Check internal resistance of DJI batteries?

[Yaros]

Hey,

So as my batteries are coming near their end of life, I thought I might get more cycles out of them by regularly checking the cells' internal resistance.

On my regular lipos this is done easily using my ToolkitRC charger, but on DJI chargers I don't see a way to do it. Is it even possible?

 

[Yorkshire_Pud]

Using a DMM, measure the voltage ,V, with 'no' current flowing through the battery then measure the voltage when passing a 'large' current , I, through the battery, you need to know/measure the current.
I recollect that when I went to school the difference in the voltages was attributed to internal resistance, R.
R = V_diff/I.
However I am not sure if that is applicable to Li batteries.

 

[DARKSeifer]

You can link your DJI account to AirdataUAV, and then check the filght logs on the bettery section, and there is all the information you need to know how in shape every battery is, and it's free.





Appart from that, the visual inspection for inflation, all those batteries that are placed on top of the drone (Air 2, 2S, Mavic 2, etc) have a design flaw where they can pop out of the connectors midflight if they inflate.

Drones with internal battery bay, like the Mini 2, Mavic 3, Air 3, etc don't suffer from that, if the battery inflates it will get stuck untill it cools down, but the drone won't lose power and fall.

 

[Yorkshire_Pud]

Regarding Airdata, the battery charge count appears to be derived from the number of time Airdata has seen the battery charged, mean its voltage has significantly increased between flights.
I do not know if other battery data is monitored the same way.
For the free version you are limited to 100 logs.

Question for @DARKSeifer do you have a paid account?
I am just wondering about the charge count being 119.
If you don't have a paid account then it means that some battery data is retained when a log is deleted from the freebie account.

I recollect that I have seen things in Airdata data that does suggest that Airdata does do this with some drone data.

 

[DARKSeifer]

Regarding Airdata, the battery charge count appears to be derived from the number of time Airdata has seen the battery charged, mean its voltage has significantly increased between flights.
I do not know if other battery data is monitored the same way.
For the free version you are limited to 100 logs.

Question for @DARKSeifer do you have a paid account?
I am just wondering about the charge count being 119.
If you don't have a paid account then it means that some battery data is retained when a log is deleted from the freebie account.

I recollect that I have seen things in Airdata data that does suggest that Airdata does do this with some drone data.

Yes, you only have active access to your last 100 logs, but even when you can no longer explore the log actively, that log is still used by Airdata to gather information. They don't delate the old logs, they just restrict your access to them.

 

[Yorkshire_Pud]

Thanks

 

[Droning on and on...]

Can't be done. You don't have access directly to the individual cells.

Internal resistance is determined by measuring voltage across the cell during charging. For a naked LiIon battery, current is limited during the CC phase, the charger executing this by adjusting the charge voltage to maintain the target current.

This voltage, divided by the charge current, is the cell's internal resistance.

DJI Intelligent Batteries do not monitor and store this information per cell during charge.

 

[Yaros]

Gotta stop using this battery I guess

 

[Droning on and on...]

I'd keep using it. That "normal deviation" figure is ridiculous. I'd like to know how they came up with it.

If I had to guess, I'd say it's probably an average across all data, which would of course be biased to show "normal" as what deviation looks like for most of the battery's life.

It gets worse as the battery approaches EOL. It doesn't mean it's faulty. Packs will show they're near the end by storing less and less charge. So long as the pack isn't swelling, deviation in the thousandths doesn't mean a lick of spit in terms of pack viability.

 

[DARKSeifer]

Check the battery cell tab, dyeing batteries will have a lot of major deviations there.