Deep cycle batteries M3E

[TechTerrae]

Hi, does anyone know if the new M3E batteries technology requieres to deep cycle the batteries? After how many cycles? Which will be the correct procedure? Thanks!

 

[slup]

The deep discharge procedure is something from the past when the "Battery Management Systems" in the battery pack was prone to come out of sync with the actual capacity the battery had... the % in the app could slowly start to show a wrong remaining battery percentage. A deep discharge could "calibrate" the BMS again

Nowadays the BMS chips are of a much higher quality, they no longer creep off the real remaining battery capacity... so the deep discharge process is no longer needed.

Some do it still & in general it will not harm your batteries, 0% in the app is approx 3,5V/cell... so still within the safe span for a LiPo battery use. But doing it will not add any benefits... you will only throw away one of your LiPo batteries charge cycles.

 

[TechTerrae]

Thanks! For the benefit of the battery life, I learned to always store them between 40-60%. Is this also valid for modern BMS? How many "cycles" do an M3E support? Does one battery cycle mean to start flying from 100% to 40% or less? Thanks for your complete answer!

 

[slup]

Pure voltage wise a LiPo battery should be stored (or returned back to within a couple days) 3,7-3,8V/cell (that's approx 30-60% in the app)... this is still valid.

Keeping them in a too high charge state will speed up the electrolyte decomposition which release gases, so the battery can start to swell & the internal resistance will increase making the battery very prone to major voltage drops when put under amp draw.

Keeping them too low will first risk a shutdown of the BMS chip (mainly make the battery not take charge anymore & usually it's nearly impossible to "wake" that BMS up again without special equipment)... then secondly the battery might self discharge under 3V/cell & there the cells will be permanently damaged.

One charge cycle is from wherever it is percentage wise, the discharged... & then returned to the same "wherever percentage"... so, from 100% down to 0% & charged up to 100% = 1 charge cycle.

A M3E battery isn't anything special... it's a LiPo with a model specific outer plastic casing... depending on age, use & care a LiPo should perform "good" up to 200-300 cycles... but the capacity it can store will slowly degrade over use & age. So not impossible that a LiPo can be dead with only 1 cycle if it have been stored wrongly & are very old.

 

[TechTerrae]

Thanks! And what about flying the maximum, lets say until 10% and then charging to 30% just for storage? This counts as 1 or 2 cycles? Is it a good strategy?

 

[slup]

First of all... you always charge the batteries full right before you fly (or no longer than 2 days before). You then fly them low & when you come home (or at least within 2 days) you charge them up to storage level (30-60%). If you don't fly some of the fully charged batteries (or if some is still over 60%) you discharge them to 30-60% within 2 days.

Then a word of warning regarding how low you should fly the batteries... on a regular basis.

All DJI drones have a safety feature that will see to that the drone reaches solid ground before they are totally discharged & start to free fall. It's called Low voltage forced auto landing... & you can't cancel it, just delay it by constantly holding the throttle stick applied for ascending... but as soon as you release the stick it will start to land again. The battery percentage when this happens is height dependent (obviously it will take more battery percent to reach ground from heights then from lower altitudes). The lowest threshold for this is usually around 10%. But note that when this forced landing is active you can still delay it with the throttle & at the same time fly the drone horizontally to a suitable emergency landing spot.

The second warning is about having enough battery juice left for unforeseen events like headwind on the way back or a landing procedure that takes longer than you thought due to some reason. I would say that if you in general aims for having 20% left in the battery when landed & motors stopped... you usually manage to have at least a minimum of 15% left in reality.

...lets say until 10% and then charging to 30% just for storage? This counts as 1 or 2 cycles?

That isn't even 1 full cycle. If you start on 100% you need to discharge first 100% then charge 100% again for 1 cycle. In your case you have discharged from 100%, then drained 90% & charged 20% (to reach 30%).

With the long flight times a Mavic 3 has the most effective would be to just fly them down to 30-35% ... in this case you don't need to charge them up to storage levels when you come home.

 

[waynorth]

I meticolously follow DJI's advice when maintaining the batteries. Here is an excerpt of what they say about battery maintenance of their LiPo batteries:


The steps below are critical to making sure your batteries are ready to go and are properly calibrated. Specifically, charging and discharging the battery ensures an accurate digital readout of battery percentage which is a vital metric when operating your drone. If this process is ignored the battery percentage margin of error will be amplified by continued operations.
Complete the following every 3 months or 50 cycles (whichever comes first)

1. Charge and discharge batteries per instructions below.
2. Make sure the cell voltage difference is less than 0.1V after the battery is fully charged and left stationary for 6 hours.
3. Make sure the battery is not swollen, leaky, or damaged. See more “Common issues to watch out for” below.
4. Clean battery terminals with a clean dry cloth and make sure they are clean.
5. Make sure battery firmware is updated to the latest version.

Charge and Discharge Instructions:

1. Charge the battery to 100% and leave the battery stationary for more than 24 hours.
2. Install the battery into the aircraft. Fly the aircraft and when the remaining power level is less than 20%, land the aircraft and remove the battery.
3. Leave the battery stationary for more than six hours.
4. Check cell voltage.
5. Charge the battery to 100% power level.
6. Repeat the above steps 1-4.

 

[TechTerrae]

Thanks for your time, really appreciate it!
What about the storage voltage for the RC pro? Isit the same logic?

 

[slup]

...What about the storage voltage for the RC pro? Isit the same logic?

In general yes... this as it's a LiPO there also.

But the battery in the RC isn't working under the same amp draw as the battery in the drone, the current drawn from that battery is only a fraction of what the drone battery experiences. This stresses that battery far less, meaning that the electrolyte decomposition will go slower & the increased internal resistance will not cause any major performance problems.

The care for the RC battery should mainly be aimed to preventing the battery to self discharge to too low levels, which risk destroying it, this should be carefully noted if the RC should be stored during a longer period (several month).

So if you fully charge your RC before a flight day & come home with it "nearly" fully charged... you don't need to try to discharge it to 30-60%. If it on the other hand is nearly empty you can put it on the charger & take it up to the 60-80% level... then you can top it off at the same time you charge your drone batteries when you're gona fly the next time.

 

[TechTerrae]

Thank you so much Slup! Another question, are M3E self-heating batteries? I'm saying this because where I bought them they told me it's not exactly the same battery as a regular Mavic3. I know the charger is faster but not so sure about the batteries difference. Thanks!