Battery Care

[Wacha McCallum]

Greetings, I have a MavAir2 FlyMore Combo so I'm rotating 3 batteries. As I use them, I recharge them fully so I always have 3 fresh batteries to fly with. What is the best way to recharge?
1) Should I wait until the battery is fully run down?
2) Is it OK to recharge a battery that is only partially discharged?
3) Should I be discharging the batts beyond the point that the MA2 won't boot up? I read that you can leave the bottom LED on until the battery is completely dead.
Thanks! ~Wacha

 

[slup]

It's easy ... being outside the storage cell voltage of 3,7-3,8v damage your batteries ...

The wear & tear increases the closer you get either to full (4,2v/cell) or empty (3,0v/cell). (For DJI batteries a level between 30-60% is approx equivalent to 3,7-3,8v/cell)

The damage you inflict to your batteries by having them out on the edges of the voltage span shows up as either swelling due to that oxygen is created when the chemistry breaks down ... an increase of the internal resistance which leads to major voltage drops when putting the battery under load. Over time & use the total battery capacity will also become less, leading to shorter usable flight times but with abuse this will go faster.

Your strategy should be ...

Charge up just before use (48h before is ok but not longer).
After use, let them cool down to room temp ...
... and charge them up to storage voltage (3,7-3,8v/cell).
If fully charged ... never keep them there longer than 48h, instead take them down to storage level again (3,7-3,8v/cell).

Never store your batteries longer than 48h outside storage level (3,7-3,8v/cell) ... the closer they are to either full (4,2v/cell) or completely empty (3,0v/cell) the more damaging it will be.

Never fly with a partial drained battery that have been laying around for a while, the cells are imbalanced & that may get worse during flight & make a cell fail.

Never fly the batteries lower than 15% on a regular basis, plan your flight properly & see to that you land before letting them go that low.

Be careful in colder ambient temps with high amp draw (single full stick commands, or combined full stick commands (like full forward & up)... & avoid Sports mode.

Keep in mind that if a cell just momentarily goes under 3,0v, DJI will force auto land your craft right there & then ... being over water or another total loss area will not end well.

Don't rely on any "smart battery" discharge functionality if you can't set it to have them down to storage level within 48h ... 10 days and such is way to long having your batteries full.

 

[eEridani]

I have an Air 2, I only charge the day before I go to fly.

At the end of a flight day, if one battery is at 15%, another at 40%, I just let them sit. I do try to rotate the batteries so I keep each at a similar recharge count (warranty is 200 charge cycles). The exception is if a battery is really low, under 10% -- 1st LED flashing. I'll put it on the charger a half hour or so until it is 20%, then it sits until I plan to fly again. One solid LED is my minimum storage level.

This is based on reading here - not on any bad experience with dead batteries. Plus, the Air 2 batteries are "Smart" and will self discharge a bit after 24 hours and a lot after 5 days to levels DJI thinks is best.

 

[slup]

... if one battery is at 15%, another at 40%, I just let them sit
...The exception is if a battery is really low, under 10% -- 1st LED flashing. I'll put it on the charger...until it is 20%
...One solid LED is my minimum storage level.

The lowest level you're working with is too low ... at 30% the cell voltage reaches 3,7v & it's there you should have them. The four LED span rule is: between 1 solid+1 blinking to 2 solid+ 1 blinking.

Having a battery laying around on 15% will damage it ...

...the Air 2 batteries are "Smart" and will self discharge a bit after 24 hours and a lot after 7 days to levels DJI thinks is best.

Yeah ... they think it's best to see to that the battery survives the warranty period of 12 month. If you want a longer life out of your batteries, not risk swelling & a major internal resistance build up you don't rely on a 7 days discharge functionality.

 

[Wacha McCallum]

It's easy ... being outside the storage cell voltage of 3,7-3,8v damage your batteries ...

The wear & tear increases the closer you get either to full (4,2v/cell) or empty (3,0v/cell). (For DJI batteries a level between 30-60% is approx equivalent to 3,7-3,8v/cell)

The damage you inflict to your batteries by having them out on the edges of the voltage span shows up as either swelling due to that oxygen is created when the chemistry breaks down ... an increase of the internal resistance which leads to major voltage drops when putting the battery under load. Over time & use the total battery capacity will also become less, leading to shorter usable flight times but with abuse this will go faster.

Your strategy should be ...

Charge up just before use (48h before is ok but not longer).
After use, let them cool down to room temp ...
... and charge them up to storage voltage (3,7-3,8v/cell).
If fully charged ... never keep them there longer than 48h, instead take them down to storage level again (3,7-3,8v/cell).

Never store your batteries longer than 48h outside storage level (3,7-3,8v/cell) ... the closer they are to either full (4,2v/cell) or completely empty (3,0v/cell) the more damaging it will be.

