Dean,

I recently bought some new Thunderpower V2 3300 5S to run use on my T33 stunter.

I set the hubin timer to 2 minutes 45 seconds to see what the half "MaH use" would be for a normal 5 minute 30 second flight time, and so not to damage the battery by over discharging them. After dialing in the proper lap times, triming etc with the APC 13-4.5 prop, the amount of milliamp's I am replacing according to the charger is on an average 1480 for the 3 batteries I am using.

I have several questions:

1. How accurate is the reading that I am getting from my charger (ElectriFly Triton) on the replacement amps??
2. The charger seems to get to (5S) 21 volts pretty quickly, say around 1200 replacement milliamp's and then spends the next 300 Milliamp's and say 15 minutes cycling up and down a few tenths until it says it is completely charged, What is it doing during this time, balancing the cells??
3. I am trying to stay at 70-80% discharge, but if I go with the full charge cycle the charger indicates it is replacing I am more like 90% if I were to fly a whole pattern.
4. Could I twist in some more pitch and lower the RPM to save amps, or would the extra pitch pull more, even at a lesser RPM??
5. Based on what I have stated do you think I am likely to over discharge that batteries if I make a full flight??
6. What other info to you need to determine?

Lots of questions I know but I am frustrated.

Dean,

I recently bought some new Thunderpower V2 3300 5S to run use on my T33 stunter.

I set the hubin timer to 2 minutes 45 seconds to see what the half "MaH use" would be for a normal 5 minute 30 second flight time, and so not to damage the battery by over discharging them. After dialing in the proper lap times, triming etc with the APC 13-4.5 prop, the amount of milliamp's I am replacing according to the charger is on an average 1480 for the 3 batteries I am using.

I have several questions:

1. How accurate is the reading that I am getting from my charger (ElectriFly Triton) on the replacement amps??

I would expect the reading to be accurate -- but the charge needed after half a flight may not be half the charge of a full flight.  I couldn't say for sure, not being steeped in LiPo lore -- but in general, battery charging isn't a simple science.

I'd try a four minute flight, and see how things trend.

2. The charger seems to get to (5S) 21 volts pretty quickly, say around 1200 replacement milliamp's and then spends the next 300 Milliamp's and say 15 minutes cycling up and down a few tenths until it says it is completely charged, What is it doing during this time, balancing the cells??

That's a normal charge profile for a LiPo, even without the balancing.  They can only accept charge so fast, and that's reflected by the charge current tapering off.

3. I am trying to stay at 70-80% discharge, but if I go with the full charge cycle the charger indicates it is replacing I am more like 90% if I were to fly a whole pattern.

If that's really true, then you just need bigger batteries.

4. Could I twist in some more pitch and lower the RPM to save amps, or would the extra pitch pull more, even at a lesser RPM??

Good question (and what motivated me to answer).  The motor/ESC combo is going to be somewhat less efficient; depending on how much extra pitch you use the prop may be more efficient, and may be worse.  If there's improvement it'll probably be slight -- but engineers live to be surprised, so it doesn't hurt to give it a whirl.

What might give you more efficiency is if you lower the RPM, and increase both pitch and diameter.  If you take two props generating the same thrust, then in general the bigger one will be consuming less power.  How this translates when you throw all the stunt variables at it---I don't know.

5. Based on what I have stated do you think I am likely to over discharge that batteries if I make a full flight??

Running a battery down to 90% once isn't going to hurt it terribly much.  It's doing so over and over again that wears it out fast.  Perhaps the best thing to do is just go for a full flight, and see how the plane performs.

6. What other info to you need to determine?

Lots of questions I know but I am frustrated.

Take what I say with a grain of salt---I'm an electronics engineer with aerodynamic pretensions.  The proof is in the pudding, which means you've got to 'speriment. a bit.

Just for chuckles, make sure that you don't have any obvious problems.  Nothing rubbing the motor case, no bad bearings, prop on frontwards, connections tight, ESC good, etc.  I couldn't count the number of working days that I've wasted over my career looking for design problems when the fault was in a broken part.

