Charging multible batteries

[randym]

I have a hobby launching high power rockets and we use 12V gel cells to power our lunch system. We've had issues in the past because the batteries don't always get taken home to charge them, so I would like to setup a solar charging system in our equipment trailer.

My question is about trying to figure out the best way to go about doing that.

Our system currently uses 6 batteries and because they are all on different banks, they all have different rates of discharge.

I would like to just have one panel on top of the trailer, so my question is:

Would it be best to use one controller and just connect the batteries in parallel considering they are all going to be different at the end of the day?
Or would it be better to use a controller for each battery all connected to the same panel? (not sure this would work)
Or use a smaller panel and controller for each battery?

We normally only have one launch a month, so they would have plenty of time for them to charge between launches.

I do have a little experience with solar since I have my own trailer with a 100w panel so I can have 110v available while at a launch since we tend to be in the middle of nowhere. (That's actually a good thing!)

Curious to hear pros and cons to each setup.

Thanks in advance for answers.

Randy

[bob-n]

One good solution is to use one charger per battery and have all chargers powered by one inverter from one panel. For small gel cells, I like Battery Tenders, but there are other good 3-state chargers available.

There may be solar powered chargers that can handle multiple batteries, but I don't know of any.

Connecting batteries in parallel is possible but has risks. If the batteries are much different in voltage, then they will back feed eachother and high current (danger) is possible. There are safe ways to connect batteries in parallel, but if you are leaving things to the mercy of unskilled operators, the risk is too high for my comfort level.

Connecting batteries in series is also possible, but that creates a higher voltage, which many would consider a safety risk. In general, anything above 48V is considered hazardous. Also, charging a series connection of batteries that are at different states of charge is not recommended. Some cells may not fully charge, resulting in shorter battery life.