Battery Discharge < 10 days

[WithTheBirds]

I just did some more testing. Your math is correct but actually drawing 20w per hour is not realistic with modern phones and tablets. They don't charge (draw) at a constant rate and are often drawing much less. So in a real world test I used two fast charging devices, each at or below 20% battery level and it took two hours to get the M2 battery to 50%. Also, I have 4 M2 batteries so if I want to go for a flight and they are charged it isnt realistic to use phones to discharge them.

Your sample size is too small ‘-p

Seriously- while your playing with numbers have a think about this.

As you have mentioned it is well known that LiION chemistry does experience accelerated capacity loss with time if kept at a high state if charge. Some numbers from battery university indicate that at 100% SOC and 25deg C capacity loss after 12 months might be 20% (compared to 4% at 40% SOC). Lower temp will reduce these numbers and newer battery tech might have improved but let’s take them as a safe conservative reference for some simple maths.

Assume your pack will be good for 150 full charge cycles. It’s a fair number based on user experiences with the phantom drones and reasonable attention to battery care.

Let’s say twice a week you find yourself with a pack your concerned about leaving at 100% so you bring it down to 40% storage level. Over a 12 month period that is 62 charge cycles, over 40% or the pack life. This battery has 24% less available capacity than if you had not bothered to discharge it.

 

[WithTheBirds]

Controller discharge rate per C might not be as low as you suspect in a Mavic. Those batteries can't be that big and only last about 3 or 4 flights. So if they are only 1S, it's about matched per C to the M2 battery at 4S.

3 to 4 flights of say 25 mins, make it 87 mins runtime... That’s 7/10 C. The Mavic Is over 2C.

 

[WithTheBirds]

The DJI powerbank adapters are good, I would say too good to be able to quickly bring several flight batteries to storage voltage, the conversion to 5 volts is done with 90% efficiency. I mentioned it already ... There are devices specifically for the purpose of discharging batteries. Such devices generally cost less than a single DJI battery. In addition, only a matching charging cable with XT60 connector is needed, nothing more. Discharging devices such as the ISDT FD-100 or the SkyRC BD-200 are reliable and fast. Of course, both devices can be discharged to a predefined voltage. The automatic discharge of Mavic batteries already ends at 3.89V per single cell (3S-M1P 11.67V / 4S M2x 15.56V). That's 10mV above the recommended storage. Excitement for, probably because it's HV LiPo's. Anyway ... Who does not want to use a discharger, can empty the unused batteries at any time in his Mavic, because the high-tech wonders eat a lot of energy, even without a single flight minute ...

Internal fan or not- I wouldn’t recommend anyone to use a static Mavic to discharge batteries. The unnecessary heat soak can’t bode well for long term longevity of the electronics.

 

[mnis]

Internal fan or not- I wouldn’t recommend anyone to use a static Mavic to discharge batteries. The unnecessary heat soak can’t bode well for long term longevity of the electronics.

For occasional use, I think it is not critical, when a discharge of the battery in the Mavic takes place. I think it's definitely better than letting full flight batteries lie around for up to 10 days.

Approximately 20 watts (M2P) or 15 watts (M1P) must be sucked out. How long will the Mavics have to be on standby until 35 percent have been used up? I mean it's about 30 minutes per battery.

Not quite seriously meant: "If the operation in standby mode can already lead to a noticeable premature failure of a mavic, better nobody should worry about updating, configuring or flying."

Even if better cooling may be available during the flight under certain conditions, the devices must be designed to avoid abnormal overload / overheating in any conceivable operating situation (of course in the specification range).

 

[WithTheBirds]

For occasional use, I think it is not critical, when a discharge of the battery in the Mavic takes place. I think it's definitely better than letting full flight batteries lie around for up to 10 days.

Approximately 20 watts (M2P) or 15 watts (M1P) must be sucked out. How long will the Mavics have to be on standby until 35 percent have been used up? I mean it's about 30 minutes per battery.

Not quite seriously meant: "If the operation in standby mode can already lead to a noticeable premature failure of a mavic, better nobody should worry about updating, configuring or flying."

