Need help with new build

frankster

New Member
Joined
May 11, 2021
Messages
4
I have been reading for weeks, maybe months now and the more I read the more confused I get. I am trying to design a system for my office. My office is just a gutted single wide trailer. (old school classroom). I am wanting to power 2 laptops, 2 LED tv's, printer, credit card machines, few phones, and a string of plug in led shop lights. All of this just plugs into 1 surge protector/power strip. Very simple. When everything is on and running, it uses 600watts. (via my killawatt meter). We do not use any of the wiring in the building. Currently we just run an extension cord through a hole in the floor to a generator outside to power everything. Everything is plugged into 1 power strip. I would like to build a solar system to power this. But the more I read, the more confused I get. The generator works great, I'm just tired of dealing with it daily. I would like to come in and start working without having to crank up a generator everyday. I use the office almost daily, but really only 3 days a week I'm there all day. Some days I'm only there for a few hours..

I would like to "over panel" so I can run my load just off the panels, while keeping the batteries charged for mornings, evenings, and night. From my research, it seems 1000-1200 watts of panels will suffice. I plan on keeping the generator for extended times of bad weather. (when its cloudy or rains for a week straight) I want to use the solar as much as reasonably possible. I would also like to be able to use my generator without having to unplug from the solar system. Also, if I need to use the generator, I would like for it to charge the batteries while I do. IE: if its cloudy for a week and my batteries are low, I would like to crank up the generator to power my stuff, but also charge the batteries at the same time. Then when batteries get full, turn off the generator and finish my day on battery power. Something with a grid tie/generator tie function is a must.

Now since its only for an office with out any high draw items or anything that really surges, it seems a 1000 watt inverter would work, but a 2000 watt might be better if I decide to add down the line. But, its never going to be much more than general office equipment. Obviously a Pure Sine Wave is best.

I got excited and purchased 2 batteries. I bought 2 of the ampere time 200ah lithium batteries on amazon. So I have a total of 400ah. That should be a good start. I can always add 2 more if I end up needing more battery run time. After that, I started reading more and got more confused and didn't want to buy anything else until I had a solid plan.

So now I need the rest of the stuff. I have been looking online at wiring diagrams, tutorials, etc and they all seem to be geared for campers and RV's. They have things that I wont need like alternator charging and 12v fuse boxes for appliances that I don't have. Then they get into fues, busbars, shunts, breakers, shut off switches, etc. All I need to power is 1 power strip with several small electronics. That's it. Are there any diagrams available for a simple 1000-1200 watt system? Should I go 12v or 24v? Where and what type of panels should I get? I have plenty of roof space, but installing 12x 100 watt panels seems dumb when I can get the same wattage out of 4x 300 watt panels. What are the benefits of smaller 100-200 watt panels that are available on amazon vs the used panels from santan solar? I understand that santan shipping is quite expensive, but the total price paid per watt can be far less.

Now, as I look though prices of victron charge controllers, inverters, battery monitors, shunts, etc.. It quickly approaches the cost of a solar generator. Just the price of a victron multiplus and a charge controller is almost as much as the bluetti ac200p. Looking at the bluetti ac200p, it look like that will do almost everything I need. It will only accept 700 watts of solar, but that might get me through the day. If needed, I can crank up the generator and charge the bluetti off the generator while I work. I would like something a little more powerful than the ac200p, but for the price it seems like the best bang for my buck. And I dont have to wire a bunch of stuff and deal with fuses, breakers, whatevers....

There's just so many options and I get lost looking at all the diagrams.. What about a solar generator where I just add my own batteries? Does that exist? I guess that's what a modular solar system is. I've looked at the all in one inverter/charge controller/grid tie systems. They look nice, but seems like getting one might be tricky. All the victron stuff plus others is readily available on amazon, but the all in one units seem to have counterfeits.. But they also have inverter/charger combos but would still need a seperate charge controller.. I also don't want to throw down a bunch of money on something that comes out of china with no way of getting a warranty handled if I have problems with it 6 months later. Any suggestions?

