| Thunder Power 4S 1320mAh Battery Report Date: 26th February 2005 Battery Type: Thunder Power Li-Po 4 x series Lithium-Polymer battery pack) Weight: 121g Dimensions: 67mm x 36mm x 27mm Manufacturers Rating: 14.4V 1320mAh, max discharge current 10-12C (13-15A) const, 22A peak. Note: All tests are carried out in a controlled 24C ambient for consistency. Author: Mark Hopkins |
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| Mechanical. The battery is in a 4 x series Li-Po configuration, with the cells stacked horizontally on top of each other, and covered with heatshrink. The two out-put wires (+ve & -ve) exit from one end, and appear quite adequate for small model helicopter use without too much of a problem. The cells are professionally connected to each other by spot or US (Ultra Sonic) welder. As mentioned in previous reports of other batteries, there was no protection circuit fitted to the pack to protect from over voltage, under voltage, over current, over/under temperature, cell imbalance, etc. All four cells are stacked with no air gap for the middle cells, these cells are therefore likely to get hotter than the other cells during use and are likely to be the first cells to fail in this pack. Electrical The voltage of each cell was measured before commencing charge and the pack was found to be well in balance. The pack was then charged to 16.8V (4.2V per cell) with a current limit of 500mA, in a 24C ambient, and with a termination current of 40mA at 16.8V. At end of charge the cell pack was still well balanced. The pack was discharged at C rate (1320mA) with a 12.0V cut-off voltage. The capacity at this rate was 1.23Ah, 18Wh, the cell pack reached a maximum temperature of 34.2C. The battery was then charged as before then discharged at 5A and 10A respectively, the following results were recorded: At 5A the capacity was 1.18Ah, 17Wh, the cell pack reached a maximum temperature of 58.9C. At 10A the capacity was 0.87Ah, 12Wh, the cell pack reached a staggering temperature of 71.5C. At the end of the discharge tests the cells exhibited the following voltages after a 5 minute rest: Cell 1 - 3.76V Cell 2 - 3.76V Cell 3 - 3.76V Cell 4 - 3.77V Well within acceptable balance parameters, however the high voltages on the cells show that there is plenty of energy left in the pack, and the reason for the battery cutting off by going below the safety cut-off voltage is indicative of the batteries inability to handle the discharge current, which in this instance was 10A |
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| Inside of the Battery | ||||||||||||||||||||||
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| Pack Performance at a Glance | ||||||||||||||||||||||
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| Discharge Graphs | ||||||||||||||||||||||
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| Conclusion The lack of protection which seems to be standard in the model market is, as usual a concern. The cells in the middle of the pack are likely to fail early if used at high current levels. The battery performed ok at C rate and the voltage held up well at 5A, with the temperature staying within acceptable parameters. At 10A the battery really struggled with the voltage sagging considerably, and the temperature exceeded what is generally considered to be the acceptable limit for this cell chemistry (70C). In a high temperature environment (mid summer etc) the unit under test would almost certainly exceed these levels. I feel that the battery I tested did not perform well at 10A, and the high current ratings claimed on the pack, 10-12C constant, were not realistic. However it performed reasonably at C rate and at 5A. Mark Hopkins (Research & Development Engineer/Designer and ISO 9001:2000 Auditor for PAG Advanced Battery Systems Ltd) |
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