I figured out why a few of my batteries don't make the whole flight. They are over temping and the ESC is saving them. Now they are charged to 16.97 or better. Other batteries of the same brand and Amperage complete the flight with no problem and are much cooler. I measured the cells and I can't detect a weak one. This is on the same plane same day charged an hour before flights. 20 minutes between flights. 60 Amp ESC from Brodak. From what I read in the directions over heating is the culprit. Am I missing anything else?

Perry, I read your previous thread about "battery switch."  What is your charger?  Are these cells meant to be over charged, over 4.2v/cell?  I'm guessing 4s packs, and if not HV packs, then 16.8v for 4S packs.

The info sheet doesn't say but the 110 degrees is Celsius

Normal operating temperature for Lipo is up to around 110°F, not C.  That is however the top temperature range for ESC's, (110°C). 

There is an online manual for the "Hornet series" from HTIRC which says that the ESC has overheat protection at 110°C, when the ESC is that temperature.

https://img.banggood.com/file/products/20170112214632HTIRC%20Hornet%20Series%20ESC%20User%20Manual.pdf

I didn't see an online manual specific to Brodak Hornet, but probably similar.  Some of these manuals are translations, and not great ones.  That said, your specific of 110°C would be for the ESC.

While charging, you can likely look at the individual cell voltages on the charger.  Are they very close to the same?  Especially look at the cell voltages when you first put the pack on the charger after use.  You should be able to see a low volt cell if that is the problem.

I'm not sure why you would charge a pack, and then balance charge the pack, as opposed to using a balance charge the whole time. It sounds like you are charging a pack to 16.8V cutoff and then putting the pack on balance charge when it already has 16.8V?  If 16.8V and not balanced, are some cells over-volt?  Again, look at the individual cell voltages.

Are the hot packs older then the cooler ones?  Internal resistance on the packs can go up and they will get hotter.  Also, a single cell can be going bad as your concern.  Looking at the individual cells, especially when first hooked up, will help to see than.

15.1V/4 is 3.775V which is well over 20% left, so that does not seem the problem, unless the bad cell.  So, see if each cell is about that. There are lots of these devices available, but I have 2 of these, one with the charger and one in my flight box.  They are inexpensive and probably only semi accurate, but give decent information.

http://www.valuehobby.com/accessories/batttery-accessories/battery-capacity-checker.html

This will add to William's post, he was faster.

Perry, I’ll give this a try.  There are going to be many opinions on battery charging and best practice.  There is what is best battery care which will help longevity and number of cycles, and then there may be what is best for flying.  Obviously on one end of the spectrum, you can place the batteries in a box and not use them and they will last for a long time, though not many cycles.  Most agree that batteries don’t like to be discharged to less than 20% capacity and this is around 3.74-3.75v as rest.  The voltage will likely be a bit lower while flying/discharging.  Many smart phone with Lithium batteries have a low volt warning at 20% to help battery life.

Batteries don’t do well being held at full charge.  Longer time at full charge decreases longevity.  Some studies show that 80% charge may greatly increase the number of battery cycles over full charge.  Of course this is not practical for flying as we need to keep battery size and capacity (weight) to a minimum.  But, keeping batteries fully charged (or close) is not good for the battery.  Longer time is worse, so charging the day before is not best for the battery, though it may be best for the flyer’s schedule. 

Fly the battery and when done, charge it to storage if not flying the pack again.  There should be a storage charge setting on the charger and it will shut off at somewhere between 40 – 60% charge, usually around 50% and not critical.  In general, batteries of same age and health will use about the same number of “mah” for a flight, so that they will take about the same number of mah to reach storage charge.  You can also look at cell voltage as you have found.

On the day of use, balance charge to full.  Balance charge is a bit slower than regular charge because of the balancing where the smart charger keeps the cells equal or balanced.  Many chargers also have a fast charge function and this usually slightly undercharges. Part of the reason that it is faster is that the tapered slow top off isn’t done, so slightly less full, less mah input.  You can actually use this to your advantage if you are not close to 20% after flight.  Say the fast charge leaves off a couple of % from full slower charge, but if you have 25% left, that works fine.

