Mavic Pro Battery Mod

digdat0 · Sep 21, 2017

Dont beat me up too hard on soldering guys .. ed, db you know lol

Ed209 · Sep 21, 2017

Nice video. You did some things a little differently but for the better I think! I never disconnected the battery plug housing from the frame but that made for tighter quarters to work with. If I ever had to do it again, I'd do it your way. As for your soldering...I'm not a solder nazi! If it works, who cares!

dirtybum · Sep 21, 2017

soldering is 50/50 for me, A couple times in a row I'll make things look like glass and I feel like I'm a pro and then I'll tackle something that looks like dried lava rock and I say to myself "I don't even think I know what I'm doing"

when I changed the main board and had it lifted out, that's when I soldered the leads in this time. it was so much easier. I think when I have to do in the future I'll unscrew the board and lift it out of there a little bit.

CyberNate · Sep 21, 2017

digdat0 said:
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Dont beat me up too hard on soldering guys .. ed, db you know lol

That's exactly where I soldered mine, right in the middle of those wires. That way you have the least resistance. If you try to solder to the board, it's possible that there's no metal to metal contact, but rather solder between. Solder is not as conductive as you'd think. Much better to have metal on metal contact with solder over. I actually wrapped my XT60 leads around the main power wires before adding solder. I made the iron very hot and just let the solder flow in and around the wiire contact points. I will say that I'm the worlds worst with hands-on stuff. You are like a pro compared to me.

MacIak · Sep 21, 2017

SkyNinja said:
@digdat0, I have it set to non-DJI battery and LED warning only

@Lightspeed, both of my critical landing perimeters speeds are set to 0. The bird will say critical landing but doesn’t land.

@lolo780, ok i’ll go in to assistant and see if I can find the discharge rate after the DJI battery shut off.

Guys don t be too hard on me but i do not understand 1 thing:
Did a quick flight with the mav today, still in the phase of getting used to the bird ( have an issue with the gimbal, it's jumpy during forward flight, like it's gusty but actually calm wind, giving the jello thing...if anyone knows a fix id like to know).

I used 2x 3000 lihv, direct mod. Duration 31 mins, covered 25.500m in oval patterns, landed at 7%.
After flight checked the voltage on externals: average 3.58v/cell. (10.8v total).
With the externals plugged off rebooted mavic and main battery cells show 3.58v/cell, total 10.8v at 6%.
Now to me it looks like a good deal but i read some are able to burn the externals down (towards 3.21 volts??) even further and still %left in main battery?
How does that work without totally destroying the externals?

lolo780 · Sep 21, 2017

MacIak said:
Guys don t be too hard on me but i do not understand 1 thing:
Did a quick flight with the mav today, still in the phase of getting used to the bird ( have an issue with the gimbal, it's jumpy during forward flight, like it's gusty but actually calm wind, giving the jello thing...if anyone knows a fix id like to know).

I used 2x 3000 lihv, direct mod. Duration 31 mins, covered 25.500m in oval patterns, landed at 7%.
After flight checked the voltage on externals: average 3.58v/cell. (10.8v total).
With the externals plugged off rebooted mavic and main battery cells show 3.58v/cell, total 10.8v at 6%.
Now to me it looks like a good deal but i read some are able to burn the externals down (towards 3.21 volts??) even further and still %left in main battery?
How does that work without totally destroying the externals?

If you're directly wired, and only drawing ~2c, then all three packs should match in voltage at the end. Internal resistance of individual packs can affect how much each one contributes. It would be interesting to have voltage monitoring on each pack...

On full throttle I can drain the DJI battery down to 15% in 800 sec, but the external battery has somewhat more in it for sure. Specs on the TP4500HV are:

Max Charge: 2C
Max Cont. Discharge: 6C
Max Charge Current: 9A
Max Burst Discharge: 10C
Max Burst Current: 45A
Weight (g): 245
Max Cont. Current: 27A

SkyNinja · Sep 21, 2017

@lolo780, so what you’re saying is because the DJI battery has lower resistance than the external battery it will drain down faster under full throttle?

Does we know more specs than weight and mAh DJI battery?

lolo780 · Sep 21, 2017

SkyNinja said:
@lolo780, so what you’re saying is because the DJI battery has lower resistance than the external battery it will drain down faster under full throttle?

Does we know more specs than weight and mAh DJI battery?

That's my best guess for a low C rating external battery. I have a high C 4000mah pack to test this out with. Porky 296g though.

MacIak · Sep 21, 2017

lolo780 said:
If you're directly wired, and only drawing ~2c, then all three packs should match in voltage at the end. Internal resistance of individual packs can affect how much each one contributes. It would be interesting to have voltage monitoring on each pack...

On full throttle I can drain the DJI battery down to 15% in 800 sec, but the external battery has somewhat more in it for sure. Specs on the TP4500HV are:

Max Charge: 2C
Max Cont. Discharge: 6C
Max Charge Current: 9A
Max Burst Discharge: 10C
Max Burst Current: 45A
Weight (g): 245
Max Cont. Current: 27A

Still does not explain how you can pull down the externals to 3.2v /cell with still juice in the main battery. If id try that with any lipo on one of the heli's it would become pretty dead.

lolo780 · Sep 21, 2017

DJI + TP4500HV + TP3500 hover test. Motors 1 and 3 were noticeably warmer than 2 and 4, and the PMW numbers are clearly uneven. Not sure why though. At the very end my throttle input is visible where I 'cheated' a bit to get 40:29.

The voltage step after takeoff was me switching the DJI battery on. I wasn't quick enough plugging both batteries in and lifting off, so I turned the DJI back on in the air.

