Thanks for the calculations and insight. I would like to go with the LI tech for weight savings and space. Is there much degradation if you have the pack scattered around (a couple different spots I have in mind but are separated by 8 feet)? Also, I would like to put in a dc/dc converter to run the other "12v stuff" on board. That way I have one bank to monitor. I know it reduces the range, but I may just build it bigger to compensate. Currently I use two flooded batteries that have around 50 amp hours for house bank. I would just add that into my system. Other options are to keep my current system and make that the house bank but have the option to divert it to my motor to gain another 92ah. This would also give me the option to charge one while using the other. I know of another person that has their system set up like this. Again, thanks for the insight. I wish I knew about this group 3 years ago when I started this project.
Brian
--- In electricboats@yahoogroups.com, "Eric" <ewdysar@...> wrote:
>
> Brian,
>
> I bought my Thundersky batteries for $3350 delivered to my door. Unfortunately, that vendor is no longer in business. I spent another $250 for the BMS modules for a total price of $3600. These BMS modules will shut down the controller feed if any individual cell drops below a set voltage or shut off the charger if any cell goes above a set voltage. The pack is 16 TSLFP160AHA cells giving a nominal pack size of 160Ah at 50V or 8kWh. This works out to $0.45/Wh. There are some vendors that charge more than $1.20/Wh, with at least one above $2.00/Wh for LiFePO4 cells. For racing purposes, some other types of Li batteries may justify additional investments. However, for our boats, I would not pay more than $0.50/rated Wh for LiFePO4 batteries with BMS. By comparison, when I estimate battery packs, I use $0.11/rated Wh for flooded batteries (T-105s) and $0.20 to $0.25/rated Wh for AGM.
>
> I'm impressed by your performance numbers. For the following estimates I will use these assumptions: 25A = 4kts, FLA = 60% DoD, AGM = 70% DoD, Li = 80% DoD. Here we go....
>
> (8) Trojan T-105 (225Ah) - $1200 - 500 pounds
> Capacity @ 25A = 4.42hrs, range = 17.5nm
>
> (16) Trojan T-105 - $2400 - 1000 pounds
> Capacity @ 25A = 10.5hrs, range = 42nm
>
> (4) Odyssey PC1800 (214Ah) - $2600 - 530 pounds
> Capacity @ 25A = 5.5hrs, range = 22nm
>
> (8) Odyssey PC1800 - $5200 - 1060 pounds
> Capacity @ 25A = 11.8hrs, range = 47nm
>
> (16) TS-LFP160AHA (160Ah) - $3600 - 200 pounds
> Capacity @ 25A = 5hrs, range = 20nm
>
> (32) TS-LFP160AHA - $7200 - 400 pounds
> Capacity @ 25A = 10.2hrs, range = 41nm
>
> These battery packs are close to each other because the amp load is fairly low. Heres the same info using 5.5kts = 70A
>
> (8) Trojan T-105 (225Ah) - $1200 - 500 pounds
> Capacity @ 70A = 1.2hrs, range = 6.7nm
>
> (16) Trojan T-105 - $2400 - 1000 pounds
> Capacity @ 70A = 2.9hrs, range = 16nm
>
> (4) Odyssey PC1800 (214Ah) - $2600 - 530 pounds
> Capacity @ 70A = 1.75hrs, range = 9.7nm
>
> (8) Odyssey PC1800 - $5200 - 1060 pounds
> Capacity @ 70A = 3.8hrs, range = 21nm
>
> (16) TS-LFP160AHA (160Ah) - $3600 - 200 pounds
> Capacity @ 70A = 1.7hrs, range = 9.4nm
>
> (32) TS-LFP160AHA - $7200 - 400 pounds
> Capacity @ 70A = 3.5hrs, range = 19.25nm
>
> So if you're performance numbers are as stated, you can see what these various packs can deliver. You can also see how dramatically higher speeds (higher loads) reduce your available range. Even though my boat is fairly heavy already, I chose the Lithium batteries to reduce the space that the batteries take up. Since my ketch is an older full keel hull, all of the storage spaces are very irregular, there is very little space that has floors that are anywhere close to level.
>
> Let me know if you have any other questions.
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
> --- In electricboats@yahoogroups.com, "drmsudo" <drmsudo@> wrote:
> >
> >
> > Thanks for the insight. I have played alot with my set up. It appears that in dead calm conditions at roughly 20 amps, I can push my boat around 3.7 knots, sometimes 4 knots. That is not bad to me. I would prefer to go hull speed, but if I need the distance I must be patient. The advantage to the LI bank would be on day sails or shorter motor distances, I would be more inclined to push the boat at 60-80 amps and get 5.5+ knots. Yesterday I sailed to a local port about 8 miles away and on the way back no wind. We motored around 3.5 knots at around 15-18 amps. The starting voltage (with the motor off) is approximately 52v. The measured voltage at the end of the trip was 48v. I have pushed this pack to as low as 43v. The motor controller has a protection that it will shut down at anything less than 36v as a protection measure. Have you had any problems with your Thundersky batteries? Also, how much did you pay. Thanks again.
> > Brian
>
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