Battery issue

[ifixwell]

I was flying my P3S and received a low voltage warning for the first time ever. Thankfully It was very close by because it auto landed. Battery was at 36% and voltage at 14.64V. Each cell was 3.8v. I saw a tip about holding down battery button to see how many leds light up and I only see two. Recharged 65 times

So I did a discharge to 8% and full recharge. DJI App shows now:
98%
17.09v
4367 mAH
4.28v each cell
Button test still shows 2 bars on battery. Does this mean battery is defective?

 

[epicdoom]

when you press and then press and hold a second to turn the battery on how many lights light up? that is your available voltage in bars of 25% approx. I wouldn't put much stock in the holding down the button method. If your showing 4.28volts in each cell its obviously holding more then half total voltage the 17 volts total is also an indicator. you can run the battery up to 100% if you wait a couple hours and put the battery back on charge and this time power the battery up with a press and press hold till it powers up this will most times allow the battery to start charging again and this time will take it to full 100% charge.

If your looking at only 2 lights with your method of holding down the button that doesn't jog well with what your drone is saying the battery is at so IMO that method is completely unreliable

 

[ifixwell]

If I turn on the battery with 2 pushes of the button (like I'm gonna power up) it shows 4 bars. What got me is the low voltage warning and immediate descend. Like I stated, I have never seen an issue before. I read that holding the button until it flashes will show you how good your battery is by how many green led bars you see.

 

[sar104]

Holding down the button for 5 seconds shows the lifetime status of the battery rather than its current charge level. Phantom 3 manual, page 17.

 

[ifixwell]

So 2 bars means it has half it's life left? What does the battery info from the app say about the health of the battery?

 

[With The Birds]

when you press and then press and hold a second to turn the battery on how many lights light up? that is your available voltage in bars of 25% approx. I wouldn't put much stock in the holding down the button method. If your showing 4.28volts in each cell its obviously holding more then half total voltage the 17 volts total is also an indicator. you can run the battery up to 100% if you wait a couple hours and put the battery back on charge and this time power the battery up with a press and press hold till it powers up this will most times allow the battery to start charging again and this time will take it to full 100% charge.

If your looking at only 2 lights with your method of holding down the button that doesn't jog well with what your drone is saying the battery is at so IMO that method is completely unreliable

The button press procedure the OP is invoking does not depict and is unrelated to state of charge. Two LED’s depicts the battery health as being over 50%. Whole this seems low for 65 cycles it is what is being reported.

It would be useful to upload the flight log to Airdata or phantom help for the flight where the error was reported to get a better idea of what is going on with this pack.

 

[epicdoom]

the low voltage warning is selectable in the APP what is it set to? I set mine to warn me at 30% and critical at 10% as sar104 pointed out what that button hold is for you have to keep in mind as a battery is uses its capacity lowers over time so even a full 100% battery can have a diminished capacity which effects run time the total mAh on a new battery is 4480 mAh yours is showing 4367mAh so this lends itself to what I'm saying

 

[ifixwell]

I use the default settings of 30 / 10. I had read also that DJI sets the batteries for 200 charge cycles.

 

[ifixwell]

I haven't flown it that much as charge cycle shows. Sometimes weather or another reason did not make it to fly. Is this counter re settable?

 

[epicdoom]

I use the default settings of 30 / 10. I had read also that DJI sets the batteries for 200 charge cycles.

I cant say how many cycles as I haven't gotten to that Bridge yet I suspect that's something in the onboard chip that permits that. I have a junk battery that I've pulled the board off of I fully plan to try and explore the data on the chip if I come to that I will see if that's something resettable by reprogram or just bumping the numbers up. It wont be till after the holidays till I get to hacking that board though. I am ok with 200 flights per battery but not all batteries will be unusable after that amount of time. I have at least two lipo batteries that I fly planes on that have well into the 300s of flights I've had to replace a motor, but the batteries are still going strong

 

[sar104]

So 2 bars means it has half it's life left? What does the battery info from the app say about the health of the battery?

