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Tripling battery life span

this is no way to encourage a good technical discourse. To say there is no evidence of charging cycles causing failure is probably inaccurate. I have heard of a few batteries puffing up during charge, especially on Mavic Air 1.
yes, I agree. I thought it was a rather common knowledge too...
 
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Have you looked at the cell voltages after your limited charging?

What voltage are you supplying for a 90% charge?

What you are calling the “charger” is simply a regulated DC supply.

Is the BMS actually completing the charge routine or is it shutting down before charge completion?

If it’s the later then you might find the BMS might not have done a great job of balancing the cells.
oh, i havent thought about it this way. But does really it matter if you are not charging to full capacity?
 
Yes, the quoted V/cell are what I am reading after stopping at 50% or 90%.
Voltage applied before cutting off for 90% charge is about 13.03V.
Once that level is reached and current source is disconnected, per cell voltage drops to around 4.25V.
"Charger" is the brick.
I believe it is a current-limited source with maximum voltage of 13.2V.
That's usual for charging Li cells with constant current.
The batteries are disconnected from the source once predefined level is reached.
I am hoping BMS or more specifically the balancer is active throughout charging, not necessarily kicks in towards the very end of charging.
For that, I am constantly keeping an eye on balance of the cells until I am confident that balancing is happening without having to reach 100%.
You ask good questions.
This might help you


My fear is your solution might be no different to pulling the battery off charge before it has finished (the balancing routine seems to be running right until the end point set in programming the SOC.
 
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balance charging is done by the battery internal BMS. All chargers that I know just supply a max Voltage and let the battery do its own balancing
I would agree with that.
I could leave a battery disconnected from a DJI charger and the battery would do its own balancing as needed.
Just no good reason to think it wouldn't.
 
oh, i havent thought about it this way. But does really it matter if you are not charging to full capacity?
Yes, it matters a LOT in our application. An out of balance cell can cause the pack to shut down in flight. Many reports of this happening with otherwise healthy packs that have just entered self discharge and are reporting 90%+ capacity at launch.
 
This might help you


My fear is your solution might be no different to pulling the battery off charge before it has finished (the balancing routine seems to be running right until the end point set in programming the SOC.
That is exactly what my mod is doing.
Only automatically and one wouldn't have to sit next to it and pull batteries out without knowing accurate SoC.
 
I would agree with that.
I could leave a battery disconnected from a DJI charger and the battery would do its own balancing as needed.
Just no good reason to think it wouldn't.
There is no good reason to think the battery might perform cell balancing off the charger. I’m fact the TI data sheets make no mention of it so best to assume it doesn’t happen.
 
That is exactly what my mod is doing.
Only automatically and one wouldn't have to sit next to it and pull batteries out without knowing accurate SoC.
Your mod isn’t performing cell balancing. It can’t. What it might do is prevent the battery electronics from performing a proper balance.
 
There is no good reason to think the battery might perform cell balancing off the charger. I’m fact the TI data sheets make no mention of it so best to assume it doesn’t happen.
The battery cell management chip is this example:


Which mentions that the battery internally does the charge / voltage balancing.

Your mod isn’t performing cell balancing. It can’t. What it might do is prevent the battery electronics from performing a proper balance.
We probably have to check each cell voltage from the battery contacts (if they do expose such thing) if not from battery SM data, which will need decoding if we want some definitive information i suppose.
 
The battery cell management chip is this example:


Which mentions that the battery internally does the charge / voltage balancing.


We probably have to check each cell voltage from the battery contacts (if they do expose such thing) if not from battery SM data, which will need decoding if we want some definitive information i suppose.
Yes- cell voltage balancing is performed during the charge cycle by circuitry contained in the battery enclosure. I didn't suggest otherwise.

My point was that balancing is not performed while the battery is not connected to the charger and charging. A fact which seems to be supported by the application notes issued by the SOC manufacturer.

You don't need to suppose- the external battery contacts do not provide a path to the individual cell taps. Individual cell voltages are reported in the flight applications and are readable from flight log files.
 
Yes- cell voltage balancing is performed during the charge cycle by circuitry contained in the battery enclosure. I didn't suggest otherwise.

My point was that balancing is not performed while the battery is not connected to the charger and charging. A fact which seems to be supported by the application notes issued by the SOC manufacturer.

You don't need to suppose- the external battery contacts do not provide a path to the individual cell taps. Individual cell voltages are reported in the flight applications and are readable from flight log files.
Actually, :
8.3.5.5 Cell Balancing The device supports cell balancing by bypassing the current of each cell during charging or at rest. If the device's internal bypass is used, up to 10 mA can be bypassed and multiple cells can be bypassed at the same time. Higher cell balance current can be achieved by using an external cell balancing circuit. In external cell balancing mode, only one cell at a time can be balanced. The cell balancing algorithm determines the amount of charge needed to be bypassed to balance the capacity of all cells

there is a capability to self balance at rest.

