There are papers on this on the JPL Technical Reports server....but it seems to be very broken at the moment so I can't have a look
I do remember a chart showing capacity as a function of cycles - and it drops to about 80% over a few thousand cycles. - I think....can't quite remember.
Doug
Thanks Doug. If you come across it please post a link. I did some looking myself but found mostly generic information.
Both http://trs.jpl.nasa.gov/ and http://trs-new.jpl.nasa.gov/dspace/handle/2014/6130 appear to be very dead unfortunately
Doug
http://ntrs.nasa.gov/search.jsp appears to be working now. This paper - http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38818/1/04-2588.pdf in particular seems relevant.
Thanks. Should get to sleep early tonight!
Based on this search:
http://trs-new.jpl.nasa.gov/dspace/simple-search?query=mer+battery&submit=Go
I found and had a look at
http://trs-new.jpl.nasa.gov/dspace/handle/2014/39912
which says the capacity of the batteries will still be over 80% of original even after Launch, cruise and 1400 sols. This amazed me as I've had trouble getting a laptop battery to last more than three Earth years.
The paper is interesting and has lots of pretty graphs so well worth a read.
The Li-Ion on my Dell went from 2 hours life to less than 40 minutes in about 14 months.
Doug
I think that JPL also manages the battery conditioning substantially better than mere mortals manage the conditioning of their batteries.
For the MER's Temperature is kept near optimum and charge states are managed so that the batteries are not kept at too high a charge state or allowed to deep discharge (apart from the one occassion caused by Spirits Flash anomoly). It appears that if we could manage the same for Laptop batteries we should be able to expect 80% or more charge after 2-3 years of use.
Anyway as a comparison - here's some stats from my current battery (and IBM Thinkpad T43P - Sanyo Battery):
Manufacture Date: 19/09/2005
First used: ~01/01/2006
Design capacity: 77.76 Whr
Current capactiy: 71.14Whr
Cycle count: 101
That's 4.6% capacity loss per annum since manufacture. Not bad considering I generally keep the battery fully charged at ~20C. At that rate I'll be at around 85% when I hit 1000 sols. Right now I register about 4:00 hours battery life from 69 Whr remaining. Personally I'd like more but I can't complain.
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