Best battery discharge method?

[Former Member]

You mentioned swelling. I was discharging my batteries to 0% for the second time (twentieth cycle) and now they are swelling to the point of disconnecting in flight. Can you please expound on this?

This is a swollen battery. From the top it just looks dented, but the bottom reveals the swell. A crack in the casing makes it unusable in a drone due to expansion and lack of its ability to lock in tightly.

 

[mbsz53]

This is a swollen battery. From the top it just looks dented, but the bottom reveals the swell. A crack in the casing makes it unusable in a drone due to expansion and lack of its ability to lock in tightly.

View attachment 50131View attachment 50130

Thank you for the pictures. I'm well aware of what they look like. I have for of them. I was asking to share your knowledge of how the swelling might happen. I googled it and it seems to be an issue with faulty batteries our overcharging. Since all four of mine went at the same time, I'm guessing it's from overcharging. Thanks for your input. I really just need to get to the bottom of this so it doesn't happen again.

 

[WithTheBirds]

Thank you for the pictures. I'm well aware of what they look like. I have for of them. I was asking to share your knowledge of how the swelling might happen. I googled it and it seems to be an issue with faulty batteries our overcharging. Since all four of mine went at the same time, I'm guessing it's from overcharging. Thanks for your input. I really just need to get to the bottom of this so it doesn't happen again.

Given you have four dead ones you can probably safely rule out over charging. The charge circuitry is in the battery casing (what is often referred to as the charger is simply a regulated DC power supply). The charge circuitry includes overvoltage protection. While it may fail for it to happen to all four isn’t likely.

 

[DanMan32]

I can tell you that my P3 always started landing due to critically low battery at 10% on the occasion it got that low. Now the default critically low setting in Go3 was 10%. I never changed that to a higher setting so I can't say if I did raise it, it would try forced landings sooner but I suspect it would.
The low battery warning on the other hand, defaulting to 30% on the P3, is only an alert. It did not affect low battery RTH.

 

[mbsz53]

Given you have four dead ones you can probably safely rule out over charging. The charge circuitry is in the battery casing (what is often referred to as the charger is simply a regulated DC power supply). The charge circuitry includes overvoltage protection. While it may fail for it to happen to all four isn’t likely.

Gee thanks...lol. Just when it made sense that was the issue. You have a valid point. Why would all four batteries swell at the same time? I did everything the manual asked in terms of maintenance and stored them in conditions within the operating temperatures. I even let them cool before recharging. I had read another operator who ruined a battery in that manner.

 

[WithTheBirds]

I can tell you that my P3 always started landing due to critically low battery at 10% on the occasion it got that low. Now the default critically low setting in Go3 was 10%. I never changed that to a higher setting so I can't say if I did raise it, it would try forced landings sooner but I suspect it would.
The low battery warning on the other hand, defaulting to 30% on the P3, is only an alert. It did not affect low battery RTH.

Im not suggesting MSINGER is wrong re how it works now (P3)- it definitely worked like that on the early P3P firmware. Happened to me and I managed to reproduce the behaviour with another battery. What I can say is that if in reality the AC will land when it thinks it needs to regardless of what the critical battery % is set to in the GO app it is a completely useless setting that can be safely removed from the app. We already have a low warning. Why might we need a second one if it has no additional function?

 

[WithTheBirds]

Gee thanks...lol. Just when it made sense that was the issue. You have a valid point. Why would all four batteries swell at the same time? I did everything the manual asked in terms of maintenance and stored them in conditions within the operating temperatures. I even let them cool before recharging. I had read another operator who ruined a battery in that manner.

A couple of things.... Are you someone who has a need for rapid response with the drone and keeps the packs charged at 100%? You talk about storage temp. What about charge level?
Did you let them sit for more that 24hours before charging after the deep discharge?
Have you tried to charge them in low temperatures?

LiPO's do not like to be kept at full charge, it significantly reduces the service life. Thats why life is so much better for many with the auto discharge feature.

LiPO's don't like being charged when cold.

LiPO's really don't like being kept close to fully discharged- they like this even less than being kept at 100%


It is unlikely you killed four packs with the deep discharge routine but I probably wouldn't do it with any future packs. If you have access to a multimeter it wouldn't hurt to measure the open circuit voltage of your "charger" to make sure all is good there- would be a surprise if its not.

 

[Former Member]

Could be the charger. Which charger are you using?

 

[tcope]

That's not what the manual says.

The fact that the manual _once_ stated your should discharge and that it no longer states this is why you just let them discharge on their own.

 

[BIGDAVE]

I find the best way to discharge a battery is to fly it until it's down below 60%. If you cant fly it, the battery will self-discharge in a number of days according to the setting you have in DJI Go.

I wonder if AND WHEN DJI will give us the option to have battery's discharge when we want them to.

