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Battery discharge time the longer the best?

NovicePilot

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Good day, pilots! I have an Evo. I have some doubts about the batteries since two appeared damaged without apparent reason. Batteries come with 6 days of time to discharge. What happens if days to discharge change for more or less days? For example, if it is changed to 3 days, battery's life is extended, time to recharge is shorten? Or vice-versa, if it is changed to 10 days? I do not understand what is the relation? Any tip for batteries care?

Thank you much!
 

herein2021

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Good day, pilots! I have an Evo. I have some doubts about the batteries since two appeared damaged without apparent reason. Batteries come with 6 days of time to discharge. What happens if days to discharge change for more or less days? For example, if it is changed to 3 days, battery's life is extended, time to recharge is shorten? Or vice-versa, if it is changed to 10 days? I do not understand what is the relation? Any tip for batteries care?

Thank you much!

I would just leave it at what they are set at from Autel, if they discharge too quickly it could shorten their life or they are more likely to be dead when you go to use them, and if they discharge too slowly they will also have a shorter life.

What is far more important is how you store them and what temps they are exposed to. I live in FL, so I go out of my way to try not to leave the batteries in my car one min longer than needed.
 

G_G

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Good day, pilots! I have an Evo. I have some doubts about the batteries since two appeared damaged without apparent reason. Batteries come with 6 days of time to discharge. What happens if days to discharge change for more or less days? For example, if it is changed to 3 days, battery's life is extended, time to recharge is shorten? Or vice-versa, if it is changed to 10 days? I do not understand what is the relation? Any tip for batteries care?

Thank you much!
Recognize that batteries are an item of consumption. No matter how you treat them, they will still outlast the useful life of the drone. If they don't, you are using the heck out of them, and can then justify replacing them, when their flight time deteriorates below what you find acceptable. Best tip for batteries is to use them! They are meant for flying, not for storage! Don't store them discharged, and let their discharge algorithm handle any discharge in storage. The more frequently you fly, the longer you should set the auto-discharge period. That way, they are always ready to fly at a moment’s notice.
 

herein2021

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Recognize that batteries are an item of consumption. No matter how you treat them, they will still outlast the useful life of the drone. If they don't, you are using the heck out of them, and can then justify replacing them, when their flight time deteriorates below what you find acceptable. Best tip for batteries is to use them! They are meant for flying, not for storage! Don't store them discharged, and let their discharge algorithm handle any discharge in storage. The more frequently you fly, the longer you should set the auto-discharge period. That way, they are always ready to fly at a moment’s notice.

I agree you should just use your batteries as you need to, but you should definitely not store them charged, LiPo batteries when used in drones have maybe 200 cycles if you are lucky and maybe 2yrs of service life and far less than that if you store them charged, that is why there is discharge circuitry. Pretty much any LiPo battery guide will tell you never store them fully charged such as the one here or here. I tend to store mine around 20% charged. Of course you also should not leave them discharged for too long either so you should use them at least once a month. With my EVO, I have 4 batteries so I make sure to use each one in rotation, in my drone case I use them from Left to Right and place the last one I used in the back of the line to the right to ensure to use all of them regularly.

I use my batteries as needed, but after a day of flying they should stay discharged until you need them again. When I know that I have a project the next day, I only charge the number of batteries that I will need for that project and I leave the batteries discharged after the project until the next one. Even with that much care my batteries last on avg 18months - 2yrs at which point they start swelling and become unusable.

Battery cycles are like miles on a car, you wouldn't unnecessarily drive your car an extra 1000 miles a month just because you felt like it.....that's the same thing you are doing to LiPo batteries when you store them charged, or recharge them after a day of flying even though you know you won't use them for another week.
 
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herein2021

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Herein2021, you absolutely right! It makes sense from to to bottom. I was doing exactly the other way, full charge to store and the charge again before flying. Thank you. Great tip!

I used to fly RC helicopters before drones were invented and when flying those you learn a lot about LiPo batteries, everything from what a balancing charger is to nominal cell voltage, to 1C - 6C, how much of a fire hazard they are, etc. You also learn how to manually discharge the individual cells for storage, signs of danger (swelling, low cell voltage, charging errors, etc.).

With modern drones everything is so much more user friendly (professional grade battery packaging, chargers, discharge circuitry, monitoring, etc.) but behind all of that fancy wrapping is still just LiPo 3C batteries and balancing chargers, and the same LiPo concepts apply.

