Hi Bill,
Like James said, Dow Kokam cells are very expensive. I know guys that own them, but they are regularly driving the batteries at discharge rates of 10C or greater. They are not indestructable (I've seen a blown up pouch in person), but they do take considerable abuse.
You are going to be operating at the other end of the spectrum, with typical loads of 0.1C so regular prismatic cells will be just as effective. I don't see any justification for the more expensive cells for your use case.
The two vendors that I recommend for prismatic LiFePO4 cells are Evolve Electrics in Colorado http://www.evolveelectrics.com/
and Current EV Tech in Washington http://currentevtech.com/
They can help with BMS decisions too. My BMS modules are from EV Works in Australia.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "Galstaf" <richard@...> wrote:
>
> Batteries:
> Goals –
>
> Use a Li based system for energy density, lower mass, and ease of use. Really interested in something that is as easy to manage as possible. As Eric estimated I would need 110,000 Whr approximately to go for 24 hours at 5 knots without any replenishment at an estimated cost of $46K, I have revised that to half that figure for weight and expense reasons.
>
> 12 hours of drive time should be sufficient 90%+ of the time. If I need the extra umph at that point, it is time to kick on the genset.
> So that would put me at 55000Wh of capacity at an estimated cost of $23K, right?
>
> I have been interested in the Dow Kokem marine duty batteries for a while now just because they claim they are pretty much indestructible regardless of DoD and charging rates. They also say each battery has it's own web server engine to provide centralized health stats on each battery.
>
> http://www.corvus-energy.com/marine.html
>
> Questions:
> * Are these claims pie in the sky?
> * Does anyone know of anyone that has used these batteries and BMS in production?
> * Does anyone know approximately what these Dow batteries cost per Wh?
> * Does anyone know anyone else that can boast of these properties at a lower cost?
> * What are your recommendations on where to shop for Li batteries?
>
> The manufacturer claims that you cannot hurt these batteries by fast charging them. They also claim no damage even with a full 100% discharge. Would it make sense then to buy an oversized genset and charging system so that a replenishing charge could be dumped into the batteries in short order and the genset (with it's incessant vibration noise) could then be shut down?
> The oversized Genset could also help push the motors along in case of emergency when speed IS key to avoiding a storm or getting to safe harbor. Comments?
>
> Any other comments about the BATTERY portion of this project, please feel free to be as verbose as possible. Links to manufacturers, and any and all pricing and performance data is sincerely appreciated.
> My best,
> Bill
>
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