Jim,
I'm not sure what number that you're looking for, but here's a bunch of data comparing my battery bank to a set of T-105s.
8kWh bank of LiFePO4 batteries, cost $3600 including BMS, tax and shipping, weight 200 lbs. Manufacturers lifespan is > 2000 cycles at 80% DoD.
Assuming 1 deep discharge per week for 10 years:
6400Wh x 500 cycles = 3,200,000Wh delivered
3200kWh / 200 lbs = 16kWh/lb
$3600 / 200 lbs = $18/lb
$18 / 16kWh = $1.125/1000Wh delivered
From what I know about Trojan T-105s
11.25kWh bank of 8 T-105 batteries, cost $1200 including tax and shipping, weight 500 lbs. Manufacturers lifespan is less than 500 cycles at 60% DoD.
Assuming 1 deep discharge per week for 5 years:
6750Wh x 250 cycles = 1,687,500Wh delivered
1687.5kWh / 500 lbs = 3.4kWh/lb
$1200 / 500 lbs = $2.4/lb
$2.4 / 3.4kWh = $0.70/1000Wh delivered
But these numbers aren't the whole story. Because of the different battery chemistry and Peukrert's Effect, T-105s deliver much less energy under load than the Li batteries do. Assuming a 2kW load, the T-105s should deliver 4920Wh in a 60% DoD cycle, the Li batteries will deliver 6100Hh in an 80% DoD cycle. Here's the same calcs again:
Assuming 1 deep discharge per week for 10 years:
6100Wh x 500 cycles = 3,050,000Wh delivered
3050kWh / 200 lbs = 15.25kWh/lb
$3600 / 200 lbs = $18/lb
$18 / 15.25kWh = $1.18/1000Wh delivered
Assuming 1 deep discharge per week for 5 years:
4920Wh x 250 cycles = 1,230,000Wh delivered
1230kWh / 500 lbs = 2.46kWh/lb
$1200 / 500 lbs = $2.4/lb
$2.4 / 2.46kWh = $0.98/1000Wh delivered
So for this usage pattern, the lithium batteries cost 20% more per delivered watt hour but are only 40% the size and weight of the T-105s.
I don't know how relevant these numbers are, since they are based on a broad set of assumptions, but those assumtions are stated here. Change the assumptions and the results will change. From my perspective, this is a fair comparison.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "luv2bsailin" <luv2bsailin@...> wrote:
>
> Right on Steve, but I suggest running them down more to increase range without increasing weight. If you only go to 50%, then half that lead is just ballast. Even if they only last 5 years, that's about $200 per year at today's prices. I'm sure most power boaters spend more than that on maintenance.
> It would be interesting to compare cost per pound per cycled watt-hour or some such bench-mark for various usage patterns. I know there are a couple spreadsheet gurus on this site...
> Cheers,
> Jim McMillan
>
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