What do you do with half a battery?

[BigAl07]

That is true they don't have "memory" and I should have made the clear. I don't think there has been a standard set yet for battery life other than monitoring cell balance and health.

You mentioned DJI algorithm and to be honest I can't figure it out. So I came up with my own that seems pretty close I used 25.92 or 4.32 volts per cell as fully charged, and 19.92 or 3.32 volts as 0% drone falls out of sky. and based my discharge percentages on that 6 volts from full to 0%. I know it is simple but seems to come out close to their numbers especially mid voltage percentages. These are obviously no load percentages. The funny thing is I end up with a couple of new batteries showing 100.17% so mine isn't perfect.

I like how you think.

 

[The Editor]

Perhaps it is just me but when I read this thread I find it amusing that everyone is going on about battery percentages which are totally meaningless.
If you Google 100 Lipo Percentage v Charge graphs you will more than likely get 100 different results.
As a professionwl you should by flying by voltage which is absolute rather than percentage which is arbitrary and inaccurate.
I have never taken any notice of DJI's daft percentage display and only fly by cell voltage information. DJI developed the battery percentage ''fuel guage" and 'intelligent' (read that as stupid) batteries in an attempt to weed out the idiot gene on their lower end aircraft.
For some inexplicable reason they have carried it over to their so called professional systems and it is meaningless.
Lean to fly by cell voltage and read these under load allowing for cell recovery/rebound after load removal/motor shut down.

 

[R.Perry]

Look if you understand the voltage value that the percentage is indicating then you are using their percentage the same way you would monitoring voltage. The thing is some apps don't give the pilot voltage but rather give percentages and that is better than nothing.

One thing about it, when that percentage says 0, you are done flying and your battery voltage will tell you that you have about 3.32 volts per cell or 19.92 volts. I've always enjoyed being a number cruncher but reality is the KISS system DJI has does work.

 

[R.Perry]

I thought I would give you a little time to do the math, because I made a mistake, or posted a mistake. Apoximately 22 volts is the 0% mark, not 19.92 and as I said earlier I haven't figured out DJI algorithm yet but it is most definitely a sliding scale. Once past the 50% mark the percentages drop at a much faster rate and yes I did miss that, but will figure it out.

So if you went by the 6 volts from full to falling out of the sky you would have been really shocked when your drone stopped flying at 22 volts. I'm posting my mistake so other will fly by DJIs percentages and not my miscalculations.

So how did I discover this, by flying the Inspire until it wouldnt fly. fortunately it was about two inches off the mat when she said that was it, I'm done flying. I know, this isn't the orthodox way of doing things. Funny thing percentages showed 0% when she came to rest.

 

[The Editor]

I thought I would give you a little time to do the math, because I made a mistake, or posted a mistake. Apoximately 22 volts is the 0% mark, not 19.92 and as I said earlier I haven't figured out DJI algorithm yet but it is most definitely a sliding scale. Once past the 50% mark the percentages drop at a much faster rate and yes I did miss that, but will figure it out.

So if you went by the 6 volts from full to falling out of the sky you would have been really shocked when your drone stopped flying at 22 volts. I'm posting my mistake so other will fly by DJIs percentages and not my miscalculations.

So how did I discover this, by flying the Inspire until it wouldnt fly. fortunately it was about two inches off the mat when she said that was it, I'm done flying. I know, this isn't the orthodox way of doing things. Funny thing percentages showed 0% when she came to rest.

