Battery Discharge < 10 days

[SteveCA]

YMMV but my experience with Lipos, first with RC helicopters and later with RC cars and now with drones suggests that keeping them fully charged will cause early failure. Most consumer devices never see the rate of discharge that high powered RC aircraft see. I have LIPO packs that sustain 50c discharge rates (my 600 size helicopters). The Lipos in our drones dont see that high level but still relatively high compared to virtually any other consumer device.

You will see cell failures under high discharge rates that other devices would never experience. I've toasted thousands of dollars of LIPO's before learning to never keep them fully charged. Yes, it happens pretty fast with high discharge LIPO's ad I simply never keep my LIPO's fully charged for more that a day or two. With a 4 battery parallel charger, its no big deal to charge them before i fly. It only takes 25-30 minutes to get to 95% charge. It's the last 2-3% that takes forever to finish charging.

 

[WithTheBirds]

YMMV but my experience with Lipos, first with RC helicopters and later with RC cars and now with drones suggests that keeping them fully charged will cause early failure. Most consumer devices never see the rate of discharge that high powered RC aircraft see. I have LIPO packs that sustain 50c discharge rates (my 600 size helicopters). The Lipos in our drones dont see that high level but still relatively high compared to virtually any other consumer device.

You will see cell failures under high discharge rates that other devices would never experience. I've toasted thousands of dollars of LIPO's before learning to never keep them fully charged. Yes, it happens pretty fast with high discharge LIPO's ad I simply never keep my LIPO's fully charged for more that a day or two. With a 4 battery parallel charger, its no big deal to charge them before i fly. It only takes 25-30 minutes to get to 95% charge. It's the last 2-3% that takes forever to finish charging.

That’s it...... I’m in the camp of loosing big money on my first heli packs also. They would collapse and die almost immediately after launching.

 

[mnis]

LiPO is a LiION cell chemistry, it is the packaging style which differs (soft pouch vs rigid) . Yes, you can get higher C rating with most LiPO but this is largely because the pouch allows some expansion in use without problems.

The chemistry specific attributes for LiION and LiPO are shared including ageing characteristics.

Laptops and power banks use 18650 and other LiION cells as they are cheaper than LiION and the dimensions are consistent, guaranteed availability and wide choice if suppliers.

The ageing effect is partially loss of total capacity however of more relavence is the reduction in usable capacity, what you see as the remaining flight time depicted in the DJI GO app for example. This is what I was referring to in my earlier post and is simply determined by the battery ability to supply power under load.

Basically, I did not try to say anything else ... And I know that LiPo's are just a marginal variation of Li-ion's.

Nevertheless, both battery types require a different treatment regarding battery care. It would be too simple just to say that the main difference lies in the packaging, even more details such as the anodes and the electrolyte are divergent. The voltage level is also different, and so seemingly identical technologies are still not interchangeable.

Let 100 LiPo's and 100 Round Cells 18650/20700 ... be left lying around for a month fully charged, and you'll know what I mean. How much waste will you have of each variety in the end?

Just because LiPo's are fundamentally more problematic, DJI has not given any HV lipo an extended BMS without reason. This BMS not only monitors the voltage limits and balances the cell drift, it also brings the battery down automatically to storage voltage after a certain amount of time.

A similar functionality will also be available for the single cell batteries in the DJI RC remote controls. That's my assumption, anyway.

 

[WithTheBirds]

Basically, I did not try to say anything else ... And I know that LiPo's are just a marginal variation of Li-ion's.

Nevertheless, both battery types require a different treatment regarding battery care. It would be too simple just to say that the main difference lies in the packaging, even more details such as the anodes and the electrolyte are divergent. The voltage level is also different, and so seemingly identical technologies are still not interchangeable.

Let 100 LiPo's and 100 Round Cells 18650/20700 ... be left lying around for a month fully charged, and you'll know what I mean. How much waste will you have of each variety in the end?

Just because LiPo's are fundamentally more problematic, DJI has not given any HV lipo an extended BMS without reason. This BMS not only monitors the voltage limits and balances the cell drift, it also brings the battery down automatically to storage voltage after a certain amount of time.

