I received the following question from a drone pilot and I thought I’d take the time to share this great question with everyone. If you have a question you’d like to ask, click here.

Drone Battery Question

“Hi, I don’t have a new problem to report and am still waiting on DJI for a report/assessment on the stuck Battery percentage problem I reported to you on ReportDroneAccident.com a few weeks ago (M210 and M2E).

I do have a question regarding another common battery issue, however: bloating. I have researched this problem several different times over the past 12+ months and have found it difficult to get more than a cursory understanding.

We just retired 3 P4 batteries that were 3+ years old, with only 60 – 90 charge cycles on them. The common refrain is that they are always kept at full charge. We take great pains to ensure all batteries are ready to go for the next mission. They are otherwise extremely well-cared-for.

However, from some research, it strongly suggests that keeping LiPOs fully charged is the 2nd worse thing you can do (other than overcharging them which is presumably not possible to do with DJI battery chargers – or charging them hot).

We now have another 4 TB50s that are showing bloating, and a couple of M2E’s that are tending that way. This will become increasingly expensive over time.

The options don’t seem to be very good. 1) no change, keep all batteries fully charged and budget their replacement accordingly; 2) reduce the cycle time from 10 days down to 5 and alternate batteries as much as possible; 3) keep 2 sets fully charged and alternate those, and field charge as necessary (probably needs 120v to do this in a reasonable time).

What advice do you have regarding this conundrum? Have you found any guidance that provides some level of an objective measure of when the price/safety threshold is passed and the bloating is too far gone requiring the battery be (appropriately) disposed of)? Charge it till it blows … or doesn’t fit … or …

Thanks.”

My Answer

It just so happens that I just analyzed an incident with batteries swelling so much during a flight they were difficult to remove. The pilot felt that if the flight had continued there was a real risk of the aircraft falling out of the sky.

See DJI Matrice 210 – Incident – 2020-09-23.

While we are talking primarily about DJI batteries in this question and answer, the physicist involved in what makes these batteries problematic is not limited to DJI.

The guide I would turn to first for specific advice would be the advice directly from DJI about the batteries. The bloating is evidence of explosive gas building up inside the battery.

I decided to go look at the most current battery guidelines for the Matrice 300 RTK to see what advice is now being given for the proper use of the batteries. The advice seems similar to what DJI has shared for the Matrice series as well.

• Failure to operate the product correctly can result in damage to the product, or personal property, and may cause serious injury. It must be operated with caution and common sense and requires some basic mechanical knowledge and ability. Failure to operate this product in a safe and responsible manner could result in injury, or damage to the product, or other property.
• Never use or charge swollen, leaky, or damaged batteries. If your battery is abnormal, contact DJI or a DJI authorized dealer immediately for further assistance.
• DO NOT use the battery again if it was involved in a crash of any kind or heavy impact.
• DO NOT drop or strike the battery. DO NOT place heavy objects on the battery or charger.
• The battery is rated for 200 cycles. It is not recommended to continue to use afterward.
• DO NOT charge the battery near flammable materials, objects, or on flammable surfaces such as carpet or wood. Never leave the battery unattended during charging.
• DO NOT charge the battery immediately after flight; battery temperature may be too high. Instead, allow the battery to cool down close to room temperature before charging again. The ideal battery charging temperature range is from 15° C to 40° C (59° F to 104° F).
• DO NOT leave the battery inside a vehicle on hot days. The ideal storage temperature is 72F to 86F.
• Keep the battery away from metal objects such as glasses, watches, jewelry, or hairpins.
• Never attempt to travel with or transport a damaged battery or a battery with a power level higher than 30%.
• Ideally, the battery should be used in temperatures ranging from -20° C to 50° C (-4° F to 122° F). Battery usage in environments above 50° C (122° F) can lead to serious damage and in environments above 60° C (140° F), can lead to a fire or explosion. Battery usage in temperatures below -20° C (-4° F) can impact the battery’s performance, which will affect the drone’s performance. When used in temperatures ranging from -20° C to 15° C (-4° F to 59° F), the battery will warm itself up once installed onto the aircraft and turned on. Before take-off, the aircraft will first determine the battery status.
• DO NOT use the battery in strong electrostatic or electromagnetic environments. Otherwise, the battery control board may malfunction and cause a serious accident during flight.
• To extend flight times, over-discharging protection is disabled when the batteries are discharging during a very long flight. In this instance, a battery voltage below 1.8 V may cause a safety hazard such as a fire when charged. To prevent this, the battery will not be able to charge if the voltage of a single battery cell is below 1.8 V. Avoid using any batteries matching this description. Always be alert to avoid serious over-discharging to prevent permanent battery damage.
• To extend battery life, prevent the battery from float charging.
• DO NOT leave the battery near heat sources such as furnaces or heaters. DO NOT leave the battery inside a vehicle on hot days. The ideal storage temperature is 22° C to 30° C (72° F to 86° F).
• Never use the battery when the temperature is too high or too low.
• Never store the battery in environments outside the range from 10° C to 45° C (50° F to 113° F).
• Make sure the battery is fully charged before each flight.
• The Intelligent Flight Battery is designed to stop charging when it is full. However, it is good practice to monitor the charging progress and disconnect the battery when fully charged.
• Battery life may be reduced if not used for an extended period of time.
• Fully charge and discharge the battery at least once every three months to maintain battery health.
• For every 50 cycles, charge and discharge the battery as per instructions.

