T Rex battery question

[SquirrelNutz]

I have a question on lipo batteries for the T Rex.

What is the difference between lipo capacity and the Mah rating?

I can get a TP 2100mah lipo with a 15C rating for 30A OR a apogee battery with a 1500Mah lipo with a 20C rating for 30A.

My question is which would last longer and which would be the best to get?

Thanks in advance.

[rocknbil]

The C rating as I understand it is the ability of the battery to discharge under a certain amperage safely. Manufacturers define it differently, some as a continuous discharge and others as a burst rate. The bottom line is if you multiply the MAH by the C rating, it will give you the maximum amperage the pack can safely be discharged at. So,

2100 mah = 2.1 amps
1500 mah = 1.5 amps

2.1 X 15 = 31.5 amps
1.5 X 20 = 30 amps

In reality, you should only safely expect about 75% of this out of a pack as many manufacturers exaggerate the C rating.

What this tells you is they are rated by the manufacturer to handle bursts or continuous discharge at a maximum of 30 amps, a safe bet would be around 20. Which to choose? What is the manufacturer recommendation? What's the max amp draw of your T-Rex under load? If in doubt go with the higher C rating, but remember it's a value that you many not be able to fully trust.

I only have a BCP, 10C packs seem to work out fine. They never overheat if brought in before critical discharge, which is good. The BCP draws somewhere around 6-7 amps, but if the blades jam up in a crash it can spike to 30 amps. With 10C packs this would blow out the 4-in-1, so I religiously use 7.5 amp fuses on my motors. Works out great.

[SquirrelNutz]

Right, that I understand. Im a tech and have seen two identical pieces of test equipment calibrated the same way by the same facility and come back cmpletely different. In fact, it happens all the time. I can tune 60 radios with one comm analyzer and then check with a different comm analyzer and have to re-tune all 60. So, I dont play the blame game on the manufacturers and how they differ. Its more than likely their setup or calibration and the differences within the industry.

Ive been using lipos for awhile now and never had to use them with the thought about run times before. So, my question is which would last longer as I believe the 2100mah one would but wanted to confirm. I always understood the C rating as x times capacity. Which is what is making me ask this question.

[Gil]

I have a question about radios, I'm thinking about buying a Blade cx2, would the radio that comes with it work on another aircraft? Thanks in advance from a noob in Colorado. Also would a radio that comes with any ready to fly aircraft work with another aircraft, or could it be made to work with same?
Gil

[Dennis Flora]

15 c means 15 times the capacity, so if you have a 1 amp battery, and they say to charge it at 3C, that would mean to charge it at 3 amps. Or, In your case it means you can draw either 15 times the capacity or 20 times the capacity. 2100m ma or 2.1 amps times say 15 or 20 max current drain. So if it a 2100 ma 15 C batt, you can safely pull 31.5 amps from it max while in use. So the 20 C batt is capable of delivering more current than a 15 C batt of the same capacity in MA. Hows that ??? Dennis Flora

[SquirrelNutz]

Better! thanks!

[Dennis Flora]

Just dont charge anything with 15C. hahaha !!! Kaboom !!! Always follow the instructions on the battery... or the paperwork that came with it...