Welcome to our Information and Learning Guide! If you're new to 12v - 24v solar, don't worry. It's not magic. Basic systems are pretty simple.

BHA Solar on Tiny House

Install an RV or Off-Grid 12 Volt Solar System that WORKS!

By Bill Andersen

BHA Solar - updated Sept 2023

If you are a beginner and are confused about how a stand alone solar system works, the basics are not complicated. 12v systems have 2 wires, pos and neg. If you're a total beginner I always caution to start slowly before investing a lot and learn from a small starter type system and use it a while to really learn how it works and what to expect. ALL the systems are modular and can be expanded.

Basically the solar panels charge the batteries and you run everything off the battery bank. How big a system depends on what you want to run and for how long. Running an air conditioner off a small solar/battery/inverter system has always been the holy grail, but efficient air conditioning units like mini splits and lithium batteries now make it very possible. I've spoken to many people who are successfully running small AC units and window units with inverter / solar / battery systems. Most folks full time off grid are very conservative with power and use propane wherever possible, particularly cooking, propane refrigerators and hot water heaters, and space heaters, but new lithium batteries are becoming the new gold standard for solar/battery/inverter systems. They're easier to recharge (5x faster than lead acid, so a smaller solar array is needed) and they last years longer

A good starting point for running loads like that is something like this

600W 12v system, 2 x 100AH lithium batteries, and a continuous 2000W 16.7A output inverter

A separate component added to your battery bank for standard 120v residential power is an inverter. A pure sine is needed for refrigerators and anything with a compressor. Factory installed inverters in large RVs are usually 2000W pure sine. Inverters can be hard wired to an elec distribution panel or a sub panel installed by an electrician, or can be used simply with some inverters that have built in outlets and usb ports

A "solar setup" for an RV can be anything from:

A small system for running LED lights, water pump, furnace fan and controls for propane fridge and water heater on weekend camping trips w/o hookups for shore power to a larger system to be off grid in an RV for weeks at a time, or to living full time and running full sized res refrigerators, freezers, elec water heaters etc. (You usually cannot run RV air conditioners off of batteries without a soft start on the AC unit itself and lithium batteries)

System sizing isn't an exact science. Its like deciding how much water you need if you're thirsty, but if your set up isn't providing enough power you can always expand it. All solar systems are modular in that respect. (nobody ever calls me and says "Hey! These solar panels are too much power! I can't use it all!")

It's difficult to compute exactly how big a system you should build, but you can narrow it down during your planning

What will your actual usage will be? how many amp hours (ah)

example: Your Mr coffee machine is 900 watts and draws 5.9 amps. So if it's on for an hour, you use 5.9 AH out of the battery.

But predicting usage isn't usually the biggest mistake folks make in planning. It's having wildly unrealistic expectations of how much electricity they can collect

So if you can estimate your future usage, you can estimate how much solar you need to match it.

200W panels are rated at >10 amps, but they harvest the most power from the sun roughly from 10-2 and a conservative rule of thump is to figure 5 hours a day x rated module output. Just because its light outside doesn't mean a 100w panel is putting out 100 watts. Solar panels work in low light, but work better with more sun

It depends on where you're located and average amt of sun, cloud cover etc. The further north you are the lower the sun comes up over the horizon in winter. and shorter days. MPPT controllers are recommended to squeeze every drop of sun early and late in the day in low light, and tilting the panels helps also.

