CellLog 8S Cell Voltage Monitor & Logger
[[http://saturn.lynnautorepair.com/node/518|I installed the CellLog]] a couple of days ago.
I logged 7 of the 48 CALIB 130 amphour LiFePO4 batteries both while driving and again during a charge cycle. The log data is very impressive and informative.
When I first opted to go to the CellLog I had planned to use one CellLog to monitor all 48 batteries. I would just wire every 6 cells instead of every cell. Since the CellLog will give 8 separate voltage readings, that would cover all 48. Well the CellLog maximum voltage is 1.3 – 4.9VDC.
What about using voltage dividers and dropping the voltage to 1/6 of the voltage of each 6 pack? Well, voltage dividers work with measuring the center of a pair of resisters. The ground side of one signal would require a resistor that would effect the positive side of the next battery voltage signal since they are shared . Issue #2 is the voltage pack maximum voltage is 43.0VDC for the CelLog 8S not the 156 volts we are running. Issue #3 is the voltage dividers would draw 1 to 10 milliamps and would need to be disconnected while not in use.
The first log was of a short drive 10 miles. 15 minute drive cycle of 10 miles to town and back. Recorded with a CellLog8S and www.LogView.info software. 7 CALIB 130 amp-hour voltage reactions are recorded here. Notes were added.
The next image is of the charge cycle. Interesting pattern of constant current (CC) then when maximum voltage is reached constant voltage (CV).
Notice the batteries that are highest voltage are not the ones that were highest during current draw (load). Also the ones with the lowest voltage during charging are not the lowest during current draw.
: Overnight Charge Cycle of Electric Saturn www.saturn.lynnautorepair.com with a CellLog 8S and www.logview.info Using a QuickCharger SCPX 220ACvolt 20 amp that was modified by Quickcharger for the Lithium LiFePO4 technology and set maximum voltage at 168 volts. Which is 3.5 volts per 48 CALIB 130 AH cell.
Below is a zoom of the voltage peak minutes, where the largest individual battery voltage difference is.