I flew 2 properties on Wednesday this week.  Landing Batt A with 60%, and Batt B with 56%.  2 properties, starting each with a freshly charged 100% battery.

Today,  Saturday Dec 15th.....I went to the SEFSD.ORG flying field......to cycle 2 new Inspire 1 TB48 batteries, as well as burn off the 2 partially discharged batteries from the P4Pro from Wednseday.

Battery A went in,  turned on and showed about 60%....I checked the cells and they were at 3.9 or so each cell!!  That's what it should be, and what it was......To be honest THAT is NOT what I expected.
SOOO,   I flew around the field, messing around for 15 min....battery got to 35% and I checked the cell voltages,  3.65/cell  under load, and still green.....cool,  landed, and with motors off checked the cells again,  3.79 to 3.8 static per cell.....PERFECT!!

Battery B went in,  turned it on and showed about 57%....I checked the cells and they were at 3.85 or so each cell.  Hmmmm,  seems fine, but I wasn't happy....shoulda been a couple hundredths higher than that.......( keep in mind I fly and check airplane batts ALL THE TIME )  So I take off......all's fine with the flying, and go out about 300ft, 30 ft agl and stop...hovering and check the Battery....54%, then the cells ... ...3 are yellow at 3.42 and 1 is orange at 3.4vdc......WHAT THE....I come in and land.  I do not turn off, and check....%= 50% Battery on the front page.....cells unloaded = 3.6.....HAD I been at 300ft agl and 1600ft distance,  this POST would have been about a crash.......

LADIES AND GENTLEMEN,  You CAN NOT trust the percentage reading on a partially charged battery.  < That is a PERIOD....Meaning do NOT trust partially charged battery readings in DJI or any other Drone Aircraft.

You've all read......"My drone crashed for no reason"  then you see the Log, and see they took off with something less than 80% battery, and never checked their cell voltage.

RISK Management is a Factual part of Flying a Drone Aircraft.  POWER is essential.

Randy

Just wondering aloud here, if you had, on your previous charge, aloud the batteries to have shut themselves down by leaving them in the drone till they ran out of steam and then charged them, yeah, i am talking about the controversial deep cycle,  if you would have still gotten the same erroneous voltage reading?

PS, i should probably reword that but ive just got up, its 3:40am and i cannot be asked lol

This was in FACT, from Wednesday a planned test.   I have flown batteries from one job to the next from 100% to 70%,  then flown again never having an issue.

It seems however, that when things are sitting for a day or 3,  that all bets are OFF.  It could be that electrons dissipate over some period....kinda like clearing a cache.

My biggest concern was the difference between 60% and 57%......That just seems crazy to me.  Battery B literally was on for less than 2 min when the cells read 3.42 and were YELLOW in the app......

I am hoping this thread makes people LOOK at the data being provided by the app.......it can save you many hundreds of $$

Randy

Check in the app, to see where your battery’s Auto Discharge time frame, is set for.


RedHotPoker

Welcome to the world where WE HAVE BEEN SAYING THIS TILL BLUE IN THE FACE ....

DON'T FLY PARTIAL CHARGE BATTERYS !!

Thank you for posting actual data to show ...

Nigel

This is not news.
There must be 100 threads here where the warning is to only launch with a fully charged battery.
The % indication is not accurate if you start with a partly discharged battery.

Three's a charm, so I'll just reiterate what has been posted twice already.  DON'T LAUNCH WITH A PARTIALLY CHARGED BATTERY.  NO EXCUSES, NO BUTS, NO IFS.  JUST DON'T DO IT.  

RedHotPoker Posted at 12-15 21:31
Check in the app, to see where your battery’s Auto Discharge time frame, is set for.

5 days on all batteries,  P4Pro and I-1

rwynant V1 Posted at 12-16 14:19
5 days on all batteries,  P4Pro and I-1

Oh ok. That dissolves my previous thinking.



I figured it may have been set for a much shorter duration. Not.



RedHotPoker

But history repeats itself, when flying with partially discharged flight packs.
Honestly, personally, I always top off my flight packs.


Even right before leaving the home front, with my drone, for an enlightening mission aloft.




RedHotPoker

Good thread.  Everyone should read it.

ALABAMA Posted at 12-16 17:49
Good thread.  Everyone should read it.

Yes, it is a good read. The problem is, unless you know to come here and read it you won't know. And this is where DJI are lacking, there are a number of critical issues that must be kept in mind when flying a drone and DJI do not recognise them or warn about them. One is the battery thing, and the other is the place you launch from.

I too am wondering why you would launch with less than a fully charged battery.   Surely you don't run yours down to 35% every time you use them ?  Even if storage was the issue,  and it doesn't sound like it was,  55-60% surely would have been OK ?

I just checked my four Phantom 3 Pro flight packs and RC batteries, tonight.
Mind you, we Hadn’t flown in a few weeks, & two flight packs were registering one Green LED.
The other 2 flight batteries Green LEDs were blinking with two. One of those packs was stored in the drone.
While the RC battery registered with all four green lights glowing brightly when checked or turned on with a double click and hold.
I placed two flight packs on the twin DJI OEM 100w chargers and hope to utilize them all, this coming week.
Before the temperature really begins to drop, around here. Santa’s on his way soon too. Hahaha


RedHotPoker

The only time a partial battery is ok to take off ... is if you land and DO NOT power down from a flight that started with full charged battery. The APP and all then regards it as one continued flight.

Its folly in ALL RC world to use partial charged batterys.