On "average" 600 watts can recharge 2 x 100ah lithium batteries from zero in about 5 hours

Basics of how you set it up:

put the panels in FULL sun.

connect the pos and neg wires to a charge controller (morningstar is best by far and all we carry)

keep controller as close as possible to battery connections with heavy battery cables. This is critical to prevent voltage loss.

connect an inverter to batteries for 120va

Install by Durand C. in Maine 800 watts

Our kits are designed with 12v solar panels which can be configured for 12v by connecting in parallel (pos to pos and neg to neg) or 24v by connecting pairs of panels in series (pos to neg) and to be fairly easy and uncomplicated to put together yourself. Don't pay too much attention to forums or you-tube videos. Many if not most don't have a clue and some are totally wrong, giving bad advice

There is no one size fits all system design, but the basic rules are the same. RV and small off grid solar systems typically can supply power for most everything up to and including a microwave or small air conditioner. Folks off grid full time typically use propane for cooking, heat, hot water and propane fridge. Batteries easily power the elec controls for gas appliances, and everything 12 volts in an RV like lights, water pump and furnace fan. An inverter supplies 120vac power. When air conditioning is needed many RVers either move north, pay for shore power or run a generator. Hybrid solar systems can run large loads using a much smaller gen as a supplement with the inverter/batteries

To simply replicate shore power off grid like your on the grid house requires a large solar array charging a large battery bank.

The future gold standard for batteries seems to be lithium, but cost is high so many folks still use flooded deep cycle batteries like golf cart batteries. A huge advantage with lithium batteries is that they can be deeply discharged without harm and recharge 4-5 times faster. Always check to make sure there is a 5-10 year warranty. (some advertisers state "10 year possible lifetime" but only have 1-4 year warranties.

Solar panels and a Tristar controller can recharge Lithium batteries 4-5x faster than lead acid. REFILL your battery bank easily every single day!

VIDEO: HOW TO PROGRAM YOUR MORNINGSTAR TRISTAR 45A MPPT CHARGE CONTROLLER FOR BATTLE BORN 100AH LITHIUM BATTERIES

Larger off grid systems are usually 24v, but RVs come from the factory for everything 12v.

We want you to have a system that actually works well and lasts for years, but here's a critically important thing you should know

Your Off Grid or RV Solar panel system is only as good as the charge controller, the heart of your system and all controllers are far from equal.

Besides complete system failure when a controller goes bad, the chronic undercharging of your expensive batteries will cause them to fail and need replacement much sooner. Morningstar is an American company and has had over 2.5 million controllers installed in 112 countries over 25+ years. MANY are still in operation today. The finest charge controllers in the world are Morningstar MPPT. Amperage and voltage ratings differ, but more importantly, charging algorithms, protections, warranties and advanced features vary greatly between brands. The finest charge controllers in the world are the Morningstar MPPT LEARN MORE HERE - 5 REASONS TO USE MPPT (OR NOT)

BHA SOLAR 5 year warranty and 15 year expected life

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SOLAR GENERATORS LEARN MORE HERE

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The following 2 links are experts and provide a massive amount of RV / OFF GRID 12v solar knowledge.

These sites haven't been updated lately but still have mostly applicable information and are great free learning sources and a good place to start

HANDYBOB - Making off grid RV electrical systems work

I really like Bob and owe him many thanks for all his knowledge. A retired electrical engineer very compassionate about RV solar, who was off grid by 2003. He is aimed at the "frustrated, technologically challenged and budget minded RV owner who needs basic education about battery supplied electrical power."

It takes hours to read, he's long winded, and rants on the state of the RV manufacturing and RV Solar industries but If you read all of it and follow his advice, you will have a great system that works and gets the batteries 100% full so they last longer! Read it more than once, (it's free, but he welcomes donations!)

JACK MAYER RV SOLAR ELECTRICAL

Another expert, he wrote a book about RV Solar and has it available for free. His information is a little more complicated, and from the viewpoint of one who can afford to spend more money. It's well organized and has a LOT of expert advice and instructions with photos

We've distilled down and summarized a few of the most important points below

1. NO SHADE

Just shading on one small square on a panel drastically reduces the output of the ENTIRE panel

See those little shadows?
Surprise! Minus 6.4 amps from these two panels! This is 90 % of the output of a full panel. When solar panels are configured in series then the entire string will be effected, but in parallel only the panel shaded will be effected

2. USE BIG ENOUGH WIRE

Voltage loss is the enemy in these systems, and is especially critical from charge controller to battery. Keep wire runs as short as possible, and use the proper cable size. (Don't waste money on wires bigger than needed for 2% drop on MPPT systems or 5% on PWM systems) Use a wire sizing calculator like this one

3. CHARGE CONTROLLER AS CLOSE AS POSSIBLE TO BATTERIES

Distance under 3' with large wire. Max wire size accepted: 10 AWG for Sunsaver controllers, 6 AWG for ProStar, and 2-4 AWG for TriStar. Splicing a piece of 10ga onto larger wire is OK and won't get hot if done properly, or simply clip some of the fine wire strands off larger wire until it fits. This won't affect anything.

