Small Outboards and AGM Batteries

[sandiegosailor]

Getting a new sailboat with 15HP outboard headed saildrive with electric start and 10 amp alternator. Since it is electric start it has Rectifier/Regulator.

We will have an onboard shore power 3 stage charger but question the performance of the 10Amp alternator. We want to use an AGM but are concerned that they may become overcharged by the alternator on longer runs or if the battery is very low maybe burn out the alternator.

I've read about the risk of unregulated charging from small outboards but is that problem answered it Rectifier/Regulator is present?

Anyone have any experience using AGMs with small outboards? Draw on the batteries will at max be a couple of cabin lights, VHF and running lights. Most of the time the motor will be used in and out of slip only. My concern is on the longer trips.

[Valiente]

I used a Harley AGM with the magneto on my old Honda BF100. My solution was to belt around for 15 minutes or so with the clips running from the "charger" to the AGM strapped to the back of the gas tank (with non-conductive material in between!). That generally topped up the AGM and I had eight hours of nav lights.

It's not a great solution, because you have to "manually charge" according to time after you get a multimeter on your outboard's output, but it will do the trick.