Hi Steve,
I agree with you Steve that LiPo's are great batteries. However, you are one of the lucky ones. Firstly, you have the knowledge necessary to run these batteries properly. You chose the right BMS. There are so many to choose from and many BMS caused the batteries to go out of balance rather than bring them into balance. There are so many ways that an installation of LiPo's can go badly. And the average person taking on a LiPo project doesn't do the research, doesn't know what they are dealing with, and its all a huge learning curve for them. LiPo's are definitely great batteries but they deserve respect that is often not given them.
Multihulls are very weight sensitive and when you weight them down with 1800 lbs of batteries you would lose a significant amount of performance. But as a general rule of thumb, the higher the energy density of a battery, the higher the volatility of the battery. So if you are going to go into a high energy battery, then I surely hope you do your homework!
LIPO batteries have short circuit currents that are 10 x their amp hour capacity so fusing is an absolute must. If a wrench drops across the terminals of a LIPO battery, it will glow red hot in minutes so I hope that it is impossible for that to happen on your boat. For instance if you use a 200 amp hour LIPO battery, it has short circuit current potential of 2,000 amps and that is every cell.
I think a lot of people want the performance, but never use it. Seems like you use your boat, so you can get the value out of the life cycles. But many boats are only used 10 times a year and they never reach the batteries cycle limit so I think there are times when the extra money is wasted and the risk is not worth it.
In the end the type of battery used should be determined by how the boat is used.
My point is simple. More can go wrong with a LiPo battery, so if you don't need them, don't use them. Besides which, everyone is on a budget, and the extra expense is enormous when you consider the installation too - and professional installation either by a knowledgeable boat owner, or by a marine electrician is highly recommended if you are getting into any kind of Lithium chemistry.
I was unable to see your pictures. I hope the cells are in enclosures, the enclosures are firmly attached to the boat, the cells are compressed, the enclosures are fused inside the enclosure, all battery cables and voltage sense wires are double insulated, there is easy access to the cells to check for corrosion on the voltage sense wires and busbars, and that all charging sources and loads are controlled by the BMS. Hopefully the batteries are in dry conditions, the enclosures are monitored for temperature and you have no paralleled cells or unmonitored strings. These are just a few of the concerns I have. You can deduce why I make these recommendations for LIPO.
Compared to the NSB that has zero chance of internal catastrophic failure and arguably the safest battery every built. I like safety. The problem with Safety is it is hard to sell. NO one wants to talk about it. Everyone want to get the boat out on the water as quickly as possible and the last thing that is thought of is the safety of an installation. And on top of that, no one wants to pay for safety. Safety is the number one responsibility of a captain of a vessel so I really don't understand why it is not in the conversation.
Regards,
James
James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
James and all.
I've run the Northstar batteries in a string of 12 NSB's for 210AH and 144V. As pretty much as everyone has said they were GREAT batteries for the time I had them, about 7 years, until I switched to LiFePo4's. I will disagree with you James on the LiFePo4's. They are fantastic batteries. You concern with the BMS failure is not justified IF you use a good system. I'm using the Orion BMS which in all cases of failure will shut down the charging systems I have protecting the batteries from over and under charge conditions.
The 4's are 1/3rd the weight. 550lbs vs 1800lbs
The 4's will discharge to 5% with no damage vs 40%
The 4's have a life expectancy twice of the AGM's (Based on your mileage of course.
My NSB's would have cost about $8,000 to replace, the LiFePo4's cost $13,000 but if you look at the life expectancy they are cheaper than the NSB's.
0 loss of charge if they sit for 5 months over the winter (my experience) with no load.
A bunch of people are using the LiFePo4's for house batteries.
I couldn't be happier with the LiFePo4's.
Steve in Solomons MD
Lagoon 410 S2E
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