Has anyone measured the actual capacity of Mavic Pro pouch cells?

[cnd]

I pulled the 3 pouch cells out of my 3.8ah Mavic Pro battery, and measured them all. I got 1.8ah, 2.6ah, and 2.2ah respectively.
They weigh 64.7g each.

A standard 18650 cell gives me 3.1ah (it weight 48.8g)

My goal is to use 18650's (I've put them in, but looks like I need to reset the BMC SMC now. grr.).

I've added an expansion plug - so I can add an extra 3 cells on top if I want. This looks like I'll get 64% extra flight time above the stated 3.8ah original battery capacity, or more than double-and-a-half extra flight time on the one I just cannibalised... for just an extra 100grams of weight.

I'm wondering if the real capacity of the original battery is actually 3.8ah though?: I din't trust "sticker numbers" (e.g. my 3.1ah 18650's *say* 3.5ah on them) - has anyone ever *measured* one of those pouch cells? I'm using 1a CC discharge from 4.2 down to 2.5v for my tests, fwiw.

 

[Kilrah]

A standard 18650 cell gives me 3.1ah (it weight 48.8g)

Are the 18650s properly rated for the intended use? Most high capacity ones aren't rated for high discharge.

As for the MP battery I'm currently cycling my 5 year old ones and they still have about 3.5Ah capacity @ 5A, so 3.8 when they were new sounds right.

I'm using 1a CC discharge from 4.2 down to 2.5v for my tests, fwiw.

You don't discharge lipo below 3V if you don't want to damage it, 2.5 is fine for Li-ion 18650s but not for lipo.
But the MP cells are HV so they charge to 4.35, and you don't want to go below 3.3 or so.

 

[Duivelsdoosje]

I pulled the 3 pouch cells out of my 3.8ah Mavic Pro battery, and measured them all. I got 1.8ah, 2.6ah, and 2.2ah respectively.
They weigh 64.7g each.

A standard 18650 cell gives me 3.1ah (it weight 48.8g)

My goal is to use 18650's (I've put them in, but looks like I need to reset the BMC SMC now. grr.).

I've added an expansion plug - so I can add an extra 3 cells on top if I want. This looks like I'll get 64% extra flight time above the stated 3.8ah original battery capacity, or more than double-and-a-half extra flight time on the one I just cannibalised... for just an extra 100grams of weight.

I'm wondering if the real capacity of the original battery is actually 3.8ah though?: I din't trust "sticker numbers" (e.g. my 3.1ah 18650's *say* 3.5ah on them) - has anyone ever *measured* one of those pouch cells? I'm using 1a CC discharge from 4.2 down to 2.5v for my tests, fwiw.

You need to be more specific pouche cells?
Either you mean Lithium cells Or Li-po cells.
Also what do you mean with measure because you cant extually measure the Ampère output of an battery.

Both cells have standard but different valua
in Volts you van look Them up.
One is 3.5v to 4.5v the other one 3.7v to 4.7volts but it's important to know.

Next to answer your capacity question.
Or amphere of each cells.
If this is not on the cells them zelf
there must be the sticker on the power pack.

I a'm going to assume the Volts output is around the 7.4volts.
But they Will be 8.4v when charges.
Depending on the amount of cells
Lets say there are 2 cells take the Total
Capacity of the pack in Milli amphere hour
Say 2cells 3600mah Will be 3600÷2=1300
So 1300mah each cell

If the pack hold 4 cells and labels 7.4volt
Means you need to do that same sum but
So 4cells 3600mah Will be
3600÷2=1300÷2=650mah each cell.

If your battery marks 1C Then this means that your pack can discharge with the
Maximum of 1amp for the duration that
the pack specifiece.

You could measure the Volts but the Amps dont! You Will short out your pack and set IT on fire.

Good luck hope this helps you.

 

[MaximusCZ]

...

Hey Duvi, I was reading your post and I am sorry to say you got few things wrong. Ill try to explain as best as I can.

you cant extually measure the Ampère output of an battery

While you are practically right, technically you can. Just short the battery across Ampere metter. It would be bad for the battery and everyone is discouraged from doing so, but you would measure the amperage of the battery, or the highest current its able to supply. This can often happen with DIY drones when the battery is almost empty and you push every last bit from it to keep in the air, you get the maximum Aperage its able to supply (now much lower because its discharged).

Next to answer your capacity question.
Or amphere of each cells.

The Ampere is not the capacity. Ampere (A) is a unit of current. Its a instantenuous unit, it doesnt matter if the battery is big or small, full or depleted. You measure current, you know how much is the battery providing at that very moment.
If you want to measure capacity, you need to measure not only its current, but also the time over which the battery is able to supply that current. When you measure current over time, you get "Ah" unit: Ampere-hour. If the battery is rated for 2000 mAh (= 2 Ah), it means it has enough capacity to provide 2 Amperes over 1 hour, 1 Ampere over 2 hours, 0.1 A over 20h or any other combination. Just multiply the Amperage by the amount of hours to get Amperehours.

