Found some interesting stuff out about Inspire battery behavour this morning.

On sunday I went for a bit of a fly and like I always do, Batteries and remotes, Ipad etc were all charged, so off I went.
Now call it paranoia , but when I fly around area's where a crash would be ugly.....over water etc, I only run my batteries down to around 50% in flight, come in and change them......just to be extra safe.
Well I took 4x 48's and 5x 47's with me.
Buy the end of my session I had run down all the 48's to the usual 50% approx and was done flying, so packed up and went home.
Fast forward this morning.......
I didn't recharge my batteries as this was a quick flight and I knew all the 47's had not been used, so I thought they would do, having only been charged a few days back.
I got to the Job and was getting ready and about to put a battery in the bird, and just for some reason, pressed the buttons on the 48's just to see how much was left in them, and low and behold !! they were ALL fully charged again !!
Now knowing there hadn't been any sort of divine intervention take place I thought this is very odd, so I put one in the bird, fired it up and hovered just off the ground to see what would happen.
As expected, they started at 98%, but within 30 secs or so, they were down to 80% and falling fast.........so I was obviously seeing a surface charge on the batteries....all 4 behaved the same exact way.
Now because I only run mine down to 50% or so, had I taken off and flew, things would have still worked out fine, and I would have had plenty of reserve power to land safely, but had I run them down to the lowest level, I would have had around a minute or so before the battery suddenly ran out off puff, causing all sorts of grief.......you can fly a long way away in a minute or so......
So the warning is this....
Load test your batteries, even when 4 green lights all light up.....you may not be seeing what is actually in the battery.......so, hover while monitoring the battery for at least 30 secs to a minute to be confident.
Having read a lot of sad tails about sudden power loss on here, I am pretty sure this is actually happening more than you think.
I don't really consider this a fault because no battery can be fully tested without a load applied.
I haven't seen this before because typically I always charge all my batteries before going out......had I just pressed the check button, or someone else picked up the batteries not knowing they had been used.....this could have turned out differently..........be careful people

Thanks for the good tip!

Harb, there is nothing new here.
This has been done to death by many before you.

It is common knowledge now that a DJI battery that has not been charged in the past 24 hours cannot be trusted, despite whatever status it might display.
No reason to keep making repeat posts on the same topic.

Farnk666 Posted at 2016-3-8 22:17
Harb, there is nothing new here.
This has been done to death by many before you.

Agreed!!

Rich

The battery probably already started discharge so in fact you get less then four green lights. If you didn't charge your batteries for few days it would be  wise to test them first. Thank you Harb!

No reason not to either  if it saves one bird from crashing........... Forums are for conversation.....buggered if I know why people are so precious about repeat posts.....certainly not having a swing at you mate, but crickey, the battery heading should have alerted you not to open the post.........I mean we are not cutting down rain forests here to write on.
At the end of the day, If a newbie comes on here and reads these things it may save them some grief, which they wouldn't go searching for before the event.
If repeat posts are an issue, there should be no more posts on Inspire issues or crashes, because they too have been done to death.

No worries Tim, the thing I found unusual is how long it reported 4 lights (100% charge) before it finally let go and started reporting correctly.......which would not be an issue at all other than the software reacts to the way the power is reported..........Just another case for making sure everything is Aok before takeoff.

Nothing new here - Its just crap code writing from DJI that is not accounting for the battery voltage rebound after removal of load. Flying down to circa 50% would mean your packs are showing around 3.8v peer cell under load.
Once you land at 50% battery and remove that load the cells will recover around 0.2v which means the 'Intelligent' (Stupid) batteries actually see circa 4v per cell under no load.
Stupid battery then thinks its almost fully charged and lights up the LEDS accordingly. Even putting the pack into the aircraft will only report what it thinks is a nearly charged pack since no load is being applied to it.
Once you start to fly, the sag of the pack kicks in and thus you get a perceived large voltage drop to its true capacity.
All of this could be avoided if DJI just kept a record of the mAh consumed from a pack (instead of an unreliable voltage reading) in a non volatile register along with a unique pack identifier or serial number. This could be reset each time the pack is charged.
Its not rocket science but clearly DJI struggle with it.   

markjacobs.talk Posted at 2016-3-9 09:31
Nothing new here - Its just crap code writing from DJI that is not accounting for the battery voltag ...

Can't emphasise enough how much I agree with the post from Mark Jacobs above

It needs to be sorted. Even after a full charge (supposedly) I am taking off and going into my "safety hover" and I am starting to see some very erroneous voltage readings, much lower than they should be given the recency of the charge. Basically each time I fly the Inspire I'm on tenterhooks these days and I have the battery display on pretty much constantly and assigned to one of the buttons on the back of the transmitter.

I do love the aircraft, but DJI really do need to so something about the battery firmwares, or release a new version of the battery with better voltage calculation. We need to be able to trust what we are seeing 100% without any doubt whatsoever.

hear, hear to that

Don't hold your breath.
They have had multiple goes at it already.

