I've got a 3S 1800 mAh lipo in mine, and it works well.
- snipped the connector from the supplied battery pack
- soldered a JST connector to this lead. double check your polarity
- attach the battery via the JST connector
I had the junky 3S sitting around. It came with my Hawk Sky, but I use Zippy 2200s with that plane. Luckily, it is the perfect size for the battery compartment.
Voltage drop is less than 0.1V/hour. I'm careful not to let the battery go under 9V, but that hasn't been a problem so far.
On the downside, you don't get a beeping warning for low battery, but so far it hasn't been necessary. I'm not able to detect any heat buildup from the linear voltage regulators. If I would have had a spare 2S battery I would have used that one, but as I said I had a perfectly size 3S just going to waste.
There is a little confusion about the best 2S vs 3S better battery for the 9X. If conceptually it is true that a bigger dropout voltage between input and output leads in a bigger heat dissipation, the 7805 regulator has been designed to give the best performances with a differential voltage between input and output of about 5 to 10V. With the 7,5V (from 6V depending on the model) minimum input required voltage (2,5V of differential dropout voltage between input and output for 7805) the output peak current can not be achieved (the regulator can´t work at full dynamic range). In fact the factory testings of the LM7805 are done with a typical input voltage of 10V. Following this lines, and assuming that the input regulator is a 78xx, a 3S Lipo battery should be a better candidate than 2S to power the turnigy 9X. You can check the Peak Output Current Vs differential input-output voltage characteristic in the figure of page 21 of the attached datasheet or the Droupout voltage characteristic googleing "7805".
This explanation does not means that a 2S is a bad option, but in this case the regulator won´t work at full dynamic range of its output current. By the way, looking the datasheets a dropout of 5 to 7V between input and output (corresponding to an input voltage between 10 and 12V) doesn´t lead in a significative amount of heat increase.
Cheers from Spain.
I just received the one you mentioned, it works great! I did have to change the connectors though.
Hi Justin/ Other experts on forum,
Can you help me with what kind of 'connector' will I need to purchase for the battery option given earlier (long back) in your link here: http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6955 for the Turnigy 9x transmitter ??