Rob,
It may seem that your AGM batteries are heavy, but all lead acid batteries (flooded, AGM, Gel) weigh about the same for the same rated capacity. Their weight to capacity ratios are typically within 5% for all of those types. However, because AGM has a deeper discharge duty cycle, it is easy to see that AGMs have a greater usable capacity for the weight. But even without a deeper discharge, AGM have a lower Peukert's exponent, meaning that under higher loads, they deliver more amp hours from the same amount of charge than flooded cells. So, AGM could actually be lighter for that same boating experience.
To significantly reduce your battery weight and size, the prismatic format of LiFePO4 batteries seem to be the most reasonable solution available today. There are acouple of people on this group that are already using these lithium cells, I think that most of them are CALB or Thundersky batteries.
Although I am a proponent of lithium cells for electric boats, cars and cordless tools, i believe that AGM probably represent the best compromise of cost and performance today.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, Rob Johnson <dopeydriver@...> wrote:
>
> Thanks for your post James.I take your point.
> I have AGM batteries in my current boat , yes , I'm impressed.
> But gee , they are bloody heavy.....
> Regards Rob J.
>
>
>
>
> ________________________________
> From: James Lambden <james@...>
> To: electricboats@yahoogroups.com
> Sent: Tue, 22 March, 2011 12:38:46 PM
> Subject: Re: [Electric Boats] Battery Box
>
>
>
> Rob,
>
> 12 volt batteries have half the connections.
>
> The whole system is dependent on each connection so less is more in this case.
>
> It is worth the extra money in life expectancy and amp hours available over time
> to buy AGM batteries.
>
> James
>
> www.propulsionmarine.com
>
>
>
>
>
>
> On Mar 21, 2011, at 6:27 PM, Rob wrote:
>
>
> >If I was to put a diesel hybrid setup in a 27 ft wooden boat , I'd like to site
> >the batteries , say 8 6 volt as low as possible in the boat .
> >I believe a sealed box , with positive ventilation would be appropriate.
> >Any comment ?.
> >Regards Rob J.
> >
> >
>
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