DANG, LET MY BATTERY DO FLAT OVER WINTER - RECOVER? YES!

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#1
So a friend had my second P2V3+ and let it sit over winter, and one batt came back, other is dead.

Can it be recovered?

Normal answer is NO. But why not try?

So I had him give me the dead batt... Yep, nothing. Putting upto 40Vdc into the terminals produced 15ma but nothing; maybe if I left it a day it may have leaked enough in thru the on/off FET to charge enough, but I am too impatient.

So I popped the cover off (search these forum for how to do that), found the MINUS (-) batt input is direct to the 6 cells, and found the + actual batt terminal is big solder blob right above the exposed batt health led #4. If someone is is interested and really wants pix, I can post them.

Sticking my voltmeter directly across the 3 (2 each parallel) cells, showed 1.2Vdc. We all now that if you let a lithium batt go this low it may well never recover. What the heck?

So I put my lab supply to - batt terminal and then other lead to this direct +b terminal... start cranking up the volts... current begins to rise... by 4vdc current would go to 10amps if i let it. Of course I would not. I kept current around 2 amps... watched vdc come up... 4, 6, around here the RED fault led came on! 8, 10, at 10.5vdc or so the fault lite went off and the green first bar came on! I continued for a bit, then disconnected from direct batt cells and let my smart charger take over thru normal 2 batt terminals (after turning it on with 2 button pushes!)... It took off!

When my batt charger started, it was still 10.x volts and rose from there... I like to charge at 2 amps, not 4 like DJI charger, so it is slowly rising... I have it in my 30 gauge ammo box just in case... but I fully suspect tomorrow morning I will come into the shop and see a fully charged battery.

I will fly it this weekend to verify the battery has significant charge left.

Comments?
 
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#2
So came back today, and find it shows charged - to 1 bar. Volts at 8.x so 1 cell set obviously is dead still now.

For kicks charging again by hand... 2.6 amps but at least I can do it thru the normal batt contacts...

1 green flashing until
2 green flashing @ 12.3v
3 flashing @ 12.6 but still charging at full 2.6amps
4 flashing @ 12.6 but current beginning to drop; at 2 amps and going down fast (down to 1.7a in 5 minutes) and still dropping of course...

Think instead of flying on this dangerous batt I will put it on my lipo smart charger and discharge it to see how much mah it retained.

Meanwhile, for anyone with a DEAD P2 batt - IF you want to try to recover it see next post...
 
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#3
So when the batt goes too flat for the Uprocessor control card to activate the series FET and let it charge, you CAN try jump starting it...

Know this is potentially dangerous so do this with care, in a lipo bag or ammo box or...

So P2 batts can be jumped by drilling a small (I used 1/8" drill) right above the 4rth (full charge) LED -- CAREFULLY.

I attached some pix showing this.

The minus pin of the batt connector goes directly to the cells. The plug (red wire in my pix) does not - it goes to cells thru series FET switches. So when cell volts drop too low to power the uprocessor, the series FETS never turn on again so you cannot charge a dead battery.

Idea is to drill a tiny hole right above the 100% charge LED - this gives you access to the raw cells + terminal - see pix.

Then assuming you have some sort of variable power supply, you have access across the 6 cells (2 each in parallel, then these 3 sets in series for 6 total), you can try to charge the cells...

See my previous posts for how it worked for me. I have not yet tested the capacity of this charged battery brought back from the dead. I have no clue if any of these dead lipo cells will recover, but I will find out on some individual cases.
2018-07-01 12.20.21.jpg
2018-07-01 12.20.21.jpg
2018-06-30 15.26.10.jpg
2018-07-01 12.20.21.jpg
2018-06-30 15.26.10.jpg


Hope this is of value to someone who would otherwise have just tossed the dead battery.
 

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#4
So when the batt goes too flat for the Uprocessor control card to activate the series FET and let it charge, you CAN try jump starting it...

Know this is potentially dangerous so do this with care, in a lipo bag or ammo box or...

So P2 batts can be jumped by drilling a small (I used 1/8" drill) right above the 4rth (full charge) LED -- CAREFULLY.

I attached some pix showing this.

