Beware of Battery LED indicators

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As most know - the battery has LED's on the front that give Charge Indication, Life indication and condition. As I have mentioned before - the LED's work on a range principle and that range is too wide to be taken as accurate.

Example - today.

I have two batterys on charge for today, as weather has finally improved and I hope to fly later. I checked by LED and both had solid 4 GREEN LED's .... so you would think ... OK - full charge ... WRONG !

I checked both and one was at 16.68V and other was at 16.72V ...... that is IF cells are balanced about 4.17V and 4.18V per cell against the full charge 4.35V per cell.

Just passing on info ...

Nigel
 
I picked up a tip from someone here on the forum and include the battery voltage icon alongside the voltage % and use the time remaining timeline at the top of the screen and find that of more use than just relying on the battery life remaining.
The low battery and critical warnings are triggered from the % settings in the app but I have noticed the remaining voltage is well above that deemed to be the threshold for safe battery use when i land which is a bit of a mystery for me. It would seem that the smart battery is designed to restrict your flying based purely on % and not actual voltage.
In any event I will check my battery voltage tomorrow vs % as it always appears at 99% on full charge and see what the numbers are. I actually did a P vs S mode comparison but threw out the test sheet as I was looking at consumption and not starting voltages.
 
One of the biggest problems is DJI insist on taking away from owners full battery access. Any other LiPo and you can diagnose / meter / check individual cells direct and not have to go through an app. But that App is not telling you strictly true data anyway ... as you noted - 'power line' and % displayed are not strictly in line with each other.

Other factor is DJI has decided that voltage determination on charging / discharging is based on TOTAL voltage and not as should be with LiPo's - individual cell voltage.

The Battery LED's are only a very rough guide but I know that some have idea that it gives them good results. The fact that four solid green LED's as I show here is NOT full charged ... should show the folly of such.

DJI has decided to cover safety by taking worst case scenario. An owner who has no knowledge how to handle LiPo's and has built in a board to the battery to try and cover the bases. It does its job as far as that is concerned - but do not run away with the idea that it is a total answer, as it is not. Myself and others have found that some of the functions it is claimed to have - such as Balancing - are not as good as you think. In fact when it comes to Balancing - I am not only one who is trying to find out if it actually does ! as so far we have no evidence showing it does in any form.

But anyway - the point of my post was to show that charge before flight is important. Do not trust the LED's ...

Nigel
 
Hi Solentlife

It's not as simple as you state, consider 4 LED's gives you 8 possible indications if you allow a linear collimated display, eg zero LEd's would = 0% charge 1 LED = 25% charge.... 4 LED's 100% charge now however if you allow the LED's to flash, then you could have 1 LED flashing would give you 12.5% charge 1 LED on solid = 25% charge, 1 LED solid and second LED flashing would indicate 37.5% charge and so on up to 4 LED's solid = 100%. ( 8 states)
So therefore the percentage charge when 3 LED's are solid and the fourth one is flashing would be 87.5% charged and so on.

But lets take this in context, the LED's do not in fact equate to the actiual charge state of the battery, for this reason:- we just looked at the logic behind the indication status eg 3 soild and the fourth flashing would equate to 87.5% charged, therefore a reduction of 12.5%, if you now calculate the voltage when the charge is reduced by 12.5% ie 4.35 * (4.35*(12.5/100)) = 3.8 volts, that is equal to the lowest safe voltage for a LiPo. So the LED's are only a visual aid for the OP, because a fully charged cell is around 4.35V and a cell should not be allowed to fall below around 3.8V for safe flying, you can see the problem.

Well thats my take on it, anyone see it differently,,, discuss :)

Waylander
 
Waylander ... think you missed my point.

I was saying that 4 solid LED's ... none flashing ... does not mean full charged. I have not even started on the incremental part of the LED displays ! ;)

OK .. lets take your point of 3.8V ... in fact that's a resting / storage voltage point and NOT the lowest safe flying point. Lowest safe flying point is actually around the 3.2 - 3.3V point. Once you stop flying - the cells 'rebound' back to 3.6V or more because LOAD is now removed.
If you have Voltage displayed as well as the power line when flying - you will see that 3.8V gets passed quite early on in a flight and you are still flying ...

The LED's are NOT % of voltage anyway - they are % of charge state ... which means the calculation you made is in error.

As I said - I am trying to show new owners that the LED"s are not what initially thought to be. That it is best to charge before flight. If the battery is near full - then you need to switch on battery and then connect to charger.

Maybe when more understand the LED's and this - we will see less 'events' ?

Nigel
 
Waylander ... think you missed my point.

