Hi Owen,
There are other aspects of Lithium batteries that offer advantages over lead acid batteries.
One characteristic in particular that is useful, particularly for solar powered boats is their tolerance of remaining in a partial state of charge. When discharged to low levels even as low as 10% state of charge they do not deteriorate while in this low state. And depending on your circumstances an electric boat can spend a while with the batteries only partially charged.
Consider a simple weekend's boating... you leave the dock wit the batteries fully charged say on Friday evening and head for your favourite anchorage. Getting there reduces the charge to say 70% and you then stay at anchor for two days before returning to the dock. So the batteries spent two days only partially charged.
We see lots of information about how you should limit the discharge of your batteries for extended life, but not much about how long the batteries can stay at a particular state of charge, and how that length of time may effect longevity. But t does seem that this kind of treatment is detrimental to lead acid batteries, but not in the least to lithiums.
In the case of a solar powered boat the effect is even greater because the batteries may take many days to be recharged, especially in inclement weather.
I don't know of how you might quantify this effect, but it is real, and would have some effect on life expectancy.
Cheers
Chris
On 09/09/2010, at 10:45 PM, otyers wrote:
I intend to convert my 27' 7000lb sailboat to electric over the winter.
I've been reading on this group that lithium batteries should have a
~2,000+ cycle lifespan compared to ~750 for AGM, but I've also read that
one should only expect batteries to last 5-7 years. Does this 5-7 year
life expectancy also apply to lithiums? If so, it would appear that one
would need to more or less discharge the lithium pack every day for it
to make sense (365 days x 5-7 years = 1825-2555 cycles), otherwise the
capacity for these extra cycles would not get used.
For those of us that are lucky if we get out on the water 30-50 days in
a year (a range of 150 - 350 discharge cycles over a 5-7 year period),
what battery type would make the most sense? Also, any tips on where
to source these batteries inexpensively?
Thanks for any advice.
Regards,
Owen
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