Heat will always be your biggest enemy and living in FL, I do everything I can to keep them as cool as possible (short of storing them in the refrigerator)

Permanent-capacity-loss-versus-storage-conditions.png
 

G_G

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I used to fly RC helicopters before drones were invented and when flying those you learn a lot about LiPo batteries, everything from what a balancing charger is to nominal cell voltage, to 1C - 6C, how much of a fire hazard they are, etc. You also learn how to manually discharge the individual cells for storage, signs of danger (swelling, low cell voltage, charging errors, etc.).

With modern drones everything is so much more user friendly (professional grade battery packaging, chargers, discharge circuitry, monitoring, etc.) but behind all of that fancy wrapping is still just LiPo 3C batteries and balancing chargers, and the same LiPo concepts apply.

Heat will always be your biggest enemy and living in FL, I do everything I can to keep them as cool as possible (short of storing them in the refrigerator)

View attachment 14002
All due respect, but these smart batteries already are preprogrammed to self-discharge. They won't stay fully charged when unused, even if you want them to. Say what you will, but even topping off batteries continuously so they are always at 100%, ready to go for a spontaneous flight, no matter the consequences to battery life, is a price worth paying for, to not miss a unique opportunity, just because your batteries need to be fully charged first! It's about flying, not preserving batteries!
 

Detritalgeo

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To answer the initial question, the time to discharge setting is based on the operator needs. If you need the battery at full charge at any time and don't have time to top-up before flight then select a longer self-discharge interval.

In general, as stated above by others, keeping the batteries at full charge when not in active use is not ideal and will promote the development of micro-dentrites in the cell electrolytes which reduce effective capacity and may end-up contributing to the battery internally shorting in rare cases.

If you want your Lithium batteries to last a long time there are a few things you can do but not all are practical for drones.
  1. Charge to 80-90% max (4.1V or 4.2V for the HV cells) and never run the batteries down to the low-voltage cut-off, this will significantly extend the service life of the cells but obviously will reduce flight time per sortie. Most modern electric cars now only use 80-90% of the true capacity in order to do this.
  2. Never expose the cells to intense direct sunlight or high temperatures. Occasional exposure likely wont kill it but make sure the cells are in moderate climate for the majority of their lifetime. Fully charged batteries sitting the a hot car in the summer is a good way to increase the odds of cell failure and electrolyte degradation causing swelling.
  3. Store the batteries at around nominal voltage ~3.6V (50-75%) when not in use and charge them back-up to nominal voltage every 3 months of non-use.
Personally I never charge to 100% then wait for the BMS to discharge to storage voltage. This will only increase the cycle count. When I am done flying I try to keep watch on the charger and take them off at the 50-75% level. Some people fly every-day and in that case they keep the batteries always charged and ready but this is an industrial use case and should come with the expectation that the batteries are undergoing more wear and tear.

Happy flying
 
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herein2021

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All due respect, but these smart batteries already are preprogrammed to self-discharge. They won't stay fully charged when unused, even if you want them to. Say what you will, but even topping off batteries continuously so they are always at 100%, ready to go for a spontaneous flight, no matter the consequences to battery life, is a price worth paying for, to not miss a unique opportunity, just because your batteries need to be fully charged first! It's about flying, not preserving batteries!

IMO each user's use case is different. I fly commercially and due to the very limited (read non-existent) Autel support, and very limited shelf life of the batteries, I do not fly the EVO II at all for personal use. When put in that context, I never need to spontaneously grab the drone and go, the proposal and shot list requirements process as well as planning around the client's schedule and the weather takes on average 2-3 days at a minimum which gives me plenty of time to calculate how many batteries I need and to charge them.

From a business perspective, you always want to reduce OPEX where feasibly possible and this means maximizing the drone's battery life if at all possible. So, for my use cases it does not make sense to recharge them back to 100% wasting a charging cycle nor leaving them charged further shortening their life. But sure, if I was flying for personal use and frequently just wanted to grab and go then keeping them charged would make more sense.

Personally I never charge to 100% then wait for the BMS to discharge to storage voltage. This will only increase the cycle count. When I am done flying I try to keep watch on the charger and take them off at the 50-75% level. Some people fly every-day and in that case they keep the batteries always charged and ready but this is an industrial use case and should come with the expectation that the batteries are undergoing more wear and tear.

Happy flying

Great explanation, personally I keep mine around 20-30% charged because that is usually what I land with and I don't want to have to remember to take them off the charger at 40-50%. My biggest challenge is keeping them cool. A typical job for me is 2min of drone flying and many hours of filming with regular cameras; meanwhile the drone and its batteries are baking in the car at around 120+ degrees. That is why I try to limit the amount of batteries I charge and bring for a day of shooting.
 
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