Even if better cooling may be available during the flight under certain conditions, the devices must be designed to avoid abnormal overload / overheating in any conceivable operating situation (of course in the specification range).

The Mavic can fly for 30min in a battery and you think 35% charge might be consumed sitting in the ground. No way.

 

[mnis]

The Mavic can fly for 30min in a battery and you think 35% charge might be consumed sitting in the ground. No way.

In relation to the M1P, 35% is about 15.3Wh ... Yes, I'm serious, I definitely think it's realistic that this Mavic can consume up to 0.44 watts per minute in idle. I was not sitting in front of my Mavic with the stopwatch at that time, and from my memory, so maybe a few minutes more than 35 have passed, but not 45 minutes and certainly not 60 minutes. For the other Mavics, it's much more of a guessing game for me.

 

[WithTheBirds]

In relation to the M1P, 35% is about 15.3Wh ... Yes, I'm serious, I definitely think it's realistic that this Mavic can consume up to 0.44 watts per minute in idle. I was not sitting in front of my Mavic with the stopwatch at that time, and from my memory, so maybe a few minutes more, but not 45 minutes and certainly not 60 minutes. For the other Mavics, it's much more of a guessing game for me.

Would appreciate you reporting back if you get an actual number. I am very curious. I won’t be trying it. I have felt how hot these things get idling. In spec or not it is unnecessary stress on the electronics.

Flying is the best way to wear you battery’s out.

 

[mnis]

Would appreciate you reporting back if you get an actual number. I am very curious. I won’t be trying it. I have felt how hot these things get idling. In spec or not it is unnecessary stress on the electronics.

Flying is the best way to wear you battery’s out.

You are right, only numbers and facts can convince. I'll catch it soon with a good battery, and report on it. You have already noticed it yourself, there is actually a lot of waste heat when idling. I think the whole system is running at full speed, and just because the engines are OFF, less energy is used on the ground. LoL

 

[WithTheBirds]

You are right, only numbers and facts can convince. I'll catch it soon with a good battery, and report on it. You have already noticed it yourself, there is actually a lot of waste heat when idling. I think the whole system is running at full speed, and just because the engines are OFF, less energy is used on the ground. LoL

You know if you had said you timed it I wouldn’t be suspicious. Surprised absolutely. Let’s see.

 

[mnis]

You know if you had said you timed it I wouldn’t be suspicious. Surprised absolutely. Let’s see.

I'll do it ... But it will take a few hours, not days, until I can take a test.

 

[WithTheBirds]

I'll do it ... But it will take a few hours, not days, until I can take a test.

No hurry.... I would think 30mins might be 25% max. The bulk of the power must be consumed by the propulsion system.

 

[mnis]

No hurry.... I would think 30mins might be 25% max. The bulk of the power must be consumed by the propulsion system.

It turns out that my claim was very far from the facts. I have to admit, I should make better notices.

Here are my results of discharging down to -35% of a M1P battery:
-16% after 30 minutes / -20% (35 minutes) / -30% (53 minutes) / -35% (62 minutes).
I tested it with a new and fully charged battery (3930mAh determined).

Sorry for the confusion I have given.

 

[WithTheBirds]

It turns out that my claim was very far from the facts. I have to admit, I should make better notices.

Here are my results of discharging down to -35% of a M1P battery:
-16% after 30 minutes / -20% (35 minutes) / -30% (53 minutes) / -35% (62 minutes).
I tested it with a new and fully charged battery (3930mAh determined).

Sorry for the confusion I have given.

Sorry? We all remember things wrong and observations play tricks with us- it’s the human condition.

Thank you for taking the time to test.

Seems the bottom line here is an average consumption of 15 watts.

It might be the USB power adapter takes a lot longer than my observations also.

I don’t bother now. When I’m expecting to fly at short notice I keep a couple of packs at full SOC, otherwise I just charge close to when I fly. It’s a compromise I can live with. Bringing them down is using valuable charge cycles anyway- perhaps even negating any benefit you are realising.

