Battery/Solar Panels

If this is a budget issue, it might be cheaper to buy a second 12V battery and wait for both of them wear out, before buying 2*6V.

Unless his existing 12V was not taken care properly and is in a bad shape already.

Again, for a fulltimer who wants solar to be their main or the only source of charging, a pair of 12V or 6V with total 200-225 AH will be on the smaller side. Consider 3*12V or a pair of the biggest 6V that will fit in.

The Works wrote:
We've had our 2017 Montana 3661RL for about 16 months. I want to add a second battery to the unit but I don't want to buy two matching batteries. What and why are the reasons I'm being told I need to have two matching batteries. What problems would I encounter by adding a non-matching battery?

The two different batteries will charge at different rates. Either one will be overcharged or the other undercharged. This will lead to a short life on both.

Bite the bullet and get two 6V golf cart batteries. You will be happier in the long run.

The Works wrote:
We've had our 2017 Montana 3661RL for about 16 months. I want to add a second battery to the unit but I don't want to buy two matching batteries. What and why are the reasons I'm being told I need to have two matching batteries. What problems would I encounter by adding a non-matching battery? Also, solar panels, has anyone added a solar panel to keep the batteries charged? What type of solar panel did you use? Thanks for your input.

Without a doubt your 16mo. Old battery will be weaker than a new battery. Putting a weaker battery in parallel with a new battery will prevent the new battery from achieving its full potential charge as the weaker battery drags it down. At 16mo. age it may not be too much of an issue if the original battery has been carefully maintained.....

The Works wrote:
Also, solar panels, has anyone added a solar panel to keep the batteries charged? What type of solar panel did you use?

Tons of solar posts, indeed.

You should first decide how much energy you need daily. This will determine what panels and how many, and also - how big battery bank you will need.
IMO, for reliable offgrid fulltiming on solar you need more than two 12V batteries.

Like was said, if your battery is good, you can run it w/ a new one, but match the type,...deep cycle to deep cycle etc. Size capacity does not matter either,.....if you have a 24, add a 27 for more capacity, no problem.

Not a huge deal to get a second battery if the existing is in good shape. Do match the type of battery such as deep cycle flooded. Expect the new battery to be worn out when the older battery is done. So if the old battery has four years left that is all you will get out of the new battery. Expect to replace them both together at end of life.

The 12 Volt Side of Life

I bought my primary solar equipment at https://www.solarblvd.com/

About 100 watts is best for storage and for in use consider 200 to 400 watts with two batteries. Need a controller too.

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"Also, solar panels, has anyone added a solar panel to keep the batteries charged? What type of solar panel did you use?"

I've installed a solar system...not just panels. It works great. While my system is entirely WindyNation all the big companies are just fine. As SWP says, get enought panels, a good controler and use adequate wire sizes.

Don;t know anything about the batteries but we have always(been rving 40 years) had a solar panel to charge the batteries. More so for when rig was in storage. Make sure you get a quality panel with enough power to do the charging.

Tons of solar posts on here in the last 11 years. Batteries too.