Just how many times it has been charged, plus capacity.

 

[ifixwell]

thanks for the info. Im gonna keep a close eye on that voltage level.

 

[With The Birds]

I use the default settings of 30 / 10. I had read also that DJI sets the batteries for 200 charge cycles.

I suspect the often mentioned 200 (or other number) cycle count number is a myth. The battery life or state of health (“SOH”) is an integer between 0 to 100 stored in the Texas Instrument battery monitor IC. It was originally simply the full charge capacity/design capacity with FCC being determined by an algorithm measuring charge and discharge under load. Load variations and temperature obviously had an impact on accuracy with the current implementation now employing FCC rwferenced to 25degC and a preset load rate (who knows what DJI has set here but hopefully it is the ave AC load).

 

[solentlife]

The 200 cycle life was discarded long time back and now battery life can go as long as you wish to use ...

Capacity does NOT reduce on a battery as some say - what happens is USEABLE capacity changes.

The mA counter is a crude result of measuring charge IN and charge OUT ... it then derives a value to display.
Deep discharging the pack does two things .... a) it actually causes a small amount of accumulative damage to cell or cells each time you do it and b) it resets counter - it does not magically conjure up more mA's !!

I've posted about this many times - Internal Resistance (Ri) is the be all and end all of our batterys. All experienced users of LiPo's are aware of it and quite a number actually measure it through life of a pack. DJI unfortunately do not alloow us access to the cells to measure Ri but lets carry on ...

As you use a pack - it use will slightly increase the Ri and it will gradually accumulate till it causes battery to fail to provide enough power to fly ...
The first signs are shorter flight times when voltage drops faster ... this is due to resistance causing amps to increase to supply the WATTS required by motors. As Resistance increases, voltage drops, amps goes up .. flight time capability gets shorter. Note - Capacity is still there - but is used up faster by the higher amp demand compensating the increased voltage drop. You can ignore the displayed mAh capacity by GO - its not accurate.

Cycle life indication : about as accurate as just measuring voltage of pack. The real test is flying time measured against voltage levels. Example : Take a new pack ... charge and note voltage when powered up. Now fly keeping steady speed . manoeuvres ... note time when landing and voltage level ...

Now take an older pack or the same pack months later and do same - you will see similar voltage when power up but shorter time to that voltage level you landed at previously. That's the pack getting older and Ri increasing.

I apologise for the long novel - but there is so much more going in with batterys than just voltage.

Final point ... to get a battery to charge up the last bit / top-up ... Switch on battery BEFORE plugging in Charger ... this then over-rides the near full cut-off setting and allows charger to charge cells to max.

Nigel

 

[sar104]

The 200 cycle life was discarded long time back and now battery life can go as long as you wish to use ...

Capacity does NOT reduce on a battery as some say - what happens is USEABLE capacity changes.

The mA counter is a crude result of measuring charge IN and charge OUT ... it then derives a value to display.
Deep discharging the pack does two things .... a) it actually causes a small amount of accumulative damage to cell or cells each time you do it and b) it resets counter - it does not magically conjure up more mA's !!

I've posted about this many times - Internal Resistance (Ri) is the be all and end all of our batterys. All experienced users of LiPo's are aware of it and quite a number actually measure it through life of a pack. DJI unfortunately do not alloow us access to the cells to measure Ri but lets carry on ...

As you use a pack - it use will slightly increase the Ri and it will gradually accumulate till it causes battery to fail to provide enough power to fly ...
The first signs are shorter flight times when voltage drops faster ... this is due to resistance causing amps to increase to supply the WATTS required by motors. As Resistance increases, voltage drops, amps goes up .. flight time capability gets shorter. Note - Capacity is still there - but is used up faster by the higher amp demand compensating the increased voltage drop. You can ignore the displayed mAh capacity by GO - its not accurate.

