How to build a 12v DIY Solar Generator – Complete Review
Kyle
How to build your first DIY Solar Generator – Complete Review
If you are looking learn how to build a DIY solar generator setup and you are new to this, then this article and video will help.
The picture below is the 12V DIY Solar Generator setup we will building. It is a 12 volt system capable of producing 2000 watts of continuous power output and a peak surge output up to 4000 watts. This system will also have a total of 2560 watt hours (2 batteries) of storage in the battery bank. Here is a link to a blog article I did where I explain most of the baseline information to help you with the terminology and equipment. https://proficientprepper.com/diy-solar-power-generator-concepts-and-equipment-for-beginners/
Here is the video I made for reviewing this system.
This is a Battery Bank. Which just means it is multiple batteries wired together acting as one large battery. The battery manufacturer will specify for this specific battery how many batteries and how they can be combined. (either series or parallel). Typically, you can combine multiple batteries together in a combination of series and parallel. For example you could combine 2 batteries together in parallel with another 2 batteries in parallel. You could then combine those 2 banks together in series for a total of 4 batteries. Again, check with the manufacture on how they can be combined.
These two batteries are PowerQueen 100ah 12 volt lithium iron phosphate (or LiFePO4) batteries. You see 12.8 here on the side. This is the nominal voltage of this battery. When we refer to 12V, we mean the class of the battery. You have 12V, 24V and 48V battery classes for example. These batteries are actually at around 13.5V when fully charged. This battery bank is wired in parallel which means you connect the positive to positive and the negative to negative. Then you take the positive from the battery on this end to the inverter/charger and then take the negative from the battery on the other end. When you combine batteries in parallel, the voltage stays the same at 12V.
When you wire batteries in series or parallel, you should purchase identical batteries such as the same manufacturer, same model, within a month of one another and the same approximate number of charge cycles. Before you wire them together, you should fully charge each battery separately, so they are very close in voltage. Since these are 12 volt batteries, you should use a 12 volt battery charger and one that is made to charge LiFePO4 batteries. Then wait at least 30 minutes after the last battery was charged. Then check the voltage of each battery with a multi-meter and they should be within a tenth of a volt of one another. There could be a slight bit more off from one another, but If they are way off, then something is not right and you should most likely not combine them.
The next step is to balance the voltage between the batteries. Again, make sure to wait at least 30 minutes after you charged them. To balance the voltage between the batteries, you would connect the positive to the positive together and the negative together of all the batteries. Use the size wire the battery manufacturer recommends. You would then leave the batteries like this for between 12 and 24 hours. After that you can combine the batteries either in series or parallel according to the battery manufacturer instructions. These two are wired in parallel. If you had 4 batteries in parallel, you would simply just have two more batteries here taking the positive from one end and the negative from the other end. You would typically re-balance the battery voltage like this every 6 months.
These batteries have a 100A BMS. BMS stands for Battery Management System. If you were to open up this battery, you would see battery cells, some wires and a little circuit board. That circuit board is the BMS. Its like a little computer that protects the battery from being over charged or over discharged. It basically protects itself from going outside its own safety margins. Since each battery has a 100A BMS, this battery bank can output a max of 200A.
I mentioned that these batteries are 100Ah batteries. Since we have two 100Ah batteries, this battery bank has 200Ah of capacity. Amp hours refer to the storage capacity. Amp Hours are abbreviated as “Ah”. An amp hour is the amount of energy in a battery that allows for one amp of current to flow for one hour. If you are not already, amp hours can be the source of confusion. I wish all batteries has watt hours printed on the side instead of amp hours. That makes more sense to me. Remember the equation watts = volts * amps. So when using amp hours as a measurement, you must consider the voltage in order to determine the actual storage potential. A 100Ah 24V battery has twice the storage than a 100Ah 12V battery. Each of these two batteries have 1280Wh. 100Ah x 12.8V. Since there are two batteries, that would be 2560Wh. This basically means you can run a 1W device for 2560 hours. Or if you were running a 100W light bulb, you could power it for roughly 25.6 hours.
Now lets talk about the wires running between your battery bank and the inverter and solar charge controller. The wires must be of the correct size. If you use wires that are too small, there is a very real risk that the wires could melt and start a fire. So you really need to get this right.
Remember to always refer to the battery owners manual and if anything is different from what I have said. Always go with the battery manufacture recommendations over what I have said.
