pnichols wrote:
BFL13 wrote:
MEXICOWANDERER wrote:
Good grade of AGM can withstand discharging to 30% soc but the maintenance for recharge must be as strictly rigid as a Trappist monastery.
This is where thick plates pay for their room and board.
With our camping routine doing 50-85s (approx.) with AGMs for a few days and then a two hour drive home, the alternator and solar charging during that two hours brings the batts up enough so they won't accept the required 20% amps.
Huge PITA to recharge them to full once home. Have to rig a switch to kill the solar and alternator for the drive home, or else as now, run the batts back down once home so they will accept the 20%.
The recharge to full at proper voltage to 0.5 amps per 100AH is no problem. It is that dratted 20% rule. And the battery spec sheets don't even mention it as a requirement. Only gives a max amps no min amps.
It's always something.
Hmmm .... I guess that you don't keep your Class C at home?
I keep my Class C in the backyard plugged in all the time with a float voltage on it's AGM coach batteries and a battery maintainer on it's engine battery. The coach batteries after a day or two of this floating always arrive at an acceptance level of less than 0.5 amps.
You missed the point. Yes I recharge to full at home. The requirement hard to meet is that some (Mex says all) AGMs require a 20% charging rate to the spec Vabs prior to amps tapering during Abs.
If the batts will reach Vabs at 73% SOC with a 20% rate (eg) you have to start the recharge with them under 73%. If you get home with them at 77% then amps will start at under 20% and taper from there.
You can taper down to 0.5a full but you did not do the initial 20% in bulk (because you never did any bulk--the batteries were too full for that.)
Of course you do need a high enough amp charger to be at 20% or batter, and enough 120v intake to run that charger. With a 450AH bank, and only a 75 amp charger, I have to split the bank and do part at a time, which is another chore. Oh well.
Phil gets away with not doing all that somehow with some higher voltage alternator charging amongst his 13.8 volt 7345 stuff, and his particular AGMs last a good while. It is tempting to ignore Mex about the 20% "Lifeline rule" actually applying to all AGMs, but I try to do what Mex says if I can.
