Short ff flights - LiPo power loss?

[Rick Rotorhead]

Hi all, when learning hover , my Twister (Blade/HB2) CP would give 12-15 mins of air time. However, I've now progressed to buzzing her around in fast circuits and fig eights, trouble is my LiPos don't last more than 3-4 mins like this, then she only has power to hover about for another couple of mins. I find in ff she is losing height in turns and won't get it back unless I drop her back to low speed and practically hover her upto altitude again. So, do you think I've over used my LiPo batts and am suffering now from reduced capacity - or is the short, but fast flight scenario about right? PS: my stock LiPos are 1000mah 3s packs and my two packs have seen about 12 hours airtime......

[Gary JP4]

You probably already know all about batteries but what charger are you using? With the better computer chargers you can analyze your batteries by checking the capacity and voltage of the battery. You could discharge your batteries to minimum recommended voltage from a full charge and check mah capacity. You can also discharge a partially discharged battery to minimum recommend voltage and recharge noting mah capacity with only a slight error for the inefficiency loss of charging. I use 3.3 volts / cell for Lipo’s minimum discharge at 0.5 amp. 12 hours is a lot of time. I think 75-80% of capacity is about minimum 1300*0.75 = 975 mah. Throw them away at somewhere around that if performance is low. If that is the problem you are actually experiencing loss of amp draw capacity "C" but it seems to go away along with mah capacity and that is a pretty good check and easier to do IMHO.

Since you have two batteries and both are doing this it could be your motor is getting weak. If I suspect the motor after eliminating battery problems, before I replace it, I spray out the brushes with motor cleaner or contact cleaner while turning, dry it out and try again (not while it is hot or you might shock cool something and crack it). Carbon dust from the brushes wearing can severely degrade performance. They come back sometimes. Some folks recommend a time between cleaning of 15 flights or so. Brushless is so much nicer!

I have a FP bird (DF4) that has a bad connection at the battery connector and it is getting hot at the wire going to the 4 in 1. I am running 2s Lipo’s on it. It is a little weak like yours. I think I will replace it with a Deans connector. I still have the JST connector on my HB CP2 but I don't like them. Especially for 3s.

[Rick Rotorhead]

Thanks Gary, so it could be the motor then, it does get hot in use (can't keep a finger on it after flying) even with a heat sink. Unfortunately the charger I had been using was the stock supplied cheapo lipo charger, a little box with two indicator lights, though it is supposed to balance charge the packs. Maybe, its also a loss of batt capacity!!! I admit I have never cleaned the motor! The reason I suspect batt capacity to be the main culprit is that my new pack does perform much better and longer. I've got a new cellpro 2-4s balance charger coming soon so maybe that will answer the question about capacity. The stock batts are also probably not the highest quality units and are rated at 10c (not much these days).

[zooland1]

10C at what mah? 910's for example would be 9.1 amps (limiting), but 1320's would be 13.2(pretty good).

[Rick Rotorhead]

Zooland1, my stock Lipos are 1000 mah.