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Tripling battery life span
570 33 2020-12-6
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DIY_Quad
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So I made some modification to the MA2 charging hub to help my batteries last longer…a lot longer, supposedly like 3X longer.
I added a micro controller that monitors charging voltage and stops charging when it hits a preset level and then moves on to the next battery until all 3 batteries are charged to the preset level.
When I am charging to fly, the modified hub would charge to 90% (about 4.25V/cell) only instead of 100% (ie. 4.4V/cell).
It would cut flying time by that much each time I fly but if that translates to increasing number of discharge cycles by about 3X (source: batteryuniversity.com), that's a tradeoff worth taking.
Also, when storing batteries, instead of waiting 10 days for the intelligent self-discharge to kick in, I can set the modified charging hub to charge all 3 batteries to 50% only and stop.
Because I don’t like the idea of leaving batteries fully charged even for 10 days since irreversible damages however small will take place during that time and if repeated over time, it will further shorten life.

20201206_164438_1.jpg

The added tactile switch cycles through 50%, 90% and 100% charging modes and the LED lets me know mode selected.
20201206_164735_1.jpg

*edit* adding a table showing improvements in discharge cycles with respect to charge level per cell.
LIPo.JPG


2020-12-6
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fans01d4f09b
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interesting and well done, would you like to share more details ? I would be something I'm interested to do it for myself.
2020-12-6
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JohnLietzke
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Wow! Very detailed.  I would be very interested in a tutorial and components.
2020-12-6
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MisterFrag
First Officer
Flight distance : 84928 ft
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I bet you could sell the modified hubs for a small profit.
2020-12-6
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GaryDoug
Captain
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Don't you just love Microchip? Get almost any configuration you want and easy to program and cheap for 1-piece price.

No offense, but your soldering skills are horrible....like mine (<<< EE) That is the sure fire mark of a real engineer ;-)
Also love the hacked up prototype pcb. I must have a dozen like that.

2020-12-6
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liteshine
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Flight distance : 742320 ft
Poland
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Very good idea. I use similar thinking and when I do not plan to fly in the coming days, after flying I only charge the battery to 50-60% and leave it there. I fully charge it just before the flight. When charging halfway, I set the watch to about 30 minutes and turn off the charging.
2020-12-6
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DJI Stephen
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Hello there DIY_Quad. Thank you for reaching out and for these information.  Just a reminder that DJI does not recommend you to modify your DJI product. These modifications might affect the said DJI drone when in use. There is a possibility that these modifications will be able work. Since it's not optimized and tested by DJI we cannot guaranteed the stability of the said 3rd party accessory or modifications if it will work all the time with no issues and might void the warranty of the said DJI product. Thank you and have a safe flight always.
2020-12-6
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WebParrot
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Is there something that you've discovered about the on-battery circuitry that leads you to believe such significant deterioration is taking place? (by leaving a greater-than 50% charge)? From my years of RC cars/trucks using LiPO I understand the importance of discharging them to a 'storage level' but those batteries have zero circuitry to manage discharging on their own.  On my eariler Mavic Pro series batteries I was led to believe that they manage the discharge process to avoid holding the charge to the length that damage occurs.  
Not challenging your creativity, just wondering what you've learned about the batteries themselves.

Also... what about the batteries in the controller?
2020-12-6
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PAYBACK
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Brilliant but why wouldn't DJI just implement the option in that fly app? If I can remember you had this option in the DJI GO app.


2020-12-6
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DIY_Quad
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WebParrot Posted at 12-6 20:39
Is there something that you've discovered about the on-battery circuitry that leads you to believe such significant deterioration is taking place? (by leaving a greater-than 50% charge)? From my years of RC cars/trucks using LiPO I understand the importance of discharging them to a 'storage level' but those batteries have zero circuitry to manage discharging on their own.  On my eariler Mavic Pro series batteries I was led to believe that they manage the discharge process to avoid holding the charge to the length that damage occurs.  
Not challenging your creativity, just wondering what you've learned about the batteries themselves.

The moment a LiPo battery is exposed to too high- or too low-voltage, irreversible damage starts to take place.
It's not like some time-delayed damage process where there is zero damage for x hours or days.
It's a chemical reaction one cannot delay.
That's why I am not comfortable with the10-day wait before self-discharge kicks in for my MA2 batteries.
LiPo cells can be charged over their rated max voltage (within reason)  and give you more flight time but at the expense of shortened number of discharge cycles.
4.4V (for high voltage LiPo) is not something set in stone.
It is something DJI decided to settle for a balance between flight time and number of discharge cycles before battery capacy drops to certain percentage below initial level.
What I am doing with this mod is shifting that balance towards 3X more discharge cycles at the expense of slightly reduced flight time.
Same goes for the battery in the controller.
With that one, I don't have a mod for it.
I just charge it to about 75% *manually* while charging my MA2 batteries just before leaving home.
2020-12-6
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DIY_Quad
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GaryDoug Posted at 12-6 19:19
Don't you just love Microchip? Get almost any configuration you want and easy to program and cheap for 1-piece price.