 

[mnis]

I really like to fly, but I rarely get there. And I'm trying as hard as I can to plan all my flights. I charge my batteries as possible in the morning before the scheduled flight. This saves charging cycles on the one hand, but on the other hand, it takes the opportunity to get started spontaneously.

Unfortunately, the weather is never predictable, and sometimes in the evening I have to bring full batteries to storage voltage. This is for me the opportunity to determine the available capacity of individual batteries. After about three cycles, only new batteries are checked once for actual capacity. Older batteries will only be checked again in case of abnormalities. Otherwise, I check once a month for all my battery packs, if the storage voltage is still within the recommended range.

I think for me, this is also a good way, or rather a good compromise, to avoid unnecessary battery charging cycles.

 

[mnis]

I should mention:
The M1P remote controller lost about -27% (80 to 53) of the displayed state of charge during the idle test (in 62 minutes). There was a connection to the Mavic, but no smartphone was connected.

In any case, after the test, I put my remote control back fully charged to be able to more accurately determine the displayed state of charge (loss) after 7 days.

 

[Gregdd]

Got this rig from Amazon. Pulls a solid 2 amps at 5 volts so sucks out 50% of a full battery much faster than using phones or tablets to discharge. The USB adapter that plugs into the battery gets pretty hot and the actual discharging units get very hot. The discharging units are switchable between 1 amp and 2 amp so if you don't like it getting so hot just run it at 1amp but obviously will take twice as long.

Just to clarify something somebody mentioned previously: I wouldn't discharge my batteries if I knew I was going to fly them within a week or so. Discharge/charge cycles also wear down the battery so I would only use this if you know they are going to be sitting around for a while.

 

[WithTheBirds]

Got this rig from Amazon. Pulls a solid 2 amps at 5 volts so sucks out 50% of a full battery much faster than using phones or tablets to discharge. The USB adapter that plugs into the battery gets pretty hot and the actual discharging units get very hot. The discharging units are switchable between 1 amp and 2 amp so if you don't like it getting so hot just run it at 1amp but obviously will take twice as long.

Just to clarify something somebody mentioned previously: I wouldn't discharge my batteries if I knew I was going to fly them within a week or so. Discharge/charge cycles also wear down the battery so I would only use this if you know they are going to be sitting around for a while.

For use if sitting around for a while? Worst case auto discharge commencement is 10 days so presumably a while must be less than 10 days?

There isn’t a lot of advantage to be gained here.

 

[Gregdd]

For use if sitting around for a while? Worst case auto discharge commencement is 10 days so presumably a while must be less than 10 days?

There isn’t a lot of advantage to be gained here.

Dude you must be a lawyer or something. OK I will spell it out for you. If I know the bird is going to sit for a while then I discharge them immediately.

EDIT: Please feel free not to comment on my posts in the future.

 

[mnis]

Dude you must be a lawyer or something. OK I will spell it out for you. If I know the bird is going to sit for a while then I discharge them immediately.

EDIT: Please feel free not to comment on my posts in the future.

Hehe, I think I have a similar opinion on the matter as @WithTheBirds, and have a lot to do with color in my job ... LoL ... There are generally only recommendations here, so feel free to do whatever you want with your things (anytime) ...

In other words, every full-charged day is a bad day for your lithium battery. And every hour near the discharge voltage is a bad hour for your lithium battery ...

 

[Gregdd]

Hehe, I think I have a similar opinion on the matter as @WithTheBirds, and have a lot to do with color in my job ... LoL ...

There are generally only recommendations here, so feel free to do whatever you want with your things (anytime) ...

Yes you are allowed to have your own opinion . I base my decisions on science and past history. Past history has shown that lipos shouldn't be left fully charged if not used (There is a lot of evidence for this if you care to research). Until someone shows me differently I will discharge if I don't plan on using the bird for a while. No use waiting 10 days in those cases. The rig i posted above is also very handy if you are about to board a plane and don't have time (or weather) to go fly all your batteries down. It would also be handy to perform the 3 month full discharge recharge as recommended by DJI.
I am not sure how much experience people have on this forum but the ability to discharge your batteries is important.