Hi Bob,
I've noticed that prismatic LiFePO4 cells are techincally rated at 3.2V but when put four in series, we call them 12V. I know the technically your bank would be 12.8V, but what is the resting voltage on a regular 12V flooded LA battery? 12.8V. If one takes fifteen 3.2V lithium cells in series, it works out to exactly 48V, but most of us are running sisteen cells and also calling them a 48V (nominal) system. Technically sixteen cells is 51.2V but for practical purposes, it's 48V. It becomes more obvious when aiming for higher voltage systems like 144V. But I think that most lithium adopters use forty eight cells for 144V (nominal) and 153.6V actual.
Personally, when doing capacity calcs, I round up to to the nearest 50 to make the math easier. My battery pack of sixteen cells is 48V (nominal) 51.2V (actual) and at 160Ah, I consider it to be a 8kWh bank (50V x 160Ah). I often do the same for lead acid battery types.
So, why do I bring it up? I think that considering LiFePO4 cells as 3V batteries, makes the conversations simpler and the math easier.
Just a thought....
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, Robert Lemke <robert-lemke@...> wrote:
>
> I'm putting together an electric kayak and I want a 75 mile range with batteries that only weigh 60 lbs total for both packs. (2) 12 volt, 100 a/hr packs of (4) cells per pack. Each cell is 3.2 volts and if cycled no deeper than 70% DOD, will run 3000 cycles before their rating drops from 100 a/hr to 80 a/hr, so should last longer than me.
> Bob
>
No comments:
Post a Comment