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!
I spent over 6 years reading anything I could get my hands on before purchasing my system.
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.
All tools over the length that could short out a battery are coated with rubber or rapped in electric tape. I wear rubber gloves and review my procedure before any maintenance is performed. I also have rubber mats that are placed on the battery pack when the lid is opened and no metal (rings and such) is worn. As you can see by the pics my pack is very easily excessed. I take this pack VERY seriously. At what voltage pack do you consider safe if you don’t?
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.
A fair point. My pack at 144V means I run my combined motors at under 60A at 6 knots. Less ware and tear on my system as well as extended run times.
In the end the type of battery used should be determined by how the boat is used. Absolutely! I’m hoping to do the Carib. In a year or so.
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 agree 100%. I had a PRO review and help out with my system and glad I did. He added some things I didn’t think of and I’m pleased with the results. He is a boat Electrician however he also is into electric cars. That was a bonus! As soon as you think that you know everything there’s something else to learn.
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.
All great points, I sent you the pics directly to take a look at. The Pack is secured with 2 HD Cargo Straps to compress and secure as well as 8 straps to secure the pack to the decking. I’m not so concerned that the pack would flip as with a car so didn’t feel it necessary to build a box to place them in. Access is very good. Wiring is per the manufacture and I’m pretty sure it’s not double insulated. The pack is in as dry a location as can be found on a boat, location is dry. I’m using a custom program for Electra Glide with a display showing each individual battery voltage as well as the pack temperature from Andromeda EVIC. The display is at the Helm and is monitored underway. Voltage difference on the 48 batteries is .02v from the highest to the lowest. There are NO parasitic loads on the pack when off.
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.
A true statement James.
All batteries lose capacity as they age and LIPO's are no exception. Recommending cycling down to 5% is problematic over time. Within 5 years it is almost guaranteed that one of your cells will lose at least 5% of their capacity. So if the BMS is set to alarm or disconnect loads or charging sources at 5%, then there is a good chance that sooner or later you will be fully discharging the LIPO battery. Once fully discharged, a LIPO battery can short their cells if current continues to flow through the discharged cell - especially if you leave the batteries in a discharged state for any length of time. I have even heard that when they are fully discharged, they can invert - and positive can become negative - though I have no experience with this.
I’m set at 10% now but plan on moving up to the 20% number since I don’t plan on going below 30% anyway.
It would be far better to keep a large margin of error and set your lowest discharge point at more like 20% - for safety over time reasons.
The NSB can be set at 20% as its discharge floor which is the same as my recommendation for LIPO.
The other thing that everyone should think of when they install any battery on any boat is how gracefully will the battery fail at the end of the battery's life.. To be safe, any installation should be engineered to be safe through a battery failure. Batteries are one of the only components on a boat that are guaranteed to fail over time, so precautions and warning systems should be in place for this guaranteed event.
The only way to guarantee that a boat will be safe through a battery failure is through monitoring of each individual battery for voltage, and each battery or battery enclosure for temperature. This can be done manually, but far better and in real time, if done automatically.
Batteries are load tested each time you use a high power setting on an electric boat. Operators, or their monitoring system, should be aware and log system voltage at a certain current - say 50 or 100 amps. If after some time going by, the voltage under a 100 amp load starts to drop, then you know that you have lost capacity of the battery pack, or one of the cells or batteries has failed.
I have yet to come across a battery meter that changes capacity of the battery over time. This is a big issue because almost all battery meters will show 100% full, even on an aged battery. This means that at some point in time, the boat could leave the dock with an empty battery and the unknowledgeable could be going to sea with empty batteries.
Like it or not, all batteries are maintenance items in that they need to be monitored to insure the safety of the vessel. Monitoring should include voltage and temperature of each thermal enclosure. With Lead Acid, a thermal enclosure is the battery itself. With Lithium, more than one cell can be installed into one thermal enclosure.
Thanks James for being a part of this site, your knowledge is well appreciated.
Steve in Solomons MD
Lagoon 410 S2E
Posted by: "Steve Dolan" <sdolan@scannersllc.com>
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