DJI battery showing zero at 2365, and flight status changes from 2 to 1 at 2563.

Who has the longest hover time for a Mavic?

CyberNate · Sep 21, 2017

MacIak said:
Guys don t be too hard on me but i do not understand 1 thing:
Did a quick flight with the mav today, still in the phase of getting used to the bird ( have an issue with the gimbal, it's jumpy during forward flight, like it's gusty but actually calm wind, giving the jello thing...if anyone knows a fix id like to know).

I used 2x 3000 lihv, direct mod. Duration 31 mins, covered 25.500m in oval patterns, landed at 7%.
After flight checked the voltage on externals: average 3.58v/cell. (10.8v total).
With the externals plugged off rebooted mavic and main battery cells show 3.58v/cell, total 10.8v at 6%.
Now to me it looks like a good deal but i read some are able to burn the externals down (towards 3.21 volts??) even further and still %left in main battery?
How does that work without totally destroying the externals?

How are you only getting 31 minutes? You must be pushing the motors a bit. I get 34-35 minutes easy with mine on dual 3000lihv.

Regarding the lower external voltage, there is significant voltage sag on the Mavic battery under load. The Mavic batteries are high capacity LiHV and have a decent amount of internal resistance. This is apparent when you check Ed's results when attempting to use extracted mavic cells. If the externals are a high c rated battery, they will have much less voltage sag. The Mavic battery was likely reading 3.21v under load, but jumped up once the motors were stopped. The external hard very little sag and really dropped that far which isn't good for the externals for sure. I ruined my multistar 4000s doing that too many times. I think these graphene batteries are a bit tougher, so maybe it's ok?

Ed209 · Sep 21, 2017

Here’s 2 Mavic batteries

I left the circuit board in tact and just soldered my leads to the pads so this is a good representation of the IR of the DJI packs

MacIak · Sep 21, 2017

CyberNate said:
How are you only getting 31 minutes? You must be pushing the motors a bit. I get 34-35 minutes easy with mine on dual 3000lihv.

Regarding the lower external voltage, there is significant voltage sag on the Mavic battery under load. The Mavic batteries are high capacity LiHV and have a decent amount of internal resistance. This is apparent when you check Ed's results when attempting to use extracted mavic cells. If the externals are a high c rated battery, they will have much less voltage sag. The Mavic battery was likely reading 3.21v under load, but jumped up once the motors were stopped. The external hard very little sag and really dropped that far which isn't good for the externals for sure. I ruined my multistar 4000s doing that too many times. I think these graphene batteries are a bit tougher, so maybe it's ok?

What is your rpm and speed when doing so?
Did not push em too much really. Maybe a bit. My inteface (bt300) the go app does not show rpm in % at all. I have to do it with actual rpm which was around 7700rpm and average 52km/h. Made racetrack patterns, 1km legs with constant speed. Previous mav had similar numbers. Measured voltages after flight and also half an hour later. Give n take pretty well matching both main and externals. Rules out any hardware issues.
But 3.2 volts also for lihv is pretty much destructive. Just amazed they can be drained that low.

CyberNate · Sep 21, 2017

Ed209 said:
Here’s 2 Mavic batteries

I left the circuit board in tact and just soldered my leads to the pads so this is a good representation of the IR of the DJI packs

That's cool that you can check the resistance of each battery. So 16milli-ohm at 20amps gives a voltage sage of .32V. You also have a bms board on the mavic encased battery so there's a bit more. Good to know.

Edit: Actually the Mavic battery would not be pulling 20A as the current is distributed across all connected packs. It would be more like 7-8A for the Mavic battery depending on the size and resistance of the external packs.

CyberNate · Sep 21, 2017

MacIak said:
What is your rpm and speed when doing so?
Did not push em too much really. Maybe a bit. My inteface (bt300) the go app does not show rpm in % at all. I have to do it with actual rpm which was around 7700rpm and average 52km/h. Made racetrack patterns, 1km legs with constant speed. Previous mav had similar numbers. Measured voltages after flight and also half an hour later. Give n take pretty well matching both main and externals. Rules out any hardware issues.
But 3.2 volts also for lihv is pretty much destructive. Just amazed they can be drained that low.

Well you are flying at a good clip at a constant 32mph. I'm usually doing casual flying with my dual 3000s. I think Digdat0 got around 35-36 minutes with a distance flight, but he ran his batteries down to near zero to do it.

lolo780 · Sep 21, 2017

Ed209 said:
Here’s 2 Mavic batteries

I left the circuit board in tact and just soldered my leads to the pads so this is a good representation of the IR of the DJI packs

How many cycles on those packs, and how hard have they been ran before?

Ed209 · Sep 21, 2017

lolo780 said:
How many cycles on those packs, and how hard have they been ran before?

Both packs <20 cycles and never under 20%.

50Devastator · Sep 22, 2017

I'm sure somebody has one, but I have searched all afternoon on this forum and the web and can't find it... Is there a capacity chart for a new stock Mavic battery similar to these: Battery test-review 18650 comparator ? I'd like to see the discharge curves for 5-20 amps and how it compares to other batteries.

chazz · Sep 22, 2017

I did a hover test with the battery board turned off yesterday and at about 20 min into the flight the dreaded critical low voltage landing at a little under 3.5V...I had high hopes for this one...

chazz · Sep 22, 2017

Ed209 said:
Got it. Thanks. Hope I didn't F anything up on this board. I'll see what happens when the balance leads come in.

Hey man don't forget if you plug the battery into the board before you plug it into the mav there is power goin to those pins...I made sparks a few times when i didn't line it up correctly..