Maybe a better idea is one of these....go for the 5amp and 12.6v
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....derpsy doodler posted while I was writing.....
Reading the interesting and helpful reponses gives me some good ideas and reminds me how shallow my knowledge is.
One thread led to a very capable device by Renology. At $300 it is likely over kill, considering I have a charger in line for my lithium set-up.
I do like the many features.
There is also a link for some much less endowed chargers
27.88US $ |DC DC Battery Charger 12v 24v to 12v 12.6v 13.v 14.5v Lead Constant Current 5A 8A 12A 15A 20A 22A 25A CC Battery Charger|Inverters & Converters| - AliExpress
These seem to have fewer or no protections for the battery being charged (constant currant).
This is where my ignorance really starts to pinch. In both cases the devices are described as working with power sources of lessor wattage than my array. The Renology device is linked to use with 400 watts. My panels are rated at 600watts.
In my experience Watts are a function of power used as opposed to voltage which is more like pressure to be wary of. Practically speaking , I can put a 10, 40, or 60 watt lamp into a socket and none will be harmed even though my outlet is rated 1500 watts. However when I suggest attaching a solar device like an MPPT to my panels 95% of the people I talk with tell me the 600 watt panels will destroy the 400 watt rated device.
I am thinking it is "headroom" and my advisors (generally parts salesmen) consider the extra watts as device killers. Hence I am on this forum hoping for a better understanding.
Finally, having just recently moved to the Northeast where my camper and I have for the first time experienced below freezing temps, I disconnected my Lithium batteries for the season. I hope to build a self sustaining heated battery box once we are settled.
For now, The panels on my camper are serving no purpose. The starting battery in the truck is not enjoying being parked for days in the cold weather. Twice I have gone out to run the motor for a twenty minutes session and found the battery flat.
No doubt there is a parasitic leak complicating things. This starting battery also deserves a heating system in the future. But for now I want to charge it with solar energy, hopefully using the panels I have.
PS I realize this is a very long "reply"...possibly bad etiquette..... a long with Solar, I am just learning about forums