Mavic mini fly more kit batteries damaged in charger - is it possible?

[DiyTechno]

Very interesting.
But I don't like this confronting information
It would definitely be more convenient if it's true that we can charge batteries to full after flight. Charge and forget. I would like that. On the other hand this charging and discharging at around 50% is more demanding. Not to mention that if you have batteries at 50% and suddenly you have great opportunity to go out and fly then you can't do that, and that can be very sad.

But we need to be careful about this because there must be some reason why DJI stated "If the battery will not be used for more than 10 days, it is recommended to discharge the battery manually until the battery level is between 39% and 75%."

Mavic mini using battery cell from samsung. It is INR18650-25R.

Based on battery's datasheet, it just can last for 250cycle and after that it's capacity will drop >1500mA.

Dji recommend to discharge the batteries for long term storage based on that batteries manufacture.

So just follow the rules from dji manual and you will be saved from trouble.

 

[Ramjam61]

Very interesting.
But I don't like this confronting information
It would definitely be more convenient if it's true that we can charge batteries to full after flight. Charge and forget. I would like that. On the other hand this charging and discharging at around 50% is more demanding. Not to mention that if you have batteries at 50% and suddenly you have great opportunity to go out and fly then you can't do that, and that can be very sad.

But we need to be careful about this because there must be some reason why DJI stated "If the battery will not be used for more than 10 days, it is recommended to discharge the battery manually until the battery level is between 39% and 75%."

Completely agree. These are just my observations and My practices. A friend of mine used to leave his normal Lithium Polymer batteries fully charged for weeks on end to no detriment of His batteries, I always put mine into storage mode after use.
I personally will continue to ignore dji's advice and treat mine as I do all others. Maybe in 12 months time I'll be reporting my batteries are dead.?

 

[Ramjam61]

Mavic mini using battery cell from samsung. It is INR18650-25R.

Based on battery's datasheet, it just can last for 250cycle and after that it's capacity will drop >1500mA.

Dji recommend to discharge the batteries for long term storage based on that batteries manufacture.

So just follow the rules from dji manual and you will be saved from trouble.

Interesting, that's for long term storage which I can't see any details of what they term " long term". Long term for a battery would suggest to me over 12 months. That is, to be stored presale?
The batteries in my electric cycle are Samsung. The advice for them is to fully charge after use and then top up every month if cycle is not used. I think a call to dji is in order before I knacker my batteries.

 

[Ramjam61]

Just to add. 250 cycles is very poor performance. I sincerely hope dji aren't using those in their products. Battery performance drops significantly long before the last possible cycle.

 

[DiyTechno]

The batteries in my electric cycle are Samsung.

Samsung has various type of lithium battery. Do you know what model exactly that fitted on your electric bike?
Lithium batteries has a lot of chemical variety which they have their own characteristic and purpose. Here is a link to explain some of that.

Battery chemistry FINALLY explained

I've looked far and wide, but I couldn't find any resources that actually explain li-ion battery chemistry in a simple way. So I decided to make one.This table shows current 18650 battery chemistries and their abbreviations: Long-form name Chemical abbreviation Name format 1 Name format 2 Name...

batterybro.com

 

[Ramjam61]

Samsung has various type of lithium battery. Do you know what model exactly that fitted on your electric bike?
Lithium batteries has a lot of chemical variety which they have their own characteristic and purpose. Here is a link to explain some of that.

Battery chemistry FINALLY explained

I've looked far and wide, but I couldn't find any resources that actually explain li-ion battery chemistry in a simple way. So I decided to make one.This table shows current 18650 battery chemistries and their abbreviations: Long-form name Chemical abbreviation Name format 1 Name format 2 Name...

batterybro.com

Very interesting. I assume (maybe wrongly) that Lion batteries which also power the motors will be the same composition in all applications that have an electric motor. It would seem pointless as in the composition cited for a high power flashlight to fit that type in a Drone, would it not.

 

[RogerDH]

A bit more research (I find stuff like this intriguing). Allowing a Lion battery to discharge below 75% can reduce it's cycles to between 300 to 500 before it's demise. Keeping it above this can increase it's cycles to 2000 to 2500. In the case of phones/Laptops etc, keeping them on trickle charge overnight is far less detrimental than a longer charge next day. This all comes from the popular mechanics website.
The above advice has been the same as my observations. I always fit large capacity batteries in my RC gliders so even after all day flying they are still above 80% capacity. Two gliders have batteries that are 8 years old. I would love to know what dji's thinking is behind their advice. Maybe their battery tech' requires a different approach to everyone else's?

