[Rebelbase]

Help is appreciated.

[Jonty30]

My answer is a gas generator.
Happy to help.

[kiryandil]

https://www.renogy.com/content/RNG-100D-SS/RNG-100D-SS%20G3%20Datasheet.pdf

[kiryandil]

The RNG-100D-SS spec sheet says 12V right at the top.

[Openurmind]

You are good, it’s for 12v. They always put out more than 12 volts and your “charge controller” regulates the voltage down to just under 14 volts which is fine, this is what a car alternator charges the car system at. Generally it regulates it to 13.7 volts input to the battery. So you need a charge controller also to regulate your charging voltage.

If this panel was for a 24 volt system it would be rated at around 36-38 volts output into the 24 volt controller.

[Revel]

Type “RNG 100D” into Google and all kinds of stuff comes up.

[dayglored]

Going by the sticker you posted, that panel will charge a 12V DC system just fine. You need headroom of at least 15V to charge a 12V batter; that panel doesn't peak out until at least 18, that's good.

In general you can put PV panels in parallel even if they're not identical, as long as they have similar voltage ratings. E.g. open circuit 19-23V, max power at 16-18V, that sort of thing. BTW, panels for a 24V system will typically have ratings about twice the above numbers.

I've mixed-and-matched over the years with good success. Just make sure the panels all work by themselves, before you parallel them with others. You don't want to put a dead/shorted panel in your system.

[Vermont Lt]

These need to be wired to the controller which will then connect to the battery. The battery is what puts out 12V, not the panels. In my very small radio battery system, I have two panels running into the controller. I’ve put a meter on them and I never get the exact same voltage coming out of the panels.

[Revel]

If you just by the same model panel then they are made to work together. They appear to be plug and play.

[MountainWalker]

12V often isn’t exactly 12V. It’s usually higher and the charge controller puts in the voltage the battery needs to get it full. That’s definitely a 12V panel though and you will be able to add another later if you want and doesn’t even need to be the same model or brand.

[BobL]

Having spent a couple of years installing solar panels, I can tell you that the voltage from both panels mentioned here is too high for direct charging of a 12V lead acid battery. Instead you’d want the panel to not be able to force more than about 14 Volts (similar to a car alternator). Anything above that starts to put the battery at risk of damage, unless limited to a very low charge rate.

So, you will need some type of regulator/charger, if you want to use those panels.

[bosco24]

That is a 12V panel. Adding a panel has to be a 12V panel but doesn’t have to be exactly like the one you have.

If you connect them parallel the system will operate at the losest operating voltage of the panels.

If you connect them in series, the system will be a 24V system that will produce the lowest operating current of the lowest operating current of the panels.

The wattage will be the same of both wiring of the panels.

[RFEngineer]

You don’t have a 12V panel, you have a panel that will be compatible with a 12V system.

You will need to place a charge controller in between your panel and your battery. That requires that your panel voltage be higher than your battery voltage.

You might want to reconsider your choice of battery, as deeply discharging any lead-acid chemistry battery (gels too) will drastically lower their lifespan. Look at LiFePo4 batteries - costs more, but gives you a much better result.

If you don’t need an inverter, and it sounds like you don’t, then you can stop there. Otherwise, a sine-wave inverter would give you some 60Hz power if you need it.

[Openurmind]

“Here is the question, when I buy the second panel does it matter if the voltage specs do not match up perfectly?”

Nope, as long as you are running it through a charge controller this wont matter much as long as it is not rated at more voltage than the charge controller is rated. And aside from voltage, you have to be sure and have a charge controller than will handle as much or more than the combined amperage all the panels together will be putting to it.

The amount of storage battery doesn’t matter, but rule of thumb is the more storage you have the longer it will supply you until the inverter gets down to 10.5 volts and cuts it’s self off. But more also means it will take longer to charge it back up to full state again. So there is a balance that is of the most advantageous.

Only experimentation can give you an indication of you need more or less in storage and/or panels to maintain you demand at least 24 hours.

[Fireone]

Perfect panel for your application.
I’ve had those on my boat for years.

[Seruzawa]

12v is just the familiar name for a lead acid battery system. A fully charged 12v battery is actually 13.2v and most charging systems run around 14.5v. The panel will put out more voltage when not being loaded. Just get a regulator designed for solar charging. A vendor of such chargers can help you pick the right one for your needs. I did this with a solar system for my cabin. We used a golf cart battery.