I was saying that 4 solid LED's ... none flashing ... does not mean full charged. I have not even started on the incremental part of the LED displays ! ;)

OK .. lets take your point of 3.8V ... in fact that's a resting / storage voltage point and NOT the lowest safe flying point. Lowest safe flying point is actually around the 3.2 - 3.3V point. Once you stop flying - the cells 'rebound' back to 3.6V or more because LOAD is now removed.
If you have Voltage displayed as well as the power line when flying - you will see that 3.8V gets passed quite early on in a flight and you are still flying ...

The LED's are NOT % of voltage anyway - they are % of charge state ... which means the calculation you made is in error.

As I said - I am trying to show new owners that the LED"s are not what initially thought to be. That it is best to charge before flight. If the battery is near full - then you need to switch on battery and then connect to charger.

Maybe when more understand the LED's and this - we will see less 'events' ?

Nigel
You make a good point Nigel. I always "top-up" the battery prior to packing them for a trip, by powering on, as one does when it's in the drone and then reconnecting the battery to the charger. Without fail, the battery always starts to charge for a few minutes, insuring that they're at 100% when I arrive at the flight location.
 
Waylander ... think you missed my point.

I was saying that 4 solid LED's ... none flashing ... does not mean full charged. I have not even started on the incremental part of the LED displays ! ;)

OK .. lets take your point of 3.8V ... in fact that's a resting / storage voltage point and NOT the lowest safe flying point. Lowest safe flying point is actually around the 3.2 - 3.3V point. Once you stop flying - the cells 'rebound' back to 3.6V or more because LOAD is now removed.
If you have Voltage displayed as well as the power line when flying - you will see that 3.8V gets passed quite early on in a flight and you are still flying ...

The LED's are NOT % of voltage anyway - they are % of charge state ... which means the calculation you made is in error.

As I said - I am trying to show new owners that the LED"s are not what initially thought to be. That it is best to charge before flight. If the battery is near full - then you need to switch on battery and then connect to charger.

Maybe when more understand the LED's and this - we will see less 'events' ?

Nigel

Yo Nigel mate, I'm not criticising you..... I.m trying to add to the post is all, here is a good article from DJI

Phantom 4-DJI Intelligent Flight Battery - DJI Wiki

Most good LiPo chargers will not even begin to charge a cell at 3.2 - 3.3 volts, so that voltage is not really the lowest safe operational voltage for flying a drone,
Yes I know may modellers who have there alarms set at 3.6 volts as an indication that it's time to get out of the air, not an indication that it is still safe to fly.

And yes the cell voltage reading does drop a bit under load, but that is true of many unregulated power supplies, what we do not know is the algorithm that DJI uses to decide when a battery or cell is close to the critical minimum voltage for safe flying, ( which is what I was talking about ).

I agree with you newbies should not rely on the LED's to indicate the charge state of the battery, but without writing a thesis on LiPo voltage versus Charge State, which many would get bored with after reading for 5 minutes, my intention was to add to your post, to broaden out the picture, as you may know the discussion on what is safe to fly and what is minimum voltage with regard to LiPo rages all over the blog sites.

Stay Cool
Waylander
 
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Hi Waylander ...

DJI is not being completely upfront I'm afraid ... but they have created a Fools battery to avoid 'events'.

As I said - 3.8V is not unsafe ... but it is a good storage voltage.

LiPo chargers not start charge at 3.2V ? The way chargers determine if safe to charge or not is based on minimum voltage for the cell count you select. If you select for a 3S - then the charger will expect to see 3x minimum voltage of a safe level. That is usually around the 3.1v mark. The balance lead also indicates if a single or more cells are below minimum threshold ... 3V.
Easily proven by taking a lipo you don't use seriously anymore down in discharge to 3V or lower. Then try charging. If its below 3V .. it doesn't start. But if you give a short charge in NiMh mode to bring that cell up to 3V or just over ... stop and the try LiPo again - it will charge.
There are many posts splattered all over forums on that very item.

ESC's have LVC often at 3.3 or lower simply because of the voltage drop under load .. but as soon as load is taken of - the LiPo recovers to reasonable level.

Nigel
 
The Phantom manual contains a chart that explains what the battery LEDs mean. Four solid lights means the battery level is between 87.5%-100%. Now, if we could just get all Phantom owners to read the manual ;)

BatteryChart.jpg
 
As a point of past fact... the P2s have an 'hidden' (not user adj.) low batt auto-land at 10.65v. This was for their 2P3S (i.e. non-hv) LiPo pack.
 
Great input guys but my ADD has kicked in. What in flight voltage reading would send you home/time to land, and does the time remaining timeline use voltage or % for its calculations?
Thanks
 
What in flight voltage reading would send you home/time to land
It depends. How far is your Phantom from the home point? What's the temperature like? Which direction is the wind blowing? How strong is the wind? There are too many factors in play to always head back at a certain voltage/percentage.

