DJI Batteries and Cold Weather . . .

[Thomas B]

So much informative thread. Thanks for this!

Welcome to the forum from the deserts of Arizona! Enjoy

 

[TnDronePilot]

I really do trust a guy who's profile photo is him flying an RC heli inverted.? I trained on a RC heli simulator for 4 months before crashing mine in real life 30 seconds into flight.

 

[BigAl07]

I really do trust a guy who's profile photo is him flying an RC heli inverted.? I trained on a RC heli simulator for 4 months before crashing mine in real life 30 seconds into flight.

While I fully respect Mike's position, many of us have flown R/C for years but that doesn't really compare to the technical R&D experience and such that comes with the name Ken Booth who was involved in the actual design of many series of DJI batteries. I mean that should care a boat load of weight and respect.

 

[colnago]

nice infos thx

 

[realvue]

Great post. Very useful information.

 

[Avesraggiana]

I've been breaking one of these rules from Day One - charging every battery I have to 100%, and keeping it charged at that state for months on end. I don't to fly anywhere nearly as much as I'd like. Too late now, but at least now I know.

Thank you for your very important pointers.

 

[justcruisin]

I wonder if battery myths will become as powerful as oil brand myths (conventional vs synthetic, how often to change your oil, etc) ?

 

[judell]

How do I drain the batter on my mini controller?
I can drain the battery on the mini by just plugging it into my phone but not sure how to do that on the controller
Thanks
BTW awesome article!

 

[TTP]

Take the opportunity to ask in this thread where real battery experts are involved.

Need to buy more batteries for my M2P, and then comes the question:

How long can you accept that the battery has been in stock at the battery dealer to first charge and flight?

3 months, 6 months or 12 months?

And what does this mean for battery life, does it have any practical significance for me, in other words, will I get fewer charges from a battery that was 12 months from manufacture before use than a battery that was only 3 months?

 

[spudster]

What is needed is for one of the RC battery charger companies to come up with an adaptor that can be used with the DJI batteries to charge, cycle and grade them. You then then track their health, check for bad cells and how much capacity they have lost. Many are able to interface with a computer to record all phases of the charge and discharge profile of each individual cell within a pack. These types of systems are widely available for RC cars and planes.

While this one is a bit overkill for drone battery use it gives an idea of what is possible.

Tenergy T180 100W Balance charger with touch screen, metal housing

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[spudster]

large scale 30 kw systems for RV's,

Do these systems in RVs and Cars use LiPo cells or something like Lithium Ion / Iron or even LiFePO4 cells?

 

[Barbara]

Good read, thanks.

 

[Cookaboorra]

Having operated drones since 2012, I’m very conscious of battery health & am used to cycling batteries like for the I1P. Ken didn’t mention keeping the terminals clean which also seems quite important.
Also I have noticed that drones always draw down on one cell more than others during high demand, even with healthy batteries. It does recover quickly & the logs show the voltage being reduced fairly evenly overall. Not just on the M2P but also on the I1P & with different batteries. This used to bother me but it seems to be pretty normal. I would have liked Ken’s opinion on this. Thank you for recycling this article, very helpful for one living in Quebec. BTW another way to keep batteries warm is to stuff them into yr trouser pockets.

Yes, I noticed that, too. I wondered if it was normal or subjected to some eventuality.. after three or four cycles evrything has always returned right.

 

[PAI1]

Some of you may know Ken Booth who was originally active with DJI and very involved in their Battery Design. :

(the below is 100% from Ken Booth)
"First please look at the attached image, this should really explain all you need to know on how cold effects capacity. Once you understand this, most of the other pieces come together.

Now that we understand what cold does to capacity let us talk about overall discharge.

Most of us know that C is based on overall capacity, so if your capacity goes down, so will your C rating. Unfortunately, DJI does not use batteries that have much overhead, this is mostly due to keep the weight down at a certain price point. So, when we start to pull from this cold battery a few things can happen. If the pack has not been preheated, it will start to preheat itself. You are probably asking; well if that’s the case, why do I have to worry about preheating?

Well, if the battery is too cold and C rating has been affected, it will not be able to supply enough output (required C), going over its current C rating due to loss of capacity. This starts heating the pack up rapidly. Which in turn makes the pack quickly go past normal operating temperatures, which will also decrease output. This will cause immediate damage and more than likely a cell failure under extreme conditions. This is called thermal runaway.