[Bobalu]

I bought two new 100w panels just yesterday. They are 65.99ea with free shipping... at Amazon

I usually buy HQST panels but these have a good rating and are 8 dollars cheaper per panel so I thought I'd take a chance.

Generally you use something called a solar regulator to connect panels to a battery.. they are inexpensive for a smallish setup..

I would NOT get a gel cell battery. I would get a 12V 100Ah LiFePO4

The LiFePO4 will have a much longer service life and they are NOT the same as the batteries in EVs ... I wouldn't have those burst-into-flames things in my home :-/

I recommend these, about 270.00 after the coupon and free ship.

[Conan the Librarian]

We’ve 660w of solar on our boat with 300ah of Lithium (Battleborn). We DO have a 2200 Honda generator for cloudy days, but, for the most part, the solar works great.

As was said before, your solar controler is what is important. We have Victron and they have GREAT customer support and are very easy to use and adjust.

We have our stuff set to Absorb at 14.4, Float at 13.6 and and we usually get down to 12.8 over night.

Right now, we are in a marina with shore power, so, we run the DC items on the solar, and AC on shore power. With the storm in the gulf, we might lose power, but, the batteries are full. Tanks are full, and the fridge is well stocked.

We’re in the Treasure Coast, so, we aren’t expecting too much.,

[E. Pluribus Unum]

The 12-volt panels I bought put out 20 volts according to my voltmeter.

https://www.amazon.com/gp/product/B09D7BMBWP

Your charge controller does the rest.

I would highly recommend Will Prouse's book: https://www.amazon.com/Mobile-Solar-Power-Made-yourself/dp/1546567119

If you want to skip the book, he has lots of videos on YouTube.

https://www.youtube.com/@WillProwse

[Openurmind]

Here is a recent system we put in a friend’s work van. Much more than Rebelbase is wanting but it can help explain the system and how they work. One can adapt these basics to their needs. It can be adapted to be a 24 volt system also with 24 volt rated panels. And the 12 volt batteries can be hooked up in series to make 24 volts. Pre-charge controller voltage reduction with the buck converters was only needed because of the repurposing of the 40 volt home panels we acquired and it was too much for a 12 volt charge controller, it would not have needed the buck converters for a 24 volt system and charge controller.

Originally posted in another forum:

“Finally got around to sharing the solar system we set up in my friends van. But it could be set up the same stationary also and as 24V as an option.

I’m not going to show the panels because they all look the same, just the heart of the charging works. And he has 6 deep cycle marine batteries in his bank hooked in parallel, and a 120 inverter. Standard common system so no need to show those either. But he is rated enough to run an electric chain saw and still only tax the inverter to about 50% of available power output. And run it for at least an hour from the batteries even without sun on the panels.

The panels are four old take offs from a large 36 panel home system that had to be replaced with new panels. They are rated as follows:

X4 - 40 Volts - 150 Watts - 5 Amps. ( So that is 0 - 40 Volts, 600 Watts total, and 20 amps total.)

(If these had been new panels we could have divided the two circuits which are set up in series in the panels. But because these were used and not putting out what they should they would only give us a little over 12V even in the best of sun when we divided them up to try as parallel. And a 12V battery system needs an input of at least 13.7 volts to charge efficiently).

So the 34V - 40V panel voltage rating was an issue for setting up as a 12V system rather than a 24V system. But we needed to have it 12V so that it would also integrate with the 12V vehicle system and be an addon system to work with the vehicle also aside from the 120 AC inverter output. This way not only could he pull from the solar system batteries for the vehicle DC system, but could also use the vehicle charging system to help recharge the battery bank while he is driving. And he can flip a switched solenoid to jump the starting system on the van from the solar system if the van battery went dead for some reason. Redundancy for both systems.

