GEL vs AGM?

Hi everyone… well spring is around the corner and that means work on the boat.

I knew when we purchased Windseeker IP38-168 in October 2009 that we would need to replace our batteries, however I find that it is sooner than later.

The bank consists of three (3) 8G31DT batteries (GEL)

We have a CROWN II Automatic Marine Converter (obsolete) which is made by Raritan (which they stopped making 10 years ago) The charger is a B series which allows for adjustment to current limit and voltage setting. www.raritaneng.com/pdf_files/obsolete/L46_crown_II-b_series.pdf

I have done quite a bit of research (reading east penn’s technical manual on GEL and AGM batteries) comparing the GEL to the AGM’s and am interested in your feedback or experience on GEL vs AGM

There are GEL’s in the boat now, however I am thinking about going with the AGM’s to save a few bucks but realize that I may need to adjust my converter to the proper voltage setting and address the risk of burning out my alternator. (it may not be worth it from a cost perspective nor from battery life perspective)

Can someone please clarify the issue specifically related to how AGM’s can risk burning out your alternator. I get the concept of AGM’s sucking in as much voltage as they can which may result in burning out the alternator. I assume this occurs when you are running your engine or generator to recharge the batteries, but I am unclear how to best manage this from occurring.. (other than don’t drain the bank too low, right? )

What battery charger are you guys using for your gels?

Any insight or any referrals that may help me grasp the concept better is appreciated.

Thanks

Margo
s/v Windseeker IP 38-168

Margo:

The issue is not that you will burn up the alternator or charger if you switch to AGM's. Rather that unless you switch your charge sources to the AGM recommended bulk and float voltages you will ruin the batteries.

Bobby

Thanks Bobby..
I agree and recognize the issues with the proper settings so not to ruin the batteries..

I have decided to stick with the DEKA GELS specifically the 8G31DT and can get them at a reasonable cost ($268 plus tax, per Ross Dobelstein) at East Penn distribution in Ashland/Richmond, VA.

Margo:

Then what is the issue that you mentioned with burning up the alternator?

Very confusing from my perspective.

Bobby

Bobby,

sorry for the delay in my response... I may be confused as well.. THings I read online suggested that if there is no regulator on the charger the AGM's will just keep sucking during charge ... then if the alternator is not big enough for output demand .. it would burn out... I am still unclear myself .. but that was the jist of what I read... the issue is moot as the battery chargers today address this issue.. or so I think ...

hope all is well

Margo

Margo:

Sounds like you got some bad info or are confused. All chargers are regulated - the issue is that the regulation in question may not be optimized for AGMS - especially the float voltage as this is generally what kills them. The alternator generally will not burn up if it is not adequately rated for the battery bank size - it just takes a whole lot more time to reach a charge. Again though - the alternator regulator has to be suitable for the AGM batteries.

Most battery chargers today may be suitable but if the user does not set the charger to match the battery bank being charged then the bank will not last long.

Bobby

Calvigny Island, Grenada