The next thing that can happen is part of the smart logic and safety features of these packs. Since the cold does affect overall capacity, this could kick the overcharge protection in and start a self-discharge of the pack(s). In theory this is good and prevents possible damage or even a fire but can also play with the SOC (state of charge) that calculates the current charge state. While the logic is pretty darn good its not perfect. The percentage could be off as much as 20-30%. The same goes for an automatic timed self-discharge, you NEVER want to fly a pack that has been allowed to self-discharge. I would also highly advise to never fly ANY partially discharged pack unless that pack has been used that same day.

So, what can we do to help or minimize these issues?

Preheat packs in cooler weather. I would say anything below 55F you should start paying attention. One easy way to keep packs nice and warm in colder weather is dry rice and an ice chest / bag. Take a few pounds of dry rice (this depends on how big of a cooler you have) and place the rice in a large zip-lock bag(s). Microwave the rice for about 5-10mins or until very hot. Place the rice in the cooler. This should keep packs warm for most of the day. I prefer this method since the rice is reusable and does help with small amounts of moisture as well.

DO NOT Keep full pack charged for more than 24, 48 hours MAX! Any type of lipo does not like to be kept fully charge for a long period. This is not just for smart packs, any lipo will degrade over time if kept in a full charge state. Signs of this can be shorter flight times and possibly puffing (gassing) in extreme cases.

DO NOT over discharge your packs. Anything past 20%, consider it a reserve. If you commonly go past this 20% mark you will shorten you packs life. This is extremely important during extreme temps, both hot and cold weather.

DO NOT expect the same performance. In cold weather, even after preheating. Some craft keep packs warmer than others. Be easy on the packs, especially at the start of the flight, even after preheating.

Stop and hover. This is important for ANY time of year and should be included in you SOP. When you first take off, stop and hover for at least a minute. Even prior to a mapping run, take off and hover for a minute before the start of a mission. It is worth that 1 or 2mins less of mission time. Check all controls and watch the behavior of the craft. If you start to see drifting or any odd behavior, that is your clue to land and diagnose the issues. You would be surprised at how many logs of failures I have seen and the first thing the operator does is a punch out. This is probably the worst thing you can do with these types of craft. When these craft are not well, they usually show signs at the begging of flight. I simple hover with some minor control inputs can do wonders at showing a healthy or sick craft. This also allows the internals of the craft and packs to start warming up properly.

Check voltages and balances in the app and not percentages. Always have voltage options turned on. This is something to check when you are doing the hover and control test at the start of flight. Open the battery menu and check each cell, make sure everything looks good. Make sure you do not see any cells dropping rapidly and or voltage issues.

Voltages. A freshly charged pack should be around 4.2-4.3v per cell. A clue to a bad SOC is a percentage showing 99-100% but a much lower voltage. Once again, during that initial hover period check the cell voltages or overall voltage. If you see something like 3.9v at 99-100% charge, that pack either has a SOC issue or the pack is not healthy. If you do see any anomalies, do not risk it! Land and swap the packs.

Maintenance. With smart packs there’s only a few basic maintenance items you must be aware of. For older packs such as the p4 pack I would still recommend bringing these packs down below 10% every 20-30 flight or after long periods of storage. When you go past 20% make sure you are not flying hard and only hovering at a low altitude. The key here is to drain the pack as slow and gently as possible. What this does is perform something like a soft reset (calibration) on the SOC counter. Now if you are constantly using packs and not abusing them, you more than likely do not have to worry about a calibration. But remember long period of storage might require this to get the battery back to calculating accurately. After long storage periods its always best practice to monitor the pack during the initial flight. I know I am **** but if a pack has sat more than 3 months, I fully charge and then hover for the entire flight down to 20%. During this flight I am constantly monitoring the packs performance via the battery window. If the pack is not well this will usually show signs, especially voltages and balance issues.

Newer packs such as the m2 and enterprise models should not require this and most issues we see are due to storage charge and temperatures. With that being said, there are times a good battery calibration can bring back unhealthy packs in these new generation smart batteries.

I know I have probably missed some stuff, but it is simple. Keep packs above 60F in cold weather, not push them hard, do not keep batteries fully charged for long periods of time and do not store while fully charged in cold conditions.

I know for first responders, a lot of this is hard to do but you must develop a battery maintenance schedule. Batteries still need to be cycled. I would suggest at least twice a week down to 50% if kept at full levels.