Harb, I appreciate the Post, those that know Battery Quirks  need not reply.  Everyday we see the same questions over and over and we dont say, ' That has already been covered"    I think it is just with The " Paul" situation, it is kind of a touchy subject.   I for one did not know that the LED's would all show full charge even after being flown to 50 % so I learned  something. ( I admit it, Just never saw it because I place my used batteries in seperate container)    Also  being a rolling topic thread, most folks dont utilise the Search Tool . Otherwise we would have not Post's if everyone used the tool . The Forum is a way to express personal experiences and to HELP our fellow Pilots .   So thanks For 'Your Experience"  I know it helped me  becasue I  dont pretend to know everything.  Also there are 30 times ( conservative ) more people looking at  the post and never reply.  I am sure there will be more than one person besides myself  that you will help with this Post, they wont reply but will store that information for later use.   

On my RC equipment I had a Load meter for my Batteries,  Maybe some entrepreneur could devise such an item  for  DJI Batteries.

Cheers- donnie

Thank you Harb.  Although knowing about this problem I have no issues in seeing it raised as a repeat topic.  Our birds cost a lot of money and no doubt there are new members coming to this forum with their new purchase.

Thanks for posting your observations, Harb.  I'm sure new owners will appreciate the knowledge.
A hover check is always a must-do for my ops.  As you stated, checking battery cell levels (fuel!) is part of it.

markjacobs.talk Posted at 2016-3-9 01:31
Nothing new here - Its just crap code writing from DJI that is not accounting for the battery voltag ...

Thanks Mark, true simple and to the point and if you've run other rc non smart lipos you soon realize the problem. Not rocket science.

RBirtles Posted at 2016-3-9 05:16
Thank you Harb.  Although knowing about this problem I have no issues in seeing it raised as a repea ...

I second the motion, no issues with the topic being raised again.

Wow Harb I had no idea this was possible. THANK YOU for posting this honestly. I am going to check mine this afternoon cause Im going on a trip tomorrow and don't want this to happen to me. THankS! Its amazing how much we spend on these and DJI cant get it together. Id call these "dumbass batteries" instead of " smart batteries" lol

DJI-Tim Posted at 2016-3-9 07:28
The battery probably already started discharge so in fact you get less then four green lights. If yo ...

So what to do if the battery is not used for let's say 4 days, while you have set your discharge to 10 days.
Do you have to force the battery to charge?
I read an awful lot over these battery's but don't know what to do with a battery that is untouched for more than 24 hours.
Please help.

dr. D Posted at 2016-3-10 05:38
So what to do if the battery is not used for let's say 4 days, while you have set your discharge t ...

I always "recharge" a battery within less than 12 hours of knowing you are going to use them.  Even if it was charged 100% 3 days earlier.  If it is already fully charged it only takes a few minutes of going through the charging process but at least you know you are running a fully charged battery.  If the battery has discharged a bit you will know that it is lower than you thought it was when charging it.

I only have four batteries but I also try to rotate starting use order to ensure that all batteries are being used at a simlar amount.  Another thing I do is write my initials and battery number (ie 1-4) on the back of the battery (not visible when put in the Inspire) to help me know which battery to use next.  I would also say that if I ever catch up with a group of other Inspire owners for a flying session this will also help avoid any ownership problems as well if sharing batteries.

Cheers!
Rob.

What I would like clarified, is seeing the electronics are onboard the battery and NOT the charger, does the Battery throttle down the charge process if it THINKS it is full......
My Batteries definitely thought they were full....4 lights....reporting 98% for a good minute on the screen before the load actually made them report correctly.

Yes charge current is controller via FETs in the pack controller by the fuel guage and charge IC .  

Harb Posted at 2016-3-10 01:00
What I would like clarified, is seeing the electronics are onboard the battery and NOT the charger,  ...

What I don't understand in this...
When a battery state 98% with four green lights (after a few days rest) it could be drop suddenly. But when I charge the last 2 % in it,  it's good to go without power drops?

So the case may be there that these batteries are being under charged ?

markjacobs.talk Posted at 2016-3-9 09:31
Nothing new here - Its just crap code writing from DJI that is not accounting for the battery voltag ...

Mark,

there seems some sensible points in there, lets hope DJI listen and make some tweaks for the benefit of all.

That's great tips as always!  Crazy that happened to you.  I am so leary of my batteries after hearing how many of these types of issues happen. The Cell warning is enough to freak me out when it starts saying "warning"". ;)
Great point though is to hover above the ground for a good 30 seconds or so...which is something I do in all my flights.  People always ask why I sit there for the first minute...and I just want them to know I am checking all systems and letting it idle for a minute just to see.

dr. D Posted at 2016-3-10 01:39
What I don't understand in this...
When a battery state 98% with four green lights (after a few da ...

Lipo ,s have a drop moments after you first start to use them, Depending on the chemistry the battery will not release the amps when cold until the chemical in the battery warms, when it does this cold,  The demand, cant be met,  the voltage drops pulling the battery down, if you warm the battery,  you will get different results even with a partially discharged battery,  charging and topping off the battery essentially gets the juices flowing, and you wont get the battery cratering with the resulting voltage drop,