The progression of our off-grid electrical system

The progression of our off-grid electrical system

Warning: I went full geek on this one!

 

One of the big reasons to boondock for an extended period of time is to be able to experience nature in wide open spaces right from your RV.  The other of course is saving $30-$50 a night for camping.

We want to limit how many campsites that we have to park like this…

Extremely tight private campground – El Cajon, CA

… and do more camping like this:

Boondocking at Gunsite Wash, BLM, AZ

The modifications that we have made over the past 8 months are not necessary to boondock, but they sure do make the experience much more enjoyable.  Being able to run the microwave, coffee pot, vacuum and other RV systems off of solar energy in the middle of nowhere is the absolute coolest thing.  We are not quite done with where I want the rig to be, but I’m close enough to describe a system that works pretty darn good.

Let’s start out with the heart of the system.  You have to have some form of energy storage that is capable of supplying power to the somewhat heavy loads when there isn’t a charging source available.  Unfortunately, the battery that comes with most RV’s, like most of the RV electrical system is way undersized for anything other than the basics like running an LED light.  I feel RV manufactures design their electrical systems as if the RV will be continuously plugged into power at an RV park like the majority of rigs are.  The typical battery that is provided says that they have about 85 amp-hours of capacity.  However, these batteries are not deep cycle batteries and the life of the batteries will quickly come to an end if they are continually drawn down to far.  This was the first upgrade I made.

6 volt Lead Acid, Deep cycle batteries.

I replaced the 12 volt automotive style battery and replaced it with two 6V, T-105 RE Flooded/Lead Acid batteries from Trojan Battery Company.  These two batteries brought my energy capacity up to 225 amp-hours of which I should safely be able to use about 112 amp-hours between charges if needed.  These type of batteries are true deep cycle batteries with a common application being to power golf carts.  There are other battery types on the market, but at this stage of our journey, the much lower cost of the flooded batteries greatly out weighs the advantages of the maintenance free batteries.  They require a little more effort to maintain, keep charged and manage the ventilation, but since I’m not against doing a little work, they  function perfectly.

As mentioned, the other area that RV manufactures let the boondocker down is the wiring.  The wiring needs to be sized first and foremost to be safe from overheating but should go much further to limit power loss.  If you under size the wiring, all the cost and effort to upgrade your system will be wasted.  All wiring out to my catastrophic fuse and on to the inverter is 2/0 welding cable.    The 2/0 wiring will enable me to eventually run the microwave after I install another two batteries.

For fear of invalidating my warranty, I delayed putting in solar for 8 months. We took off on our journey with the new Trojan batteries and a 2000 watt generator to replenish the energy used while off-grid.  I  went with an inverter style generator from Champion.  These type of generators are enclosed in a housing and run much quieter than the open, cage style generators that you typically hear all over a neighborhood when the grid goes down.  We have had great luck with the Champion generator.  They are less than half the price of a Honda or Yamaha equivalent power output generator.  It runs a little louder, but I would rather have the extra money to eventually buy some solar panels and eliminate the need for a generator all together.

What I have learned about lead acid batteries is they love to be fully charged.  Continually leaving a battery at less than full charge will greatly reduce the life.  At $130 for one battery, I need these babies to last a few years without loss of performance.  The problem with lead acid batteries is they can only be charged up so fast.  The bulk charge, up to 90% state-of-charge, SOC can be accomplished in 2 hours with a generator and a good charger (note: RV’s do not come with good chargers). The remaining 10% requires about 6-8 hours of lower current charging.  Believe me listening to a generator, even a quiet one, run for more that 2 hours will drive you insane.

Tri-Metric TM-2030 Battery Monitor

Other than monitoring the battery voltage and trying never to go below 12.0 volts, I didn’t really know the state-of-charge, SOC of my batteries while off-grid.  So, the next thing I bought was a battery monitor from Boggart Engineering.  This device allows me to keep track of how much energy, measured in amp-hours, has been used or put back into the batteries, which provides a better estimate of my battery SOC.  I never want to drop below 50% SOC and I will know better if I am fulling charging the batteries after a discharge cycle.

Until we installed our solar system, we recharged our batteries using the charging system that was built into the RV powered by our Champion generator.  According to the Trojan battery specifications, I need 14.8 volts at the battery to optimally charge the battery.  After I installed the battery monitor I noticed the charging voltage was only around 13.8 volts – not good.  What’s worse, when I measured the voltage at the charger output, some 12 feet away from the batteries, it measured 14.4 volts.  That means, I was getting a 0.6 volt drop in the wiring.  This is a huge loss!  The manufacture undersized the wiring, probably to save money, again figuring that most people will be parked in a full hook-up RV park and never have discharged batteries.

Upgraded Battery Charger – to get the job done

You guessed it.  The next item I purchased was a new charger.  I installed it less than 2 feet from the battery with wire sized appropriately for the load.  Unfortunately, the new charger does not provide the 14.8 volts that the battery manufacture specifies, but I was getting the full 14.4 volts that it provides at the battery.  Getting more of the power into the battery means I can get to 90% SOC much more quickly, thus minimizing the generator run time.

After 8 months since we purchased the RV, I decided to risk warranty disputes and install solar panels on the roof of our RV.  I was tired of the generator noise and want to ensure my batteries are fully re-charged every clear day.  After discussions with a few solar installers, nobody had heard of a manufacture voiding a warranty because of a solar installation.  I did the install myself, ensuring that all water leak paths were sealed up tightly and all wiring was properly sized and protected from a short-circuit.