No offense, but your soldering skills are horrible....like mine (

My soldering skill took a dive when I switched from lead based solder to lead-free one.
2020-12-6
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DIY_Quad
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liteshine Posted at 12-6 19:20
Very good idea. I use similar thinking and when I do not plan to fly in the coming days, after flying I only charge the battery to 50-60% and leave it there. I fully charge it just before the flight. When charging halfway, I set the watch to about 30 minutes and turn off the charging.

Yeah, that works too.
I did that before making this mod.
But then I would often forget to disconnect the batteries at the right time and end up fully charging them.

2020-12-6
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DIY_Quad
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fans01d4f09b Posted at 12-6 18:29
interesting and well done, would you like to share more details ? I would be something I'm interested to do it for myself.

It's no big deal sharing more info, but after receiving a warning from DJI, I don't know...
2020-12-6
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DIY_Quad
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PAYBACK Posted at 12-6 21:13
Brilliant but why wouldn't DJI just implement the option in that fly app? If I can remember you had this option in the DJI GO app.

Not familiar with the GO app, but what I heard is that the GO app lets you choose the time before self-discharge kicks in.
I wouldn't think there is an option to charge to a preset voltage or percentage.
I just don't like my batteries to see anything above 4.25V/cell for any amount of time.
If you limit it to 4.2V/cell max, you quadruple number of discharge cycles!
2020-12-6
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Montfrooij
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Too bad DJI did not make it like this.
2020-12-6
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azzido
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@DIY_Quad

There is a tool quite new on the market that could be used to charge or discharge a laptop battery to a specific SoC (State Of Charge), it is called NLBA: https://www.laptopu.ro/product/professional-laptop-battery-analyzer-nlba1/

Most of new DJI batteries already have SMBus data lines (clock and data) on the external connector, I would say that this tool should the the job.
2020-12-7
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DIY_Quad
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azzido Posted at 12-7 00:24
@DJI_quad

There is a tool quite new on the market that could be used to charge or discharge a laptop battery to a specific SoC (State Of Charge), it is called NLBA: https://www.laptopu.ro/product/professional-laptop-battery-analyzer-nlba1/

Interesting.
Thanks for the info.
Learning something new every day.
2020-12-7
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azzido
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DIY_Quad Posted at 12-7 00:27
Interesting.
Thanks for the info.
Learning something new every day.

If you plan to store the batteries for a long period, I recommend you to perform a full charge-discharge cycle in order to update FCC dynamic parameter and report correct SoC.
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azzido
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DIY_Quad Posted at 12-7 00:27
Interesting.
Thanks for the info.
Learning something new every day.

Since you have already a microcontroller, you could make a simple SMBus communication and read the SoC parameter so you can disable charging when SoC reached desired value.
2020-12-7
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DIY_Quad
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azzido Posted at 12-7 00:39
Since you have already a microcontroller, you could make a simple SMBus communication and read the SoC parameter so you can disable charging when SoC reached desired value.

I didn't know the 2 wires carried SMBus protocol until you mentioned it.
Without that info, and without knowing full register map of the battery, I would not know what to read/write.
And so I opted for a less sophisticated approach, which is to monitor charging voltage to approximate SoC.
I should read up more on the SMBus and see if there is some predefined structure that battery manufacturers follow.
Again, thanks for the tip.

*edit* Given that there are 3rd party chargers and hubs, the register map for these batteries probably follow a publicaly disclosed format.
What you said should be very doable.


2020-12-7
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A J
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Interesting thread- thanks for sharing
2020-12-7
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DowntownRDB
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Very interesting DIY.  Not sure you'll actually accomplish increasing number of discharge cycles by about 3X but should at least 2X would even be a hugh improvement.
2020-12-7
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DIY_Quad
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DowntownRDB Posted at 12-7 05:26
Very interesting DIY.  Not sure you'll actually accomplish increasing number of discharge cycles by about 3X but should at least 2X would even be a hugh improvement.

what is your reason for saying 3X increase would be difficult?
just curious if there are other limiting factors I have not considered.


