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diy solar

Wire sizing help, and other basic help to start

dedoubt

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Jul 26, 2022
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8
(I did look through other similar threads but couldn't understand enough to get the information I need.)

Hi all. This is my first post in this forum, though I've posted a bit in the DIY solar subreddit. I've been reading/watching videos until my eyes bleed and my brains boil, but every time I think I've understood something, I realize I actually don't. People familiar with solar understand all the acronyms & basics so well that even when someone explains something in what they think is simple terms to me, I feel like a deer in headlights. My starting point is 100% a beginner with very little understanding of electrical work, and I've had some cognitive and memory deficits since having covid in 2020. I do have someone who has some familiarity with electrical work to help me a bit, so I'm not going to burn anything down, but I need to get all the components together first.

We are going to be living totally off grid in Maine. Our needs for power are pretty minimal right now- charging a few cell phones, a few LED lights, maybe a fan now & then and my CPAP machine (another gift from covid). We are going to be living in a 5th wheel RV & tents while we build dwellings.

I've got 1 Renogy Rover 40 Amp 12V/24V DC Input MPPT Solar Charge Controller, 1 Renogy 2000-Watt Pure Sine Wave Inverter 12V DC to 120V AC and 4 Grape Solar 100-Watt Monocrystalline Solar Panels and buying 2 more of the same panels (600 w total). I've got old lead acid batteries right now (my friend is giving me two used batteries Absolyte GP batteries to get started- he said "The batteries are high quality deep cycle dry lead acid. They are 11 yrs old and have a 20 yr service life anyway. They are 12v batts."), but working on upgrading to the LiFePO4 asap (any pointers on getting affordable ones and how much to aim for would be much appreciated). ETA- he finally wrote back and said they are 1600ah batteries.

Tl&dr:

I pretty much need everything explained to me like I'm a 5 year old who is capable of handling tools (sort of, I did manage to chop the end of my finger off recently making dinner, ha ha). I really cannot figure out what size and length wires to buy, or what the other small components I need to complete the system will be. Planning to put the panels on the RV roof for now, and I think putting the batteries/other parts under the overhang of the 5th wheel? If it’s enclosed, batteries up on pallets and in an insulated box, is that ok?

I miss having a brain so I could figure things out on my own.
 
Last edited:
(I did look through other similar threads but couldn't understand enough to get the information I need.)

Hi all. This is my first post in this forum, though I've posted a bit in the DIY solar subreddit. I've been reading/watching videos until my eyes bleed and my brains boil, but every time I think I've understood something, I realize I actually don't. People familiar with solar understand all the acronyms & basics so well that even when someone explains something in what they think is simple terms to me, I feel like a deer in headlights. My starting point is 100% a beginner with very little understanding of electrical work, and I've had some cognitive and memory deficits since having covid in 2020. I do have someone who has some familiarity with electrical work to help me a bit, so I'm not going to burn anything down, but I need to get all the components together first.

We are going to be living totally off grid in Maine. Our needs for power are pretty minimal right now- charging a few cell phones, a few LED lights, maybe a fan now & then and my CPAP machine (another gift from covid). We are going to be living in a 5th wheel RV & tents while we build dwellings.

I've got 1 [Renogy Rover 40 Amp 12V/24V DC Input MPPT Solar Charge Controller](https://www.homedepot.com/p/Renogy-Rover-40-Amp-12V-24V-DC-Input-MPPT-Solar-Charge-Controller-Auto-Parameter-Adjustable-LCD-Display-RNG-CTRL-RVR40/301741394), 1 [Renogy 2000-Watt Pure Sine Wave Inverter 12V DC to 120V AC](https://www.homedepot.com/p/Renogy-2000-Watt-Pure-Sine-Wave-Inverter-12V-DC-to-120V-AC-Converter-for-Off-Grid-Solar-Power-w-Built-in-5V-2-1A-USB-Port-RNG-INVT-2000-12V-P2/308843205) and 4 [Grape Solar 100-Watt Monocrystalline Solar Panels](https://www.homedepot.com/p/Grape-S...Boats-and-12-V-Systems-GS-Star-100W/204211365) and buying 2 more of the same panels (600 w total). I've got old lead acid batteries right now (my friend is giving me two used batteries Absolyte GP batteries to get started- he said "The batteries are high quality deep cycle dry lead acid. They are 11 yrs old and have a 20 yr service life anyway. They are 12v batts."), but working on upgrading to the LiFePO4 asap (any pointers on getting affordable ones and how much to aim for would be much appreciated).

Tl&dr:

I pretty much need everything explained to me like I'm a 5 year old who is capable of handling tools (sort of, I did manage to chop the end of my finger off recently making dinner, ha ha). I really cannot figure out what size and length wires to buy, or what the other small components I need to complete the system will be. Planning to put the panels on the RV roof for now, and I think putting the batteries/other parts under the overhang of the 5th wheel? If it’s enclosed, batteries up on pallets and in an insulated box, is that ok?

I miss having a brain so I could figure things out on my own.

Sorry to hear about your long covid experience. A business associate of mine has been dealing with some long term side effects since he got it a year or so ago.

Does the 5th wheel already have any sort of DC system and generator in place? Or does it rely on power from outside sources, like a truck or shore power?

