- Apr 18, 2020
This is my setup for battery capacity testing:
2 Multimeters with 5/12 digits resolution for voltage and charger current. Shimano charger EC-E6000 modified, removing the output fuse in order to interleave the current measuring multimeter (it´s a very low burden voltage).
AC parameters are logged too
Voltage is measured in the battery terminals, son any voltage drop is neglected, important for a good accuracy of the Wh value
I can measure accurate Wh and voltage values without opening the battery case, as I have calibrated the impedance of all terminals, bms and cables. It´s possible to get the charger efficiency too, so just measuring the AC Energy drawn from the mains outet it´s possible to get the real charged energy with great precissión without using all the test rig (for day to day charging after rides)
All this setup is controlled over the LAN Network with PC and software that logs all the values, calculates parameters and generates graphs.
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And here are the results of one test
The battery is a BT-E8010C 504Wh 83% life and 90 cycles
The battery was discharged down to assit cut and then futtly charged at 25ºC
Light is off in firmware (important!!!)
Life in Ah measured, 80.4% is close (whithin 2.6% error) to the life estimator of Shimano (83%)
Seems that Shimano is calculating Ah capacity over the nominal value on the sticker, 14Ah
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The % values with * are calculated over the Ah and Wh charged in this test (not the nominal Ah and Wh in the sticker)
As the cycles increase, the degradation will increase too, and so these % values will give an idea of the real life decrease and how many cycles it take for certain degradation to be reached from this point
Very interesting! Keep up the good work! Would be nice if you could do this with batteries from other manufacturers aswell also with measurements over time so that we can see how the batteries degrade over time.