Main Battery Cable
The most important cable in you DIY Solar Generator setup is the cable between the battery and inverter (positive and negative). If not sized properly, this cable can melt the insulation and even start a fire. In this setup, I am using a 2000W inverter on a 12V system. So to calculate the wire size, you divide the max watts of the inverter by the system voltage. 2000 / 12 = 166. 166 is max amps that will flow through the wire between the battery and inverter. The amps can actually go a little higher than 166 because the inverter can produce up to 4000W for a few seconds before it shuts off. So you want a buffer in there and you want to choose a wire that will support more than 166. The general rule of thumb is to calculate the calculated amps by 1.25. I’ve seen other numbers such as 1.5 also. But I use 1.25. So 166 x 1.25 is 207. So we need a wire size that has a max amperage rating up to 207. You won’t find one that exact, so you have to choose the next highest. I use Windy Nation battery/welding cable. The 2 AWG wire they have has a max amperage rating of 205. That is too low. You always want to go up to the next level above the amperage we are using. So the next size they have is 1/0 which has a max amperage rating up to 285A. This 1/0 is the correct one to use.
I’m using a ANL 250amp fuse in a fuse holder (see yellow circle in picture below). It should be the closest component to the battery so all of the wire is protected. ANL fuses are good for any system 12-32 volts. If you go over 32 volts, you should use a Class T or Mega fuse. You could also use those on this 12V system. https://amzn.to/4146Ebj
Battery Switch
The battery switch allows you to cut the power from the battery so that you can work on your system. It could also be used in case of some kind of failure to quickly shut off the power. This battery switch is rated 12 – 48 volts and up to 275 amps. https://amzn.to/3MFtUrR
Bus Bars
The bus bars allow you to easily connect multiple components to the current without stacking everything on a single stud. This nickle plated brass set is a little on the cheaper side but good enough for this application. It is rated up to 48V and 250A. https://amzn.to/3pNJDfr
Giandel 2000W Pure Sign Wave Inverter
In this DIY solar generator setup I am using this Giandel 2000W inverter. It can produce up to 4000W surge. It has 2 AC outlets, 2 USB-A ports, remote port, power button and hard wire terminals. The remote port is for use in something like an RV where you may have your inverter tucked under a bench or something where you can’t easily get to it. The inverter comes with the remote and wire, but I am not using it here. I am using the hard wire terminals to connect to a L14-30R outlet where I run an extension cord over to my Power Transfer Switch. I created and article and video about that transfer switch.
The MPPT solar charger I am using comes from BougeRV. Its job is to charge the battery from the power produced by the solar panels. It is a 40A charge controller. It is compatible with 12 – 48V. However, it can only accept 600W from the solar panels on a 12V system like this. Here are the specs – 600W/12V, 1200W/24V, 1800W/36V, 2400W/48V. It comes with a recently updated mobile app where you can check the current status of the charge controller.
I use a 2 pole 20A breaker for the PV wires coming in from the solar panels. I can use this to easily switch off power from the solar panels if I need to work on something. You should always turn off the power from the solar panels first if you are going to disconnect the charge controller from the batteries. You don’t want power coming into the solar charge controller from the solar panels if the charge controller is not connected to the battery. This breaker also protects from some kind of short in the solar panels or PV wire. It will most likely not protect against a lightning strike.
https://amzn.to/3MFpAZG
40A Breaker for Charge Controller
The charge controller is a 40A charger. So I use this 40A breaker going out of the charger to the battery to protect the system in case of some issue with the charge controller. https://amzn.to/434nVlM
Victron Mobile App
Solar Panel Array
The last component I will cover is the my mobile solar panel array. I did create an article and video specifically for this also. This is 4 solar panels wired in series producing up to 800W. The panels are the BougeRV 9BB 200W panels. If you remember from above, the solar charge controller can only accept up to 600W from this array because it is a 12V system. When I move to a 24V system later, all the power this produces can be used. https://amzn.to/40itNa4
Wrap up
Well, I hope this helped you understand better how to build your own DIY Solar Generator.
Later
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About
I cover a variety of preparedness and self sufficiency topics such as DIY Solar Generators, Living Off Grid, Generators, Vegetable Gardening and growing your own food, Water and Food Storage, Water Catchment, Emergency Lighting, Product Reviews and other topics I’m interested in.
