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HeliHobby . Ron’s HeliProz South . Century Helicopter

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e-Electric Batteries & Chargers > put back less than expected...
 
 
nmrs
Senior Heliman
Location: Austin, TX

I have 2 Kong Power 3S 25C 2200s that I use on my T-Rex 450 se v2. Up to now I've been flying them for 5 mins each and putting back about 1100 (give or take 100 or so). I know I should safely be able to discharge them down to 20% (maybe more since they are Kong Powers), so today I flew the first for 5 minutes and the second for 5 1/2 minutes. I'm just trying to slowly increase it to see what a safe time is.

When I charged them, I put back 1006 into the first (5 minute) pack, which is a little less than usual but still within standard range. When I charged the second pack (the 5 1/2 minute one), it only took 763. I'm just sport flying (hovers, FF figure 8s), and I think I flew them both about the same, though if anything I would think I flew the second pack a little harder as the first flight was my warm-up.

Is this discrepancy anything to worry about? Or just a fluke? Obviously I would be more concerned if I had to put too much back in, but this is still so far outside of the expected range that it caught my attention.
07-04-2008 09:16 AM
 
 
electricdurango
Veteran
Location: Sterling, VA

Are they charging back to 12.6 volts? Make sure they are 12.5-12.6 volts after charging to make sure your MAH put back in is correct. Its ok to go over 1760mah every now and again. They are some that do it all the time, but for full cycle life stick to 1760mah.

Your charger may be false peaking not allowing you to read correct mah back in.

450se v2
07-04-2008 11:39 AM
 
 
"Cam"
Veteran
Location: Asia

If you didn’t time your flight, you can’t be sure how much you used.

You may have a bad internal connection on your 2nd battery with high resistance – causing the charger to false peak.

It’s also possible that your collective management was better after the warm-up flight so you did use less capacity!

What charger are you using? Does it tell you the cell voltages?
07-05-2008 02:22 AM
 
 
nmrs
Senior Heliman
Location: Austin, TX

I use a countdown timer. Between the first and second battery I changed the timer from 5 to 5 1/2 minutes. I landed just as timer was beeping, so that is how I know I flew it for 5 1/2 minutes. I am using a Cellpro 4S charger, though I didn't check the pack voltage when it was done -- just the mahs it put back in. I flew both KP batteries today for 6 minutes. Charging the first one now. Will see how much the second one takes today.
07-05-2008 03:42 AM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Just charged second battery. Took 1395 today for 6 mins of flight. Guess yesterday was just a fluke... Should be able to still get more time, so tomorrow will fly them 6 1/2 and 7 mins respectively and see where that gets me.

450 se v2
07-05-2008 04:46 AM
 
 
electricdurango
Veteran
Location: Sterling, VA

It may have been a false peak.

450se v2
07-05-2008 11:04 AM
 
 
nmrs
Senior Heliman
Location: Austin, TX

How do you avoid a false peak? I'm now checking the cell and pack voltages as well as the mahs returned after charging to make sure that cells are each 4.2 and pack is 12.6. If I get an especially low number of mahs returned again, should I just disconnect and reconnect the battery and make sure the charger still reads it as full?

450 se v2
07-05-2008 11:39 AM
 
 
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e-Electric Batteries & Chargers > put back less than expected...
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