A similar functionality will also be available for the single cell batteries in the DJI RC remote controls. That's my assumption, anyway.

The 18650’s and others do suffer the same aging effects. While there are differences for the purpose of considering performance characteristics there aren’t significant differences. Higher charge density (less weight) and C ratings make LiPO the winner for sUAS for obvious reasons.

The DJI remotes don’t have auto discharge, at least not to date, and would not benefit from it. You could take a pack that was beyond flyable and the cells would still provide good service powering a controller.

 

[ff22]

YMMV but my experience with Lipos, first with RC helicopters and later with RC cars and now with drones suggests that keeping them fully charged will cause early failure. Most consumer devices never see the rate of discharge that high powered RC aircraft see. I have LIPO packs that sustain 50c discharge rates (my 600 size helicopters). The Lipos in our drones dont see that high level but still relatively high compared to virtually any other consumer device.

You will see cell failures under high discharge rates that other devices would never experience. I've toasted thousands of dollars of LIPO's before learning to never keep them fully charged. Yes, it happens pretty fast with high discharge LIPO's ad I simply never keep my LIPO's fully charged for more that a day or two. With a 4 battery parallel charger, its no big deal to charge them before i fly. It only takes 25-30 minutes to get to 95% charge. It's the last 2-3% that takes forever to finish charging.

Can I ask which 4-battery parallel charger are you using? I've seen some users complaining about early failures or running too hot. I charge these things in my home and not necessarily on a concrete non-combustible surface.

 

[SteveCA]

Can I ask which 4-battery parallel charger are you using? I've seen some users complaining about early failures or running too hot. I charge these things in my home and not necessarily on a concrete non-combustible surface.

I have the fstopper charger and it works well. It charges to around 4.35 volts so a tad under full, which isn’t a bad thing unless you are trying to squeeze every last bit out of a hyperlapse.

 

[SteveCA]

If you want to learn about best practices in Lithium battery management, google tesla battery management. Tesla batteries are never charged to 100% for a very good reason. Their battery warranty is 8 years so it has to last.

When I say never, I mean never unless Tesla issues a one time over the air update that allows 100% charging, which was done in advance of one of the huge hurricanes last year, and only to those in the affected areas.

 

[mnis]

The 18650’s and others do suffer the same aging effects. While there are differences for the purpose of considering performance characteristics there aren’t significant differences. Higher charge density (less weight) and C ratings make LiPO the winner for sUAS for obvious reasons.

The DJI remotes don’t have auto discharge, at least not to date, and would not benefit from it. You could take a pack that was beyond flyable and the cells would still provide good service powering a controller.

You may be right in saying that the RC remote controls for DJi quadcopters have no auto-discharge function, as we know it from the intelligent DJI flight batteries.

But sorry, otherwise your claim is nonsense or at least inconclusive. Of course, I can not completely rule out having a faulty remote control, which I think is very unlikely, as it still has enough power for many flights after charging.

I've found that my remote control loses about 0.5 percent per day of charge when stored immediately after charging. And so I know since May 2017 with this device. It goes far beyond a few micro-amps, which (according to your statement) would be required for a pure standby circuit, which should monitor only the power button on actuation.

In my case (M1P-Remote) about 15mAh are lost per day, which would be an unusually high self-discharge rate for LiPo's. It is most likely calculated by the manufacturer that the remote control consumes significantly more energy in standby than would be expected to avoid a long-lasting full condition.

It's similar to millions of smart phone lithium batteries, because they only last a surprisingly long time for one reason: The user usually makes sure that the battery full or empty state is never long.

 

[WithTheBirds]

You may be right in saying that the RC remote controls for DJi quadcopters have no auto-discharge function, as we know it from the intelligent DJI flight batteries.

But sorry, otherwise your claim is nonsense or at least inconclusive. Of course, I can not completely rule out having a faulty remote control, which I think is very unlikely, as it still has enough power for many flights after charging.

I've found that my remote control loses about 0.5 percent per day of charge when stored immediately after charging. And so I know since May 2017 with this device. It goes far beyond a few micro-amps, which (according to your statement) would be required for a pure standby circuit, which should monitor only the power button on actuation.