Cycle life indication : about as accurate as just measuring voltage of pack. The real test is flying time measured against voltage levels. Example : Take a new pack ... charge and note voltage when powered up. Now fly keeping steady speed . manoeuvres ... note time when landing and voltage level ...

Now take an older pack or the same pack months later and do same - you will see similar voltage when power up but shorter time to that voltage level you landed at previously. That's the pack getting older and Ri increasing.

I apologise for the long novel - but there is so much more going in with batterys than just voltage.

Final point ... to get a battery to charge up the last bit / top-up ... Switch on battery BEFORE plugging in Charger ... this then over-rides the near full cut-off setting and allows charger to charge cells to max.

Nigel

If the fundamental change is an increase in internal resistance (r) then for a constant power draw the current (I) will have to increase to compensate for the lower terminal voltage, as you noted. In that case, since the internal resistance is higher and the current is higher, the heat dissipated in the battery (I²r) should also increase, which should mean that the batteries should also run hotter as they get older. That change presumably should be visible in the battery temperature logs.

 

[solentlife]

If the fundamental change is an increase in internal resistance (r) then for a constant power draw the current (I) will have to increase to compensate for the lower terminal voltage, as you noted. In that case, since the internal resistance is higher and the current is higher, the heat dissipated in the battery (I²r) should also increase, which should mean that the batteries should also run hotter as they get older. That change presumably should be visible in the battery temperature logs.

Of course .....

Its a problem that any EDF / high power flyer gets to learn about very quickly.

As temperature increases - the resistance increases as well .. it really is a vicious circle.

Nigel

 

[Shoemaker]

Great info so far over my head but useful

Thanks
Brent

 

[With The Birds]

If the fundamental change is an increase in internal resistance (r) then for a constant power draw the current (I) will have to increase to compensate for the lower terminal voltage, as you noted. In that case, since the internal resistance is higher and the current is higher, the heat dissipated in the battery (I²r) should also increase, which should mean that the batteries should also run hotter as they get older. That change presumably should be visible in the battery temperature logs.

Actually Cell IR reduces with increasing temperature.

 

[solentlife]

Actually Cell IR reduces with increasing temperature.

Actually ... my error - I got two writings mixed up and posted wrong ... I was engaged in another matter about metals and resistance on another subject in work and mixed up. That's what you get mixing 'hobby with work' !!

Yes a battery Internal Resistance reduces with increased temp .... but only to the point where battery starts to suffer chemical or physical breakdown. But it can in fact temperature can produce damage that causes battery to have increased internal resistance as a result.

But it does not change the fundamental of the information I posted earlier .... with the higher resistance - the temperature climbs ... as the battery is working harder to provide demanded power. As the battery ages - the internal resistance rises ... battery appears to be weaker / less capacity.

Nigel

 

[With The Birds]

Actually ... my error - I got two writings mixed up and posted wrong ... I was engaged in another matter about metals and resistance on another subject in work and mixed up. That's what you get mixing 'hobby with work' !!

Yes a battery Internal Resistance reduces with increased temp .... but only to the point where battery starts to suffer chemical or physical breakdown. But it can in fact temperature can produce damage that causes battery to have increased internal resistance as a result.

But it does not change the fundamental of the information I posted earlier .... with the higher resistance - the temperature climbs ... as the battery is working harder to provide demanded power. As the battery ages - the internal resistance rises ... battery appears to be weaker / less capacity.

Nigel

What is important to note is that LiPo cell IR is a derived value. It is not a direct measurement or resistance, rather it is determined by measuring voltage drop below open load voltage and a known applied external resistance. This makes it very useful as it demonstrates the ability of a cell to deliver power under load, a direct measure of efficiency. And yes, as you say- it is a very useful indicator of cell health. Reduction in capacity is also a useful indicator as is cell balance across a pack. The DJI smart board is able to correctly report actual capacity, it performs IR monitoring of individual cells also during charge and discharge (amongst other things).