Nigel

RedHotPoker Posted at 12-16 15:13
Oh ok. That dissolves my previous thinking.

Batterys do not STOP and sit at 100% till the auto discharge routine kicks in.

ALL batterys suffer Self Discharge, we are lucky that Lithium based batterys suffer very low Self Discharge rates.

A big mistake is to accept the LED lights as accurate indicator of charge state ... they are only accurate at best to 12.5% increments. (See manual for confirmation of this).

If you take a fully charged DJI battery ... you can set that Auto Discharge to 10 days if you like. 1 day later check the charge state with the LED's ... all four lit up. So you think its 100%.
Try this then - switch on the battery and plug into charger ....... if it was 100% - the charger would soon be stopped by the battery board - but its not ... it charges for a period before switching off ... showing that a small amount has in fact been discharged while stored.
Go 3 or 4 days and you will have charger running longer till it switches off ...

This is why its good practice to top-up charge by switching on battery before plugging in charger as close to flight time as possible.

Nigel

I always top up my 4 flight packs. Before missions of discovery. ;-)


You’re singing to the choir. Haha



Thanks though. I appreciate you. Grin


RedHotPoker

RedHotPoker Posted at 12-17 03:06
I always top up my 4 flight packs. Before missions of discovery. ;-)

HI RHP ... I know we have our 'differences' ... but I wasn't aiming at you directly. Just supporting and explaining why your 'top-up' is actually a good idea.

Many people trust the LED check and are not aware how far it can be off ... and also assume that if they set 5 day Auto Discharge that at late on 4th day expect to have still 100% !!

My own personal view is that its better to set a short 2 - 3 day Auto Discharge setting to reduce charged storage time in event of non-use as I always do a top-up before flight.

Cheers
Nigel

Merry Christmas and happy New Year from Latvia.

Great post. Thanks for sharing. I haven't ever flown a partially charged battery and sounds like I should never.

solentlife Posted at 12-17 02:24
Batterys do not STOP and sit at 100% till the auto discharge routine kicks in.

ALL batterys suffer Self Discharge, we are lucky that Lithium based batterys suffer very low Self Discharge rates.

I made the mistake of leaving a battery in the drone too long, and it fully discharged to the point I cant revive it. Unless there's a trick I don't know about. Good luck!

solentlife Posted at 12-17 02:24
Batterys do not STOP and sit at 100% till the auto discharge routine kicks in.

ALL batterys suffer Self Discharge, we are lucky that Lithium based batterys suffer very low Self Discharge rates.

Solentlife,

THAT IS AN EXELLENT POINT!!  Thank you for posting!

Please, EVERYONE READ his POST.......pass that word to all your friends!!

Full voltage does NOT mean the tank is full...that's where the MAH comes in.

Randy

I want to thank you ALL for posting in this thread!

It's great to see a thread that doesn't turn into a crap pot of back and forth posts!!  This thread should be posted in every Model UAV Thread out there.

Yes,  the subject has been covered.....many many times!  But if we, as prominent users and testers of these birds continue to keep the most significant issues on the front page, then maybe WE prevent a new user from losing his or her AC in a preventable crash.

Randy

Excellent post. Thank you to all who have contributed. You are making a good point very important. I have never flown a partial charge bat and never intend to it's like a crap shoot. Sometimes it works out fine but the one time it doesn't is all it takes and then your posting about a mystery crash. Hopefully, posts like this one will help avoid problems in the future.

DanbyUrgess Posted at 12-17 08:36
I made the mistake of leaving a battery in the drone too long, and it fully discharged to the point I cant revive it. Unless there's a trick I don't know about. Good luck!

Get the Battery Manual (ignore points about deep discharge etc. as that's old hat and not removed from it ) ... it has a section about Hibernation and to get battery out of it.

Hibernation Mode kicks in when battery gets so discharged it drops into protective mode of Hibernation.

Problem is - that its not g'teed you can bring it out of the mode. But main point is - that the battery cannot be charged by just plugging in charger ... you have to 'cheat' the control board in the battery by switching on ... DON'T touch anything then for 5 minutes - THEN plug in DJI Charger ... ONLY a DJI charger or fixed regulated 17.5V PSU will do the job... You leave the battery alone .. don't be tempted to touch it ... it can be minutes - it can take all day ... you just have to leave it completely alone till it 'wakes up' ....

Nigel

I never trust the LEDs on the flight packs, but check their individual voltage within the Go app.

I wish Battery Life could be returned to the iOS app... ;-) Yes please.


RedHotPoker

For a quick total voltage check ... switch on and Multi-Meter to the main contacts ....

I agree that this does not give cell voltages - but at least you know if full or not.

Nigel

solentlife Posted at 12-17 10:52
Get the Battery Manual (ignore points about deep discharge etc. as that's old hat and not removed from it ) ... it has a section about Hibernation and to get battery out of it.

Hibernation Mode kicks in when battery gets so discharged it drops into protective mode of Hibernation.

OK, great. Thanks for the info Captain Nigel!

DanbyUrgess Posted at 12-18 08:45
OK, great. Thanks for the info Captain Nigel!

If you are lucky and it does 'wake-up' ..... please do only short close in flights for a few times and charges - till you feel OK that its performing well.

To anyone else thinking of leaving their Phantom / Mavic or whatever alone for a long period ... PLEASE do yourself a favour and charge up the batterys full every so many weeks or so ... to stop them draining down to Hibernation. The life cycle lost by charging fully ... letting auto discharge kick in and then charging up again say 1 - 2 months later is worth it ...

Nigel