Say 2cells 3600mah Will be 3600÷2=1300
So 1300mah each cell

If you got two cells with 3600 mAh, you can connect them in 2 ways: serial (the output of one cell feeds into the input of the second one - the cells are one after another), or paralel (the inputs of the two cells are connected, as well as their outputs - the cells are next to each other).
If you connect them in serie, you dont double the capacity, but you double the voltage. Two cells with 3600 mAh sitting at 3.7 Volts connected in serie will give you a battery producing 7.4 Volts with 3600 mAh. That is how the cells are connected in drones, at least in almost all cases.
If you connect them in paralel, you dont double the voltage, but you double the capacity. Two cells with 3600 mAh sitting at 3.7 Volts connected in paralel will give you a battery producing 3.7 Volts with 7200 mAh.

So if the capacity of the pack in Amperehours is 3600 mAh, split across the cells, each cell is 3600 mAh but half the voltage.

If the pack hold 4 cells and labels 7.4volt
Means you need to do that same sum but
So 4cells 3600mah Will be
3600÷2=1300÷2=650mah each cell.

No, you dont divide four times, and 3600 ÷ 2 ≠ 1300.
If the pack hold 4 cells and labels 7.4 Volt, and we are fairly confident its Li-Po battery which usually sits at 3.7 Volt per cell, we know inside must be 2 cells in serie to get us to 7.4 Volts. The other half of cells are connected in the same manner to also get to 7.4 Volts. And then those two pairs of cells are connected in paralel, otherwise the voltage would reach 14.8 Volts. So a pack that says there are 4 cells inside will have 2 cells in series to double the voltage, and 2 cells in paralel to double the capacity. If the total capacity is 3600 mAh, each cell with be rated for 1800 mAh, because we doubled capacity only once.

If your battery marks 1C Then this means that your pack can discharge with the
Maximum of 1amp for the duration that
the pack specifiece.

Close, but the other way around. The C rating tells you how quick the battery can be charged/discharged. The bigger the C the bigger the rate you can discharge at.
If the battery marks 1C for discharging, then that means the pack can discharge itself in 1 hour.
If the pack is 3600 mAh, at 1C it means its able to supply maximum of 3600 mA (or 3.6 A) over 1 hour.
If the pack is 3600 mAh, at 10C it means its able to supply maximum of 36 Amperes over 6 minutes.
If the pack is 3600 mAh at 0.1C it means its able to supply maximum of 0.36 A, and it will take 10 hours to discharge the battery.
Of course you can probably pull more current than what the pack is rated for, but that degrades the battery immensly at least, or straight up destroy it.


Its nice of you to try to help and explain stuff to others, but please make sure you know what you are talking about before teaching others. Knowing things wrong is often worse than not knowing them at all.

 

[MaximusCZ]

I pulled the 3 pouch cells out of my 3.8ah Mavic Pro battery, and measured them all. I got 1.8ah, 2.6ah, and 2.2ah respectively.
They weigh 64.7g each.

A standard 18650 cell gives me 3.1ah (it weight 48.8g)

My goal is to use 18650's (I've put them in, but looks like I need to reset the BMC SMC now. grr.).

I've added an expansion plug - so I can add an extra 3 cells on top if I want. This looks like I'll get 64% extra flight time above the stated 3.8ah original battery capacity, or more than double-and-a-half extra flight time on the one I just cannibalised... for just an extra 100grams of weight.

I'm wondering if the real capacity of the original battery is actually 3.8ah though?: I din't trust "sticker numbers" (e.g. my 3.1ah 18650's *say* 3.5ah on them) - has anyone ever *measured* one of those pouch cells? I'm using 1a CC discharge from 4.2 down to 2.5v for my tests, fwiw.

First of all, if you measured the Ah of the cells (not just A) and they show so drastically different values, the battery is dead. Three cells inside were connected in serie, so each and every cell should have 3.8 Ah of capacity. Having one cell thats less than half of it and other cells so different is a clear sign that the battery is completely KO. (I suppose you measured the capacity by charging -> discharging them, not just measuring what they currently deliver)

If you use 18650 cells, you need to use 3 of them in serie. From your "just extra 100g of weigt" and "standard cell weights 48g" it seems you are only using 2 of them. That wont work.

The original battery has a sticker for 3.8 Ah, given it comes in highly branded product its pretty safe to assume it doesnt lie. Measuring the capacity is pretty easy, and the backlash DJI would suffer by using shittier batteries than then say is more expensive than using propper batteries. Your 18650 cells, on the other hand, is something a tousand chinese factories may make, and they dont really care if the battery only delivers 80, 50 or even less of rated capacity. When their customers stop buying they just plop a new name on it and continue. I saw 18650 cell rated for 9000 mAh (the absolute best have like 4000) and in reality it only produced 260 mAh, less than 3% of what its supposed to... I would not be surprised if your 18650 was just lower capacity than it claims to, but I would be highly surprised if the battery the DJI drones comes with didnt deliver at least 95% of what they promise.


EDIT: Or after doing math: 64*3 +100 = 48*6, You mean 100g extra flying 6 18650 cells instead of original 3 cell battery, right? In that case everything but the second paragraph still apply. You will get 6.2 Ah battery (instead of original 3.8 Ah) for extra 100g of mass, seems like a great trade still. Please let us posted if you manage to reset/reprogram the BMC SMC