Thanks!
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
3,258
Please hold off on buying further equipment until you have a good plan.

600 watts max is a start, but need to turn that into KWh/ day. A 1000 watt inverter will be fine, unless any of this equipment is a motor, but computers will be fine.

With batteries, had you bought lead acid, this would have been impossible to add on later. Now with your lithium’s, it is just difficult to add on later.

Also, a 2 kw inverter down the road can mean a huge rise in power consumption as you add on higher wattage items.

For 12 volt or 24 volt, that’s your choice At 1000 watts. It’s nice to break out of the 12 volt mold, but truth is if you power anything except your inverter off this, like a string of DC LEDs or fans, etc., finding 24 volt appliances is hard, and finding 48 volt appliances could be impossible.

If this needs to be a money saving thing, because perhaps the church is funding this, just run a line to the trailer from the main breaker box. The 400 ah of lithium you bought will just be the tip of the expenses.
 

frankster

New Member
Joined
May 11, 2021
Messages
4
Its hard to do kwh/day. some days we are not here, some we are here all day.
No motors, just small electronics that are stated above.
Not looking to power more than the 600 watts. wiggle room to 800 is nice, but will prob never see that.
There are no DC appliances. only 120v electronics stated above that plug into 1 power strip
Not really looking for something cheap.. Im looking for a system that will do what I need. We are currently 100% off grid and use generators daily. Im getting tired of filling gennys with gas, going to get gas, changing oil, all that.. I would love to just walk in, turn on the inverter and everything start working..
 

Substrate

Solar Addict
Joined
Apr 28, 2021
Messages
871
Location
SoCal
@frankster - thanks to your choice of LFP and actually taking a measurement we CAN do it the old school way.

Let's break out the napkin-calc:

600watts measured. Great. Assume use of a 12v inverter. We can napkin-calc the load appearing at the battery terminals:

600 watts / 10 = 60a draw at the battery terminals

The reason we used 10 instead of the customary 12v, is a napkin-fudging account for some ac inverter losses. If you were to put a dc-clamp meter on this, you'd be pretty close to the neighborhood of 60a continuous draw.

You have 400ah of nice LFP fully charged. Fortunetely LFP doesn't suffer peukert. How many hours can you run?

400ah / 60a = 6.6667 hours. Will that be enough daily?

One thing you can do, is make sure those televisions have their BACKLIGHT if an option turned down. Then you can adjust BRIGHTNESS turned down too. Backlight, if you have it, is more effective than brightness. You may be able to cut nearly half of what you are using now from the televisons / monitors.

Your Kill-A-Watt meter will tell you just how effective this is immediately. But will your "employees" be able to stand it with backlight or brightness turned down a bit?

So before we move on, are you totally out of the ballpark right now?
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
3,258
To charge 400 AH of 12 volt batteries, go to a site like PV Watts and see how many panels you need to produce power. You may get a number like 2 in the winter, and 5 in the summer, which means the panel will produce over the course of a day 5 times its rating in the summer and 2 times its rating in the winter. So, in my example, you’d need 2400 watts of panels planning for the winter. Plz keep in mind those are not the numbers for your area, they are random numbers just to show the difference between summer and winter. I’m in sunny AZ and my numbers are much better.

THere’s a couple of gotchas though. Your Lithium batteries probably have a max charge rate of 200 amps. That is a lot of amps. 2400 watts of panels can come close to or produce that much power, and wiring that size is probably require 2/0 or 4/0 when pushed from the SCC to charge the batteries. Still a lot more to it than that. Again, if you’re in a good solar area, 2400 watts of panels will be cut back Making the numbers between.

As far as volunteers, employees, or family, I’ve never found anyone as motivated to save energy as I am, and often times people think conservation is only meant for when I am around. It’s not that they ignore you. I had my wife plug in a 1000 watt heating element for food when we first did are build. Had no idea how much that would draw.
 
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