Best charge controllers..

Morningstar SunSaver SS-MPPT-15L
60v/15A. $200
Gel/sealed-AGM/flooded
5 yr warranty
Epoxy filled (can take weather)

Morningstar:
I have used these on my boat for many years. When anything at all went wrong, I call the number, I get transferred to their ENGINEERS, located here in the US. They get my address, a unit gets sent to me in the mail. They want the bad one back, in the engineering department to take apart and figure what went wrong. They have a 5 year warranty and I have found it to be very solid.
I have used the single PWM unit and now the Sunsaver Duo that charges two different batteries at the same time.

WindyNation TrakMax MPPT 40A. .... $40 (too good to be true??)
Flooded/Sealed-AGM/Gel/Li
Some type of Bluetooth module.
Max operating temp. 113F. (This seems concerning)

MidNite Solar -- Classic or Kid.

My WindyNation MPPT has worked without a problem for three plus years.

My thought leans toward one of the Renogy Rovers for the simple reason they will accept a #4 gauge conductor on the input and output. I like big conductor.

groundhogy wrote:
Please elaborate as I thought there was only one thing to do to batteries.

Batteries can have different charging protocols. Find out from the manufacturer what's needed for your specific batteries and narrow it down from there.

I have the EpSolar
charge controller with 200 watts of solar.
The controller is 8 years old and has been charging the same batteries (a pair of GC2's) for the full 8 years. The batteries are still going strong.

You can get lower cost but my Morningstar has been perfect.
Very flexible programming.

Please elaborate as I thought there was only one thing to do to batteries.