Do you have anything like a killawatt meter so you can figure out how much battery capacity you will need to run your cpap and other items?
 
Sorry to hear about your long covid experience. A business associate of mine has been dealing with some long term side effects since he got it a year or so ago.

Does the 5th wheel already have any sort of DC system and generator in place? Or does it rely on power from outside sources, like a truck or shore power?

Do you have anything like a killawatt meter so you can figure out how much battery capacity you will need to run your cpap and other items?

Thanks so much. Yeah, the long covid is not much fun, and even with the pain, fatigue, etc. the cognitive impairment is the worst part. I can force myself through the fatigue to get things done at this point (I couldn't a few months ago) but I still can't think well enough to learn new things.

The RV is very old & had a pretty bad leak & the ceilings and walls are coming out. I assume the electrical systems are fried in it and will not be using them (it has a propane stove/oven, fridge & heating system), am planning to just plug things into the inverter. The RV is not a long term dwelling so I'm not putting a lot into fixing it.

I don't have a meter but have estimated using online calculators that we'll need about 1500 watt hours per day.
 
Thanks so much. Yeah, the long covid is not much fun, and even with the pain, fatigue, etc. the cognitive impairment is the worst part. I can force myself through the fatigue to get things done at this point (I couldn't a few months ago) but I still can't think well enough to learn new things.

The RV is very old & had a pretty bad leak & the ceilings and walls are coming out. I assume the electrical systems are fried in it and will not be using them (it has a propane stove/oven, fridge & heating system), am planning to just plug things into the inverter. The RV is not a long term dwelling so I'm not putting a lot into fixing it.

I don't have a meter but have estimated using online calculators that we'll need about 1500 watt hours per day.

Will you still be in this living situation come winter? I don't think you will have enough solar panel production to power that load and keep those batteries topped up, not now, and certainly not in the winter, in Maine.

Do you have access to a running vehicle or generator that can be used as a power source to top up the batteries as needed? There are cheap ways to use a car to do so if you don't have a generator or don't want one, but leaving your car running for prolonged periods, potentially unsupervised, for however long it takes to recharge might not be something you want to do.
 
Will you still be in this living situation come winter? I don't think you will have enough solar panel production to power that load and keep those batteries topped up, not now, and certainly not in the winter, in Maine.

Do you have access to a running vehicle or generator that can be used as a power source to top up the batteries as needed? There are cheap ways to use a car to do so if you don't have a generator or don't want one, but leaving your car running for prolonged periods, potentially unsupervised, for however long it takes to recharge might not be something you want to do.

We will not be staying there this winter, and by the next winter we will have better batteries/more solar if needed.

I do have a gas powered generator- good to know it can be used to charge the batteries, I hadn't even considered that. Wasn't planning on using it much because I hate how loud and stinky they are, but we can use it as needed,

Is the issue that the batteries are not going to hold enough charge or we don't have enough panels?
 
? Is your response just not showing up, or is that period your only response? If so, why?
I decided to give this thread a pass.
I would probably just confuse you behind the point of madness.
 
We will not be staying there this winter, and by the next winter we will have better batteries/more solar if needed.

I do have a gas powered generator- good to know it can be used to charge the batteries, I hadn't even considered that. Wasn't planning on using it much because I hate how loud and stinky they are, but we can use it as needed,

Is the issue that the batteries are not going to hold enough charge or we don't have enough panels?
That solves the winter problem then.

I can't say for sure without detailed specs on the batteries, but they probably just won't be enough battery for your system due to old age / possible mistreatment. Maybe, if they have been in active use and treated very kindly with no periods of disuse. Lead acid, and AGM ones in particular, don't like being stored and not kept charged up.

Then there is also the solar issue, solar panels rarely produce anything approaching their rated wattage, even in good southern sunny climates like mine here in Texas. I see about 80% of my panels ratings on a good day. I would guess you would probably see about 300-400 watts when the sun is shining at it's peak with no clouds.. maybe get about 4 hours of that a day in Maine, with the rest of the day being significantly lower production.

The fact that you have a generator is helpful though, all you need is a 12 volt AC powered battery charger that can do lead acid / AGM batteries in an amperage that is within your generators output, and you can charge your batteries back up if you didn't get enough solar for the day. Worst case scenario is you have to run the generator a lot more often than you would like.

Alternatively, you could get another smaller inverter to run from your car (with it on) and use that same 12 volt AC powered battery charger to recharge your batteries from your car instead. Your car is probably much quieter than your generator, and likely easier to turn on and deal with, probably always has gas in it as well.
 
Wire sizing is based on load in amps and length of run. Higher voltages reduce amps for a given load. Watts= Volts X Amps
Higher voltages also suffer less voltage drop as distance increases.

12 volts at 10 amps = 120 watts
24 volt at 5 amps = 120 watts.

So if you were sizing a wire based on that you would look for a gauge that was large enough to carry the amperage. As you can see the larger voltage would mean that you could go with a smaller wire.

But distance the voltage is transported also plays a factor. The greater the distance the more resistance and thus the voltage drops. The larger the conductor the less resistance.

There are tons of charts you can pull up on the internet that give you wire amp ratings and percent voltage drop for length of run.
 
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