These experiments are an attempt to see what would happen if one were to construct two parallel strings of Thundersky LiIon cells and Hawker Genesis batteries. The basic idea is to use the Hawker cells for power, and the LiIon cells for range. The LiIon cells have a much higher internal resistance than the AGM lead acid cells. Two low-voltage strings are used, since I only have a small number of electronic loads to be able to apply the desired current. Two ACDC EL750B 750 watt loads are in parallel to provide the load, and they are controlled manually. An Agilent 34970A data acquisition system with a 34901A module is used to acquire the data. It is controlled by Agilent Benchlink Data Logger software with a TCP/IP I/O library on a Dell Inspiron 5150 laptop via a Agilent E2050A LAN/GPIB gateway, and the data is exported as a CSV (comma separated values) file. The temperatures are measured with type J thermocouples. (No ice bath or other fancy stuff to get more accurate measurements). (No semi-annual equipment calibration either!) For the three Sep 23 runs, the instrument channels are as follows: 101 ambient temperature type J thermocouple (degrees C) 102 air temperature between TS cells 92 and 91, type J again (degrees C) 103 shunt voltage for 13AH Hawker battery (only one) (50mv == 500A) 104 shunt voltage for 90AH TS LiIon string (50mv == 500A) 105 13 AH Hawker #29 voltage 106 90 AH TS LiIon cell #92 voltage 107 90 AH TS LiIon cell #91 voltage 108 90 AH TS LiIon cell #89 voltage (yes, I skipped higher resistance cell 90) A positive shunt current indicates charging the string, a negative discharging of the string, respectively. I used 1-0 welding cable between strings and from the strings to the electronic load. However, I only used 4 gauge cable between the two testers (about 1 foot). In file Sep23LiIonHawker1, I ran three sessions of 50A, 100A, and 35A corresponding to freeway driving, hill climbing, and secondary road driving (45 mph). (Of course, your current load with vary with voltage and vehicle!). I didn't really analyze files 2 and 3 from Sep 23. It was clear that the Hawkers were doing all the work at this ratio. On Sep 24, I reconfigured the experiment to use 2 12V 13AH Hawkers and 7 3.6V 90AH TS LiIon cells. This is closer to the ratio that I would really use (currently, I'm considering 10 TS cells for every 3 Hawkers). However, I can only pull about 70A at 24V with the two electronic loads. The 34910A channels are as follows: 101 ambient temperature 102 TS cell 92 and 91 temperature 103 Hawker string shunt voltage (50mv = 500A) 104 TS LiIon string shunt voltage (50mv = 500A) 105 Hawker 28 voltage 106 Hawker 29 voltage 107 TS LiIon cell #92 voltage 108 TS LiIon cell #91 voltage 109 TS LiIon cell #89 voltage 110 TS LiIon cell #88 voltage 111 TS LiIon cell #87 voltage 112 TS LiIon cell #86 voltage 113 TS LiIon cell #85 voltage File Sep24LiIonHawker1 is a test of a 70A draw. I watched the two strings equalize afterwards (somewhat slowly!). File Sep24LiIonHawker2 is a 15 minute 27A draw. File Sep24LiIonHawker3 is a initial attempt at stop-and-go traffic (but no acceleration nor regen!). Anyway, that was the thought. The period starts at 1.5 minutes and gets longer as the test proceeds, for what it's worth. I don't have any firm conclusions at this point, but it does seem that putting a string of TS LiIon cells in parallel with a smaller-than-normal Hawker string should give better range per pound than just Hawker batteries. One might experience having to wait for the Hawkers to recharge before tackling a hill, etc, but also always have extra energy if you can wait a while (such as is the case in a trip with a reasonable delay before the return trip, but no charging at the destination). However, it seems that the Hawker pack would be cycled a lot, and consequently would not last very long. Nevertheless, this might be an intermediate step before connecting the two packs with a CC/CV high power DC- DC (perhaps a PFC30 or 50). Gary September 26, 2004