In this article I will explain how to set up a solar grid. I will also explain the basics of electricity, wiring, batteries, and power. I did this on my boat. If you are doing it for a house you wouldn’t need a battery bank for a starting battery (used to start an engine).
Supplies:
12v Deep Cycle Marine Battery
- Gel: Renogy Deep Cycle Pure Gel Battery 12V 100Ah
- Lithium-ion: Lithium Ion Technologies – 12V 20AH Advanced
- Lead-acid: EverStart Marine Battery, Group Size 29DC
Dual Battery Charge Controller
- RENOGY 20 Amp PWM Dual Battery Charge Controller
100 Watt Solar Panel
- Renogy 100 Watts 12 Volts Monocrystalline Solar Panel
Battery Selector Switch
- Perko 8501DP Marine Battery Selector Switch
MC4 Connectors
- LilyGlory Solar Panel MC4 T Y Branch Connectors Cable Splitter Coupler
Solar Panel:
I used WindyNation’s 100W Flexible Solar Panel on my set up because I installed them on my sailboat’s fabric bimini. I would recommend using the rigid ones because they are cheaper and more durable. However if you are putting them on a bimini or want them to be flush with the roof of your RV I would recommend the ones I have here.
Charge Controllers:
MPPT is justified on larger systems. On a small system it is less costly to add a few more panel watts to get the desired production, than to spend the extra on a MPPT Controller. The balance point varies associated with the regional cost differences A good designer can tell you instantly which is the least expensive.
The price difference in a 100W system leans heavily toward PWM, when you get to 300w or more, then the prices even out. But if you have limited space, go with a high voltage panel and MPPT. (a 60V 100W panel)
Low power systems are better suited to a PWM controller because:
A PWM controller operates at a relatively constant harvesting efficiency regardless of the size of the array
A PWM controller is less expensive that a MPPT, so is a more economical choice for a small system
A MPPT controller is much less efficient in low power applications. Systems 170W or higher tickle the MPPT’s sweet spot
Watt, Amps, What!?
Watts are basically just a measure of how much power a device uses when turned on, or can supply. A watt is a watt – there is no such thing as “watts per hour”, or “watts per day”. If a something uses 100 watts, that is simply the voltage times the amps.
Watt-hours:
A watt-hour is simply how many watts times how many hours that is used for. If a light uses 100 watts, and it is on for 9 hours, that is 900 watt-hours.
Amps:
An amp is a measure of electrical current at the moment. Amps are important because it determines what wire size you need. All wire has resistance, and amps flowing through a wire makes heat. If your wire is too small for the amps, you get hot wires. You can also get voltage drops in the wire if it is too small.
Amp-Hours:
Amp-hours (usually abbreviated as AH) are what most people mean when they say “amps per hour” etc. Amps x time = AH. AH are very important, as it is the main measure of battery capacity. Since most inverters run from batteries, the AH capacity determines how long you can run.
Batteries
When shopping for your batteries there is one main requirement. They need to be deep-cycle NOT standard or starting. There are a lot of battery types that fall under that including flooded, gelled and AGM. I have learned that the batteries from Walmart do the job fine and are a lot cheaper than the fancy AGM ones. I have two EverStart Marine Battery, Group Size 29DC. It has 845 cold cranking amps and 65 amps reserve capacity. I have a refrigerator on board that uses 0.7- 2.5 amps an hour. It charges from my solar panels daily so it runs the refrigerator perfectly. Monitoring your batteries is very important, I use this cheap battery monitor to make sure the batteries are in good condition. It is so important I even included it in my Top 10 Essentials. I have heard great things about using 6 volt golf cart batteries in this setup as well.