How Detrimental To Leave Batteries Fully Charged?

[raymacke]

I know what the manual states and I understand leaving them fully charged will shorten their life. But my question is by how much?

I have already had my fill of trying to leave the batteries at a partial charge. I bought the Mini for its portability and want to have it with me when out and about and happen on to an interesting subject to shoot. But I have no way of knowing if that will happen in the next 10 days. Low wind, good lighting plus a worthy subject is just not that predictable. But when I do find it I want full batteries, not 40%. Nor do I want to wait an hour to have a serviceable battery. If I can't fly it when I need it - what's the point of having it?

Not to mention I am actually losing flight time per charge cycle if I fly it down to only 40% or 50% but then recharge it back to 100%. It is my understanding that battery life is measured by the number of charge cycles. So, although storing at mid charge will theoretically yield more charge cycles my actual hours of flight time may actually be reduced by a similar amount. And NO, I won't mess around launching with a 40% charge. For me, if it is not at least at 80 it's not worth the time.

Unless I find it will kill the batteries in short order I am to the point I think I will ignore the manual on this point. I want to fly when I want to fly.

Although at the present it seems availability is somewhat limited, once that is remedied the batteries really aren't that expensive. So what are we talking here - reduced life cycle of 10%, 25%, 40%? Does anyone have anything more than a guess about this?

 

[Meta4]

Not to mention I am actually losing flight time per charge cycle if I fly it down to only 40% or 50% but then recharge it back to 100%. It is my understanding that battery life is measured by the number of charge cycles. So, although storing at mid charge will theoretically yield more charge cycles my actual hours of flight time may actually be reduced by a similar amount. And NO, I won't mess around launching with a 40% charge. For me, if it is not at least at 80 it's not worth the time.

Leaving lithium batteries sitting fully charged or empty is bad for them.
If you are not flying for a while, leaving them at +/- half full is best.
A charge cycle is a full charge and a part charge is not a full charge cycle.

Your % indicator will give a false reading with a battery that's been sitting around slowly discharging.
80% is not 80% ... it could be quite a lot less.
Only fly with freshly, fully charged batteries.

 

[bumper]

Good info:

How to Prolong Lithium-based Batteries - Battery University

 

[Lastrexking]

Try search. You’ll find lots of helpful info.

Search results for query: Leave batteries charged

mavicpilots.com

 

[old man mavic]

when it comes to the batteries in a drone, the way that they are used and stored is much more crucial ,
than the same batteries in a power tool or phone or indeed any device that stays firmly on the ground,
its not only about battery life, but the implications of battery failure due to misuse
if you want to always have some charged batteries with you for that unexpected picture moment then the best way to go about it would be to get
a lot of them all numbered and keep some charged, used ,and charging, that way you will always have some available, if after 10 days of none use discharge those ones
and you will have another batch charged and ready to go say you do them in threes then 9 batts would be enough keep a record of use so you know whats what

 

[Capt KO]

Just buy a decent sized USB battery pack. Use it to charge and discharge anywhere.

 

[DanMan32]

The mini uses metal can type Li-Ion which are less prone to issues such as swelling.
The plastic type Li-Po cells are very prone to swelling which even if the battery is electrically sound, may unlatch in flight and lose power.

The biggest killer is heat. Heat plus full charge is worse.

I don't think one has to go crazy about not going below 10% as there's a margin of safety built in on the % scale so it's probably better to leave it at 10% than 100%, assuming you don't leave it that way so long (like months) where self discharge brings it dangerously low.
The only issue with getting below 20% is having enough power to get home and not auto-land. That and Mini may be more prone to "insufficient power" when charge gets low.

 

[raymacke]

I appreciate the input but I am looking for specifics. The "Battery University" link had a lot of info but I struggle trying to sort through it for the long term "storage" data. The searches recommended yield the general info - it's not good - but again no specifics.

I have a high-speed charger in my vehicle but still, it takes 30 to 45 minutes to top it off from 40%. When you arrive and the sun is setting that doesn't help. I don't like to fly below 20% 0r 25% so flight time from 40% is short. (This is more about safety than battery life - when stuff goes wrong I want to be able to get it home)

Rather than buy 9 batteries my thought is to just replace the 3 on a regular basis. What I am trying to determine is how often this needs to occur. WIll they degrade badly in a year? Two years? If I could get two years this becomes an easy decision - I'll keep them charged.

BTW - how many people try to keep their laptop batteries at 40%? Mine normally sits on the chargers 95% of the time and are held at 100%. Yes, they do finally fail but usually, that takes several years.

 

[Gkinghrn]

I’m kind of with you on this. Given how slowly this battery recharges and the fact that flying is so weather dependant I keep mine topped up ... the discharges though are less frequent than a laptop so not sure that’s a good comparator for me.

But yeah if I had to replace it even once a year I’d probably suck it up.