 

[mbsz53]

I wonder if AND WHEN DJI will give us the option to have battery's discharge when we want them to.

We already have that option. The setting is in the GO app.

 

[mbsz53]

The fact that the manual _once_ stated your should discharge and that it no longer states this is why you just let them discharge on their own.

Thank you for this input. I did not know that the manual had been amended to exclude complete discharge as part of the normal maintenance. Would you agree the best plan is to continue to fly with them to about 30% and then charge?I read somewhere outside of DGI, that is the best way to get the maximum life from nicad batteries.

 

[WithTheBirds]

Thank you for this input. I did not know that the manual had been amended to exclude complete discharge as part of the normal maintenance. Would you agree the best plan is to continue to fly with them to about 30% and then charge?I read somewhere outside of DGI, that is the best way to get the maximum life from nicad batteries.

These are LiION chemistry, not NiCad. 30% is a good landing % for reasonably good life from these packs. You can go lower, with less cycles expected or higher with more.

 

[WithTheBirds]

We already have that option. The setting is in the GO app.

Actually we have no option to set the days to self discharge behaviour with the M2- currently we are stuck with 10 days as default. I suspect thats what @BIGDAVE was getting at.

 

[tcope]

Would you agree the best plan is to continue to fly with them to about 30% and then charge?I read somewhere outside of DGI, that is the best way to get the maximum life from nicad batteries.

As mentioned below, these are lipo batteries. Two important things to remember about them.... they like to be stored around 30-50% (basically, around 1/2 charge) and don't like to go down to _very_ low volts. They don't develop memory. Personally, I charge them up before use to 100% and fly them down to about 25% and just leave them. But I usually charge them up again within 30 days. Every once in awhile I'll charge them to 100% and not fly... so they discharge automatically over the course of a week or so.

I'd say it is not bad to drain them down to 8% or so but I'd then charge them at least a little before any storage. This really serves to correct any problems with the software in the battery that controls charging and discharging.

 

[BerndM]

Just curious.
Does anyone know what the actual battery cell voltage is in relationship to the % reading?
Thanks

 

[WithTheBirds]

As mentioned below, these are lipo batteries. Two important things to remember about them.... they like to be stored around 30-50% (basically, around 1/2 charge) and don't like to go down to _very_ low volts. They don't develop memory. Personally, I charge them up before use to 100% and fly them down to about 25% and just leave them. But I usually charge them up again within 30 days. Every once in awhile I'll charge them to 100% and not fly... so they discharge automatically over the course of a week or so.

I'd say it is not bad to drain them down to 8% or so but I'd then charge them at least a little before any storage. This really serves to correct any problems with the software in the battery that controls charging and discharging.

What might you be proposing could or might be corrected in the battery software ny discharging to 8%?

 

[WithTheBirds]

Just curious.
Does anyone know what the actual battery cell voltage is in relationship to the % reading?
Thanks

No. The voltage only gives an approximation of capacity. Also it varies with applied load, operating temperature and is further changed by age and overall condition of the cells.

 

[tcope]

Just curious.
Does anyone know what the actual battery cell voltage is in relationship to the % reading?
Thanks

What would be far more useful is to know what voltages a person should be concerned with. That is, at 4.xx the battery is fully charged, at 3.xx you should be at or near the home point, at 3.xx you should be landing, at 3.xx the Mavic will start to land and at 3.xx the battery will shut off. This are much more accurate then percentages. It is my recommendation that people should always turn on the voltage display in the settings and watch that as well as the percentages. There is a charge for these voltages for the Phantom batteries. I'm not sure that a chart exists for the Mavic but it is possible that they would translate over. I've not looked into that. I do know that @msinger keeps the phantom voltage list available. Perhaps he knows if there one for the Mavic.

 

[WithTheBirds]

What would be far more useful is to know what voltages a person should be concerned with. That is, at 4.xx the battery is fully charged, at 3.xx you should be at or near the home point, at 3.xx you should be landing, at 3.xx the Mavic will start to land and at 3.xx the battery will shut off. This are much more accurate then percentages. It is my recommendation that people should always turn on the voltage display in the settings and watch that as well as the percentages. There is a charge for these voltages for the Phantom batteries. I'm not sure that a chart exists for the Mavic but it is possible that they would translate over. I've not looked into that. I do know that @msinger keeps the phantom voltage list available. Perhaps he knows if there one for the Mavic.

Keeping a track of individual cell voltages, or more specifically the variation between cells is a useful indicator of battery condition. The pack is only as good as the weakest cell and large variations are good cause to be suspicious of the battery condition and probability of failure.

Overall voltage isn't reliable in determining remaining flight time. Simply because remaining charge as it relates to voltage will change as the pack ages and with changing temperature and load. The remaining % and flight time depicted in the GO app is significantly more reliable. The battery management SOC calculates this in real time based on numerous available data, voltage being only one factor.