Some flyers have found that if they try to maximize what is best for the battery, they spend too much time getting ready in the morning, so they charge at night.  If you have 4 packs and fly 200 flights in a year, that is 50/pack and you might not notice any problems.  If you accurately keep track of cycles on a pack, you tend to get more cycles with better battery care.  But, do you get more flying or more time caring for batteries  :-)

When you put them on the charger, did you see a total pack voltage, and individual cell voltage?  Most chargers will either charge or discharge to storage, whichever is needed.  I'm not sure what overcharged meant, unless you didn't use much battery and they were above storage charge.  Again, most storage cycles will either charge or discharge and switch automatically to which is needed.

While working on this problem, please document more.  If you can't charge on storage, but can on regular charge, look at (record) the total voltage of the pack and individual cell voltages.

Why regular charge for 30 minutes?  Does the charger have a time setting or are you timing?  What if they don't need 30 minutes?  Just trying to understand your process and charger.

In particular, please document voltage total and individual cells for the problem packs, at start and finish.

Individual cell voltages will help in the future.  3.2v/cell x 4 cells is 12.8.  15.2/4 is 3.8v/cell and if you have that after a flight, you aren't using much battery.  I picked 4 cells from previous posts, is that correct?  How long a flight?

Please record the mah input for the 30 minutes, and then the mah input for the completion of charge for a pack tomorrow.  That total will be your usage for a flight.

Also, please note your charge rate.

I prepped the batteries and one showed a very weak cell. I was going to leave it home but put it on another charger and it showed fine readings. I'll give it a try in an hour.

Here is an online manual for B6 charger.

http://www.milehighrc.com/Manuals/ImaxB6manual.pdf

On page 14 under heading Charging lithium battery in the balance mode one screen shown has the heading "supplied capacity and other screens called charged capacity."  The supplied/charged capacity is the amount of charge going into the battery.  Units of charge capacity are the "mah," so think of the terms as interchangeable.   Please keep track of supplied capacity (mah) as noted above. 

I don't understand the "one that was good, now not good?"

How are you measuring voltage?  Voltage on the charger while charging will be higher than resting voltage (voltage measured while not charging).  That voltage may remain high for several minutes.  Voltage just off discharge, immediately after a flight, will be lower for several minutes and will settle a bit higher.  Cell chemistry, resistances, heat.... come into play.

You may have a cell problem, still not defined.  Again, please check battery voltage and individual cell voltages on the charger shortly/just after flying.  Read them just after you turn the charger to start charging so that it will show the voltages before any significant charge.  You can make this easy by selecting a charge rate that is very low, for long enough to get the values.

You may have a charger problem, it shouldn't charge to over 16.8v for four cells.  Is that the same on each of your chargers?  It may charger to 16.8v and then settle a bit, but 16.9 seems too high. The charger doesn't seem to be sensing the peak and shutting off properly.  If that was proper for your charger, then all batteries should do that.

How much charge in during 85 minutes and what charge rate?

I flew the problem batteries on my smallest electric plane. It has an Aerowind 2820/07 motor, APC 11 x 5.5, 40 Amp ESC and Hubin basic timer. Flight time was 5 min. 20 sec. All three batteries performed well. The plane is scratch built profile using the Legacy 40 wing and modified tail. Beginning voltage, using a digital multi meter, 16.86, 16.86 and 16.92. End of flight voltage, taken within a minute of landing, 14.92, 14.89 and 14.89 respectively. Voltage when I got home 15.07, 15.07 and 15.13.  I popped them on the charger/balancer, initial cell voltages, 3.76, .76 .78, .74. / 3.76, .76, .74, .76. / 3.79, .80, .79, .79. I'm probably over charging and actually taking power out by doing so. I didn't do any extra charging of these batteries before flying like I have been doing.
  My chargers are at least 3 years old and one has 4 stations the other one station. Bought from reputable vendors, not Amazon or ebay. I think they are working properly but I'm not. More experiments tomorrow with the Legacy size profile and equipment.

I'm printing the chart now.
I have 4 batteries on discharge at the moment.
 I have been mistreating them all along.
At least I learned how to best use the chargers.

The charger reads 16.8 when it stops charging. I check the battery right after and get 16.9xx.
I charged the three batteries in this investigation yesterday about 1000 am. I went to the field 27 hours later, without recharging, to run them down and starting voltage was 16.8xx on two and 16.7xx on the third. All three flew full flights 5 min 20 sec. without complaining. end voltages are 14.89, 14.81 and 14.76.
It seems I have been torturing the batteries. From now on I will only charge them the day of flying.
Your help has been very valuable. Thank you.