Since as you pointed out correctly each cell can be read via log or in the app, what's the big mystery? OP can easily read per cell voltage after his device stops it at 90% and we can all know.
 
The battery cell management chip is this example:


Which mentions that the battery internally does the charge / voltage balancing.


We probably have to check each cell voltage from the battery contacts (if they do expose such thing) if not from battery SM data, which will need decoding if we want some definitive information i suppose.
Actually, :
8.3.5.5 Cell Balancing The device supports cell balancing by bypassing the current of each cell during charging or at rest. If the device's internal bypass is used, up to 10 mA can be bypassed and multiple cells can be bypassed at the same time. Higher cell balance current can be achieved by using an external cell balancing circuit. In external cell balancing mode, only one cell at a time can be balanced. The cell balancing algorithm determines the amount of charge needed to be bypassed to balance the capacity of all cells

there is a capability to self balance at rest.

Since as you pointed out correctly each cell can be read via log or in the app, what's the big mystery? OP can easily read per cell voltage after his device stops it at 90% and we can all know.
Yes, I recall reading this earlier and did consider it.

Could it be “at rest”, in the context of an active charge cycle simply means one or more cells is being 100% bypassed while others are subject to charge? The answer is probably yes. What current might be bypassed off charge or absent a connected load? If the cell isn’t presented with a load or connected to an external voltage source higher than the terminal voltage no current can flow (there is nothing to bypass).

The fact we observe our batteries to be out of balance after resting (a common finding) suggests that to the extent at rest balancing might be possible it isn’t implemented by DJI.
 
The self-discharge function basically uses the balance circuitry, so it's definitely custom programmable. Now as to when they do balancing since both continuous and at end of charge are common approaches there isn't really any way to know but to try it, but for that you need a badly balanced battery...
 
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The self-discharge function basically uses the balance circuitry, so it's definitely custom programmable. Now as to when they do balancing since both continuous and at end of charge are common approaches there isn't really any way to know but to try it, but for that you need a badly balanced battery...
Yes 100%.... I would not classify auto discharge as being “at rest” though and, from my direct observation, self discharge doesn’t do a great job of keeping cells balanced.

It would seem almost certain balance at rest might be implemented without difficulty. There is more to suggest it doesn’t happen however based on observations of battery performance.
 
I love my DJI, but for as little as I've flown it, the number of batteries that suddenly resist charging like normal, give weird flashing light sequences' is annoying and expensive. I am not impressed, but when every thing works as it should its a great little tool.
 
This is very interesting, I was thinking in the past of lowering voltage of my MA1 batteries as well.
Two things I have in mind:
SOC algorithm may calibrate at full charge, so repeatedly under-charge may induce some drift in state of charge calculations.
And second, ballancing may be less efficient because of terminating charge prematurely, at lower voltage.

Probably if you charge at the correct voltage in one of 3 to 5 charges, all would be OK for a healthy battery. The possible problems I listed above may get worse for worn battery packs.
 
Lithium batteries have made inroads to spacecraft usage. As for most low Earth orbits the batteries are cycled every hour and a half to two hours, the cycle life is of critical importance. The charge rates, discharge rates, high and low voltage levels are very carefully managed during design and operation. The power group gets very nervous allowing the charge state to drop below 50% or above 80%. The satellites for these missions generally have a projected life of four to six years requiring a useful life of 30,000 cycles at this 30% duty cycle.
Sadly, this low duty cycle virtually eliminates any energy density advantages of the lithium chemistry, but this option does allow use of commercially based production compared with the traditional nickel hydrogen batteries that have no non-aerospace applications that I am aware of. Satellite companies and the Space Force are are actively exploring chemistries and manufacturing processing to expand the depth of charge and discharge battery capability. Perhaps at some point, some of this research will be available for drone and other energy storage applications.
 
Hi, the discussion is wayward since the lipo gets killed due to high discharge rate. This is just a starting point of discussion since current increases by about 25% between 100% charge to about 30% discharge. So people going to 20% are actually killing the battery instead of this post point. Also DJI uses very light 10c batteries which are highly stressed during end of flight. My 2 cents is to land at 30 or 35% and never do sports mode below 60% battery. You battery life is going through roof
 
What do you mean "current increases"? The AC demands what it needs. If anything, current capabilities would decrease at low SoC, not increase.

10C will probably be sufficient. It's C, not A, and C in the MA is 3500mAh so peak current is 35A.
 
What do you mean "current increases"? The AC demands what it needs. If anything, current capabilities would decrease at low SoC, not increase.

10C will probably be sufficient. It's C, not A, and C in the MA is 3500mAh so peak current is 35A.
It’s a simple reality- lower voltage available from the supply will mean higher amps for a given power. Applying your logic the AC will, and does, need more current from the supply as the voltage sags...
 
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