My battery pack is 16 Thundersky 160Ah cells in series with Mini-BMS modules from EV Works on each cell. My experience lines up with Jason's. Minimal draw over long storage periods. I have measured cell performance through annual controlled deep discharge and recharge cycles since the pack's installation in 2010. There has been minimal capacity degradation over the last six years, however, the cells are still outperforming their manufacturer's specs. I have adjusted my E-Xpert Pro battery monitor to account for my overall self-discharge rate, I believe that my present setting of 2.6%/month is very close. That rate includes the effects of the BMS cells.
I have stored my batteries starting at states from 100% down to 60%. As I stated earlier, the cells are still outperforming their stated specs. It does not appear that leaving them at 100% for months at a time has had any measurable effect. That said, maybe it has cost me something in cycle life. Since I am still under 100 cycles after six years, I doubt that I will get the chance to observe a small percentage reduction in the stated 2000+ cycle lifespan.
After owning this battery pack for 6 years, I am a solid proponent of the technology. Previously, the average lifespan of a lead acid battery in any intermittent duty has been something less than 3 years for me, in spite of my well intentioned, but apparently inadequate, attention to battery maintenance. This includes classic cars, utility vehicles and my boats.
I have found LiFePO4 cells to be lighter, smaller, take less attention, and safer than the various types of lead acid batteries (wet, AGM, gel). I have blown up a wet cell L/A battery with a trickle charger. This lead to extensive corrosive damage, luckily, the car and my garage did not catch fire. For me, the lithium cells have already proven to be cheaper, based on my personal history, I would be getting ready to buy my third set of lead acid batteries for my boat. That would offset any cost savings that I would have gotten during my initial install.
I purchased my cells and BMS in 2009 for just under $0.45/Wh, including shipping and taxes, which is still an excellent deal today for new, not used or reclaimed, product. So for those of you that are waiting for the prices to drop 20% in the year or so as promised by "experts", I can tell you that they were saying the same thing seven years ago. Maybe Tesla and cordless drill manufacturers are saving money, but those savings have never materialized for small volume, end user customers like us. That said, the prices have been stable while most things have been affected by inflation, so that is a net effect of getting relatively cheaper. Bottom line, other than your ability to afford the initial purchase, it is my belief that every other concern with LiFePO4 batteries that has been listed here recently, is really not an issue in the real world.
This is all based on my first hand experiences. Good luck with your decisions.
Eric
Marina del Rey, CA
1964 Cheoy Lee Bermuda 30, 5KW Propulsion Marine drive, 8KWh LiFePo4 battery pack.
Posted by: ewdysar <ewdysar@yahoo.com>
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