In my case (M1P-Remote) about 15mAh are lost per day, which would be an unusually high self-discharge rate for LiPo's. It is most likely calculated by the manufacturer that the remote control consumes significantly more energy in standby than would be expected to avoid a long-lasting full condition.

It's similar to millions of smart phone lithium batteries, because they only last a surprisingly long time for one reason: The user usually makes sure that the battery full or empty state is never long.

What might you have in mind for a standby circuit? The power switch doesn’t need to consume anything in standby- it is a momentary on switch which closes a circuit between the battery B+ terminal and a sense pin on the micro controller. Yes the micro controller is constantly running monitoring the pack conditions in the background and is consuming power, as said that is in the uA range, probably closer to 100 uA than 200.

I’m not sure how much you know about LiION chemistry- the self discharge effect is real. It can approach 5% in the first 24 hours from full SOC and be as high as 3 % per day (decreasing as terminal voltage reduces with 2%/month being typical). Every increase if 10 degC in your storage temperature will roughly double these self discharge rates. You can add 3%/month for the battery monitoring and protection circuitry.

I am sorry to disabuse you of your notion but the reason mobile phone batteries last so long is because the discharge rate in use is comparatively low. If it runs for 10 hours that a 1/10C discharge rate. Compare that to your Mavic which is around 3C- that is 30 times the current demand. The higher the current demand on a cell the larger the impact of increased internal resistance. As I said earlier- a battery that is past being serviceable for a flight battery can still perform perfectly in powering a remote or other low lower application.

 

[mavicn00b]

The way I manage my batteries is with the use of a after market parallel charger. I typically store them 50-60% when not in use.

When I intend to fly, I will charge them up (~1hr or so), fly the pack down to about 20-30%. Let the pack cool down as soon as the quad lands, change batteries etc. Once at room temp, charge it back to 50-60% (set a timer for ~25mins on those generic blue chargers) until I intend on flying again, if its within the same day or next day, then just charge it up in the morning. There is also a RC Geeks charger which offers a storage mode switch but its a little on the slower side @ 2A. Not really an issue if you have a few batteries or plan ahead though. With the batteries retailing as high as they are, it pays to be more vigilant with their care unless you like giving DJI you hard earned money.




You can find this charger in the usual places, amazon, ebay etc for about $40-50.

 

[Dingo]

The RC remote controls from DJI actually have an automatic discharge function for the integrated LiPo's, only the discharge happens much slower. About -1% per day battery charge is usually lost.

Here, the standby circuit, which continuously polls the power button, ensures a low but sufficient discharge rate. It is important in my opinion that always a few electrons must flow to avoid too fast battery aging. Another circuit will be integrated to prevent over-discharge.

I noticed my mavic pro RC controller loses 1% battery per day when not being used, so this is normal??

 

[WithTheBirds]

I noticed my mavic pro RC controller loses 1% battery per day when not being used, so this is normal??

It is certainly within the realms of what might be expected.

 

[Boricua67]

What is the desired storage level?

You can always just hover the drone down to the desired storage level whenever you want.

 

[Gregdd]

I asked DJI support several times in a chat and on the Facebook page regarding the 10-day mandatory discharge time. They said that they're engineers had determined that 10 days is sufficient. I said that we should have the option to preserve our lipos even if they think otherwise. I also said that if we are going on a plane that we would like to discharger battery sooner than 10 days so that they are not fully charged when flying. The one support agent on Facebook did acknowledge that to be an issue and said he would suggest it to the engineers.

 

[mavicn00b]

10 days

Fimi, the manufacturer of the Mi drone have autodischarge set to 12 hours on their batteries. A bit over the top I'll admit but at least they are mindful of the issue of fully charged batteries and premature failure, much better than 10 days.

 

[WithTheBirds]

I asked DJI support several times in a chat and on the Facebook page regarding the 10-day mandatory discharge time. They said that they're engineers had determined that 10 days is sufficient. I said that we should have the option to preserve our lipos even if they think otherwise. I also said that if we are going on a plane that we would like to discharger battery sooner than 10 days so that they are not fully charged when flying. The one support agent on Facebook did acknowledge that to be an issue and said he would suggest it to the engineers.

