Mavic Pro Battery Mod

[Fredo]

@cruzroy , do you have the STL of that bracket you're willing to share?

Thanks

You probably know this website but i still give it. You can find a lot of model to get inspiration here:
Things tagged with 'DJI MAVIC' - Thingiverse
https://www.thingiverse.com/tag:DJI_MAVIC/page:1

Need to check how this works. It would be a clean solution for the non-extreme modders. The dji battery, even with case is lighter than the 4000mah MS lihv.
Just curious..you d need to switch on the main first and plug the ext dji batt after. Chances are likely this will cause the main to switch off as usual.

I started the main battery, it start the drone, then plugged the second battery and started it. That worked for me.
I need to test again but if i remember good, when if you start the main battery, then plug the second, and wait... it will start charging your second battery! (mine was not at 100%) Just be care that you started it if not it will drain your main batt and will decrease your flight time.

 

[angusc]

Hi all, thanks for all your reply and your ideas.
Velcros are good idea for weight but it's not what i'm looking for as it look too ugly for me. But it's my own point of view. [emoji14]

I don't want to touch anything on my mavic or batteries.
I want to be able to return to an original looking Mavic, like just out of the box.
Ok i drilled a hole, but i searched an hour where to pass this cable without drilling anything and being able to close arms and to still fit in my chinese molded case. I finally found that it's impossible without drilling. But what i did is drilling under a small side cover plate. So i can remove the cable and replace the cover that none will see the hole.
I don't want to glue my batteries with such strong velcro.
That's why i'm looking for a bracket holder.

One thing for those who find my cable to small (because i know the question will finish to come... lol)
I'm electronician, i did some search and calculate the minimum cable size for this intensity.
One battery is 3.8Ah, empty in 20min, mean current is like 12A average. We will suppose some peak to 16A.
That is what must carry the cable when used with only 1 battery.
With 2 batteries, current is divided by 2, so each battery will give 8A peak.
8A is not a lot, and my 1mm² can support it. Also the current a cable can support depend of the cable length more it is and less current it can accept. Mine is like 10cm, so small !!

@JustStig : Thank you for your job, very interesting design, very close to what i have in my head. I take contact with you to discuss it.

I'm sure it will increase my flight time ! how can't it ????

Today i flew 3 times, with my 3 batteries, but once at a time. With the added cable just retained close to the body with an elastic.
All was perfectly fine ! No error, no pb.

Next step is to fly with 2 batteries connected, but i'm affraid by the idea of the top battery move and fall on the propeller because not attached properly.
But hey, we are experimenter, no ? [emoji14]

to follow...
Fredo

He fredo,

I can't wait for your first test! I want to ask if any one like @lolo780 or @Blade slap or anyone else here have tried stripping down one stock Mavic battery to the bare Li-Po cells and then connected them in parallel directly to the standard Mavic primary battery? If so does the displayed battery data work until both batteries are exhausted and its it accurate? What is the maximum flight time like that.... Total battery weight should be around 250 + 190g = 440g for 7660mAh

Thanx in advice for info

 

[Fredo]

I will try to test this week-end. Will do a typical flight with 1 battery, like flying around me until the batt is empty. And will do the same flight with 2 batteries attached, and will compare the flights times.
Will let you know of course!

 

[angusc]

great, I cant wait.....I have some ideas myself and have ordered some goodies from online, but not home until end of month so can't try anything until early December. But really interested to know the flight times for multiple stacked DJ Std batteries. From reading this entire thread over the past few days, it seems to me that the DJI battery cells are pretty good when compared to the after market packs....but that is only my opinion and not based on factual numbers so stand to be corrected by those that are in the know.

 

[Fredo]

I'm absolutely agree with you!
Nothing is better than the standard mavic batteries. Maybe i will fly 1 or 2 min less than a 4000mAh aftermarket battery mod because of weight and aerodynamics. But i will be safe because of many reasons.
Don't forget that you already have a mavic charger (no other charger to buy and put in your backpack when travelling) and remember also that the Mavic batteries are INTELLIGENT ! Each of them carry a processor that manage well the battery (charging time, tension, current, autodischarge... )
We should be good with this mod.

Does anyone have some real times result between a normal mavic autonomy and a modded one with 4000mAh or more aftermarket battery attached?

 

[dirtybum]

So what I'm actually interested in is the standard DJI battery mods. I realised about half easy though this thread that I was reading the wrong thread! But here goes my theory......run on one battery then switch over to the backup battery and disconnect the first battery. Aren't we wasting energy of one battery charging the other with dual parallel battery setup?

I don't know if anybody answered this for you already, the problem with carrying the weight of two batteries but only one of them fueling the A/C is your work the motors too hard, lifting the extra weight and your flight time is decreased. Try carrying the weight of an extra battery just using your stock battery, you'll see what I mean

 

[Fredo]

I don't know if anybody answered this for you already, the problem with carrying the weight of two batteries but only one of them fueling the A/C is your work the motors too hard, lifting the extra weight and your flight time is decreased. Try carrying the weight of an extra battery just using your stock battery, you'll see what I mean

Dual parallel battery setup (with standard Mavic battery) will never result as one battery will charge the other because intelligent Mavic battery can not charge if they are powered ON!

