Multistar Lightweight 2C Pack Tests
Recently a fellow RCGroups poster pointed me to a new Multistar 6.0Ah/4S/2C pack with a claimed weight of 364g. Doing the math this means this pack has a power density of 244Wh/Kg which is considerably higher than any Hobby grade lipo I have seen or tested. Higher even than the hi-end Panasonic and LG 18650 industrial cells. My first reaction was that this was not very likely and that these numbers where likely marketing BS or simply an error. With that, I decided to buy and test one of these packs, to see for myself.
This then are the results of nine test runs. Three tests at 0.5C (3A), three at 1C (6A) and finally three at 12A (2C). All tests were done on the Medusa Power Analyzer Pro using a small motor and prop for load. The pack was set in open air on two edges of a small box with no active (fan) cooling. The pack was allowed to cool for 2 hours after each 3A and 6A test and 4 hours between each 12A test.
It should be noted that it is very rare that any hobby grade lipo pack lives up to their stated standard 'C' rating.
Pack Dimensions Weight - 367g with all wires and connectors Width - 45mm Length - 135mm Height - 29mm
0.5C, 3A Tests The first tests at 0.5C were run from a fully charged pack with each pack starting at room temperature. The tests were terminated at 12.4v (3.1v/cell) to keep from harming the pack. The specs shown below are from the third run and vary little from the first two tests.
Constant load - 3A (+/-0.15) Start tempurature - 68.0F (20C) End tempurature - 90.7F (32.6C) ROA (Rise over ambient) - 22.7F (12.6C) Run time - 1h:36m:48s Starting voltage (unloaded) - 16.47v Ending voltage (loaded) - 12.37 Rested voltage @ 15 min - 13.65v mAh consumed - 4919 mAh re-charge - 4997
At 0.5C the tempurature stays well within safe limits, the mAh consumed was fairly normal at 82%. At this discharge rate this battery should last a very long time.
[img] 3a [/img]
1C, 6A Tests The second round of tests at 1C (6A) were set up the same as the 3A test with the exception of termination was at 12.8v (3.2v/cell) again, to keep from damaging the pack.
Constant load - 6A (+/-0.15) Start tempurature - 64.8F (18.2C) End tempurature - 106.3F (41.3C) ROA - 41.5F (23.1C) Run time - 41m:40s Starting voltage (unloaded) - 16.54v Ending voltage (loaded) - 12.79 Rested voltage @ 15 min - 14.07v mAh consumed - 4292 mAh re-charge - 4347
The results of this test I would suggest that while 1C will run to the termination voltage without getting too hot, the ROA suggests that this is near the limit of continuous, safe discharge current.
[img] 6a [/img]
2C, 12A Tests The last round of tests were short and hot! Termination was again at 12.8v (3.2v/cell).
Constant load - 12A (+/-0.15) Start tempurature - 69.9F (21.1C) End tempurature - 123.6F (50.9C) ROA - 53.7F (29.8C) Run time - 11m:32s Starting voltage (unloaded) - 16.64v Ending voltage (loaded) - 12.77 Rested voltage @ 15 min - 14.79v mAh consumed - 2312 mAh re-charge - 2410
As you can see the pack got very hot in the short amount of time the test was run. I would definately not label this a 2C "Continuous" pack as it will not survive many discharge cycles at this current and tempurature.
[img] 12a [/img]
Hope that helps! Mark
