Battery life?

[pokercop]

I just finished my 5th flight on my inspire one. I have noticed that I am only getting between 11 and 12 minutes before my battery is at 30% and I land. Is this about the flight time you guys are seeing as well? I was under the impression I would get several more minutes than this with the standard battery. I just ordered 2 more standard batteries & 4 higher capacity batteries. Let's hope I see better flight time out of the high capacity batteries.

 

[Tahoe Ed]

I don't land at 30%. My critical is at 15%. I get an additional 2-3 minutes.

 

[pokercop]

I guess it may be my paranoia from flying the P2 with bad 1st release batteries (when it went from 30% to 5% in about 30 seconds).

 

[Wiski23]

Yeah i changed my critical landing to 10%... Was sick of it returning with a good chunk of battery left

 

[Kilrah]

I have the first warning at 30, by the time I land it's at 20, and I get 14-15min of flight time.

 

[The Editor]

The most important thing is you do not take more than 3,600mA from the stock battery (Being 80% of 4,500mA). Regularly going beyond this point will significantly shorten the battery's life.
DJI's batteries are no different to anyone else's lithium polymer technology (although they would like you to think they are) in that they work by a chemical reaction and are made up of four components, the negative electrode, the positive electrode, a separator of some sort and the electrolyte.
If DJI truely wanted to make their batteries intelligent they would have limited the capacity taken out to show as 0% when the pack was down to 900mA remaining. This would have ensured that people could NOT fly into the area where the pack runs into damage or the risk of low voltage cut-off from the electronics. Instead, for reasons I have my suspicions about, they elected to allow the cells to completely deplete under normal usage.
Furthermore, and worryingly in my opinion, they actually advocate and advise that every so many usages of the battery the user should run the battery down to zero% . The only reasoning I can see behind this thinking is twofold:
1. It serves to 'reset' or recalibrate the fuel gauge levels on each cell so that they can be graphically displayed
2. It shortens the life of the packs and therefore DJI sell more batteries!

If someone can confirm that when they fly their pack down to 0% and get to the point where the craft auto lands then check the remaining capacity on the app it is showing as circa 900mA I will gladly and happily eat humble pie....... but I think I might be going hungry for a while longer yet

 

[Kilrah]

Answer is 1 and there is no way around it to ensure a precise indication in the long run. I'll gladly take the safety and comfort of the indication over the insignificant reduction in battery life caused by emptying it fully once a month under light load.

And not allowing people to use more than 80% would be ridiculous. Imagine crashing your machine when you know you actually still had 20% left...

Just set the warning and automated higher if you believe it's useful.

 

[The Editor]

Answer is 1 and there is no way around it to ensure a precise indication in the long run. I'll gladly take the safety and comfort of the indication over the insignificant reduction in battery life caused by emptying it fully once a month under light load.

And not allowing people to use more than 80% would be ridiculous. Imagine crashing your machine when you know you actually still had 20% left...

Just set the warning and automated higher if you believe it's useful.

I've done without fancy graphics for 20 years flying R/C and have never crashed due to depleted battery so I don't think I will need them now. A FAR more accurate way would be to give telemetry data monitored on mA used which has been around for years from the likes of Futaba, Tarranis and Spektrum. All of these systems use accurate current sensors which measure capacity taken from the pack (by cell if necessary) and do not require some daft battery cycling every so many days to calibrate them.

With regards to not allowing people to use more than 80% being ridiculous - what's the difference? People would never know the difference since 20% capacity in the battery would never be displayed as it would be indicated as zero. There is no difference to this analogy than what is available now when the battery reaches critical.
The Inspire would not fall out of the sky the same way as it doesn't now... it would auto land... slowly.

 

[Kilrah]

All of these systems use accurate current sensors which measure capacity taken from the pack (by cell if necessary) and do not require some daft battery cycling every so many days to calibrate them.

They actually do. If you don't do it you'll never know when your 5000mAh battery has aged, only has 4000mAh left and you should adjust your warning thresholds.

And even 4 identical packs will evolve differently. So much more convenient to have the management in each battery than having to maintain logs for each battery yourself.

 

[Kilrah]

There is no difference to this analogy than what is available now when the battery reaches critical.
The Inspire would not fall out of the sky the same way as it doesn't now... it would auto land... slowly.

And why is it better to have an auto land at 0 with 20% of "hidden" capacity than having auto land at 20% exactly?
If I want/need to use the last 20% at least I can.

 

[The Editor]

Because autolanding with 20% still in the battery means you do not run the risk of damaging the cells - which for a lot of R/C newbies will be important.

And I agree with you - which is why I have turned off all low voltage protections on my Naza based airframes - I want to be in control of getting my multirotor back to me and would rather sacrifice and pack than my aircraft.

My argument is simply towards the less educated flyers out there who do not know the best way to look after their packs and may think it is acceptable to maybe set their low battery warning at say 10% and their critical at 5%. Doing this will not do their packs any favours!

 

[jimcolyer]

In actual fact, the reverse is true. Not fully depleting the battery will actually *slightly* shorten its life.

Especially for lipo cells, complete cyclic charging helps to keep the battery in optimum condition, and if the cells are not fully cycled, they will deteriorate slightly faster.

The best way to do this is slowly, so use a constant current dummy load of a few amps, then recharge the cells, usually at a rate of c/10 (where c is the rating of the cell in amperes)

 

[The Editor]

In actual fact, the reverse is true. Not fully depleting the battery will actually *slightly* shorten its life.

Especially for lipo cells, complete cyclic charging helps to keep the battery in optimum condition, and if the cells are not fully cycled, they will deteriorate slightly faster.

The best way to do this is slowly, so use a constant current dummy load of a few amps, then recharge the cells, usually at a rate of c/10 (where c is the rating of the cell in amperes)

I would love to know where you sourced this information from since depleting a lipo in the way you suggest and taking it below 3 volts per cell will render it fit for nothing and will destroy it!
Furthermore the c rating has nothing to do with rating in amps of a cell. It is the multiple based on the pack capacity which may be drawn without damage (usually expressed as continuous and burst values)

 

[jimcolyer]

I work for one of the largest manufacturers of batteries in Europe

Correct, the minimum Limit of 3.2vpc should not be exceeded too often, but as 0% would still equate to be 3.7vpc (under no load) you can still drop to 10 or even 5% BATTERY PERCENTAGE assuming of course how these percentages are figured is accurate.

The c factor is indeed the capacity of the overall battery, not each cell, but as you cannot charge each cell individually, the method of restricting the charging regimes (constant current charging) still applies, and will certainly make the pack last much longer than using fast chargers or constant voltage chargers.




Sent from my iPhone using Tapatalk

 

[Kilrah]

I would love to know where you sourced this information from since depleting a lipo in the way you suggest and taking it below 3 volts per cell will render it fit for nothing and will destroy it!

He never said to go below 3V, he said "fully depleting". Which means lowest acceptable voltage / cell, i.e. 3.1-3.2.

The Inspire battery will shut itself down at about 3.1V/cell from my observations, so doing the recommended procedure is fine.

 

[pepeticos]

it will be nice if we can disable this option ... i will prefer ruin 1 lipo than landing over water for example.

 

[pepeticos]

Also DJI on the Inspire Tech Specs said aprox 18 min. flight time and i roughly get 12 !! that's a big difference ...

 

[AllanM]

Late at the party here, but the 10% autoland frightens me to death, just about all my flying is over water, I do come in at 25-30% as a rule, but the thought it may autoland a short way from land just simply kills.

Minimum height (with gear up) would be 'rather helpful' flying over water....