Steve, I'm right with you on this one.
We bought our trailer back in February.
It came from the dealer with a 12v group 24 battery.
I just bought a 2nd one from Sams Club.
It's not the same brand but they are similar and
both read nearly identical voltage when fully charged.
I'm gonna use them until they get too weak and then
most likely go with a couple 6 volt replacements.
I also have a small generator and am experimenting with
the best/quickest way to re-charge my batteries if needed.
I have the luxury of parking my trailer at home so I can
plug it in at any time and let my power center do the
charging. It fully charges my single battery in 24 hours
no problem and I expect it to charge the pair in a day also.
What I am trying to find is a way to fast charge the pair
in an hour or 2 at the longest.
Maybe not full but a significant charge in 60 minutes.
My power center wont' do it.
Read my discussion here--
Tank/battery monitor is Inacurate
My previous trailer had a different brand of power center. It would toss as much
as 40 Amps at your battery when you first plugged it into shore power if the
battery was really low.
The one in my Rockwood starts out with a good charge rate but quickly drops
back. This is good for battery life but bad if you are trying to charge the
stupid batteries in a hurry!!
I'm looking for an external charger in the 20 amp + range that I will only
use a couple times a year when we are dry camping and need to boost the batteries.
When I find it I will do some testing on charge rates and times necessary and
report back here.