A great option to knock the top off any lipos you find yourself with is the DJI battery-USB power adapter. Use it to load up your controller and any other devices that need USB charge/power.

 

[mnis]

What might you have in mind for a standby circuit? The power switch doesn’t need to consume anything in standby- it is a momentary on switch which closes a circuit between the battery B+ terminal and a sense pin on the micro controller. Yes the micro controller is constantly running monitoring the pack conditions in the background and is consuming power, as said that is in the uA range, probably closer to 100 uA than 200.

I’m not sure how much you know about LiION chemistry- the self discharge effect is real. It can approach 5% in the first 24 hours from full SOC and be as high as 3 % per day (decreasing as terminal voltage reduces with 2%/month being typical). Every increase if 10 degC in your storage temperature will roughly double these self discharge rates. You can add 3%/month for the battery monitoring and protection circuitry.

I am sorry to disabuse you of your notion but the reason mobile phone batteries last so long is because the discharge rate in use is comparatively low. If it runs for 10 hours that a 1/10C discharge rate. Compare that to your Mavic which is around 3C- that is 30 times the current demand. The higher the current demand on a cell the larger the impact of increased internal resistance. As I said earlier- a battery that is past being serviceable for a flight battery can still perform perfectly in powering a remote or other low lower application.

Yeah, I honestly don't know which donkey I sat on so I thought wrong about standby circuits. Probably I had thought of something with IR sensor. But clearly, with the power button on the remote control of the M1P, only one circuit is closed to activate.

Obviously, I do not know enough about battery chemistry. I have to admit that I'm not an expert in this field.

Nevertheless, I already know enough about the energy consumption of smartphones and other small devices. In this category, there is hardly a device that requires more than 1C of the battery used there. Yes, none of this is comparable to the required C rates of a Mavic. For example, the M1P requires between 1.6 and 2.3 watts per minute of flight time.

Thank you very much for taking the time to clarify things.

Nevertheless, the high self-discharge of my remote control continues to be a mystery to me, because I tried again to look back a little more precisely:

There were -40 percent within 4 to 6 weeks. The room temperature was between 19.5 and 20.5 degrees Celsius. The typical self-discharge rate of rechargeable lithium batteries is around 4 to 5 percent per month. So it is calculated generously -5% immediately after the full charge. -4.5% for the BMS. And -7.5% self-discharge.

Thus, less than 20% capacity loss over the specified period would be expected.

 

[WithTheBirds]

Yeah, I honestly don't know which donkey I sat on so I thought wrong about standby circuits. Probably I had thought of something with IR sensor. But clearly, with the power button on the remote control of the M1P, only one circuit is closed to activate.

Obviously, I do not know enough about battery chemistry. I have to admit that I'm not an expert in this field.

Nevertheless, I already know enough about the energy consumption of smartphones and other small devices. In this category, there is hardly a device that requires more than 1C of the battery used there. Yes, none of this is comparable to the required C rates of a Mavic. For example, the M1P requires between 1.6 and 2.3 watts per minute of flight time.

Thank you very much for taking the time to clarify things.

Nevertheless, the high self-discharge of my remote control continues to be a mystery to me, because I tried again to look back a little more precisely:

There were -40 percent within 4 to 6 weeks. The room temperature was between 19.5 and 20.5 degrees Celsius. The typical self-discharge rate of rechargeable lithium batteries is around 4 to 5 percent per month. So it is calculated generously -5% immediately after the full charge. -4.5% for the BMS. And -7.5% self-discharge.

Thus, less than 20% capacity loss over the specified period would be expected.

It’s a strange sort of nonesense this battery business eh....

Almost everything I learnt about LiPOs was the hard way and at significant cost. I destroyed plenty not having a clue how to treat them, mostly by leaving at full charge closely followed by over discharge (that’s the quickest way to puff them and permanently destroy them). That’s also where I learnt that a pack that might not even get a big rc heli off the ground for more than 20 seconds was still fine for other low current draw applications.