Never fly with a partial drained battery that have been laying around for a while, the cells are imbalanced & that may get worse during flight & make a cell fail.

Never fly the batteries lower than 15% on a regular basis, plan your flight properly & see to that you land before letting them go that low.

Be careful in colder ambient temps with high amp draw (single full stick commands, or combined full stick commands (like full forward & up)... & avoid Sports mode.

Keep in mind that if a cell just momentarily goes under 3,0v, DJI will force auto land your craft right there & then ... being over water or another total loss area will not end well.

Don't rely on any "smart battery" discharge functionality if you can't set it to have them down to storage level within 48h ... 10 days and such is way to long having your batteries full.

It's easy ... being outside the storage cell voltage of 3,7-3,8v damage your batteries ...

The wear & tear increases the closer you get either to full (4,2v/cell) or empty (3,0v/cell). (For DJI batteries a level between 30-60% is approx equivalent to 3,7-3,8v/cell)

The damage you inflict to your batteries by having them out on the edges of the voltage span shows up as either swelling due to that oxygen is created when the chemistry breaks down ... an increase of the internal resistance which leads to major voltage drops when putting the battery under load. Over time & use the total battery capacity will also become less, leading to shorter usable flight times but with abuse this will go faster.

Your strategy should be ...

Charge up just before use (48h before is ok but not longer).
After use, let them cool down to room temp ...
... and charge them up to storage voltage (3,7-3,8v/cell).
If fully charged ... never keep them there longer than 48h, instead take them down to storage level again (3,7-3,8v/cell).

Never store your batteries longer than 48h outside storage level (3,7-3,8v/cell) ... the closer they are to either full (4,2v/cell) or completely empty (3,0v/cell) the more damaging it will be.

Never fly with a partial drained battery that have been laying around for a while, the cells are imbalanced & that may get worse during flight & make a cell fail.

Never fly the batteries lower than 15% on a regular basis, plan your flight properly & see to that you land before letting them go that low.

Be careful in colder ambient temps with high amp draw (single full stick commands, or combined full stick commands (like full forward & up)... & avoid Sports mode.

Keep in mind that if a cell just momentarily goes under 3,0v, DJI will force auto land your craft right there & then ... being over water or another total loss area will not end well.

Don't rely on any "smart battery" discharge functionality if you can't set it to have them down to storage level within 48h ... 10 days and such is way to long having your batteries full.

Thank you for this comprehensive explanation! I'm a cautious novice and at $100+ per batt, I want them to last ALAP!

 

[MAvic_South_Oz]

Never fly with a partial drained battery that have been laying around for a while, the cells are imbalanced & that may get worse during flight & make a cell fail.

This includes never fly a partial battery that has started auto discharge, say discharged down to 70%, tempting to take up for short flight for a few pics.

This would possibly include those Air 2 batteries of @eEridani , but not sure if the 24hr discharge to 96% might be considered self discharge yet, or affect cell balance at that early stage.

I think DJI is learning about leaving batts charged fully too long.
Used to be I could set my M1P batts to anything from 1 to 10 days, now can be set from 1 day to max is 5 days.

I usually let any remaining full batts discharge 5 days after an outing flying.
If I land with more than 50%, I just leave them to discharge further at 5 days.
If I land less than 50%, I charge until 3rd led starts flashing then take them off.

Do this for Spark too.
So far M1P x 6 batts (inc original 3 flymore), and Spark x 5 (also inc original 3 flymore) are still all good after 4 years.

 

[eEridani]

So @slup - a couple of questions.

1) Exactly what battery formulation are you basing all this on?
2) Do all DJI drone batteries use the exact same formulation?
3) Where can I find the information to research the specific battery formulation parameters?

When I designed with Panasonic batteries, I went to Panasonic for specs. When I designed with Gates batteries, I went to Gates. So who is providing you with the charge/discharge and cycle life characteristics for the DJI batteries?

 

[VenomXts]

I got my air2 in April of 2020, I run 4 batteries and I have to say I USE the smart battery discharge.. I tend to fly outside my backyard and have the fly more charger sitting next to the door inside then plug them in.

I agree, don't run them to critically low by any means and rotate if you have multiple but if you fly and just pop them on the charger it will charge when they are ready. Plus these aren't dumb lipos (your paying for that). Dont fly for 4 days rember to go pop em off and pop them back on.

I have seen a little degradation but not much really and I have no doubt they will go south eventually but use the smart technology your paying for.....

about 90% of below is from a single air2 with 4 batteries.

 

[slup]

So @slup - a couple of questions.

1) Exactly what battery formulation are you basing all this on?
2) Do all DJI drone batteries use the exact same formulation?
3) Where can I find the information to research the specific battery formulation parameters?

