehicle for a few weeks and then I'm going to use firewood at camp. They said 10A max current but closer to 2-3 A/hr. I'm not really worried about carbon monoxide, if I died that way it would be 6 years overdue lmao.

It probably is easier to just run 24v lights/fridge etc. I've seen some 24v chest freezers.

Here comes the stupid question, how do I wire that for 24v dc? Would I just have a panel wired to the battery?

 

[Alphacarina]

The advantage to a 24 volt RV system is primarily that you can run a large inverter using manageable wire sizes. If you're thinking you only need a 1,000 or 1,500 watt inverter, maybe you would want to rethink the need for 24 volts

The disadvantages of 24 volts are that all your 12 volt loads now require a DC to DC step down from 24 to 12 and also, you would have to run your solar panels in series, which means when any panel is partially shaded (as often happens on an RV roof) then you lose almost all your solar power

Sticking with a 12 volt system, with panels in parallel might make more sense in an RV with several 12 volt loads

Don

 

[John Frum]

Sticking with a 12 volt system, with panels in parallel might make more sense in an RV with several 12 volt loads

Why would you need to keep the panels in parallel?
Just choose a solar charge controller to accommodate your panel configuration.

 

[Diysolar123]

regarding the AOI units, good idea, makes things simple. Do not go to cheap or it will not work/kill your batteries.
You want to make sure the devices will safely support whatever battery chemistry you will be using.
I mentioned the simple 24-12v downconverter (called buck converter) because you may not need much for the generator and you should get a 24v fridge/freezer as that is going to be your main load. Actually, whatever device is the biggest draw on your system that you want to run directly off the battery pack should probably be the "design driver"; e.g., 24V fridge==24volt system, 12v fridge==12volt system. This makes things easier if you lay it all out and think about the easiest path to your goal.
It is always helpful if you lay out your resources and goals first. It sounds like your "goal" is to have lighting, cold storage, and heat in an easy and cost effective way. Now if your goal is "I want to build a 24V solar system and will shoehorn in other things as needed", well, thats a different goal hehe

take some paper or perhaps your favorite drawing tool and layout your plans with measurements.
add in each physical device and how far apart they may be (longer runs with higher current will need larger guage wires).
so far you have lights, refridgerator/freezer, generator, solar panels (probably want some usb outlets in there for phone/tablets).
Do you have any 120v items that may be big power users?

you then should decide on what connector type you want to use to distribute the DC power and stick with whatever you decide to connect devices to the power bus.

for solar use MC4 cables, the solar standard...

common DC connectors are:
(1)anderson powerpole - they are a bit pricey but a standard for distributing low voltage power; they are crimped and you will probably want to get a powerpole crimp tool; use 45amp connectors/housing for everything for compatibility; you can buy powerpole bus bars with fuses as they are popular in the ham radio community (go on youtube and lookup diy ham radio battery box...sometimes it may make sense to just get a small quite generator and a propane tank for fuel hehe)
(2)amass - XT90 connectors: cheaper than powerpole connector, you solder them(you need a pretty good solder iron), good to 90amps; popular with the remote control model community;10awg; these are single units and the cases are marked with +/- so easy to get right when building
(3)XT150 connectors - barrel connectors that are seperate unlike the xt90's , you need to watch how you solder the female/male connectors and cases so you do not goof it up hehe; flexible, not to costly, handle upto 8awg wire easily so better for longer cables

I would lean towards anderson powerpole connectors and depending on available funds you could just buy prebuilt cables (cheaper to make your own however).

oh.. do NOT buy cheap cable such as aluminum and the most vile.. CCA.. copper clad aluminum, which is often called copper and the CCA tag is in super fine print so they hope you will not notice, sigh...

 

[Alphacarina]

Why would you need to keep the panels in parallel?
Just choose a solar charge controller to accommodate your panel configuration.

I thought I explained that. On an RV roof, where you don't have much control of what might shade a portion of your panel(s) at some period during the day, with series panels you lose ALL your solar output when a portion of any panel gets shaded, but if you parallel your panels and one panel gets shaded, the other panel(s) still produce, so you don't lose everything. One BIG disadvantage for a 24 volt system in an RV is that it requires you to put your panels in series

Don

 

[Alphacarina]

Probably, but you'd need a pretty big RV to be able to handle 300 watt panels. Most RV's have so many other things on the roof, A/C units, ventilation fans, antennas, tank vents, skylights, a vent for the propane refrigerator that large free areas are pretty hard to come by, so usually solar arrays are a series of smaller panels, typically 100 to 150 watts, placed where you can find the space and arranged in either series or parallel

Don