I bet these instructions will surprise you. These come from the official DJI guide.

“Standard charge and discharge operation instructions
(1) Charge the battery to 100% and leave the battery stationary for more than 24 hours.
(2) Install the battery into the aircraft before flight. If the remaining power level is less than 20%, land the aircraft and remove the battery.
(3) Leave the battery stationary for more than 6 hours.
(4) Charge the battery to 100% power level.
(5) Repeat the above steps.”

And then there are these official DJI battery storage instructions:

1. Charge or discharge the battery to 40% ~ 60% if NOT intended to be used for 10 days or more. This can greatly extend the battery’s overall life span. It takes approximately 6 days to discharge the battery to 60%. It is normal that you may feel moderate heat emitting from the battery during the discharge process. You can set the discharging thresholds in the DJI Pilot app. It’s recommended to store the batteries in the Battery Station.
2. DO NOT store the battery for a long period of time with its power fully discharged. It may lead to irreversible damage.
3. The battery will enter hibernation mode if depleted and stored for an extended period of time. Recharge the battery to bring it out of hibernation.
4. Remove the battery from the aircraft when planning to store it for an extended period of time.
5. Always store Intelligent Flight Batteries in a well-ventilated place.

You can see the complete guide I just quoted from, here.

Where Does That Leave Us?

I’m not sure there is a ranking or the worst thing you can do to your drone battery. There sure are a list of things you should never do. But complying with the guidance to use the batteries seems impossible.

For example, you are not supposed to transport a battery with more than a 30% charge but you must make sure the battery is fully charged before each flight and the battery charging should be stopped when it becomes full. After fully charging, you are supposed to leave the battery stationary for more than 24 hours. How in the world can you do that?

You should never charge a swollen battery. You should not leave your battery unattended while charging. You can’t use a battery you’ve dropped. You should not charge a battery immediately after a flight. You can’t leave a battery inside a vehicle on hot days. You should not use the battery in a strong electrostatic or electromagnetic environment.

After discharging the battery you should leave it stationary for more than 6 hours. And if you are not going to use a battery for more than 10 days the battery should be in a 40% to 60% power state.

And while all of this is going on, make sure the area is well ventilated.

The Conclusion I Came to From Experience

In my case, DJI advised all batteries should be replaced after one year of service. The cost to replace all of our batteries would be more than the cost of a new drone. It makes no sense to buy new batteries for an older tech drone. Get a new, smaller, lighter, and disposable drone to use till the batteries die again.

In a public safety role, it is impossible to comply with the DJI safety warnings regarding battery use so you should expect that when your batteries explode or catch fire you will be left as the person to blame.

I wound up taking all of my TB55 batteries, that had become swollen, for proper battery disposal and waved goodbye to thousands of dollars. We are not replacing them at the fire department. It makes no sense.

Thank you for reaching out to me and asking your question.

Steve