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Hi Eric,
I know that 50% is a commonly stated rule of thumb, but it's not a hard limit. It depends on your usage. For something like an off-grid solar installation where the batteries cycle every day, obviously you'd want to maximize your cycle life. On a boat that's only run hard once or twice a week, you could go to 80% discharge and still get years of service.
Anyhow, battery performance is a topic worthy of it's own thread.
I just wanted to point out that one can get very useful performance without investing in cutting-edge (expensive) battery technology.
Jim
--- In electricboats@yahoogroups. , "Eric" <ewdysar@...com > wrote:
>
> It's a pretty common mistake to use published battery ratings for maximum range, but the rating that you quote below is for a 100% depth of discharge. Using the accepted 50% DOD for maintaining healthy wet cells, the 8 T105s will have a usable capacity of 66 minutes and the 12 T105s will have a usable capacity of 110 minutes at a 3000w load.
>
> This is why many people run AGMs that can be run to 65% DOD without negative effects or LiFePO4 batteries that are rated for over 2000 cycles at 80% DOD. AGMs are also less affected than regular wet cells by the Peukert effect, the reduced capacity of batteries under high amperage loads, and Lithium batteries even less so.
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
> --- In electricboats@yahoogroups. , "luv2bsailin" <luv2bsailin@com > wrote:
> >
> > Thanks for the numbers James. I assume that 3KW @ 5.75MPH is measured performance from your Catalina, right? Sounds reasonable.
> >
> >
> > The Trojan T105s are rated for 115 minutes at 75A, so lets say an easy 2 hours at 3000W (62A). That'll give you 10 miles at 5 KT.
> > If you go to a 72V system (4 more batteries), the range should about double.
> >
> > Not sure what my point is, but it's an interesting comparison.
> >
> > Cheers,
> > Jim
> >
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