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Battery Charging & Maintenance
1178 20 2017-10-17
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allanart
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Hi folks.
We all know that LiPo packs are best stored at 50% state of charge. However, I'm pretty sure that when using the standard DJI charger, the pack is balanced by the internal Battery Management System and then only and the END of the charge cycle (I would like to confirm this). If this is indeed the case - it would appear to me to be best to fully charge the packs and then leave them to self-discharge over the pre-set number of days. I currently have this set to 2 days, and I know that it takes a lot longer than that to self-discharge to 50%.
Any suggestions?

Regards
Allan


2017-10-17
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DJI Mindy
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No problem, if you enable the self-discharge function, you can fully charge the battery then leave it alone. It will discharge on its own.
2017-10-17
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Rodger8
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I believe 10 days is the normal time between fully charged and the start of the discharge cycle.
2017-10-17
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Viper Pilot
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That is not correct.  The time that the battery self discharge time begins is selectable in the Go 4 App.  
2017-10-17
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Farnk666
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Charging to 100% and then storing batteries is a sure way to reduce their working life or worse.
This topic has been covered dozens and dozens of times on the forum.

Storage charge of 50% and full charge before flight ops and consumed within 24-48 hours is best practice.
2017-10-17
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Rodger8
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Viper Pilot Posted at 2017-10-17 04:14
That is not correct.  The time that the battery self discharge time begins is selectable in the Go 4 App.

Yes, and 10 Days is the time suggested.
2017-10-17
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Flying Visions
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2 days it the best pratice. It will take another 24h to 48h to storage.
Consumed within 24-48 hours is best practice also.
2017-10-17
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fansa84fe8a4
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Setting a shorter time may also lead to it being DOA.  I leave it at 10 days, but usually recharge at some point within a month.  If these things were shipped with 2 days as the default instead of 10, there'd likely be more DOA ones sitting on store shelves.

My local hobby shop has plain Li-Po's without this attached intelligent nonsense sitting on their shelves for years awaiting sale and they still charge up and work.  The DJI ones, not so much.
2017-10-17
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allanart
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DJI Mindy Posted at 2017-10-17 01:50
No problem, if you enable the self-discharge function, you can fully charge the battery then leave it alone. It will discharge on its own.

Hi Mindy. Can you please confirm when in the charge cycle cell balancing occurs - is it:
(a) over the full duration of the charge cycle (i.e. always active)?
(b) at the end of the charge cycle?

Thanks
Allan
2017-10-17
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Drone-Mike
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Just had an update about a blog post about battery maintenance that seems really decent. https://www.heliguy.com/blog/201 ... attery-maintenance/
2017-10-25
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allanart
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Drone-Mike Posted at 2017-10-25 01:32
Just had an update about a blog post about battery maintenance that seems really decent. https://www.heliguy.com/blog/2017/10/25/drone-battery-maintenance/

Yep, all good stuff, but still dopes not answer the question as regards cell balancing. Is it done at the end of the charge cycle, or during the charge cycle?
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Allan
2017-10-25
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Drone-Mike
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allanart Posted at 2017-10-25 09:42
Yep, all good stuff, but still dopes not answer the question as regards cell balancing. Is it done at the end of the charge cycle, or during the charge cycle?
Regards
Allan

Definitely one for the moderators.

Any ideas @DJI?
2017-10-26
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Mark Guille
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allanart Posted at 2017-10-25 09:42
Yep, all good stuff, but still dopes not answer the question as regards cell balancing. Is it done at the end of the charge cycle, or during the charge cycle?
Regards
Allan

You may get a better response starting a new thread for this question Allen. I'm guessing the balancing takes place during the self-discharge process.

Mark G.
2017-11-3
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allanart
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I don't think so Mark.
I am *almost* sure that balancing takes place at the very end of the charge sequence and for this reason I think its a bad idea to only partially charge to batteries to 50% for storage. For this reason, I fully charge them, assume that the cells are balanced, and then allow them to self-discharge (over the preset period). I would still like to confirm this - but I cant help but get the impression that DJI only seek to answer the really easy questions and disappear altogether if anyone digs a little deeper!

