A Derived Run Time Procedure test was completed using the newly configured 3S IMR 10440 resultant battery. The procedure for a Derived Run Time Procedure test is found here. The link opens a new tab so that the procedure can be reviewed. Video showing the Derived Run Time Procedure test, when using the 3S IMR 10440 resultant battery configuration, is here.
The throttle setting now looks like this at 1/2 throttle.
 Derived Run Time Test 1 (Batteries #4, #5 & #6)
Note that the voltage difference between each timed run decreases. That is caused because, as the voltage drops, so does the current. To verify the approximate capacity used, after the Derived Run Time Procedure Test 1 was completed, Battery #5 was charged using the Revolectrix GT500 charger, as it notes the returned mAh capacity. After Battery #5 had rested for 2 hours from the Derived Run Time Test 1, the battery was charged at 350mA (0.35A) to 4.2V . Battery #5's stabilized and resting voltage was 3.611V before the charge started. The charger's screen noted that only 8% of the battery's capacity remained. That value was based on the voltage detected by the charger at the beginning of the charge. That begs the question, "8% of what?". Is it 8% of the stated capacity on the battery label of 350mAh (0.350Ah). 8% of 350mAh is 28mAh (0.028Ah) left in the pack, which means that 322mAh (0.322Ah) would have been used? Is it 8% of the measured capacity with the average load, which is 300mAh (0.300Ah) as noted here as 0.300Ah. The graph on the linked page shows about 0.300Ah (300mAh) between a constant current load of 0.2A and 0.5A. 8% of 0.300Ah (300mAh) is 0.024Ah (24mAh) remaining or 0.276Ah (276mAh) used. The average amp draw for this locomotive was previously calculated as 373 milliamps (mA) or 0.373 amp (0.373A) at Step 4. The average amp draw of 0.373A (373mA) was calculated using a 6 minutes discharge from a full charge, therefore, it would be on the "high side" of the full discharge average amps. The GT500 charger returned 232mAh (0.232Ah) in 56 minutes and 49 seconds. The Math to Verify:
Once again, this demonstrates why using voltage is not a very accurate way to evaluate the state of charge (SOC) for Lithium-ion based batteries. A battery's usable capacity is dependent on the discharge current. Batteries #4 and #6 were fully charged on an EBL charger, as more testing was planned soon. Derived Run Time Test 2 (Batteries #1, #2 & #3)
After completing the Derived Run Time Procedure Test 2, the Revolectrix GT500 charger was used to charge Battery #2 using the same charging values. Battery #2 had rested for 2 hours from the Derived Run Time Procedure Test 2. Battery #2's stabilized, resting voltage was 3.608V before the charge began. As previously noted, the Conrail's average amp draw is 0.373A (373mA). 231mAh (0.231Ah) was returned to the battery in 56 minutes and 39 seconds. The Math to Verify:
The two 3S IMR 10440 batteries tracked very closely with 232mAh returned to one battery and 231mAh returned to the other. Batteries #1 and #3 were fully charged on an EBL charger, as more testing was planned soon. By "removing" a battery from the 4S IMR 10440 resultant battery, which was supplying more voltage, to form a 3S IMR 10440 resultant battery, the amp draw went down. Using a 3.5V loaded cut off also allowed an extra twenty minutes of Derived Run Time compared to the 4S resultant battery with a 3.7V cut off. When reconfigured for the 3S IMR 10440 resultant battery, it put the maximim speed of 65 mph into a more efficient area of operation of the electronic speed control (ESC) circuit in the LocoFi™ decoder. A Note on Storage Voltage: Once an operating session is totally completed for a resultant battery, let the individual batteries rest for at least an hour. Measure the stabilized, resting voltage of each individual battery. If the resting voltage is between 3.7V and 3.85V, put that battery away. If the battery is less than 3.7V volts, charge that battery on the EBL charger for about 20 minutes. Immediately read the voltage once the battery is removed from the charger. If the voltage is between 7V and 8V, put that battery away. Repeat for 10 minutes only if the resting voltage is significantly under 3.7V. While the physical test proved correct, I'd also looked for other "proof" that the about 12V, supplied by three fully charged 3.7V nominal Lithium-ion batteries was about right. The following section about using a prototypical run to find the Actual Run Time is the original based on a 3.7V loaded cut off. The new data, using 3.5V as the loaded cut off, indicates that 35 minutes to 40 minutes of prototypical run time is most likely. A timer was set at 25 minutes since the demo layout is flat and there is only a boxcar and caboose available to switch. The train was run in a prototypical manner with picking up cars, running them point to point, dropping them off on sidings, etc. At the end of 25 minutes a battery's voltage read 3.780V. That might be the run time for this IMR 10440 Lithium-ion battery/Loco combination, but... Obviously, having more sets of multiples of 3 of the IMR 10440 Lithium-ion batteries charged can extend the run time, and with this set up they are easily and quickly swapped, even with a dummy removable load covering them. A second run was made in a prototypical manner. The timer was set for 30 minutes for this timed test. That was a 5 minute increase of time over the first run. After the 30 minute prototypical run, a single battery voltage read 3.684V when immediately pulled from the gondola/battery car. One half hour later, that battery read 3.711V. This clearly demonstrates the voltage "bounce back" after the load is removed. What did these two runs of the 3S 10440 pack prove? For my flat layout and a couple of cars, that had been set to the NMRA Recommended Weight, I feel that I can safely run this unit for half an hour, but that is just for this particular unit with my cars on my layout. With 6 of these Lithium-ion IMR 350mAh 10440 batteries charged and ready to go, the run time doubles with a simple replacement of the used batteries with a fresh set. At this time, I believe that the Dead Rail Conversion, using LocoFi™ and the 3S IMR Lithium-ion 350mAh 10440 pack has proven quite feasible, relatively easy and relatively safe to do. Using the lower 3.5V loaded cut off demonstrates that 35 minutes to 40 minutes should be doable, but has not been tried yet. |