AGM battery charger overvoltage?

[mooder]

I have the Deka 8A31DT. In the manual, it says that for a temperature of 21-27C, charge voltage should be optimal 14.3 & max 14.6 and the float at 13.4 to 13.7 (max).
On the battery's sticker (it is a die hard rebrand), it says charge voltage 13.8 to 14.6v.
I have the charger Noco genius G3500
https://www.amazon.com/NOCO-G3500-Ul.../dp/B004LWVEKS
and also the motomaster
MotoMaster Eliminator Intelligent Battery Charger, 75/25/12/4A | Canadian Tire
The problem is that both overvolt the battery. I've seen 14.8-9V supplied to the battery! I got this one as a replacement from my DieHard 31M platinum after just ~20 uses. I am afraid overvolting the AGM is killing it too fast.
On the Noco genius, I made sure to select the AGM mode. I don't get why it keeps supplying so much... Should I ditch these two chargers?

[ranger58sb]

Can't tell at quick glance if either of those chargers are 3-stage type. Looks like you can only control amps to "high" or "low".

A typical 3-stage charger will give you bulk, absorption, and float stages, and many will give you more charging "profile" choices (separate voltage selection for bulk/absorption and float stages) so you can better match to what the batteries want.

If your previous Sears battery was a Platinum Plus AGM, it was made by Odyssey and shouldn't have died in ~20 cycles. Could have been a lemon, but i'd first suspect that something on your boat is the killer. The AGM-hood-ness (?) of the batteries is likely not germane; same could have happened with wet batteries, too.

-Chris