I have started this thread to post experiences with the Shimano battery, mainly fixes, reverse engineering, issues..
This first post deserves some electrical explanations to help understand the battery behavior to non EE. The following are just my deductions, I have not confirmed them by opening my BT-E8010 battery.
Shimano BT-E8010 battery characteristics are:
The voltage of the Lithium cells will decrease during the usage/discharge of the battery and if it drops below a safety threshold, the cell will become damaged and without recovery , so to avoid this damage, the Shimano battery includes a complex electronic board named BMS (Battery Management System) that monitors the voltage of each single cell to prevent it reaching this voltage threshold
But not all the cells are created equal, some of them are weaker than the others, good manufacturers like Shimano will install similar cells in each branch so they will discharge at the same rate, but if spite of this there is a weak cell (out of 10) in a branch, then during the discharge the voltage level of this weak cell will drop faster than the remaining 9 cells in the branch, then the BMS will protect the cell and will shut down the branch in which the cell is included, thus stopping the discharge, the voltage drop and avoiding the damage. A good firmware should characterize the discharge and know that there is a weak battery and show the bars according this, but I doubt that firmware is that good, so this shutting down of a branch out of five means that the battery capacity will be suddenly reduced by 20%, and the last bar can not be fully trusted.
Also, this means that if despite of Shimano efforts to make a quality battery, if there is a weak cell that gets damaged during use, then its branch would be shut down and the total battery capacity will be reduced forever by 20% from 504W/h to 404W/h. I have been told that some riders in my country have got this battery issue during the warranty period and they tried Shimano to replace the battery but Shimano is not recognizing this as an issue and is not doing a warranty replacement.
E-Tube APP does not include the capacity or cell check in the battery diagnostics so there is not a clear proof of the capacity decrease, owners know it because riding while riding a known trail, the battery indicator has one less bar than previous rides.
Are there other experiences about this? Has Shimano replaced batteries because of this issue?
This first post deserves some electrical explanations to help understand the battery behavior to non EE. The following are just my deductions, I have not confirmed them by opening my BT-E8010 battery.
Shimano BT-E8010 battery characteristics are:
- Nominal Voltage is 36V
- Nominal Capacity = 504W/h = 14A/h
- Nominal voltage of 3.6-3.7V
- Current capacity may vary depending on brand and quality of the cell but a standard value is 2800mA/h = 2.8A/h
- The voltage of each branch is the result of adding the voltage of the 10 individual cells in the branch = 36V
- The current from each branch is the nominal current of the cells, as they are in series the current is the same for all of them, so it is 2.8A/h
- The total current from the 5 parallel branches is the result of adding the current from each branch = 5* 2,8A7H = 14A/h
The voltage of the Lithium cells will decrease during the usage/discharge of the battery and if it drops below a safety threshold, the cell will become damaged and without recovery , so to avoid this damage, the Shimano battery includes a complex electronic board named BMS (Battery Management System) that monitors the voltage of each single cell to prevent it reaching this voltage threshold
But not all the cells are created equal, some of them are weaker than the others, good manufacturers like Shimano will install similar cells in each branch so they will discharge at the same rate, but if spite of this there is a weak cell (out of 10) in a branch, then during the discharge the voltage level of this weak cell will drop faster than the remaining 9 cells in the branch, then the BMS will protect the cell and will shut down the branch in which the cell is included, thus stopping the discharge, the voltage drop and avoiding the damage. A good firmware should characterize the discharge and know that there is a weak battery and show the bars according this, but I doubt that firmware is that good, so this shutting down of a branch out of five means that the battery capacity will be suddenly reduced by 20%, and the last bar can not be fully trusted.
Also, this means that if despite of Shimano efforts to make a quality battery, if there is a weak cell that gets damaged during use, then its branch would be shut down and the total battery capacity will be reduced forever by 20% from 504W/h to 404W/h. I have been told that some riders in my country have got this battery issue during the warranty period and they tried Shimano to replace the battery but Shimano is not recognizing this as an issue and is not doing a warranty replacement.
E-Tube APP does not include the capacity or cell check in the battery diagnostics so there is not a clear proof of the capacity decrease, owners know it because riding while riding a known trail, the battery indicator has one less bar than previous rides.
Are there other experiences about this? Has Shimano replaced batteries because of this issue?
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