When I designed with Panasonic batteries, I went to Panasonic for specs. When I designed with Gates batteries, I went to Gates. So who is providing you with the charge/discharge and cycle life characteristics for the DJI batteries?

The battery cells inside a DJI battery aren't any special ... depending on drone model it's either LiPo or LiION chemistry ranging from 2S to 4S packs (how many cells inside the battery).

The specs for LiPo doesn't change depending on brand ... it is what it is. The usable voltage span is from 3 (under load) - 4,2 volts (with a high voltage LiPo max is 4,35v & they are labeled HV) with a resting voltage on 3,8v where the battery is very stable & very little happens to the chemistry (storage voltage). A Lipo going below 3v becomes permanently damaged ... & these shouldn't be let to go below 3,3v to be on the safe side. The voltage sag is about 0,2v when put under load ... ie. the battery will recover it's voltage per cell with 0,2v when disconnecting them.

A LiION battery have the similar behavior ... but with slightly different voltage figures. The usable voltage span is here from 2,5 (under load) - 4,2 volts with a slightly lower resting voltage on 3,7v/cell. The voltage sag is about 0,5v when put under load ... ie. the battery will recover it's voltage per cell with 0,5v when disconnecting them.

What the "SMART" in DJI batteries does is that these packs have a built in BMS (battery management system). It takes care of the charging/discharging parameters, it communicate info back to the flight controller, balance the cells in the end of the charge cycle, auto discharge them after a set time & can "ground" a battery & make it unusable (happens if letting them go to a very low voltage). With a BMS the charger can be a "dumb" charger ... it's enough that it can provide a correct voltage, the rest the BMS takes care of.

All of this can be found in all existing LiPo & LiION care descriptions ... just google LiPo battery care & read.

Battery wear & damage aren't digital ... it's a slippery slope, at resting voltage nearly nothing happens with the chemistry & they can be stored for years. But the further out to the low & high limits you come the more wear the battery will see. And it's also about how often & long you have them on max & min ... always have them stored at 100% vs. have a battery on 100% longer than 48h once in a while is a big difference. Store them really low is also quicker damaging than on high.

 

[infomed]

I use the Guardian Angel to recycle and keep my batteries at storage voltage when not in use. So far so good.

 

[eEridani]

Well - batteries from two different manufacturers can and usually are different. Electrolyte formulations and types are key elements to battery performance. Guessing about what is in a battery is worse than just letting the battery be.

DJI built these things, they sell a lot of them and probably know the characteristics well enough they probably know how to manage the battery. I laugh a bit when people connect their battery to an off brand charger and expect factory performance. Take swelling. How many of these swollen batteries were charged on a non-DJI charger? It only takes once to destroy a battery - even the BMS doesn't stop all foolish attempts to charge faster than acceptable for the battery design - they help, but BMS's aren't perfect.

As for lower charge states being damaging, the batteries are shipped in a hibernation state, below what we'd call fully discharged. They are in this state from manufacture until a user first charges it. This can be years. If a low charge state were damaging, you'd expect users to demand a date stamp to know they are buying a "fresh" battery, sort of like buying meat at the grocery store. But I don't see that happening with most any battery retailer, let alone DJI.

The other part of this is that even people on this forum have said they use elaborate charge mechanisms like day timers to keep their batteries at 100% charge - bypassing the BMS's attempts to make the batteries last longer and avoid detrimental storage conditions. When their batteries swell, I doubt they'll mention what they've been doing all along.

Until I see a spec sheet for the battery in my DJI Air 2 packs, I'll trust that what DJI tells me is probably accurate.

 

[EricJT]

I use the Guardian Angel to recycle and keep my batteries at storage voltage when not in use. So far so good.

Given the cost of my M2P batteries, I only fully charge the evening before flying and if not planning to fly in the next 24 hours, charge or discharge them to storage level until the next planned outing.

I have a 4 battery simultaneous charge/store after market charger. It makes it easier to maintain these costly batteries and get longer lives out of them.

 

[slup]

Well - batteries from two different manufacturers can and usually are different. Electrolyte formulations and types are key elements to battery performance...

Yes, the electrolyte can be slightly different between different manufacturers but the effect of that is, as you say performance regarding low internal resistance... not how well they can stand repeated abuse or which voltage levels that we can use without damaging it. What matter most during LiPo manufacturing is a controlled environment regarding oxygen & moist.

DJI built these things, they sell a lot of them and probably know the characteristics well enough they probably know how to manage the battery.

The keyword here is ... DJI design brand & model specific battery packs & sell a lot of them as people don't have alternatives ... and they make loads of money on this business. It's no magic regarding these LiPo batteries, the pouches inside are just regular ones ... have seen far to many DJI battery problems to believe that they have invented the holy LiPo grail. DJI have a economical incentive to just keep them going during the warranty period.

I laugh a bit when people connect their battery to an off brand charger and expect factory performance...