One more thing, please know that warm weather works in a very similar way. You do not want packs starting off too warm. Try to keep packs below 90F prior to flight. Also, the same with storage, never store fully charged packs in extreme temperatures.

I have tried my best to not get too technical and put it laymen terms as best as I could."
(all credit goes to Ken Booth)

View attachment 123882

Excellent post!

 

[danae]

I've noticed that Grepow has a YTB channel called Battery Monday, one of the videos describes the low temperature affects the battery. The link is https://www.youtube.com/watch?v=trFZrNzC5Nk .

 

[danae]

Low temperatures can affect batteries in several ways:

• Chemical Reaction Rate​

• Battery Resistance​

• Discharge Capacity​

• Others​

Article source: Grepow Blog:

Why does low temperature affect the battery? | Battery Monday​

 

[Mave76]

Some of you may know Ken Booth who was originally active with DJI and very involved in their Battery Design. :

(the below is 100% from Ken Booth)
"First please look at the attached image, this should really explain all you need to know on how cold effects capacity. Once you understand this, most of the other pieces come together.

Now that we understand what cold does to capacity let us talk about overall discharge.

Most of us know that C is based on overall capacity, so if your capacity goes down, so will your C rating. Unfortunately, DJI does not use batteries that have much overhead, this is mostly due to keep the weight down at a certain price point. So, when we start to pull from this cold battery a few things can happen. If the pack has not been preheated, it will start to preheat itself. You are probably asking; well if that’s the case, why do I have to worry about preheating?

Well, if the battery is too cold and C rating has been affected, it will not be able to supply enough output (required C), going over its current C rating due to loss of capacity. This starts heating the pack up rapidly. Which in turn makes the pack quickly go past normal operating temperatures, which will also decrease output. This will cause immediate damage and more than likely a cell failure under extreme conditions. This is called thermal runaway.

The next thing that can happen is part of the smart logic and safety features of these packs. Since the cold does affect overall capacity, this could kick the overcharge protection in and start a self-discharge of the pack(s). In theory this is good and prevents possible damage or even a fire but can also play with the SOC (state of charge) that calculates the current charge state. While the logic is pretty darn good its not perfect. The percentage could be off as much as 20-30%. The same goes for an automatic timed self-discharge, you NEVER want to fly a pack that has been allowed to self-discharge. I would also highly advise to never fly ANY partially discharged pack unless that pack has been used that same day.

So, what can we do to help or minimize these issues?

Preheat packs in cooler weather. I would say anything below 55F you should start paying attention. One easy way to keep packs nice and warm in colder weather is dry rice and an ice chest / bag. Take a few pounds of dry rice (this depends on how big of a cooler you have) and place the rice in a large zip-lock bag(s). Microwave the rice for about 5-10mins or until very hot. Place the rice in the cooler. This should keep packs warm for most of the day. I prefer this method since the rice is reusable and does help with small amounts of moisture as well.

DO NOT Keep full pack charged for more than 24, 48 hours MAX! Any type of lipo does not like to be kept fully charge for a long period. This is not just for smart packs, any lipo will degrade over time if kept in a full charge state. Signs of this can be shorter flight times and possibly puffing (gassing) in extreme cases.

DO NOT over discharge your packs. Anything past 20%, consider it a reserve. If you commonly go past this 20% mark you will shorten you packs life. This is extremely important during extreme temps, both hot and cold weather.

DO NOT expect the same performance. In cold weather, even after preheating. Some craft keep packs warmer than others. Be easy on the packs, especially at the start of the flight, even after preheating.

Stop and hover. This is important for ANY time of year and should be included in you SOP. When you first take off, stop and hover for at least a minute. Even prior to a mapping run, take off and hover for a minute before the start of a mission. It is worth that 1 or 2mins less of mission time. Check all controls and watch the behavior of the craft. If you start to see drifting or any odd behavior, that is your clue to land and diagnose the issues. You would be surprised at how many logs of failures I have seen and the first thing the operator does is a punch out. This is probably the worst thing you can do with these types of craft. When these craft are not well, they usually show signs at the begging of flight. I simple hover with some minor control inputs can do wonders at showing a healthy or sick craft. This also allows the internals of the craft and packs to start warming up properly.