The minus pin of the batt connector goes directly to the cells. The plug (red wire in my pix) does not - it goes to cells thru series FET switches. So when cell volts drop too low to power the uprocessor, the series FETS never turn on again so you cannot charge a dead battery.

Idea is to drill a tiny hole right above the 100% charge LED - this gives you access to the raw cells + terminal - see pix.

Then assuming you have some sort of variable power supply, you have access across the 6 cells (2 each in parallel, then these 3 sets in series for 6 total), you can try to charge the cells...

See my previous posts for how it worked for me. I have not yet tested the capacity of this charged battery brought back from the dead. I have no clue if any of these dead lipo cells will recover, but I will find out on some individual cases. View attachment 100701 View attachment 100701 View attachment 100702 View attachment 100701 View attachment 100702

Hope this is of value to someone who would otherwise have just tossed the dead battery.
Hi yorlik, I have done as you suggested drilling the hole and am now feeding 3Ma from a 12volt battery connected to a trickle charger. The P2 battery voltage is now up to 2.2v. At what voltage should the circuit board switch on?
Regards, Paul
p.s. Now have 24v feeding 7.5 ma feeding and resting voltage of P2 battery seems to be 2.5v
 
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#5
Paul,

I kept pushing the on button to see when it would turn on; IIRC it was around 8-9v...

I think you should up the current! you show at least one cell is taking a charge... I assume you have a resistor or some other current limit method you are using to keep the current so low? Assuming you do, then 2.5v/7.5ma= .3mohm resistance - good (2.2/3= .7milliohm battery internal resistance...) I don't think you will get much higher voltage with that low a current.

BTW, my batt was puffed so it may not have fit in the dji; after the first charge it dissipated the gas and is rock solid on sides again. weird.

Be safe: set your MAX ps voltage to 12.4v Anything higher and you forget and walk away will overcharge and probably do the fire explosion thing.

I got impatient and ended up at 3.5amp charge (set by my ps) - with 12.4v supply... when it finished it turned off the batt like normal - when current dropped to about .4amp.

3 days now and it still shows 100% charge. I have not had time to cycle discharge to test real capacity. Good luck
 
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#7
not having resistor in series and not being able to get hi amps is not good sign. Ihad to current limit and/or keep the volts just a volt or two above my cells or the current would go to 10+ amps.

This all may be for naught anyway; I tried a discharge test @ 2amps and it turned off the smart battery in 1/2 second, leaving red light on...

Even tho it took an hour to charge, meaning those mah went into it. And did not make any heat... So I assume I am now going to fight the smart battery chip memory thinking it has no mah left and so it is shutting off. I will have to do discharge test directly to the drilled hole cell contact to verify if the cells output goes to near 0v instantly or it the smart batt logic permaturely decides that.
 
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#8
Second battery accepting only 3.6Ma at 13 volts and 7Ma at 26 volts. Now waiting for a battery to arrive. Can you power the drone from and external 12 supply to set it up? What do the two tiny probes on the battery do?

Aussie Paul.
 
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#9
I "killed" 2 P3S batteries over the winter. I fixed both with my old HeathKit variable power supply.
I applied a voltage just above the present voltage of the battery. ( I did not take it apart. Clipped leads to external terminals). Using minimum current. Not sure what that was the HeathKit has no meters and I did not bother to check current, only voltage.
I gradually over several hours increased the voltage. Then plugged them into the DJI charger and they both charged. And they fly about the same time as before.

Guess I got lucky.
 
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#10
I "killed" 2 P3S batteries over the winter. I fixed both with my old HeathKit variable power supply.
I applied a voltage just above the present voltage of the battery. ( I did not take it apart. Clipped leads to external terminals). Using minimum current. Not sure what that was the HeathKit has no meters and I did not bother to check current, only voltage.
I gradually over several hours increased the voltage. Then plugged them into the DJI charger and they both charged. And they fly about the same time as before.

Guess I got lucky.
Were the "killed" batteries at zero voltage?
 
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#11
No they were not zero. I don't recall the exact voltage. on the order of 1 - 2 volts. The DJI charger would not charge them.
 

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