big fancy lipo outpaced by little crappy one... whaa??!

[pmbou]

I can't figure out why my fancy new batteries give crumby flight times compared to my stock ones...

I just got 2 thunderpower 1320mAh 3-cell lipos in addition to the 2 stock eflite 800mAh 3-cell lipos that came with my cp pro. I charge these at 1C on a hobbico accucycle elite, and they all charge right up to about 95% of rated capacity. They charge up to 12.6V and charging stops when current drops to about 0.06 amps. You set the charger to the mAh rating and charge rate (I use 1C rate, so 0.8 A or 1.3 A, depending on battery)

I run a stock blade cp pro with symmetric blades. It hovers for 20 minutes on the stock eflite 800mAh batteries but only a few minutes on the thunderpower batteries :arggg:. I think the thunderpowers would probably spin the blades for 30 minutes but not hard enough to fly. The Thunderpower batteries are not much heavier and I have determined that the weight difference is not the cause (by adding weight when using the 800 mAh).

When I run a cycle of discharge to 0.9V followed by charge at 1C, all batteries charge up to 95% of full capacity. When the eflite batteries crap out, they are drained down to 20% of full mAh capacity - they take in 600 mAh to refill. When the thunderpower batteries crap out, they're still at like 85% capacity - they only take in only about 200 mAh to fill up... whaa?

I guess I should try to measure the current and voltage under load but this seems a little hazardous. Could it be that the eflite batteries are pumping out more current at the same voltage? The thunder power batteries are rated for 13A-15A continuous/22A burst. Eflite are unknown.
svc?

What is going on here??!? What should I do? Run them in a plank at lower current? Call customer svc? Recharge every 2 minutes? Toss em in the ole fire pit :dontknow ?

[Hughes500Bob]

Most LiPos need about 5 full 75-80% discharge / full charge cycles to come up to speed. Maybe the new ones need that conditioning?

20 minutes? WOW :shock:

"When the Thunderpower batteries crap out," What exactly do you mean by that? :dontknow Exactly how are you determining your flight times?

[kgfly]

If you discharge lipos down to 0.9V/cell you will have killed them. Normal use should never go below 2.8V/cell and I recommend not below 3.3V/cell if you want decent life out of your packs. Anything under 2.5V/cell will lead to permanent damage.

[pmbou]

I was timing my flights roughly from start to finish, all right side up flying. Climb and return to land, or hover. Not a lot of turning either. Nothing aggressive. I am getting 20 minutes on 800 mAh batteries.

On 2 occasions, I tried to run a thunderpower battery with bad results.
Once, I had been flying with the 800 mAh battery and heli was well-tuned. Then I put the 1300 mAh battery in, expecting to take right off and fly. Instead, there was barely enough power to lift off the ground and land safely.

The next time, it flew for a while but it got real doggy right away, then I spun it up while holding in my hand, and the headspeed sounded low and the pull force was poor.

Since the original post, I had a good 10 minute flight that consumed about 500 mAh off of a 1300. Then I switched to the other 1300 was climbing nicely, then had a horrible crash and have been rebuilding...

I can't explain what's going on here. I thought that the 1300s were fully charged when they provided poor results, but maybe they weren't. Maybe one of them is weak and the other is not, I will number them and try some more flights.

Does anyone know how much current a stock CP pro draws with symmetrical blades at full pitch and rpm?

[peterob]

Can't provide the info you asked for, but I'd say using a decent charger would be a good start. You need to know how much has been put back into the pack to calculate your average current and estimated flight duration. Personally, ThunderPower packs have always given me great results.

It's been said before, but the FMA CellPro 4S is a bargain for the price.

[pmbou]

A rough calculation of mean total current draw is (800 mAhour / flight )* (60 min/ hour) * (1 flight / 20 min) = 2400 mA

This seems really low. But, I am hovering and landing a lot, rather than the high RPM high pitch 3D stuff... Maybe I would only get 5-7 minutes if I was flying super hard all the time? (I don't have the skills to do that yet!)

[peterob]

Average current = Ah USED (recharged into pack after flight ) / (actual flight duration in minutes / 60).

My point is you should never use 800mAh from a 800mAh pack. LiPos prefer 80% usage or less if you want to use the pack for a reasonable amount of flights.

Knowing how much you actually used per flight is critical to getting any value for money from LiPos.

[Skiddz]

Crappy soldering on the 1320 connectors?? Or on the electronics side??