diy solar

diy solar

Hi from Texas! Who's built a mobile workshop?

Whitemystery

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Jun 1, 2022
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Hey Y'all, I'm Aaron. Welder/Fabricator, Blacksmith, Handyman type fella!
I recently purchased a 16' Enclosed trailer to convert into a workshop space. I've begun installing 12v lights and fans in the cargo trailer and needing a way to power them. I also plan to set up shore power inside the trailer, and it will be used stationary (and on grid-power) probably all of the time at first. After spending all of my savings on the trailer itself, this is going to be a paycheck to paycheck build and the budget is tighter than a duck's ar$e for the time being! So I'm hoping to build this piece by piece based on my current needs.
One important thing to note is that I plan to always be on Shore power in the beginning of this Trailer's use, but want to build toward the ability to go Off-grid with it down the line.
Please if these questions have already been covered, or there are Keywords I might use to find these answers, I'm happy to start there. I just don't even know exactly what to search for since the majority of information I find is geared toward Van/RV/Home builds. I'm just trying to confirm my understanding of concepts I've yet to find explicitly confirmed.

So far the Growatt SPF 3000TL LVM looks like my best bang-for-the-buck as for my long-term needs balanced with my budget.
I will pretty much always be on Shore power in the beginning. This brings up question number...
1. Am I making any fatal errors in my understanding that this device could charge my batteries (while plugged into shore power) with no solar panels connected? And also basically convert the 120v input into 12v power to run those lights and fans safely? Are there any real downsides to this plan that would make another device a far better choice here?

2. I know that such a charge controller/Inverter must be connected to a battery/bank in order to operate, but is there any minimum limit to the Amp hours (size) that would make it dangerous as long as the voltage is correct? I've looked through manuals and haven't seen any such warnings, but maybe they just assume that someone wouldn't be so stupid as to try such small batteries with a device like the Growatt or similar MPP.
The idea here is to try to start as small as possible with battery capacity, so I can begin the savings for some lovely (expensive) LiFePO4 batteries, and waste as little money as possible on a Lead Acid "starter kit."
Ex. Could I run 2x 12v 20ah Lead Acid batteries in Series (to make 24v) on that 24v Growatt unit while plugged into Shore power?

A final note: I don't expect my 12v loads to be much more than 100w at any given time. The reason to reach for the 24v Growatt is to allow expandability when I do need the Solar power more. If hope this wasn't too much to ask for a noob. Thank you to anyone who made it this far!

Cheers!
Aaron
 
Howdy Aaron, welcome to the party. I have a 16' enclosed trailer which will be solar powered when I have time to do it, so there are a bunch of ideas in my head.

Do any of your tools, or future tools want split phase 240volt? I don't know the specs on the Growatt you mention. Including more info in posts reduces the Q&A sessions and keeps everyone from having to search for what you're talking about. Links to products help also.

Your first purchase will limit your system so I suggest designing your system to your anticipated needs.

Some AIO (All-In-One) units will charge your batteries from shore power. Download and read the manual.
I know I am not offering up answers but am trying to help.

Figure out what your loads will be and design your system around those loads.
There is an Energy Audit link in my signature which may help.

Here are very good resources.

 
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2. I know that such a charge controller/Inverter must be connected to a battery/bank in order to operate, but is there any minimum limit to the Amp hours (size) that would make it dangerous as long as the voltage is correct? I've looked through manuals and haven't seen any such warnings, but maybe they just assume that someone wouldn't be so stupid as to try such small batteries with a device like the Growatt or similar MPP.
The idea here is to try to start as small as possible with battery capacity, so I can begin the savings for some lovely (expensive) LiFePO4 batteries, and waste as little money as possible on a Lead Acid "starter kit."
Ex. Could I run 2x 12v 20ah Lead Acid batteries in Series (to make 24v) on that 24v Growatt unit while plugged into Shore power?

Most batteries will have the maximum charge current in their spec sheet. For LiFePO4 it's usually not more than .5C (half the Ah rating). 100 Ah battery, no more than 50 amp charge rate.

Some chargers can be programmed to limit the charge current.
 
Most batteries will have the maximum charge current in their spec sheet. For LiFePO4 it's usually not more than .5C (half the Ah rating). 100 Ah battery, no more than 50 amp charge rate.

Some chargers can be programmed to limit the charge current.
Thank you for this reply! That did help me dig a bit deeper and understand batteries better.
This Growatt model does appear to allow you to limit the charge current (when using Lead Acid batteries) as low as 10a.
However, something I missed before is that it says to use a minimum of 200ah battery with the 24v unit. Maybe I can attempt to contact manufacturer and see if they’ll give me more insight on this suggestion.
 
Do any of your tools, or future tools want split phase 240volt? I don't know the specs on the Growatt you mention. Including more info in posts reduces the Q&A sessions and keeps everyone from having to search for what you're talking about. Links to products help also.

Your first purchase will limit your system so I suggest designing your system to your anticipated needs.
Hey! Thanks for the welcome and your reply. I was attempting to provide relevant specifics (without getting too long winded on first post. Haha) but you’re right that a link to the product or some relevant specs could be helpful.
I’m trying to and hoping it’s possible to create a system that’s scaleable and really surpasses my initial needs. The fact that this Growatt 24v has a 3000w inverter and can be paralleled with additional units for more power and yes even split-phase 240v capability were definitely selling points towards that goal!
Realistically, I’d probably get a generator to run 240v equipment (like my welder) remotely, but just the idea of someday being able to do that with solar seems pretty awesome!
Anyway, thanks again for your tips, resources and suggestions.
 
You're welcome. @rmaddy is the "King of the Road" when it comes to trailers like ours.

The thought of paralleling inverters doesn't give me a warm fuzzy feeling. The trailer is a finite area & where 1 box will work instead of 2 boxes makes good sense.
A split phase 240V inverter & large battery will, instantly and quietly continue to provide the power you need with little to no maintenance.

A generator will always, forever and ever, require fuel, oil and more maintenance than solar power. And then there is the space for the generator.
 
I'm using one as my full time office as it turned out to be so comfy. :)

Mine is a 7x14 v-nose (so more than 14' into the nose). I have 1700 W of PV on the roof and 7 kWh of LFP battery.
 
I'm using one as my full time office as it turned out to be so comfy. :)

Mine is a 7x14 v-nose (so more than 14' into the nose). I have 1700 W of PV on the roof and 7 kWh of LFP battery.
Cool, how do you keep your batteries warm in the winter? Whitemystery will have the opposite concern with LFP; Texas heat is HOT & LONG.
 
Cool, how do you keep your batteries warm in the winter? Whitemystery will have the opposite concern with LFP; Texas heat is HOT & LONG.
I keep the entire space above 5ºC as I don't want anything in there to freeze when I am not in it. This requires the grid during the coldest months, until I install a diesel furnace.

A.
 
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