Hi Kirk,
That matches what I've seen in documentation from a couple of LiFePO4 manufacturers. They state that batteries sould be left with no more than 65% charge for long term storage. Charging them to 100% and letting them sit for months may actually reduce the battery life. Even Torqeedo mentioned this on their website a few years back to extend the life of their batteries, but I don't think that this information is still posted.
So more than a year ago, I started leaving my pack at 60-70% if I didn't expect to use it again in the next few days. Typically I will only throw a quick charge on up to the 80-90% mark before I leave the dock for the day and I expect extra motoring. If I'm going offshore to Catalina (30+ miles one way), I charge to 100% before I leave and carry my 2kW Yamaha generator, just in case.
As a result, last fall, I went about 4 months without putting any charge in my batteries, just went on a half dozen days sails until the SOC dropped below 50%. It's kind of like before the conversion where I would put 2 gallons of diesel in the tank and sail the whole summer without getting more.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, Kirk McLoren <kirkmcloren@...> wrote:
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> http://www.designnews.com/document.asp?doc_id=261882&cid=NL_Newsletters+-+DN+Daily&dfpPParams=ind_184,industry_auto,aid_261882&dfpLayout=article
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> The wrong charging techniques can also shorten a battery’s life. Lithium-ion battery packs need to stay as close as possible to a 50 percent charge, he said, usually going no higher than 80 percent and no lower than 20 percent. Moreover, electric car owners should refrain from doing too many “fast charges,†in which an EV battery can be recharged in under an hour.
> â€At high power, there is deformation of the material on a particle scale,†Cugnet said. “If you’re really in a hurry, it’s OK to do it a few times,†he said. “But most of the time, you should charge your car overnight.â€Â
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> I thought the state of charge interesting.
> Kirk
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