I have used headway cells, headway specs them as 5% per month self
discharge! so have close to zero, worse is 5 in practice. found it to be
a big problem, if you charge every day it's ok, but the ebike i got them
for may go a while without charging, also, If it is not left on charge
long enough they still will not equallize. at the moment, there is no
way to tell when eq is complete, could be 400+ hours if they are out by
their capacity! I won't use them again.
On 12-May-18 6:09 PM, Cor van de Water via EV wrote:
I also did tests on LiFePO4 cells and while self-discharge was low, I was able
to prove from my measurements over many weeks, that there is was about a factor
2 difference in self-discharge current between the best and worst cell. Sample
size was over 40 cells.
This is exactly what the author of the quoted article found, that the capacity
of the cells had not degraded, but the cells had gotten out of balance, so the
protection circuitry allowed an ever shrinking overlap between best and worst
cell. Simply balancing the cells brought back the original available pack
capacity, which is logical.
Hope this clarifies,
Cor.
BTW, this email address will soon cease to work, please find me at
[email protected]
On May 11, 2018 10:58 PM, paul dove via EV <[email protected]> wrote:
Actually I do have evidence. I did extensive testing with LiFePO4 cells. I
found no evidence of self discharge or of balance issues with cells connected
in series.
Sent from my iPhone
On May 11, 2018, at 4:43 PM, Bill Dube via EV <[email protected]> wrote:
Paul,
Do you have any evidence of this or is it speculation?
(Sorry, I just couldn't help myself.)
Bill D
On 5/11/2018 12:47 PM, paul dove via EV wrote:
Thanks that was interesting. It’s more likely that the Dakota BMS was causing
the imbalance with parasitic unbalanced loads, however.
Sent from my iPhone
On May 11, 2018, at 11:56 AM, EVDL Administrator via EV <[email protected]>
wrote:
On 10 May 2018 at 6:35, paul dove via EV wrote:
Do you have any evidence of these batteries failing because of out of balance
conditions or is that speculation
The battery I mentioned ("Dakota" brand) was advertised as having a true
balancing BMS.
Discussion of PCBs vs BMSes here:
http://ka7oei.blogspot.com/2013/05/lithium-iron-phosphate-lifepo4.html
David Roden - Akron, Ohio, USA
EVDL Administrator
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