From my perpective, the biggest advantage for AGM in our applications is that AGM are much more tolerant to high amperage loads and are not nearly as effected by the Peukert effect. Technically, wet cells have a Peukert exponent of 1.3 and only 1.1 for AGM. This means that battery banks with identical capacity ratings will deliver more minutes (range) for AGM rather than wet cells.
Beyond that, LiFePO4 batteries have a Peukert exponent of 1.02 and are almost not effected by the Peukert effect at all. This means that LiFePO4 batteries will deliver almost their entire rated capacity even at loads of 100A or more.
Fair winds,
Eric
Marina del Rey
--- In electricboats@
>
> Positives: No periodic watering, much slower self discharge, no spilling acid if the boat is heeled way over (more important for a sail boat), no acid fumes when charging, can be installed in any position except upside down.
>
> Negatives: 2x to 3x cost.
>
> ----- Original Message -----
> From: alex
> To: electricboats@
> Sent: Tuesday, December 22, 2009 5:28 AM
> Subject: [Electric Boats] Re: My conclusion
>
>
>
> Denny, why do you recommend AGM batteries over flooded wet cells ?
>
> --- In electricboats@
> >
> > That sounds like a great solution - get AGM batteries and a good charger that will put out at least 10 amps at 48v and you will have trouble free silent non-polluting boating. (4) 12v gp31 batteries would probably give you 2-3 hours at 4-5 mph, (8) 6v would more than double that range.
> >
> > Denny Wolfe
> > www.wolfEboats.
> >
> > ----- Original Message -----
> > From: greenpjs04
> > To: electricboats@
> > Sent: Sunday, December 20, 2009 2:17 PM
> > Subject: [Electric Boats] My conclusion
> >
> >
> >
> > Hi everyone,
> > I have been lurking here for a few months now and have learned a great deal from all of you. Thank you! I now realize my project is much simpler than what all you sailors have to deal with when using electric motors in open waters. I have a 24' pontoon boat that is exclusively used on a chain of small inland lakes here in northeastern Ohio. The boat currently has a 10 year old 40 hp Mercury 4 stroke outboard. While I occassionally open up the throttle in the speed/ski zone, most of time is spent a little above idle puttering around the lakes. The Mercury is now getting finicky. It is hard to start if it hasn't been used for a week and vibrates at low speeds (which is 99% of the time). I want to change to an electric motor which is why I subscribed to this group.
> >
> > I seldomly need to worry about high winds. I never have to worry about currents. Battery weight has very little impact. Even safety isn't an issue since even though I can take a 17 mile trip around the shoreline of these canal-connected lakes, I am never more than 1/4 mile from shore and am usually within 50 feet of shore. My conclusion is a Torqeedo 4.0R with four 12 volt deep cycle marine batteries would easily meet my needs. Does anyone have a better idea or disagree with my conclusion?
> >
> > Thanks,
> > Pat
> >
>
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