However if I know I am not going to be flying in the next few days it’s probably worth discharging it a bit to the recommended levels ... timing is key though...

Interesting question...

 

[DanMan32]

Modern laptops now can detect if you leave it on AC often and not fully charge the batteries, and may have settings to manually set the top charge level. Swelling is the reason for the option.

As they say with cars, your mileage may vary depending on use.

I can say that the mini uses the metal can type Li-Ion rather than the plastic pouch type Li-Po that other DJI's use. Li-Ions are less susceptible to issues but not immune.

Heat is the biggest enemy, especially when fully charged. If you leave it in your car all the time fully charged, it is more likely to deteriorate than in a conditioned house.

As for specifics, I doubt you'll get a clear answer as there are too many variables including cell quality, design and chemistry as well as opinions when it comes to the extremes of fully charged and low SoC. I'm of the opinion better to leave it at 10% after flight than leave it at 100%.

 

[sar104]

DJI batteries self-discharge to a storage level automatically if not used, so the question seems somewhat moot.

 

[CarstenB]

DJI batteries self-discharge to a storage level automatically if not used, so the question seems somewhat moot.

the MM batteries don't have that functionality hence this discussion .

 

[sar104]

the MM batteries don't have that functionality hence this discussion .

I had not realized that - thanks for the clarification.

 

[Dbez1]

Check out the last 4 posts in this thread, I think it will answer some of your questions.? Better to store with charged or discharged batteries?

 

[Meta4]

I don't like to fly below 20% 0r 25% so flight time from 40% is short.

40% is not 40% - see post #2.
Make a habit of launching with a 40% battery and your flight might be shorter than you anticipate.
There's a very good reason for the Mini Manual (p37) to have this as the first item in the pre-flight checklist:
1. Make sure the remote controller, mobile device, and Intelligent Flight Battery are fully charged.

 

[djndrone]

My first post here. I'm new to drone flying but have some experience of Li Ion batteries as I have an electric car and an electric golf cart.
The golf battery recommends always put it on and keep it on charge after every game even if you only did a few holes. My car recommends keeping it to approx 20 to 80% to extend battery life but if your going on a long trip charge it to 100% but use the car straight away! . I'm going to keep two of my mavic mini batteries at around the 3 lights showing whilst not using but have one battery and the controller fully charged all the time. Only time will tell!

 

[dirkclod]

Welcome to the forum.
You might be right but unless I’m just going to do a short flight I won’t use a battery unless it’s fully charged.
Have seen them drop fast with voltage doing that.
Now haven’t had enough time with these mini’s yet
to know that is the case with these but from my phantoms and other Mavics that’s how I work em.
Safe flights. ?

 

[old man mavic]

if anything is to be taken from this thread,then to me there are 3 certainties

(1) dont leave batteries fully charged for extended periods
(2) dont leave them at a low charge for extended periods
(3)there are so many variables,that affect battery life that everyone will have a different outcome

 

[raymacke]

Again I appreciate the input but I guess my point is still not totally understood. I am a pragmatist. I view life as a series of risk assessments - compromises if you will. Everyone riding a motorcycle knows it is dangerous but the risks are weighed and some do and some don't. I have chosen to ride - for the past 50 years. And it has brought me much pleasure that would have been missed if I had not. In this case, for me I feel the risks were worth the reward. But not all are.

And that was my intention with this thread as I need to make a judgment call as to battery life vs usability. But I was looking for some hard data that I guess does not exist beyond - not a good idea - I wouldn't do it - life span will be reduced. (BTW - I did the recommended search and spent 45 minutes reading but kept finding nothing more than basically the aforementioned responses.)

So it appears I need to make a decision based on the limited information available. This will be my choice and I in no way suggest it for others as accurate or wise.

I like the logic proposed by djndrone. I believe I will maintain one battery at full charge and the other two at the suggested level. This fulfills the need for a fully charged battery at short notice and its flight time would allow time to at least bring another up to a more suitable state of charge. A perfect solution? No - but for me workable.

I guess the only remaining question for me to sort out is to use one specific battery to hold at full charge or rotate it around. Rotating would spread the adverse effects but using just one would limit the life reduction to just one. I'll have to give that some thought.

BTW - This will not be the battery state 100% of the time. I am sure there will be times (winter sucks) I will know I won't be flying for extended periods. In those situations, I will adhere to the suggested levels.

 

[mavicn00b]

I like the logic proposed by @djndrone. I believe I will maintain one battery at full charge and the other two at the suggested level. This fulfills the need for a fully charged battery at short notice and its flight time would allow time to at least bring another up to a more suitable state of charge. A perfect solution? No - but for me workable.

For me I got a YX parallel charger, I can typically have 4 batteries ready to go within the hour. That's short notice enough for me. That way I can preserve their health keeping half charged and not wait 3hrs+ to charge the other 3.