Mex's 20% AGM Rule Sucks.

Mex says deep cycle AGMs need to be recharged at a 20% of Bank AH rate even if they are not Lifelines (which do specify that).

My AGMs are not that brand, and no mention is made of a minimum charging rate in their specs, just a maximum (about 27%) at the charging voltage specified for "cycle use" (as opposed to "storage use" -might mean UPS duty)

So that's fine until you get into shallow cycling, where the batts don't get down to a low enough SOC to accept that many amps on a recharge. So now what? Are you supposed to run them down a bunch more before recharging them, so they will accept at least 20% charging rate?

EG, after four days off grid with my 450AH of AGMs, with solar and a general variety of draws on the batts from microwave, television, etc, all the usual daily ups and downs, when finally on shore power at home, and ready to get the batts to "true full", the bank starts off accepting 29 amps with the charger set to the spec 14.5v.

The story used to be that all you had to do was leave it there until amps tapered to 0.5a per 100AH of bank. That's easy, just watch the amps on the Trimetric come down and when the batts are full, crank the voltage down to 13.6ish,adjusted for temp.

BUT--29 amps on a 450AH bank is hardly 20%!!! So whatinheck are you supposed to do? (Actually, what do Lifeline owners even do????)