f250 4 stroke and AGM batteries

I understand that Yamaha does not recommend the use of
"maintenance free" batteries. I have heard that it is due to the
potential damage to the batteries from the charging system
on their outboards - does this apply to the newer AGM batteries??

What is the charging voltage (range) applied to batteries by the
F250hp 4 stroke? The particular AGM batteries that I am looking
at are sold by West Marine. The charging voltage for these
batteries is listed as ~14.6 volts. The range is written on the side
of the battery - I believe it was something like 14.2 to 14.8 volts.

Since AGM battery technology and design appear
to reduce the chances of explosion, I wonder if the restriction
(by Yamaha) of using "maintenance free - sealed batteries" actually
applies to the AGM technology ? or is their warning related to the older
"sealed" (flooded) battery technology - which is still available.

I appreciate any responses that can shed some light on this topic
and perhaps detail the issues that are at play - as I am impressed
with the specs on the AGM batteries and I currently am in the
market for new batteries.

Please see the Battery FAQ below for some details on the AGM
battery technology -

http://www.windsun.com/Batteries/Bat...at%20Batteries
thanks

[boats.net]

I don't have the answers for you even though this question comes up a lot. That engine is capable of charging more than 14.8 volts. I ask the battery salesmen that come in our store this if the engine manufacture doesn't recommend this type of battery and you say it will work with no problems. Will your company or the battery manufacture pay this customer for his boat if burns down due to the battery? So far I haven't got a yes answer for that question.

[jb123]

ive a friend that has used them for a few years w/250's and no issues.... BUT will it void a warranty ???

I spoke with Yamaha Customer Service earlier today and posed the
question regarding AGM batteries. The technician told me that Yamaha's
primary concern regarding "maintenance free" or sealed batteries is
related to "Gel Cell" batteries. It is due to the charging voltage
required by Gel Cells. He went on to explain that the charging regulator
on the F250 Yamaha 4 stroke puts out 14.5 volts - this is precisely
what the AGM batteries require - which happens to be the same voltage
which is recommended for standard lead acid (flooded) batteries.
The technician was very knowledgable and politely listened to my question
and concerns. He answered my questions and explained that the
charging voltage was the issue (with Gel Cells) but did not present a problem
with the newer AGM batteries as they very closely mirror the same
charging requirements as standard lead acid flooded batteries.

The customer service number for Yamaha, in Kennesaw Ga., is
(866) 894-1626.

Hopefully this will address future issues with AGM batteries and
Yamaha outboards.

regards

Another point of view

My understanding of why you should not use maintenance free batteries is that in the event that the charging voltage is too high it will boil the electrolyte and once the electrolyte falls below the level of the plates there will be serious problems. As long as the voltage is in the correct range there will not be problems. The thinking is that when the electrolyte level falls in a non-maintenance free battery you can fill the battery with distilled water and be on your way.