Since this is DJI's first use of 18650 li-ion cells, maybe they just copied boilerplate text from a manual for a drone that uses li-po cells. I see a lot of sources that don't distinguish between the two, but they are different, so there's no reason to expect them to behave the same. 18650s are used in flashlights that are typically kept fully charged, and in laptop batteries that are continuously charged when plugged in.

 

[DiyTechno]

Very interesting. I assume (maybe wrongly) that Lion batteries which also power the motors will be the same composition in all applications that have an electric motor. It would seem pointless as in the composition cited for a high power flashlight to fit that type in a Drone, would it not.

IMHO maybe reason dji using INR batteries is because it is saver and has high drain current which can go up to 20A. Based on battery's manual, they tested it to overcharge the battery with 20A 20V for 3 hours and the battery is still ok. No fire

 

[Ramjam61]

The great thing about these types of discussion is it throws up all sorts of questions which others can research. From this they can then make an informed opinion for themselves. Not relying on any one opinion. Maybe dji have got it wrong?, unlikely but it does happen. So far I'm getting 35 minutes in hover and around 28 minutes sport flying out of mine. Still no sign of battery degradation.

 

[DiyTechno]

The great thing about these types of discussion is it throws up all sorts of questions which others can research. From this they can then make an informed opinion for themselves. Not relying on any one opinion. Maybe dji have got it wrong?, unlikely but it does happen. So far I'm getting 35 minutes in hover and around 28 minutes sport flying out of mine. Still no sign of battery degradation.

Yup, totally agree with you in this. People can have their own opinion and preference. I just share the fact based on batteries manufacture manual.

 

[Ramjam61]

IMHO maybe reason dji using INR batteries is because it is saver and has high drain current which can go up to 20A. Based on battery's manual, they tested it to overcharge the battery with 20A 20V for 3 hours and the battery is still ok. No fire

I believe you are correct in your assumption. I intend to continue to "abuse" my batteries in the name of further knowledge. Keeping them fully charged all the time. This is purely for my interest and I don't advise anyone to follow suit. I have lots of RC experience (50 years) and will know the moment I see performance dropping. I'll keep this updated for interested parties

 

[Ramjam61]

My car tells me when to change gear. I ignore that as well.LoL

 

[DiyTechno]

I believe you are correct in your assumption. I intend to continue to "abuse" my batteries in the name of further knowledge. Keeping them fully charged all the time. This is purely for my interest and I don't advise anyone to follow suit. I have lots of RC experience (50 years) and will know the moment I see performance dropping. I'll keep this updated for interested parties

Thats great, and please note the temperature where you store your batteries as temperature play a role in that

 

[DiyTechno]

My car tells me when to change gear. I ignore that as well.LoL

My car ask me to change engine oil and I ignore that. LOL

 

[Ramjam61]

Thats great, and please note the temperature where you store your batteries as temperature play a role in that.
Good point. I bet a few people live where they can get above the 100F limit.

 

[Ramjam61]

Whoops somehow got inside your post. Told you I was a mavic.

 

[OldEd]

After 10 charging cyclus, my batteries show a performance of 99%. I always store them as instructed by DJI. You can see the health of your batteries in airdata.

 

[Ramjam61]

After 10 charging cyclus, my batteries show a performance of 99%. I always store them as instructed by DJI. You can see the health of your batteries in airdata.

An interesting fact. Lithium ion batteries should never be fully charged. When they are, they get hot and this reduces battery life. The dji charger will probably stop at 95%. I used to charge my RC batteries at around 25% of their capacity ( ie 2500mah battery at 650mah) thinking I could sqeeze more electrons in because they would stay cooler, they always finished the charge hot. When I learned how the chemistry works I always charged at their full capacity (ie 2500mah battery, charge at 2.5amps). The battery finishes it's charge in a relatively cool state and at around 95% of it's capacity. I am sure dji know what they are doing. I'm just adding my experience with Lion batteries.

 

[Ramjam61]

Add on. Both my mini and Air 2 batteries come out of the chargers at the exact cooked temperature to suggest they have been charged correctly.

 

[Capt KO]

That is quite different to what some others here recommend, and to what is stated in Mini's Manual: "If the battery will not be used for more than 10 days, it is recommended to discharge the battery manually until the battery level is between 39% and 75%."


Will that rapid charge hurt the batteries in any way?
I agree that Mini battery pack is very slow so I an interested in faster charging, but I am concerned will that harm batteries.

No problems, yet. Let you know in a year. Or if any problems appear. Don't expect any though as they have been out for quite a while for other models as well. Can't live without it for now. It's so fast!