The battery monitor allowed me to get a good feel for how much energy we used daily.  Based on our usage, I decided to go with only two, 145 watt panels from Kyocera.  Each panel can put out about 8 amps during peak sun hours.  Figuring 5 hours of peak sun in the winter in southern Arizona and conservatively estimating that I would get only 50% of the max current, I should easily be able to replenish the energy we use each day.  So far so good.  Since completing the installation we have not needed to fire up the generator.  Our typical energy use is usually replenished by noon on a clear day.  I have room on the roof and solar charger capacity to add panels down the road if we feel we need to live like royalty.  A little conservation goes a long way.

These Kyocera panels are very well constructed and seem to be extremely high quality.  I purchased a tilting mounting system to make sure I capture as much energy as possible when the sun is lower in the sky during the winter months.  I have read of people getting systems installed that should have been adequate for their energy consumption, but their batteries would still eventually die.  The biggest reason appears to be that the wiring is not properly sized for the load causing too large of a voltage drop across the wiring.  The batteries were not getting the voltage they require to get an optimal charge.

Panel and combiner box mounting – don’t skimp on the Dicor.

For my wiring, I went with 10 gauge (AWG) wiring from each panel to my combiner box on the roof.  The maximum length is 6 foot.  From the combiner box, I ran 4 awg down to my solar controller and 4 AWG wire again from the solar controller to my batteries.  The 4 AWG may be excessive, but it will absolutely minimize losses and allow for the addition of more solar panels down the road.  The combiner box sits right above the space I will be bringing the 4 AWG wires into the RV.

Running the solar wiring through the bathroom wall

I found a great spot to bring the wires into the RV from the roof.  There was a little space behind the bathroom wall that I spotted with a mirror from underneath.  I’m a little worried by the vent pipe size hole in the wood as I have always wondered why I have 3 tanks, but only 2 vent pipes on the roof.  (Anybody want to wager that the assembler didn’t install it and it got by quality control?!!!  That will be a job for another time.)

To take full advantage of the available solar energy, a charge controller is needed to drop the panel voltage down to levels that are usable for your battery system.  I went with the Tri-Star 45 from Morningstar.  This is a programable PWM type controller that I was able to program to provide the 14.8 volts recommended by my battery manufacture for optimal charging.  This controller is very high quality.  It isn’t often you open a box and are blown away by the quality of a product these days.  This controller looks, feels and works incredible.  Probably the best value of every gadget I have installed to date.

Tri-Star Solar Controller

One more handy device that I installed is an inverter.  In order to be able to use this stored solar energy to run things other than a few lights, I required a way to generate 120 volt AC power from my 12 volt battery system.  120 volt AC power is required to run things like cell phone chargers, computers, microwaves, coffee pots and TVs.  For this I found a deal on a Nature Power, true sign wave, inverter, capable of delivering 2000 watts of power.  Once I get another two 6 volt batteries installed in the system, this inverter, along with my properly sized wiring, will be able to easily run a microwave or a coffee pot.

Make’n some AC power

With all my goodies installed it looks like quite a mess.  The wiring right in the middle of my control center was installed by the manufacture to control the jacks for leveling.  They took up some prime real estate.

Electrical System “Control Center”.

DC power is not something to mess with.  The amount of current that can be drawn from a battery is extremely high and can quickly heat up wiring and cause a fire in the event of a short-circuit.  Any wire coming off of the battery positive post needs to be fused as close to the battery as possible.  I installed a 250 amp catastrophic fuse as the first connection coming out of the battery box in event the other devices should short.  I installed a 40 amp circuit breaker on output of the solar controller which will also blow if the controller itself shorts to ground.  Every sense lead coming off of the battery is also fused, with a fuse small enough to protect the wire from over heating if shorted.  Some may noticed that I did not fuse between the solar panels and the solar controller.  The max current is only 16 amps which the 4 AWG can handle all day long without getting hot.  However, I do plan to add a breaker so that I can disconnect the solar output from my system for service and eventually protect the wiring if and when I add more panels.

After adding the solar panels and solar charger controller, life off of the grid has been great.  We still conserve how much energy we use, however we could increase our energy use on a clear day quite a bit and cut back if extended cloudy days are in the forecast.  If we have to, we can always pull the generator back out.  So far, we are generator free and love’n it.

4 thoughts on “The progression of our off-grid electrical system

  1. Great details and specifics. You might also want to mention your electrical engineering background so some fool doesn’t try to rewire their rv and electrocute themselves! Good luck with the solar.

    1. I wish I could say my electrical engineering degree helped with this project. Unfortunately my 4 years spent in college didn’t really prepare me for real world things like this :).

  2. I’m so glad to have been notified of your blog here! I’ve only been researching off-grid living for the last couple of years and haven’t implemented much of it as of yet. I look forward to hearing about your experiences and perhaps sometime in the distant future, be able to follow in your foot-steps. Thanks again for sharing your adventures! -Rob

    1. Thanks Rob. I definitely prefer the off-grid camping. We are camp hosting for 6 weeks at a state park, I’m already missing the wide open spaces and freedom that boondocking and off-grid living provide.

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