Hi Andrew
The load conditions for all tests were roughy similar and the beginning of each test was the running of the motor under normal operating conditions, just a normal trip, for maybe 30% of the capacity.
Then the remaining capacity was discharged at the mooring with the motor running in reverse at various speeds but mostly 1 to 2 kw. Because these cels are not much effected by peukerts effect I wasn't too worried about the tests being at the same rate of discharge. But even so the tests were under pretty similar conditions. The last bit of capacity was at low power to eke out the last few electrons.
After running various tests and trying to collect various speed power data over the years one of the striking lessons to me is how difficult it is, in practise, to do such testing and reporting under ideal conditions.
What I am sure about is that these LFP cells are really robust and long lived and I would not be interested in using lead-acid again except for the most budget strained circumstances.
Cheers
Chris
On 13/06/2012, at 12:29 PM, AJ Gilchrist wrote:
Chris
Great information.
Whatever the stated capacity it was achieved under the optimum temperature and at a very low discharge rate.
Measuring available capacity under a working load and conditions (on balance a cool) should produce a significant drop in capacity over the rated capacity.
The rule of thumb for lithium cells suggests they at 5% in 24 hrs. However two thirds of that occurs in the first 8-12hours so that can knock the available capacity compared to immediate use. On top of that you are meant to be loosing up to 4% per year just to aging. So 20% after 4 years seems brilliant.
So how do the latest tests compare to your first tests or were they done under different load conditions?
Look forward to hearing more
Andrew
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