Off Grid Solar Shed - Choosing Batteries - First Post and PV Project

[unt0uchable]

I get it. I'll just pick up 2 of the lower end batteries at Wal-Mart and go from there. My inverter will be in today, so before I tear down the cheap HF stuff and return it, I'm going to hook up this old Autozone battery I have and see what I can do with it. It's been sitting in my garage for a year now. I charged it up yesterday so we'll see how it goes....

Everything else is ordered and on the way. I'm excited, but this put me back another 3 weeks or so on getting the solar power going. At least I have 90 days to return the HF stuff...ha.

[Mike90250]

Since most folks ruin their first battery I would suggest an inexpensive marine hybrid battery in the 100 ah range. ....

AKA Costco/Sams/Kmart Marine Battery in the $90 ballpark Leave out the word Hybrid when asking for it. Just Marine Deep Cycle

How can I avoid ruining my first battery?...

95% of folks don't avoid it, so it's best to practice with a cheap one. Often it's a setting on the charge controller set wrong, or using 40ah a day, and replacing with only 35ah, works for about 2 weeks, then you are gone for a couple days, battery charges back up, and has had 1 year taken off it's life in those 2 weeks of deficit charging. And don't forget to add water.

[Naptown]

By keeping the water level up
Never discharging more than 20% of capacity
Checking specific gravity with a temperature compensated hydrometer
And applying an equalize charge when the battery becomes stratified and finally by making sure a partially discharged battery is recharged in a timely manner

[unt0uchable]

How can I avoid ruining my first battery?...

[Naptown]

Since most folks ruin their first battery I would suggest an inexpensive marine hybrid battery in the 100 ah range. This would be a learning battery to be replaced with better quality when dead and some battery maintenance items become second nature

[unt0uchable]

Well, it looks like this system has gone into the redesign process. I've got a 30a mppt controller on the way and a 100w monocrystalline 40x27 panel on order. It was all in all about $30 more than the harbor freight setup with the coupon I had. I'm glad I decided on this. The setup will provide me with closer to 8a of charging instead of 2-3... Now I should be able pin point which ah battery I want to get. Any more suggestions?

Thanks so far.

[Naptown]

You can pick up a 250 Watt grid tie panel for under a dollar a watt.
The controller will be a bit more but look for a 20-30 A MPPT charge controller.
The operative word there is MPPT
You get what you pay for so beware of a deal that seems too good
Best IMHO at lowest cost is the Morningstar sun saver mppt
That set up although more costly will give you more than 6 times the available power to use in the shed and will support about a 250 amp hour battery

[unt0uchable]

I do still have the box for the Harbor Freight stuff panel setup and charge controller. I am working on a fairly tight budget so what would you recommend I get in place of these? I'd love suggestions!

[Naptown]

Those panels and the controller can only support about a 30 ah battery
You will lose 1/3 or more through that controller. So you effectively have about 30 watts to work with
That inverter may use more for self consumption than it will produce for you.
Once you pull more than about 36 watts from the battery the voltage on the battery will start to sag and the capacity will go way down.

Can you return that stuff and perhaps get some real panels and controller?

[unt0uchable]

I'll start by introducing myself. I'm David. My father in law and I just built a shed for myself and although he could have easily dug up my yard and ran electricity to it, I chose to make it solar powered instead. This is my first go around with the technology. I'm really enjoying learning about this and he is too (being over 50, he enjoys learning about new technologies, and with myself being 23, and my wife 25, we are always helping them learn the newer age stuff, lol)

Here is the equipment I used (nothing fancy)

-Harbor Freight 45w 3-Panel Setup w/Charge Controller
-Bestek 2000w 12v-120v inverter (I know, overkill. But It was a decent price on Amazon. I don't plan on maxing it out)
-Batteries: That's why I'm here. Read below please.

Here are some photos to show the setup thus far.



Closeup of the panels...(before I tied up the wiring nicely)


I'll point it out now that you're correct if you're saying "boy his panels are laying down quite a bit". They are only sitting at around 22* facing directly South. When we did the measurements with the latititude+15* or so, the angle came out to somewhere around 55* and they were nearly standing straight up off the shed. How much is this going to effect my charging? I live in SE Michigan and the sun hours avg 4, 2.7 on the low side, and winter is approaching.

I'll basically be running lights, and maybe a radio off of this setup. The shed is wired with 6 110v outlets as well which will be powered by the inverter listed above, so I might see how it works with a dremel tool or something. But that will all be trial and error to see what it can handle at this point

The inverter will be here tomorrow. I currently have 1 regular old lead acid car battery waiting on my shelf just to hook up and try the system out with. I don't expect it to hold much energy for me. That leads me to my next question, and ultimately why I joined the forum and posted my project.

I'm on a smaller budget since this is only my work shed and I'm not trying to go over the top here. I'd like to run 2 12v batteries in parallel. So far, I have learned that what I want is a higher aH rating. I've found a couple of low cost options available via eBay that I'm watching currently. I just want some yay's or nay's from the pros around here so I know whether or not I'm wasting my money on garbage.

The first one that caught my attention was a Max Life 12v 35aH Deep Cycle Solar Battery. Two of these can be had for around $130 shipped, which would ultimately give me 12v @ 70aH.

The next one is a UB12500 which is a 12v 50aH Wheelchair Battery. I can get one of these for around $95.

Another one I found was similar to the one above but it's a Group 24 12v 75aH rating instead, still advertised as a Wheelchair battery. These cost $150 each.

I don't think I'll need more than 2 batteries for what I'll be using this setup for. When I am in the shed, I'll be running three 4' shop lights that call for 110v@.8amps from the inverter, and possibly a 12v car stereo that I plan on mounting and wiring into the shed so tunes can be heard around the yard.

Am I on the right track with any of those battery choices? I'd like to spend around $200 on batteries and be alright with the setup until I find a need to grow the battery bank.

Thanks for any tips and help with my setup.