Thanks.
2020-12-7
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Pappy3
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For those who lack the skills needed in order to hack the battery charging hub, there is already an AC/DC charger for the Mavic Air 2 which has a "Storage Mode" charge option. This mode will charge or discharge the batteries (up to 4 at a time) to around the 55% level. I "Storage" charged three of my batteries after flying and here are the results:
StorageChargeResults.png


Hanatora Battery Wall Charger & Car Charger for DJI Mavic Air 2 Drone and USB-C Remote Controller Cable,5 in 1 Rapid Multi Parallel Charging Hub with Charge and Storage
2020-12-7
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DIY_Quad
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Pappy3 Posted at 12-7 15:29
For those who lack the skills needed in order to hack the battery charging hub, there is already an AC/DC charger for the Mavic Air 2 which has a "Storage Mode" charge option. This mode will charge or discharge the batteries (up to 4 at a time) to around the 55% level. I "Storage" charged three of my batteries after flying and here are the results:
[view_image]

Like I mentioned earlier, while this charger is capable of charging to storage voltage, it won't double or triple discharge cycles for your batteries.
Because it does not let you charge to ~90% (4.25V/cell) or somewhere below 100% to reduce voltage stress when you fly.
Limiting voltage stress during storage as well as flights is the key to make your batteries last many times longer.
Merely keeping at 50~55% while storing isn't going to increase discharge cycles if you charge them to 100% every time you fly.
2020-12-7
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The Saint
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long ago, i learned to stop "tampering" with oem equipment and thus taking responsibility for the risk of fire and resulting destruction.  much rather throw away batteries and buy new ones.  not trying to rain on the parade but this is just silly if it's for recreational purposes.
2020-12-7
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DIY_Quad
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The Saint Posted at 12-7 17:55
long ago, i learned to stop "tampering" with oem equipment and thus taking responsibility for the risk of fire and resulting destruction.  much rather throw away batteries and buy new ones.  not trying to rain on the parade but this is just silly if it's for recreational purposes.

Yes, tempering with something you don't understand can be dangerous and silly.
This mod is for those who are not afraid to learn and try new ideas.......it's probably beyond you.
2020-12-7
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luciens
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I thought the time before the smart batteries began to discharge on their own was configurable? I think it is on the batts for my Mavic pro, but my memory is faulty.

Otherwise, agree about not charging to full. Years ago on my R/C LiPos for my Helis and rotorcraft, I charged only to 4.1v/cell and they lasted for years and uncounted number of cycles. As for storage, I always used 3.8-3.85v resting for storage (about 50% cap) and they would sit literally for a year and still be fine afterwards.

Don't know about LiIo tho.....
2020-12-12
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DIY_Quad
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luciens Posted at 12-12 09:37
I thought the time before the smart batteries began to discharge on their own was configurable? I think it is on the batts for my Mavic pro, but my memory is faulty.

Otherwise, agree about not charging to full. Years ago on my R/C LiPos for my Helis and rotorcraft, I charged only to 4.1v/cell and they lasted for years and uncounted number of cycles. As for storage, I always used 3.8-3.85v resting for storage (about 50% cap) and they would sit literally for a year and still be fine afterwards.

You are correct about configurable time before discharge for Mavic 2 Pro/Zoom smart batteries.
Unfortunately, that is not an option for Mavic AIr 2 batteries :-(
2020-12-12
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luciens
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DIY_Quad Posted at 12-12 09:42
You are correct about configurable time before discharge for Mavic 2 Pro/Zoom smart batteries.
Unfortunately, that is not an option for Mavic AIr 2 batteries :-(

Ah ok... Oh well. I tend to wear them out from strenuous use long before then anyway so I guess it doesn't matter . I fly pretty aggressively in sport mode almost all the time so I'm used to batteries not lasting very long...

2020-12-12
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DIY_Quad
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luciens Posted at 12-12 10:00
Ah ok... Oh well. I tend to wear them out from strenuous use long before then anyway so I guess it doesn't matter . I fly pretty aggressively in sport mode almost all the time so I'm used to batteries not lasting very long...

Think of it this way, with your aggressive flying style, let's say you normally get ~100 discharge cycles per battery before they no longer give you meaningful amount of flight time.
If you limit your charging to 90% instead of 100% each and every time you fly, you would get ~300 discharge cycles out of the same battery.
If normally 50 discharge cycles, then you'd get ~150 discharge cycles and so on.
Wouldn't you like that? :-)
2020-12-12
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Bob-Mavic Pro Platinum
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Flight distance : 12421 ft
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Yes, the trade off is clearly worth it.  Good job, and thanks for the information.
2020-12-12
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The Duck
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This is great feature.  I wish aftermarket chargers could do this.  
2020-12-12
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DIY_Quad
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The Duck Posted at 12-12 19:43
This is great feature.  I wish aftermarket chargers could do this.

Thanks.
DJI advertises MA2's long flight time as one of main selling points.
Introducing this kind of feature would mean less flight time and selling less batteries.
I still love you DJI

*edit*
ah..you said aftermarket....yes, it would sell I think.


2020-12-12
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