Wiring a Solar Battery Bank
…can be a bit nerve-wracking, we know.
Your solar battery bank is a key component of your off-grid solar system (and an expensive one). You don’t want to mess it up.
Here is how we set up our solar battery bank. We’ve had zero problems since installation, and it has served all our energy needs many times over!
A solar wiring diagram is included, please refer to it closely when following this tutorial. It might also be helpful to watch how we wire the rest of our solar system.
Our upcoming tutorial will show how we installed our solar panels (stay tuned!)
Solar Wiring Diagram
Liabilty Disclaimer
We are not electricians nor certified solar installation technicians. The steps outlined below are those we took to install our own system. If any of the following terminology or procedures are unfamiliar to you, please learn the basics of electrical or have an certified electrician do your installation for you. We are not held liable for actions taken on your part if you install your solar system without proper knowledge.
Materials Used to Wire Our Solar Battery Bank
- 2AWG Cables (to connect the batteries in parallel): https://amzn.to/39PsCqy
- 3ft 2/0 AWG Inverter Cables (to connect the bank to the inverter): https://amzn.to/3cp0pbI
- 1ft 2/0 AWG Cable (what components does this cable connect?): https://amzn.to/3qDcZIh
- 8ft 10 AWG Cable (to connect the charge controller to the bank): https://amzn.to/2PuYMA6
Main Components of Our Solar System
- (1) 3000W Renogy Inverter Charger: https://amzn.to/30wc69J
- (2) 40amp Renogy MPPT Charge Controllers: https://amzn.to/3bAQ4sJ
- (5) Weize 100W Solar Panels (recommended): https://amzn.to/3fKIjmM
- (5) Inergy 100W Solar Panels (not recommended)
- We do not recommend these solar panels. Here’s why: they are designed to work with only an Inergy solar generator, which we don’t recommend using as your full-time power source. It’s just not built for it. We had to modify the connection of these panels to work with our upgraded system.
- (5) Expert Power 100Ah 12V LiFePO4 lithium batteries (5% discount code: AWTY)
Full disclosure guys, some of these are affiliate links, so we get a commission if you buy something from the list. As an Amazon Associate we earn from qualifying purchases. Not much, but something. This is really important: we only link to tools and materials we actually used and highly recommend. We do these guides completely for free, so these links are the only way we get a little something back (except for the satisfaction of knowing we helped you build your dream skoolie, of course!)
Don’t have Amazon Prime yet? Here’s a link for 30 days free.
All About Our Batteries
Our solar battery bank consists of five Expert Power 100Ah 12V LiFePO4 lithium batteries. We installed them February 2021, and so far they have changed our life. We never run out of power, and we are saving a lot of money and time. We had AGMs before, and the difference isn’t even comparable.
How Our Lithium Solar Battery Bank Saves Money & Time
Lithium costs more on the front end. But if you do five minutes of math, you’ll see that going lithium saves a lot in the long run. Here’s why:
- As a rule of thumb AGMs batteries should only be discharged to 50% in order to increase their lifespan. So in order to have 500Ah of safely accessible energy, you’d need 10 AGM batteries.
- 10 100ah AGM batteries = around $1800 depending on the brand you go for.
- AGMs have a short lifespan compared to lithium batteries. In our case, we had three UPG UB121000 AGM batteries. When these particular batteries are being fully discharged at 77°F (25°C) for the first ~150 cycles, the batteries will operate almost without a loss of capacity. However, the capacity will drop to 50% of nominal capacity after a total of ~250 cycles. And when these batteries are discharged down to 50% of nominal capacity at 77°F (25°C), you could get between 350-400 cycles without a loss of capacity. After 400-550 cycles capacity will drop down to 50% of nominal capacity.
- In an application like ours (living full-time off grid and cycling our batteries on a daily basis), the realistic lifespan for our AGM battery bank is about 2 years.
- So that’s an estimated ~$9,000 in batteries over 10+ years.
- Alternatively, Expert Power lithium batteries are rated for 2500 cycles with 100% depth of discharge and 7000 cycles at 50% depth of discharge at 77°F (25°C).
- 5 lithium batteries = $3500 ($3200 if you use our Expert Power discount code)
- Expert Power lithium batteries have a lifespan of about 10 years or 2500-7000 charge cycles depending on the DOD.
- So that’s an estimated $3200 in batteries over 10+ years.
~$3200 vs ~$9000 over 10+ years. The difference is clear. Plus, just think of the space and weight of 10 AGM batteries!
Our bank also helps save money in unexpected ways:
- With this much power, we can run our absorption fridge on electric during the day. This saves a lot of propane.
- Before our lithium bank, Jose cooked three meals a day, and Cora did three sets of dishes per day. Now we can make one big meal, save the leftovers in the fridge, and reheat in the microwave (yep, we can use a microwave!). This saves us a lot of time, propane, and precious water.
Putting Expert Power Batteries to the Test
We’ll be putting our battery bank to the test. We’ll be using them full-time for 5+ years, powering a journey through deserts, jungles, mountain passes, and everything in between. We’ll give updates on their performance as we go. Stay tuned!
Our Expert Power Discount Code
If you’re looking to go lithium and eyeing some Expert Power batteries, here is a code that can save you some cash. It’s good for 5% off storewide and it never expires, so use away! (We’ll also get a 5% commission which helps us buy paint for murals, so it’s a win-win)!
Expert Power Discount Code: AWTY
How to Wire a Solar Battery Bank
Step 1: Decide how you are going to wire your batteries (Series or Parallel)
We have a 12V system, so we wired our five 12V 100ah lithium batteries in parallel, which means that you connect Negative to Negative and Positive to Positive.
Make sure to use the proper gauge cables to connect the the batteries together and to connect the battery bank to the inverter. For the battery connection we used 2AWG 1ft cables. For the connection between the inverter charger and the battery bank we used 3ft long 2/0 AWG cables.
Step 2: Wire the battery bank to inverter and charge controllers
- Connect the charge controller and inverter negative cables to the negative terminal of the battery bank.
- Connect the charge controller and inverter positive cables to the positive terminal of the battery bank.
- Make sure to connect all the negative cables to one end of the battery bank and all the positive cables to the other side of the battery bank as shown in the diagram above. Failing to do so may cause severe damage to your battery bank.
Tip: Use safety gloves when connecting batteries and be extremely careful that cables ends do not touch!
Step 3: Turn the inverter on and you should be ready to go!
If you have any questions about all these steps, shoot us an email! We’re usually out painting a wall somewhere. Or hunched over our computers in post-production. Wherever we are, we’ll take time to help you out: [email protected]
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So you’re building a skoolie, huh?
We feel your pain, my friend! We also know how good it feels to finally make a dream reality.
Our skoolie took 9 months and $28,000 to complete. We documented the entire build and are slowly building a series of guides on every step of the bus conversion process.
We spent a crap ton of time figuring out how to do this and that. We also could have saved a few bucks along the way. We hope our tutorials help save you some time and money!
Our TOP 5 Bus Conversion Tools & Materials:
- 5-in-1 Painters Tool (you will use this a MILLION times)
- Impact Driver & Drill Combo Kit (there won’t be a day you won’t use this)
- 100% Silicone (buy in bulk to save a LOT of money!)
- Angle Grinder (get used to using this ALL the time!)
- Table Saw (it will be nearly impossible to complete your conversion without this. It’s WORTH the investment!)