You should monitor your battery and try to land by the time the first battery cell reaches ~3.4V.
 
But, what if the leds are indicating a binary status...........4 bits = 16 status indications. :)

Hi Phil soz you can't have a full binary 16 bit display status form 4 LED's because the array is collimated ie you can not have the first LED in the array ON and the second OFF and the third LED ON and so on so you can not generate a binary number...;)

Waylander
 
Hi Phil soz you can't have a full binary 16 bit display status form 4 LED's because the array is collimated ie you can not have the first LED in the array ON and the second OFF and the third LED ON and so on so you can not generate a binary number...;)

Waylander


Nobody mentioned 16 bit.............I said 4 bit display......:)
 
Hi "msinger" .... too true !

My whole point was to try and get the new owners who come here to understand that just checking LED"s on the battery does not actually give a straight exact answer.

My example in first post showed a significant variant in voltage from the 4 solid LED's lit up on the front. Yes it agrees with the chart - but as you so rightly say - people need to read the manual.

I'm unusual - I will download manuals for gear BEFORE buying and study them. I suppose the work I do has instilled that into me. But many people prefer to buy ... try ... then find a forum and a Youtube video. They just don't seem to want to read a manual !

Bit like the wife with a new washing machine !!

Nigel
 
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But, what if the leds are indicating a binary status...........4 bits = 16 status indications. :)

Ok ... a 4 bit word will allow a count from 0 - 15 ( 16 states ), termed as a Hexidecimal number, however as I said in my post the 4 LED's are arranged in a column, and the LED sequence can only be show in an incremental order, ie No LED's, first LED flashing, First LED solid, First LED solid + second LED Flashing, and so on which if you work it out will give you only 8 unique states because they can only be switched On or flashing sequentially 1 after the other, you can not have 16 states from that array, sorry dude :)

It's all getting a bit pedantic, over and out.....
 
Ok ... a 4 bit word will allow a count from 0 - 15 ( 16 states ), termed as a Hexidecimal number, however as I said in my post the 4 LED's are arranged in a column, and the LED sequence can only be show in an incremental order, ie No LED's, first LED flashing, First LED solid, First LED solid + second LED Flashing, and so on which if you work it out will give you only 8 unique states because they can only be switched On or flashing sequentially 1 after the other, you can not have 16 states from that array, sorry dude :)

It's all getting a bit pedantic, over and out.....
Are you pissed or what...........If you include the tri-state (flashing) it gets much more than 16........
 
Just to complete the voltage story ... two flights just now and I compared GO with Litchi for display ..

GO showed a voltage of 3.60V and 30% when landing. Just as it was touching down - my low battery alarm went which I have set for 30%.

Litchi landed similarly about 30% but strangely the voltage shown under the % was 4.26V which is wrong ! It never changed.

Videos on my channel if anyones interested..... "solentlifeuk"

Nigel
 
Are you pissed or what...........If you include the tri-state (flashing) it gets much more than 16........

Rather Rude Phil... why would I be pissed...?

I don't think you are seeing the point, yes 4 binary bits can represent numbers from 0 to 15, but only if each of the bits can be turned on or off individually.

How often have you seen the first LED on your battery and the third LED switched on at the same time...... NEVER unless the battery was faulty.

Aassuming that the first LED which could light up is on the right hand side of the row ( we will call that LED 1 and the last or fourth LED that could light up when the battery is fully charged is on the left, and further assume that all of the LED's are switched "On" you would have a representation of the decimal number 15 ie 1 1 1 1 in Hexadecimal notation.

On a DJI flight battery you will not get a tri-state representation, because all of the LED's only light up or flash sequentially from the first LED to the last LED.
So you will not see LED 1 "On" LED 2 "Off" LED 3 "OFF" LED 4 "On" eg 1001 the Hex notation for the Decimal number 9.

If DJI had arranged it so that the LED's were able to switch on individually, you could get 0 1 1 0 = decimal 6, but they have not done so, how further confusing would it have been if DJI had allowed for example, 0 1 1 (0) but the last LED the one in () was flashing.

Look at the " Battery Protection LED Display" chart in the manual, where individual LED's can flash on and off to display a type of error code, Would it not further confuse an OP if the LED's flashed in a non sequential order.

Phil I'm not raining on your parade... I see that you do understand Hex notation and Tri-State conditions, but I think you are missing the point, DJI have used a SIMPLE code to visiually indicate the charge state of the battery, so exactly what was your meaning in #7 of this post, enlighten me please.

Waylander
 
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