Regards
Allan
2017-11-3
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Mark Guille
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allanart Posted at 2017-11-3 09:49
I don't think so Mark.
I am *almost* sure that balancing takes place at the very end of the charge sequence and for this reason I think its a bad idea to only partially charge to batteries to 50% for storage. For this reason, I fully charge them, assume that the cells are balanced, and then allow them to self-discharge (over the preset period). I would still like to confirm this - but I cant help but get the impression that DJI only seek to answer the really easy questions and disappear altogether if anyone digs a little deeper!

Hi Allen,
This is interesting, what makes you think that they are balanced at the end?

Mark G.
2017-11-3
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Henry M.Y.
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allanart Posted at 2017-11-3 09:49
I don't think so Mark.
I am *almost* sure that balancing takes place at the very end of the charge sequence and for this reason I think its a bad idea to only partially charge to batteries to 50% for storage. For this reason, I fully charge them, assume that the cells are balanced, and then allow them to self-discharge (over the preset period). I would still like to confirm this - but I cant help but get the impression that DJI only seek to answer the really easy questions and disappear altogether if anyone digs a little deeper!

Hi Allan,

You may find some clues for the answer to your query by looking at the voltage differences amongst individual cells of a 50% charged battery, and at those of a 100% charged battery, both when hovering.  If the voltage differences of a 50% charged battery are similar to those of a 100% charged battery, the cell balancing should have been done throughout the whole charging process.

Regards,

Henry
2017-11-3
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allanart
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Mark Guille Posted at 2017-11-3 14:05
Hi Allen,
This is interesting, what makes you think that they are balanced at the end?

The packs have an internal Battery Management System (BMS) and the chip-set deployed in all the BMS solutions that I have seen balance the cells at the end of the charge cycle - prior to terminating the charge. That said, its only my assumption. Hence the question.

Regards
Allan
2017-11-4
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allanart
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Henry M.Y. Posted at 2017-11-3 17:42
Hi Allan,

You may find some clues for the answer to your query by looking at the voltage differences amongst individual cells of a 50% charged battery, and at those of a 100% charged battery, both when hovering.  If the voltage differences of a 50% charged battery are similar to those of a 100% charged battery, the cell balancing should have been done throughout the whole charging process.

I very much doubt that any cell balancing takes place during  the discharge cycle Henry.
Regards
Allan
2017-11-4
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Henry M.Y.
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allanart Posted at 2017-11-4 03:11
I very much doubt that any cell balancing takes place during  the discharge cycle Henry.
Regards
Allan

Hi Allan,

I didn't mean discharge balancing in my earlier post.

What I meant was to (1) charge a battery from say 15% to 50%, and then (2) analyse the voltage differences between cells of that 50% charged battery by hovering, and then (3) charge the same battery from 50% to 100%, and then (4) analyse the voltage differences between cells again by hovering.

Henry
2017-11-4
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Mark Guille
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allanart Posted at 2017-11-4 03:10
The packs have an internal Battery Management System (BMS) and the chip-set deployed in all the BMS solutions that I have seen balance the cells at the end of the charge cycle - prior to terminating the charge. That said, its only my assumption. Hence the question.

Regards

Thanks Alan,

The reason I'm thinking it's happening during self-discharge is, I have never (since new, Feb 2015) manually discharged my TB47/48's before storing, leaving it up to the batteries to discharge themselves to the appropriate voltage for any long periods of non-use. My motto was "Fully charge before AND after every flight" (leaving the "intelligent" batteries to look after themselves). I have never had any problems with this method but recently I experimented with two batteries, one TB47 and one TB48, discharging them to around 50%  before leaving them for any period longer than 24 hours. Within half dozen or so cycles, these two batteries were out of balance. Still only an assumption and until DJI can enlighten us, we're all guessing

Mark G.
2017-11-4
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allanart
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Mark Guille Posted at 2017-11-4 07:32
Thanks Alan,

The reason I'm thinking it's happening during self-discharge is, I have never (since new, Feb 2015) manually discharged my TB47/48's before storing, leaving it up to the batteries to discharge themselves to the appropriate voltage for any long periods of non-use. My motto was "Fully charge before AND after every flight" (leaving the "intelligent" batteries to look after themselves). I have never had any problems with this method but recently I experimented with two batteries, one TB47 and one TB48, discharging them to around 50%  before leaving them for any period longer than 24 hours. Within half dozen or so cycles, these two batteries were out of balance. Still only an assumption and until DJI can enlighten us, we're all guessing

Yep - that's my experience also Mark.
Regards
Allan
2017-11-4
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