Hi Tim,
Seems to me like you've already received a bunch of good information. Let me add my two cents worth ...

Taking your questions in order (but only so that I can digress!)
1) First, i have to assume that you are using the new triton EQ that has the balancer built-in. True or no? As to how accurately it measures the charge put back in, I can't say authoritatively: Electrifly do not even publish a specification for this. On the other hand, I'd be surprised if it wasn't accurate to within just 2 or 3%, just based on the needed voltage measurement accuracy and the moderate cost of 1% tolerance components.
2) The LiPO charge cycle has two distinct stages: in the first, the charger "tries to" supply 21.0 Volts (5S) but it cannot because the adjustable current limit gets in the way. This is the Charging Current setting that you chose for nominal 1C charging rate. Eventually, the pack achieves 21V but it is still charging. The current now begins to "tail-off" from its original limit and the remaining 10% of charge will take maybe one-third of the total charging time. The charge is actually declared complete when the current tail drops to maybe 1/50th of the initial current.
2b) If your charger balances the pack, then balancing ideally takes place during this second phase of the charge cycle.
2c) If the pack is substantially unbalanced, then the first cell will achieve 4.20 (really 4.22 for some chargers) Volts before the entire pack has reached 21.0V. If and when this happens, the charger will (should / must?) "throttle back" to a charge rate that is no greater than the "thieving" or bypass current. In the Triton specifications sheet it is called the "node current". The thieving current is steered around the fully/overcharged cell so that it does not charge any more but the other cells still get charged ... BUT AT ONLY 300 mA! If you were charging your 3000 mA-h pack at 3 Amps before, now you are charging 1/10th as fast. This substantially lengthens the time needed to finish phase 1 of the charge, if the cells are unbalanced more than 0.01 or 0.02 Volts.
2d) ALL balancing chargers on the market do this, and must do so, unless they are built using a dramatically more expensive architecture.
2e) 2C, 3C and 4C charging will lose their time advantage if the cells become unbalanced, and the fastest way to unbalance them is to ... wait for it! ... charge them really fast. The other ways to unbalance them are to run them down past 80% capacity and to get them too hot.

3) Yes, 90% discharge is too deep. You will probably need to use bigger batteries ... but let's not get too far ahead of ourselves.
4) Changing the pitch and running RPM may (or may not!) do what you want. In general, motor efficiency suffers when you drop the running RPM but prop efficiency improves a little. For minimum battery consumption, you want to drop pitch and raise RPM until you barely have enough voltage left at 75% discharge to maintain lap time. (If you have a Castle ICE you'd see the %DRIVE approach 95% just before the clover)

Here we need a whole lot more information from you: plane weight, line length, how draggy is it, motor, ESC, battery and desired lap time.

For starters, get the plane slowed down to the desired lap time. This has a dramatic effect. Then if the results are encouraging, sneak up on the flight time. Also try to trim the wasted time off the end of the flight, and lengthen your walk-to-the-handle delay so that you waste as little capacity as possible. The downside of dropping the pitch as far as possible is that you lose punch in the hourglass/overhead 8 / and clover when you don't have excess voltage available at the end of the flight.
5) Yes! Like I said, slow the lap time first then sneak up on the flight time.
6) I'll say it again, we need every bit of info you can think of. An explanation of why the sky is blue would be helpful too!

I think you see from the enthusiasm with which answers have accumulated, that we all want you to succeed, so let's git to it!
Dean

Hi Tim,
At that weight and 5S you should be fine: using maybe 2.4 ~ 2.6 A-H of capacity.
I would think you are running closer to 10K RPM with a 4-1/2" pitch and 66' of line.
Assuming you have the lap time you want, then bump up to 5 minutes and see where you are at. I think you'll be alright at the eventual 5:45 or so.
What's with the tractor prop in the pictures?

Oh yeah ... love the looks of it!
  Dean