Given the 43.6wh rating of the flight pack for a 30min flight taking the battery to 0% in the GO app (optimistic) the average power consumption would be 87.2W (127mah/minute). Most importantly the C rate would be 2 (average). Higher obviously during increased load conditions.

It definitely seems you might have a higher than might be expected self discharge with your controller. I’m going to charge mine and watch it. I never have but haven’t been suspicious about it.

 

[mnis]

I noticed my mavic pro RC controller loses 1% battery per day when not being used, so this is normal??

According to my current assumption, -1% per day is unusual. It is immediately after the charging process, ie after 1 to 2 days, with max. -3% expected. But during the following days it should be significantly less.

I rarely fly, so I have to keep track of all my batteries as best I can. I check the battery charge levels about once a month. And if possible, I do not rely solely on integrated status LEDs.

That I stored the RC remote control fully charged was unintentional a mishap. It would be interesting to know if other Mavic pilots have already found similar inconsistencies ...

 

[mnis]

It’s a strange sort of nonesense this battery business eh....

Almost everything I learnt about LiPOs was the hard way and at significant cost. I destroyed plenty not having a clue how to treat them, mostly by leaving at full charge closely followed by over discharge (that’s the quickest way to puff them and permanently destroy them). That’s also where I learnt that a pack that might not even get a big rc heli off the ground for more than 20 seconds was still fine for other low current draw applications.

Given the 43.6wh rating of the flight pack for a 30min flight taking the battery to 0% in the GO app (optimistic) the average power consumption would be 87.2W (127mah/minute). Most importantly the C rate would be 2 (average). Higher obviously during increased load conditions.

It definitely seems you might have a higher than might be expected self discharge with your controller. I’m going to charge mine and watch it. I never have but haven’t been suspicious about it.

You addressed it:
An aged battery that does not have enough power for high current purposes can still do a good job for less performance critical applications. Absolutely, I think so too.

In February 2019, my five original M1P batteries would be two years old.
According to current measurements, the weakest battery still has 3697mAh (measured with -1 amp load).

At a 1C discharge rate, I still get good 3560mAh).


I believe measurements of the internal resistance of the entire battery pack make little sense, and the resistances of the three individual cells can not be determined without destroying the battery case. So I think, it remains for me as the only way to determine the health of these batteries by means of simulated load. On the basis of the determined capacity I can calculate at least a theoretic time of flight.

So the question remains: When is it recommended to use these batteries NO longer for flights with the Mavic?
Right now, I tend to the point where I only get 75% of the original indicated capacity.

Because of the possible PC connection I prefer to use the SkyRC BD200 and a Mavic charging cable with XT60 connection for capacity tests. Alternatively I use the ISDT FD-100 together with a Turnigy 2in1 PowerMeter.

So then, if the battery pack falls below the mentioned 75%, but otherwise is still in good condition, I would consider a non-critical application.

What do you think about it?

For another use, you mentioned the DJI USB PowerBank adapter. By the way, it's a very good thing with almost 90% efficiency. Again, I agree. However, I would not leave an aged DJI battery pack lying around in a fully charged state for many days. I think such old battery packs may even be better suited for small RC models, such as vehicles or boats. Also, I see an excellent opportunity to use tools such as a TS-100 soldering iron with it.

In any case, these so-called intelligent batteries are relatively safe to handle in any alternative use. Battery, BMS and charging electronics in a compact housing. Since it would be almost a shame to think of a quick disposal.

Finally, I would like to say that in the past I had less bad luck with RC batteries. But that's more because I only use a few RC batteries for boats myself, and most of the time I build these battery packs myself. More and more often I build battery packs in the desired configuration for a variety of applications. My biggest and most recent project for a friend: 4s8p (32x Samsung INR18650-35E / LiNiCoAI02 / 1825g / Max. 408.96Wh). A true monster package for me. He wants to realize a mobile Mavic battery charging case near 3 kilograms total weight. I gave my 2 cents for this thing, and for about 8 complete recharges this package should certainly be enough.