Summary
This post updates the graphs which I put up in Feb 2012 when my Kalkhoff - BMZ 18Ah Li-ion battery was 11 months old. Now after 24 months and 46 charge ups the capacity reduction appears to be very little. Projecting forward it looks as if my battery may retain over 80% of its initial capacity after 5 years. I might be still using this battery after 10 years. This is a great improvement over the experiences of other pedelecers with earlier types of Li-ion batteries which I read about on here 3 years ago.
Yesterday, exactly 2 years since I received my bike on 1 April 2011, I did my 46th charge up of my Kalkhoff BMZ 18Ah Li-ion battery. I use my bike a few times per month and average 2 charge ups per month. I am not going to wear out the battery through the number of charging cycles since the expected life of these sort of batteries is 1000 charge cycles or more - it is going up all the time as batteries improve. As an occasional user, what I was anxious about was that the deterioration of the battery chemistry over a few years of time would mean I would have to face the heavy replacement cost long before I reached anything like a 1000 cycles.
For an explanation of the following graphs please see my previous post
13 months ago I said it looked as if my battery would last at least 5 years.
Flecc wrote
That decay rate prediction has been falling like a stone over the last four years. Starting at around 35% but as much as 60% in some circumstances, it's very obviously been falling rapidly with each new generation of batteries, roughly in line with the number of charges predicted. The best ones seem to be well under 10% over the last year or so.
D8veh warned that my linear projection of loss of capacity might prove optimistic if a rapid drop of occurred as the battery aged.
Scottyf wondered if an increase of internal resistance might occur which would also have the effect of lowering the the useful capacity.
After two years data my straight line prediction is less than 20% loss over 5 years - ie 4% per year.
There is no sign of a worsening decay rate
The voltage drop under load measured with my wired in voltmeter does not appear to have changed markedly. However, I have not been recording values of voltage drop values in a consistent manner. Perhaps I had better start doing that. Certainly there is no loss of power from a subjective view point.
The two year old Kalkhoff Agattu is absolutely brilliant and has revolutionised my cycling up hills, into the wind, and over long distances. When I am on it I feel at least strong as ten years ago. I have had a few loose bolts needing tightening and two new sets of brake pads. The electrical side has needed absolutely no maintenance and is as good as new.
This post updates the graphs which I put up in Feb 2012 when my Kalkhoff - BMZ 18Ah Li-ion battery was 11 months old. Now after 24 months and 46 charge ups the capacity reduction appears to be very little. Projecting forward it looks as if my battery may retain over 80% of its initial capacity after 5 years. I might be still using this battery after 10 years. This is a great improvement over the experiences of other pedelecers with earlier types of Li-ion batteries which I read about on here 3 years ago.
Yesterday, exactly 2 years since I received my bike on 1 April 2011, I did my 46th charge up of my Kalkhoff BMZ 18Ah Li-ion battery. I use my bike a few times per month and average 2 charge ups per month. I am not going to wear out the battery through the number of charging cycles since the expected life of these sort of batteries is 1000 charge cycles or more - it is going up all the time as batteries improve. As an occasional user, what I was anxious about was that the deterioration of the battery chemistry over a few years of time would mean I would have to face the heavy replacement cost long before I reached anything like a 1000 cycles.
For an explanation of the following graphs please see my previous post
13 months ago I said it looked as if my battery would last at least 5 years.
Flecc wrote
That decay rate prediction has been falling like a stone over the last four years. Starting at around 35% but as much as 60% in some circumstances, it's very obviously been falling rapidly with each new generation of batteries, roughly in line with the number of charges predicted. The best ones seem to be well under 10% over the last year or so.
D8veh warned that my linear projection of loss of capacity might prove optimistic if a rapid drop of occurred as the battery aged.
Scottyf wondered if an increase of internal resistance might occur which would also have the effect of lowering the the useful capacity.
After two years data my straight line prediction is less than 20% loss over 5 years - ie 4% per year.
There is no sign of a worsening decay rate
The voltage drop under load measured with my wired in voltmeter does not appear to have changed markedly. However, I have not been recording values of voltage drop values in a consistent manner. Perhaps I had better start doing that. Certainly there is no loss of power from a subjective view point.
The two year old Kalkhoff Agattu is absolutely brilliant and has revolutionised my cycling up hills, into the wind, and over long distances. When I am on it I feel at least strong as ten years ago. I have had a few loose bolts needing tightening and two new sets of brake pads. The electrical side has needed absolutely no maintenance and is as good as new.
