After delving into this subject for hours, it has become clear that the task of hooking up a solar backup generator to your battery bank is quite complex. Not that the actual task of physically hooking it up is complex, rather the calculations and inversions required to make the system safe and effective is not as clear as one would think.
I have watched multiple videos, combed many forums, and gathered information through piece-working information from old and outdated websites, but the answer is highly variant on the specifications of your system.
What has become clear from all this research is that seeking advice from a professional installer would behoove you greatly. This is one of those moments where it pays to ask an experienced electrician for the answers to properly setup your system.
That all being said, I want to provide you with helpful resources and basic advice that may assist you in getting the information you need for a DIY installation.
If you are new to solar power, check out my Guide to Home Solar Power Systems to get started.
I also encourage you to leave any questions or comments below with resources and advice to help others.
Disclaimer: Use the information from these websites below at your own risk. Do your own research!
There really isn’t a whole lot of information on websites that pertain to this topic. The ones that do exist are quite vague. I only found a couple that offer any genuinely useful information.
http://www.solarray.com/TechGuides/Generators_T.php Provides some helpful, but basic, information about what type of generator to use along with some standard conversion tables.
http://solarhomestead.com/charging-batteries-with-a-generator/ Contains some more complex information and calculations with some standard schematics of hooking up the generator to a battery bank.
Forums can be very helpful to get advice from experienced people, however, keep in mind they are not professionals.
https://thesurvivalpodcast.com/forum/index.php?topic=11546.0 There are quite a few experienced members on this forum that seem eager to help out other members. This particular post is from a guy who is a complete noob that doesn’t understand electricity at all. The experienced members offer some really good advice that is explained in layman terms.
https://forum.solar-electric.com/discussion/352512/charging-batteries-using-generator-mppt-charge-controller Another good forum with experienced members. This particular post is a little amusing as the person is contemplating a pretty interesting rig setup, which is ill advised from other more experienced members.
https://www.solarpaneltalk.com/forum/off-grid-solar This forum has lots of content including a battery/energy storage section.
http://www.small-cabin.com/forum/3_626_0.html A forum devoted to building cabins and includes a section for off-grid power source.
Again, there is a plethora of information for very specific setups, which may or may not pertain to your system. What I enjoy is reading the comments below to get little gems of advice from more experienced people.
https://youtu.be/17sm6WcNrQ8 “Champion 2000 watt inverter generator charging batteries”
https://youtu.be/nYbJa8KTIio “More off (g)rid generator talk. Charging a large battery bank with an alternator.”
https://youtu.be/mVC0PPAGGg0 “Preppers back up power DC generator to charge 48 volt battery bank”
Visually looking at a schematic can help assist in the placement and setup of the generator in relation to the rest of your system.
Image Courtesy https://www.thesolarplanner.com/optional_page2.html Website has very basic information and is outdated, but the schematic is informative and well laid out.
Image courtesy http://www.aurorapower.net/alternative-energy/solar-electric.aspx Another basic and outdated website with small gems of information.
Image courtesy https://www.bluepacificsolar.com/off-grid-solar/magnum-980w-mnemm1524aecl150.html Blue Pacific Solar sells products, this is a sales page.
Inverter generators are the standard choice for charging battery banks. These generators run A/C battery chargers efficiently which is a needed component to safely charge your battery bank.
Do not use the DC output to charge your battery bank. The generator will not regulate the charge when the battery is reaching maximum capacity, therefore putting your batteries at risk of frying out.
Use the AC output with a battery charger instead. The charger will regulate the amount of energy flowing into the batteries.
Only use your solar power generator for charging in the bulk stage; let your solar panels finish charging the batteries to their extent.
The generator’s continuous watts should be just slightly bigger than the continuous rating of your AC battery charger. If the generator is too small, it will take many days to recharge the batteries or simply become overloaded and shut down. If t is too large, the generator will burn more fuel which will cost more to operate and be louder.
You will also need to consider the altitude; generators make less power at higher altitudes due to thinner air. 2-3% deration per 1000 feet above sea level is the standard.
A remote temperature sensor is highly important to monitor your battery temp. As batteries change temperature, energy demands wax and wane. The bulk voltage needs to be adjusted to these fluctuations. Purchase an inverter or charger that has one pre-installed.
I have read over and over again to not go cheap on the generator. Cheap generators wear out quickly and off-grid veterans attest to using them.
One recommendation made by a vet is to install the MEP 802A government surplus generator.
These military generators are the go-to for the serious setup.
However, this type of generator is not for the typical DIY installer. This is not a plug and play generator and needs to be installed by a professional. There are certain models that are not compatible for home use as well.
That leaves the majority of users with the option of purchasing the cheaper, big-box version of plug and play generators.
WEN 56200i Super Quiet 2000-Watt Portable Inverter Generator, CARB Compliant
The WEN generator is fully loaded with features that go beyond charging your battery bank. I also like that it has a 2-year warranty and a customer helpline for troubleshooting and repairs.
It has the EcoMode throttle which will adjust the fuel consumption, saving money and having to refill as frequently.
If you need more power, you can purchase two and parallel them.
With a bunch of high-quality reviews, this generator could serve as a good backup for your system.
- two three-prong 120V receptacles, two 5V USB ports, indicator lights and parallel connection ports.
- The Eco-Mode Throttle feature automatically adjusts fuel consumption.
Champion 3800-Watt Dual Fuel RV Ready Portable Generator with Electric Start
What’s nifty about this generator? It has dual fuel options, either gas or propane, that could get you out of a pinch. The price point is really low for the number of watts it pumps out and has great reviews to boot.
- Dual Fuel – Runs on propane or gas right out of the box.
- up to 9 hours runtime on a full tank.
- push electric start button.
- Two 120V 20A household outlets all secured by Volt Guard which protects your household appliances from power surges.
- 3 year limited warranty with lifetime tech support.
I hope you found my solar power generator article informative and helpful in your solar power journey. If you have any questions, comments, or constructive criticism, please leave a comment below!
I use an ME1003 brushed motor as my backup generator for my 48 volt system. It works very well Rated 72 volts(open circuit) 200 amps continuous.
That is a great suggestion, thank you!