Check voltages and balances in the app and not percentages. Always have voltage options turned on. This is something to check when you are doing the hover and control test at the start of flight. Open the battery menu and check each cell, make sure everything looks good. Make sure you do not see any cells dropping rapidly and or voltage issues.

Voltages. A freshly charged pack should be around 4.2-4.3v per cell. A clue to a bad SOC is a percentage showing 99-100% but a much lower voltage. Once again, during that initial hover period check the cell voltages or overall voltage. If you see something like 3.9v at 99-100% charge, that pack either has a SOC issue or the pack is not healthy. If you do see any anomalies, do not risk it! Land and swap the packs.

Maintenance. With smart packs there’s only a few basic maintenance items you must be aware of. For older packs such as the p4 pack I would still recommend bringing these packs down below 10% every 20-30 flight or after long periods of storage. When you go past 20% make sure you are not flying hard and only hovering at a low altitude. The key here is to drain the pack as slow and gently as possible. What this does is perform something like a soft reset (calibration) on the SOC counter. Now if you are constantly using packs and not abusing them, you more than likely do not have to worry about a calibration. But remember long period of storage might require this to get the battery back to calculating accurately. After long storage periods its always best practice to monitor the pack during the initial flight. I know I am **** but if a pack has sat more than 3 months, I fully charge and then hover for the entire flight down to 20%. During this flight I am constantly monitoring the packs performance via the battery window. If the pack is not well this will usually show signs, especially voltages and balance issues.

Newer packs such as the m2 and enterprise models should not require this and most issues we see are due to storage charge and temperatures. With that being said, there are times a good battery calibration can bring back unhealthy packs in these new generation smart batteries.

I know I have probably missed some stuff, but it is simple. Keep packs above 60F in cold weather, not push them hard, do not keep batteries fully charged for long periods of time and do not store while fully charged in cold conditions.

I know for first responders, a lot of this is hard to do but you must develop a battery maintenance schedule. Batteries still need to be cycled. I would suggest at least twice a week down to 50% if kept at full levels.

One more thing, please know that warm weather works in a very similar way. You do not want packs starting off too warm. Try to keep packs below 90F prior to flight. Also, the same with storage, never store fully charged packs in extreme temperatures.

I have tried my best to not get too technical and put it laymen terms as best as I could."
(all credit goes to Ken Booth)

View attachment 123882

 

[Mave76]

So again you use your own experiences in order to claim that nothing will or can happen with LiPo batteries ... furthermore no one have claimed that the problem consists of batteries getting over or under charged.

LiPo batteries don't last forever ... it's as simple as that. The internal resistance increases due to a number of reasons which will regulate how prone they are for voltage drops. If cells goes under 3v they becomes unstable & the chemistry inside breaks down which again increases the internal resistance. At 3,7v a LiPo cell is most stable & can be long term stored without to much degradation of the chemistry.

And as you yourself have said earlier ... LiPo batteries are less effective when cold, meaning they have an increased internal resistance. This make them more sensitive for higher sustained amp draw ... & if a DJI battery is pushed in a condition like that, cells can fail & fall under 3v which leads to a immediate forced auto landing.

Below is facts from a recent flight log from a Mavic 2 Pro flown hard in sub freezing temperatures ... cell 3 failed & dropped below 2,5v (yellow graph) & the craft started to land. The pilot managed to negotiate the craft to a safer landing spot on the side of a road & salvaged it.

In the cutout from the log event stream pasted into the chart below ... you can read about what DJI thinks of the situation.

(click on the chart to make it larger)

Hi BigAl07 - did you mean to check DJI "I Fly app" for the battery condition. Thanks.

 

[Me262]

What is the best charge to keep batteries at? I generally keep my batteries discharged (after a flight) and only charge them when I'm almost sure I will be flying current day or next day. That means my batteries are somewhere between 15-30%, depending when I land my drone. Is that ok?

 

[slup]

What is the best charge to keep batteries at? I generally keep my batteries discharged (after a flight) and only charge them when I'm almost sure I will be flying current day or next day. That means my batteries are somewhere between 15-30%, depending when I land my drone. Is that ok?

The sweet-spot for a LiPo storage wise is 3,7-3,8V/cell ... if you don't want to degrade your battery's prematurely they shouldn't be outside that storage voltage longer than 48h as a thumb rule, it's equal bad to keep them too full as too empty.

For a DJI battery the storage voltage translates to approx. 30-50% ...