I am a new owner of an Inspire 1 with 5 hours flight time on it.  Have flown RC helis for years and am really liking this aircraft so far.  A concern I have about batteries: I have 3 additional TB48s that I purchased with it   Flew two yesterday and both landed with between 27%-29% on them.  Plugged one into the Inspire this morning to check something quickly, expecting it to be in the 25% range.  However, both gave CRITICALLY LOW warnings on the App and were at 1% and 0% each.  Both at 3.74-3.76V.

Each battery has about 4-5 flights on it and have never landed below 25% since I follow the low battery warning and land immediately.  The history on both the batteries in the App is listed as NORMAL.  Should I be concerned or is it normal for the battery to drop so much overnight when discharged to 30%?  Also, both seem to hold full charge for at least a few days between flights.

Thanks,
Tom  

Same here from time-to-time. Something is up with these batteries.

In addition, since the firmware update prior to the .06, I've noticed the fourth LED does not illuminate on any of my six (TB47 & TB48) batteries while charging. The third LED blinks about twice as long as expected and that's it, charge completed. They test good otherwise:  Pressing the check/power button illuminates all four LEDs and checks good on the app.

Yes my batteries do this.  

After a flights with about 22 - 24% remaining if they are left uncharged for a few days, they fall to 1% or so, but I have just viewed this as I can then re-charge from a fully discharged battery.

As a test, I flew a battery down to 30% yesterday and landed.  Let it sit in the case (not the inspire) overnight.  Plugged it in this morning and it's down to 4% 3.78V per cell.  I wonder if the latest battery firmware has something to do with this, I don't remember this happening before but may not have noticed it.  It also seems like 3.78V is high for just 4%?  I read other posts about never flying unless you start with a 100% charged battery, reports of people starting at 60% and it dropping to 8% very quickly.

GravityStorm Posted at 2015-6-22 21:07
As a test, I flew a battery down to 30% yesterday and landed.  Let it sit in the case (not the inspi ...

Yes, those reports do reinforce the need to the fly with full charged batteries only.

GB44 Posted at 2015-6-22 21:32
Yes, those reports do reinforce the need to the fly with full charged batteries only.

I concur re: starting with a fresh battery prior to each new flight - if and when possible.

But now I'm curious if I should charge the battery up to 50% after flight if I wont use if for a couple days, thereafter. Typically, after a flight I have about 18%-25% capacity left and I wont recharge it unless I plan to fly again soon. But hearing the drop in voltage/capacity when left at 25%  makes me question if I should continue leaving it at that %, or charge up to 50% and store that way.

MSD17 Posted at 2015-6-30 08:39
I concur re: starting with a fresh battery prior to each new flight - if and when possible.

But n ...

I have asked this question via another post and specifically for DJI to comment as there is nothing about this in their manual only that you can top up when battery is above 95%.

I got some good feedback from some members who advise to charge to 50% after respective flights then top up prior to flight.

I am just concerned that this is resulting in potentially two charge cycles that reduces the overall charge capacity of the battery.   No one knows if there are any constraints in the battery software that prevents charging over the max recommended charge  cycles, so it would be good feedback from DJI just to clarify how long these batteries can be left after a flight without charging to 50%.

After a short flying session yesterday, I deliberately left my batteries uncharged until today ( Next day) the results are :

One battery with a Pre-flight charge 99%  had a post flight charge of 29% and the next day ( Less than 24hours)  this reads 3%.
One battery with a Pre-Flight charge of 100% had a post flight charge of 32% and the next day ( Less than 24 hours ) this reads 9%
One battery with a Pre-Flight Charge of 100% had a post flight charge of 58% and the next day ( Less than 24 hours) this reads 56%

This would indicate that if the batteries are to have some meaningful charge in them whilst not being used they must be re-charged within a day of use unless 50% or more remains post flight

GB44 Posted at 2015-6-30 20:43
I have asked this question via another post and specifically for DJI to comment as there is nothin ...

My understanding is that a "charge cycle" is based on the application of charging AND discharging a battery. For example...charge to 100% (base), discharge to 50%, recharging and discharging the same amount would equate to a single charge cycle.

Math:
100% base
- 50% discharge
= 50% REMAINING battery charge
+ 50% top-off charge #1 (1/2 cycle...battery is now at 100%)
- 50% discharge
= 50% REMAINING battery charge
+ 50% top-off charge #2 (1/2 cycle...battery is now at 100% again)

Both 50% top-off charges equates to 1 charge cycle

I could be wrong, but that's what I take from the term.

Basically, I look at it as the process of arriving at 100%. So another example would be... If I charge to 100% (base), discharge to 20%, then recharge to 100%...at this point I've only added  80% to the previous 20% discharge state so it's not considered a cycle. However, as soon the battery sees the remaining 20% in a future charge session it marks it a single charge.  Hopefully that makes sense, but again...I could be wrong.

The reason I believe my theory could be correct is because the "Times Charge" on the pilot app is never the same as the number of manually documented times I've charged the battery.

GB44 Posted at 2015-6-30 22:55
After a short flying session yesterday, I deliberately left my batteries uncharged until today ( Nex ...

Those results certainly shown a correlation between the amount of additional discharge occurring within a 24hr period (when left uncharged/unused), and the amount of remaining battery charge (post-flight)...i.e. Higher post-flight charge % results in slower discharge (when left unused).

Unfortunately, most people use most of the available charge during flight (prior to receiving a low charge warning), so having a remaining post-flight charge above +50% isn't typical. I'm sure you did it as a test, but I think I'll just try recharge after each flight (at least to 50%).

Question, how much flight time are you getting on your TB48 battery @ 100%? I only got about 15mins on a brand new battery, charged once. Seems low considering it's rated at 22mins. Will test again though.

MSD17 Posted at 2015-7-1 10:49
Those results certainly shown a correlation between the amount of additional discharge occurring w ...

Yes there were a couple of reasons for the 50%+ post flight.  

1.  There were two bulls fighting further up the field from me and on decided to come a little bit too close for comfort.

2.  I wanted to test how long the discharge or battery level was left if battery was above 50% post flight.

Sorry I don't have any TB48's   Can get up to 15 mins on a TB47 looking at landing or returning to take off  when reaching the 30% level.