No need to laugh ... the use of a non branded charger is possible due to the BMS. The charger can be "dumb" as it manage nothing besides providing enough voltage & current ... all other processes regarding cell balancing, current needed during different stages in the charge cycle, cut-off limits & error flags is handled by the BMS.

This is the reason why standardized LiPo packs for quads require a much more advanced charger ... those packs doesn't have a BMS.

As for lower charge states being damaging, the batteries are shipped in a hibernation state, below what we'd call fully discharged...

That a DJI pack is in hibernation doesn't mean that they are totally empty ... they are on storage voltage 3,8v which make it possible for them to be stored for years without damage. During hibernation the BMS is deactivated & needs to be woken up by being put on the charger.

Until I see a spec sheet for the battery in my DJI Air 2 packs, I'll trust that what DJI tells me is probably accurate.

Their strategy regarding a BMS governed auto discharge is certainly better than nothing ... it will in most cases save a battery during the warranty period ... but it's not the best way to treat a 100$+LiPo battery if you want it to last as long as possible, & want to avoid airborne mishaps at all costs.

 

[MAvic_South_Oz]

That a DJI pack is in hibernation doesn't mean that they are totally empty ... they are on storage voltage 3,8v which make it possible for them to be stored for years without damage.

Of course people have to watch them as they do lose charge slowly down form the storage charge.
I cycle my 6 batteries as best possible, whatever is in my drone when going to fly next day, I charge up the following x number of batteries I think I'll need / have time to fly.

I've see once or twice an odd battery that were on 2 solid / 1 flashing led, go down to 1 solid 1 flashing over a longer period of not flying.
I now check them all with a quick level check at least once every couple of months.
Any I find not 2 solid / 1 flashing I'll pop them on the DJI charger and take off when they hit say 3 solid, put away again.

 

[slup]

...I've see once or twice an odd battery that were on 2 solid / 1 flashing led, go down to 1 solid 1 flashing over a longer period of not flying...

That's usually a sign of that one cell in the battery isn't fully healthy ... doesn't mean that it will not work in regular use but I bet that cell have a much higher internal resistance than the others in the battery & much of the cell deviation after use comes from that cell. Be extra careful regarding putting that battery on high sustained load, especially in colder ambient temps.

Have over the years received brand new LiPo batteries to my quads from very reputable brands where one of 6 cells haven't been on 3,8v on arrival ... instead down to like 3,2v. They have taken charge & been balanced after a charge but after use that cell have been much lower than the others & nearly held 90% of the total cell deviation ... That battery behaves cell deviation wise like a very well used one & shows large voltage drops during sustained high amp draw.

 

[MAvic_South_Oz]

That's usually a sign of that one cell in the battery isn't fully healthy ... doesn't mean that it will not work in regular use but I bet that cell have a much higher internal resistance than the others in the battery & much of the cell deviation after use comes from that cell. Be extra careful regarding putting that battery on high sustained load, especially in colder ambient temps.

Thankfully mine seem fine.
Just did an 11 battery (6 M1P / 5 Spark) check of cells, deviations on all from 0v to no greater than 0.02v.

Also great we don't have those VERY cold winters to deal with, heat yes . . . but then mostly I avoid cold (wet) winter flights, and also heat over the DJI recommended.
I'd say most Aussie pilots would avoid 35c + days, it's just not much fun, and heat haze terrible for any sort of camera work (early / very late flights aside).

Cheers for all your knowledge shared here on the forum, your flight / crash analytics (along with the others here) are very good to peruse and soak up.

 

[umanbean]

DJI built these things,

I'm almost positive DJI is not in the business of making batteries, or even assembling the packs. Someone else makes them to their specs.

 

[eEridani]

During this discussion it was fun to think about the claim "all LiPo are the same" then think back to all the lead acid formulations, all the NiMH formulations, and even back to all the carbon-zinc and alkaline formulations.

So sure, all LiPo batteries use the same innards and all can be charged and used the same way.

 

[Paint Rock Drones]

I’m going to be grounded for the next 3 days due to rain. Thanks to this thread I just ran my mini 2 in my living room (with prop guards) to get my second battery from 84% to under 60% for storage. Now I just have to remember to charge them back up when I do want to fly.

 

[MAvic_South_Oz]

I’m going to be grounded for the next 3 days due to rain. Thanks to this thread I just ran my mini 2 in my living room (with prop guards) to get my second battery from 84% to under 60% for storage. Now I just have to remember to charge them back up when I do want to fly.

Yeah, a shame the auto discharge takes 9 days to initiate on the mini 2.
Ok, some might think that's good if they want to fly say a week later and not have to recharge, but long term you are doing the right thing there, drop them down either flight day, and or top off to about half charge when you go lower.
Maybe a future update can make it user programmable, change it to discharge at 1 or 2 days.