Comparison of batteries seems useful and desirable. Zippy 2700 mah packs are about 1/4 of the cost of ThunderPower 2700 and most others fall between. Of course the recent TP sale cut that difference in half, and other sales have been about 1/3 off. A comparison of capacity and useful battery cycles would be useful. Of course the guarantee and customer service is better at TP, if needed.
Actual battery capacity may not be stated battery capacity. Battery capacity is self rated by the supplier. Safe usage is about 80% of the actual capacity often observed and calculated by charge replacement. Battery percent from voltage is not a very accurate number and may not prove very useful. More than one voltage vs. percent capacity remaining plots are used. If similar calculations and curves are used, it seems that battery capacity may be compared.
http://www.helifreak.com/showthread.php?t=333661 However, hopefully some useful information can be gained when comparing batteries using similar methods, and therefore similar voltage vs. percentage curves/calculations. Usage numbers were obtained with a FMA PL8 charger with reported percent remaining as a basis to help determine capacity. Hopefully while the percentage may not be an absolute number, the comparisons may be made using the PL8 as a standard. Similar tests may be done on another chargers comparing various brand batteries, using that charger as a standard, but it seems that similar equipment is needed to compare.
Capacity is then [(charge in mah) / (% charge increase)] x 100%
For example
Battery usage based on replacement mah was about 1835 mah/ flight with about 25% left, so 75% increase back to full charge. Capacity is then (1835 mah/75%) x 100% or 2446 mah.
And the same batteries on another plane, about 1950 mah/flight with about 22% remaining, so (1950 mah/78%) x 100% is 2500 mah.
Very similar numbers were found when using the values from storage to full charge and then that % charge increase, in the PL8, almost always about 50 – 52% storage charges when allowed to sit overnight. That calculation gives (1225 mah/50%) x 100% equaling 2450 mah.
Those numbers were very consistent over the summer with 4 packs and many flights suggesting that Zippy 2700 mah batteries may have closer to 2450 – 2500 mah. That may suggest that if you routinely need 2100+ mah per flight, that the Zippy batteries may prove inadequate and may low volt out before a flight is over by set timer duration. Or they may work for a while but have less usable cycles.
In my use Zippy compact 2700 mah 6S packs were good for about 115 – 125 cycles each, something like 25 cents per “tank.” Weight of my 6S packs average 369 - 370 gms. Most charges were 1C at home and 2 – 2.5C in the field. Discharges were about 1900mah/5 min 20 second average rate. Because the ZIppy capacity seems about 2500 mah, I did not have room to undercharge. Undercharge could have resulted in over discharge since 1900 mah used.
Zippy 2700 mah 5S packs were used the prior year, with appropriate change in line length and props, and yielded essentially the same capacity calculation of about 2450 – 2500 mah for the 2700 mah packs. Of course the cells are similar, so as expected.
A good resource article is listed below about extending battery life by undercharging to less than 4.2v, selecting the correct charge current termination (C/X), avoiding high charge and discharge rates for the given battery, avoiding deep discharges, and avoid over heating.
http://lancair.net/lists/lml/Message/56976-02-B/Li-Ion%2520Battery%2520Life.pdf and, pardon the drone reference, but there is some useful battery information following.
http://www.dronethusiast.com/ultimate-drone-battery-care/ I believe that FMA PL8 and PL6 both have similar % charge determinations and could be used as a comparator to calculate battery capacity and compare brands. Actual useful number of battery cycles would also be useful.
Another popular battery is the ThunderPower Prolite 2700 mah 25C. Does anyone have similar information to compare and estimate actual capacity of the TP’s? Also, what is the weight of a 6S pack. TP says 351 gms, but actual weights with wires and battery plug would be useful information.