I'm sorry but this is a very dangerous assumption to make.
The problem is there is no true correlation between cell voltage and percentage - only a bad approximation.
As said before, DJI ''Smart" packs were introduced to weed out the idiot gene.
As professional operators you really shouldn't be flying by a 'best guess' arbitrary percentage approximation of fuel capacity.
Percentage is simply a guess (by the software/algorithms, whereas voltage is an absolute (and accurate) measurement.
There are too many variables to factor into a percentage reading including but not limited to - age of cells, internal resistance of cells, how a pack has been treated and/or stored in the past. The weakness of any particular cell. How the cells track together and mV difference between them under load. How well the cells recover when load is removed (rebound).
If you Google Lipo voltage v Percentage you will get 50 different opinions!
Obviously any discharge curve will not be linear. Lipos simply don't work like that - they never have done. Lithium Polymer chemistry means they give a faily flat discharge initially and will plateau. However, there is a very small difference between the last phase of discharge and falling off that plateau which ''Fuel type guage or percentage readings" can never do accurately.
What will be '15%' battery one day will be '12 or 10%' another day as the packs age or so many other factors.

Fly by voltage - it is safe, it is absolute and you will not get any surprises.

 

[The Editor]

if you want to know more about the battery care info, here are some guides for you Lipo Battery Guide - What is a Lipo battery?

Very outdated article.
No mention of LiHv cells (which DJI use exclusively in their packs) which can and should be charged to 4.35v per cell.
This means all the voltages quoted in your linked article are wrong I'm afraid.
Case in point is take an Inspire (1) TB48 pack which quotes 22.8v. This means a nominal per cell voltage of 3.8 volts not 3.7 as per standard non LiHv packs.

 

[R.Perry]

The reality is if the average person flying a drone uses percentages and always keeps a decent reserve power they need not worry about specific voltages. When I drop below the 30% mark I'm looking to land very soon, that is 22.6 to 22.7 volts and from my observation the voltages and percentages have always been consistent, at least within 0.02 volts. The Inspire 2 stops flying at about 21.1 volts.
The thing is I don't like overheating my batteries and once I drop below the 30% mark the battery head goes up very quickly. I think most of understand your point, I think some find your presentation a little abrasive at times. This isn't a group of rocket scientist here, just a lot of folks like myself looking for good ideas and learning from each other.

 

[aerialimagery]

Very outdated article.
No mention of LiHv cells (which DJI use exclusively in their packs) which can and should be charged to 4.35v per cell.
This means all the voltages quoted in your linked article are wrong I'm afraid.
Case in point is take an Inspire (1) TB48 pack which quotes 22.8v. This means a nominal per cell voltage of 3.8 volts not 3.7 as per standard non LiHv packs.

Do I need to know all this stuff? I'm flying and it says "low battery." I land it and change batteries. I charge batteries at home until the green lights stop blinking. Then I repeat the process. I have no clue about charging to 4.35v per cell. What am I missing by not knowing about all the voltage specs? Do I have control over that anyway?

 

[R.Perry]

Do I need to know all this stuff? I'm flying and it says "low battery." I land it and change batteries. I charge batteries at home until the green lights stop blinking. Then I repeat the process. I have no clue about charging to 4.35v per cell. What am I missing by not knowing about all the voltage specs? Do I have control over that anyway?

You make a very good point, and as with most, we fly until it we feel it is time to land, change batteries, charge them when they need it and not sweat the small stuff. I like understanding how things work, and like digging into things like this, but it doesn't make me a better pilot or photographer. One thing it does do is give me an understanding of what to watch for with my batteries.

 

[Moosewax]

I'm sorry but this is a very dangerous assumption to make.
The problem is there is no true correlation between cell voltage and percentage - only a bad approximation.
As said before, DJI ''Smart" packs were introduced to weed out the idiot gene.
As professional operators you really shouldn't be flying by a 'best guess' arbitrary percentage approximation of fuel capacity.
Percentage is simply a guess (by the software/algorithms, whereas voltage is an absolute (and accurate) measurement.
There are too many variables to factor into a percentage reading including but not limited to - age of cells, internal resistance of cells, how a pack has been treated and/or stored in the past. The weakness of any particular cell. How the cells track together and mV difference between them under load. How well the cells recover when load is removed (rebound).
If you Google Lipo voltage v Percentage you will get 50 different opinions!
Obviously any discharge curve will not be linear. Lipos simply don't work like that - they never have done. Lithium Polymer chemistry means they give a faily flat discharge initially and will plateau. However, there is a very small difference between the last phase of discharge and falling off that plateau which ''Fuel type guage or percentage readings" can never do accurately.
What will be '15%' battery one day will be '12 or 10%' another day as the packs age or so many other factors.