Try it on your desktop charger, start your battery then plug it. It will not charge!

 

[dirtybum]

Very familiar with running batteries this way, but he had stated after using up one battery shutting off and turning on the other battery

 

[MacIak]

To be honest i have not tried a main+ 4000mah external yet. Was planning to but the winds have been annoying during other testruns, see previous posts. Strong gusty winds drastically reduce the flighttimes when carrying load.

 

[lolo780]

He fredo,

I can't wait for your first test! I want to ask if any one like @lolo780 or @Blade slap or anyone else here have tried stripping down one stock Mavic battery to the bare Li-Po cells and then connected them in parallel directly to the standard Mavic primary battery? If so does the displayed battery data work until both batteries are exhausted and its it accurate? What is the maximum flight time like that.... Total battery weight should be around 250 + 190g = 440g for 7660mAh

Thanx in advice for info

I've never tried that, but I thought someone did.

 

[angusc]

Dual parallel battery setup (with standard Mavic battery) will never result as one battery will charge the other because intelligent Mavic battery can not charge if they are powered ON!

Try it on your desktop charger, start your battery then plug it. It will not charge!

Very familiar with running batteries this way, but he had stated after using up one battery shutting off and turning on the other battery

Ok so I need some clarifications please, you are saying that if one Mavic battery is turned on and then a second battery connected and also turned on that the second battery will NOT charge the first battery? However people report that if their second battery has higher voltage than the Mavic primary battery that changing of the Mavic battery will start? This seems to result in the primary battery switching off.....when this happens the guys have to run the AC on the secondary battery for a few minutes to pull down its voltage bellow the primary battery voltage before starting the primary battery and start their flight.

Did I miss understand something?

 

[lolo780]

You have to plug the external(s) in quickly and take off before the stock battery kicks in to charge mode.

 

[angusc]

You have to plug the external(s) in quickly and take off before the stock battery kicks in to charge mode.

So what does that imply? Does the Mavic prevent the primary battery going in to charge mode when flying?

Or does the power draw down during takeoff and initial flight pull down on the secondary batteries first?

 

[MacIak]

So what does that imply? Does the Mavic prevent the primary battery going in to charge mode when flying?

Or does the power draw down during takeoff and initial flight pull down on the secondary batteries first?

I never tried what lolo says: quick takeoff.
I just charge the externals to max 4.3v/cell and confirm all 4 leds are steady on the main battery before takeoff.
Cause i carry the externals on top i cannot observe the main led's after takeoff, that 's why i stick to this particular routine.
If you sideload the externals it s different story.

 

[Blade slap]

He fredo,

I can't wait for your first test! I want to ask if any one like @lolo780 or @Blade slap or anyone else here have tried stripping down one stock Mavic battery to the bare Li-Po cells and then connected them in parallel directly to the standard Mavic primary battery? If so does the displayed battery data work until both batteries are exhausted and its it accurate? What is the maximum flight time like that.... Total battery weight should be around 250 + 190g = 440g for 7660mAh

Thanx in advice for info

2 DJI Battery Estimation always in hovering to avoid any fly mode impact

 

[dirtybum]

So what does that imply? Does the Mavic prevent the primary battery going in to charge mode when flying?

Or does the power draw down during takeoff and initial flight pull down on the secondary batteries first?

Don't charge the external batteries to a full 4.35 on the Mavic & P4, stick to somewhere around the 4.32 area, on the P3 you can charge externals all the way to 4.35, on all models the trick has always been to take off as quick as possible so the thrust will balance them together. by the time you run to your controller, the lights may even start flashing already but if you take off quick enough, they can go solid on take off. Then observe main battery lights for but a few seconds while hovering ,you'll know real quickly if it's going to keep blinking or go solid.

 

[lolo780]

I take off and check the battery screen to make sure voltage and temp are reading. If the main battery shuts off those will go blank.
Seconds wasted at takeoff is flight distance gone. With externals I warm the aircraft up on a non flight Lipo until the home point updates, then plug in the externals and lift off immediately.

 

[angusc]

I take off and check the battery screen to make sure voltage and temp are reading. If the main battery shuts off those will go blank.
Seconds wasted at takeoff is flight distance gone. With externals I warm the aircraft up on a non flight Lipo until the home point updates, then plug in the externals and lift off immediately.

@lolo780,

Careful! You are giving away all your best kept secrets

I'm going to go with a different approach entirely.......watch this space.......maybe.

 

[JustStig]

@Fredo here is my first attempt at the extra battery holder.

 

[Fredo]

Wow, Look good for this first prototype.
Congrats!

Some thinks:
- Maybe trying to center the extra batt+holder on the gravity center of the mavic. Just to prevent extra stress on front propellers and motor.
- keeping holes to push the start and stop button and to see the leds of the main battery.
- Growing the front to help keeping the plug in place.

However it look good. Can't wait to see the final version of this project.
Thank you juststig for your time.

Didn't tried yet a full double battery flight, I was far from home and it was too windy to get proper values. BUT, tomorrow is THE day! No wind, great weather and all my day for me.
See u tomorrow for the results!
Fredo