When setting up a system you have to work backwards, from what voltage and current rating your battery bank will be, and what voltage and current your charge controller will need to be. In this case we went overkill with the charge controller, that way if he ever needs to use it with more panels, or in a stationary application it is already rated for more. And now days they use very very little to keep the controller powered up anyhow. So the charge controller is rated as follows:

Max 36v input when used on a 24V system. And max 24 volt input when used on a 12V system at max 80 amp input. Now it might (risky) have handled up to 40V input, but it would have probably caused overheating issues and digital control issues. We did not want to overdrive it, better to be safe than sorry with electronics that could cause fires. So we ran the 40V panel output through buck convertors to step down the voltage going into the charge controller. The buck convertors are rated as follows:

X2 - 20A 300W CC CV Step Down Module Adjustable DC 6-40V to 1.2-36V Voltage Regulator Buck Converter Constant Current Power Supply. The efficiency can be up to 95%,(measured at 20A, converting 24V to 12V).

https://www.amazon.com/ACEIRMC-Adjustable-Regulator-Converter-Constant/dp/B099S2VQ2Q/ref=sr_1_14?keywords=buck+converter&qid=1665481469&qu=eyJxc2MiOiI1LjcxIiwicXNhIjoiNS4wMSIsInFzcCI6IjQuNzQifQ%3D%3D&sr=8-14

Because of the max 300 watt rating of each buck convertor we had to use two and divide the output of the four panels (600 watts) into two sets of two panels (300 watts each set) going into the buck convertors. All that was left to do after hooking it all up was to tune the adjustable buck convertors on a good day with max sun available on the panels. A tip for buck convertor efficiency is this... You want to try and set the convertor output just under the max input to the charge controller. The more you step the voltage down the harder the convertor has to work, they operate hotter, draw more themselves, and are less efficient. Max input of the charge controller is 24V so we set the output of the buck convertors at 22V output. The only 2V difference is easy on the buck convertors and the heat sinks get warm, but not hot.

Now if one wants to make a small system like this as backup for a home there only a few important additional technical changes. A grid main switch needs to be installed so that when you turn on the solar system, it simultaneously physically cuts the grid power. Last thing you want is for the grid power to come back on while you are on your solar inverter. And unless you foot the bill for a home system inverter, portable inverters can be used but will fault if the ground is hooked up on the receiving home system, so the male plugs into the inverter need the ground post deleted. And there is a bit of careful wiring in the AC power distribution box so that you can pipe in two separate 120V circuits from the inverter. And unless you have a big high rated portable inverter you will want to temporarily shut off and live without all your 240 appliances.”

He can run a couple skill saws or cut off saws or 120 screw guns through an all day project and still be almost topped off in the batteries if it is a sunny day. It will take quite a load and hang in there well. This would make an excellent smaller scale system for a home. You could run smaller appliances like microwaves and such with no problem.

[Pollard]

18-22 is correct for 12vdc. Theory is that it's never going to run at 100% efficiency. Slightly hazy day, loss with every foot of wire distance, loss with every connection, morning/afternoon vs high noon etc. Charging voltages for a 12vdc battery are 12.7 - 14.3, so with inefficiencies, 18-22 gets you right in the ballpark. Perfectly clear day at high noon and the panel output will be close to those ratings on the back. The charge controller handles the conversion to optimum charging voltages.

FYI a fully charged 12vdc battery should be 12.7 volts.
12.0 volts is about 80%. (don't want to go much lower)
Run them down below 11.8 volts on a regular basis and you will kill them quick.(inverters etc will auto shut down at 11.8v to help prevent battery death)

200 amp hour is a lot for 100-200 watts of panel. The 100 amp hour battery ought to do what you want just fine.

BTW, we lived off grid for 5 years using a 320 watt, 12 volt solar panel setup with 4 GC2 golf cart batteries which is about 200 amp hours. We made those batteries last almost 10 years which is pretty good for GC batteries and being first timers in solar. Everyone says newbies kill their first set of batteries in 2-3 years.

I still have the panels and was looking at Renogy charge controllers and batteries just a few days ago. We had a Xantrex C40 charge controller which are supposed to be bullet proof but it up and died. Died the day before we had electric service, pole and meter installed.

From Renogy:

How many panels would I need to charge a 200ah battery?

If you have a 200ah battery, only 80% of that is usable due to depletion limitations, so you really only have 160 amp-hours of energy to draw on. If you learn that you typically can last two days with energy from that battery, that means you consume 80 amp hours a day.

Based on the earlier calculation, a 100 watt panel will produce an average of about 30 amp-hours per day (based on an average sunny day). This means you would need three 100 watt solar panels or one 300 watt panel to fully recharge your battery on the average day.

https://www.renogy.com/blog/what-size-solar-panel-do-i-need-to-charge-a-12v-battery/