4. USE A REMOTE TEMPERATURE SENSOR

It will send more voltage when batteries are cold so they still get 100% charged. It'll reduce the voltage when batteries are hot so they don't overcharge. (A temperature sensor on a controller that is located in a heated area will not see the battery temperature, so it will not work.) The Sunsaver controllers do a good job in cold weather with built in temperature compensation, and the ProStar and TriStar remote temperature sensors are a must. (adding the temp sensor to Prostar controllers requires soldering 2 wires)

5. INSTALL A TRIMETRIC METER & WHOLE SYSTEM MONITOR

Every 12 volt solar system should have a real battery monitor that includes percentage (%) of charge. Not just voltage. This is the only way to ever be confident that your system is really working. learn more

Trimetric 2030-RV

6. CORRECT CHARGE CONTROLLER VOLTAGE SETTINGS ARE CRITICAL FOR CHARGING BATTERIES

*check with the battery manufacturer

If you can get a TriStar controller it has volt set points as high as 14.8 , or Bogart SC2030 can easily be set to any voltage at all. It is even smarter than a Tristar. It will charge better and faster than any other PWM controller. The smaller Morningstar controllers are 14.4 volts with built in temperature sensors, which will get the batteries full, but it takes a little longer. The RV Battery Charging Puzzle

BHA RV Solar kits save you money. Top quality parts that maximize charging and life of your batteries

Awesome 1200 watt solar Off Grid system installed on Bainbridge Island in Wa. by Doug H.

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BATTERY INFO from solarseller.com

Contents

Battery System Sizing SIZING YOUR BATTERY SYSTEM

Deep Cycle Battery DEEP CYCLE BATTERY

Electrolyte ELECTROLYTE

VRLA (valve regulated lead acid) Battery VRLA BATTERY

Gel Cell Battery GEL CELL BATTERY

AGM (absorbed glass mat) Battery AGM Battery

Flooded Type Deep Cycle Battery FLOODED TYPE BATTERY

Self-Discharge Rate SELF-DISCHARGE RATE

Charge Rate CHARGE RATE

Electrolyte Level ELECTROLYTE LEVEL

Equalization Charging EQUALIZATION CHARGING

State of Charge STATE OF CHARGE

Battery Life BATTERY LIFE

Battery Location BATTERY LOCATION

Used Batteries USED BATTERIES

Battery Safety Battery Safety

SOLAR BATTERY WIRING DIAGRAMS HERE

How to wire 6v and 12v batteries together in series and / or parallel

Wiring of fuse / breaker devices is covered in detail in this article

SOLAR CONTROLLER DISCONNECTS

Fuses/Circuit Breakers:

"In-line fuses or circuit breakers are important to protect the wiring and components in your system from shorts and other catastrophic failures. Place one on the positive wire within a foot of your battery and another in between the combiner box and the charge controller. The size of the fuse or breaker depends upon the size of wire used in your system. Place no larger than a 30 amp fuse or circuit breaker for 10-AWG wire; no larger than a 48 amp fuse for 8-AWG; no larger than a 74 amp fuse for 6-AWG; and no larger than a 120 amp fuse for 4-AWG wire."

Fuses for Inverters to battery: Always use the exact factory recommended size fuse stated in the installation instructions

More good info and pics:

From Kelly's RV Solar Blog - Great blog with lots of interesting info and good photos.

Excellent complete wiring diagrams of 2 systems