Fly by voltage - it is safe, it is absolute and you will not get any surprises.

The Editor has the truth though dead nuts, monitor your voltages and get used to it, it could save you an aircraft someday.

Especially in cold weather the DJI percentages are very dangerous to use. I have had DJI telling me I had like 50% battery life when I was flying in 16F weather but the voltages were as low as what we get at 20% battery life in normal optimal conditions. That's even with insulation and keeping the batteries warm.

Start monitoring your voltages throughout your flight to get a feel for what it's voltage is at different stages of flight. Remember too things like going fast, climbing fast, high winds, and adding payload weight can significantly add to how much power you are drawing from the battery at any given time.

 

[R.Perry]

Moose you are correct, but the pilot needs to know what truly represents 0%, I consider 0% is when the aircraft will no longer fly. With the Inspire 2 that is 22.1 volts and the sad part is DJI percentage will say you have 13% remaining battery life. So when DJI tells you you still have 26% battery life the reality is you have 10.3% and that is why some folks have flown their drones until they fall out of the sky. That is why when DJI says I have 30% remaining I'm looking for a place to land.

The other issue I'm concerned about is battery heat, I have noticed when I have got close to the 10% (22.5 volts) mark the battery is much hotter. Tomorrow I'll be flying in 100+ heat, and I'll be looking to land when DJI says I have 35% and out of curiosity will be checking the battery temperature.

I flew the Inspire and hovered a few inches off the ground until she said "I'm done" and landed, voltage was 22.1 volts 13% indicated. So Editor and Moose you are right as long as you know what voltages your drone will fly at and really know what voltage it will no longer fly.

I have not run these tests on my P4P yet but will soon.

I'm a person that loves warmth, so 16 degrees means stay home in front of the fire and only open the door to let the dog out.

 

[Moosewax]

Moose you are correct, but the pilot needs to know what truly represents 0%, I consider 0% is when the aircraft will no longer fly. With the Inspire 2 that is 22.1 volts and the sad part is DJI percentage will say you have 13% remaining battery life. So when DJI tells you you still have 26% battery life the reality is you have 10.3% and that is why some folks have flown their drones until they fall out of the sky. That is why when DJI says I have 30% remaining I'm looking for a place to land.

The other issue I'm concerned about is battery heat, I have noticed when I have got close to the 10% (22.5 volts) mark the battery is much hotter. Tomorrow I'll be flying in 100+ heat, and I'll be looking to land when DJI says I have 35% and out of curiosity will be checking the battery temperature.

I flew the Inspire and hovered a few inches off the ground until she said "I'm done" and landed, voltage was 22.1 volts 13% indicated. So Editor and Moose you are right as long as you know what voltages your drone will fly at and really know what voltage it will no longer fly.

I have not run these tests on my P4P yet but will soon.

I'm a person that loves warmth, so 16 degrees means stay home in front of the fire and only open the door to let the dog out.

Your Inspire may have done its "critical battery level" auto-landing when you were at 13%.

Also as your voltage in the batteries decrease your amps will increase to compensate therefore much of your extra battery heat, outside of other factors, comes towards the end of your usable voltage. Good practices to err on the side of caution though.

 

[BigAl07]

Ok gang... I've cleaned up this thread a little bit. Let's not dive into the ditches and start insulting other members. We all started at the same place and are all at different levels.

If you can't say something helpful or supportive just skip it and go to the next thread.

Allen

 

[R Martin]

Just my two cents. I have one battery that is out of tolerance across the cell voltages. I still use it to preflight the aircraft and not burn up precious time in the air. My last checklist item is to remove the faulty battery and replace it with a flight battery.