P3 battery board reset.

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Ok I like fixing problems especially when they are not 'fatal' to the drone
I have a dead P3 battery, it arrived like this, it will not charge and it will not switch on. I have tried various button pressing resets to no avail. I am guessing it has, either deliberately or through lack of care, been over discharged to too low a voltage .
I opened the battery and what you end up with is a block of cells wrapped in a metal shield, a 'suspended' circuit board is attached to the "block of cells".
A multi strand cable runs from the "block of cells" to the circuit board as do +ve & -ve high current (HC) cables, I assume there must be some sort of circuitry inside the "block of cells" for the multistrand cable to connect to. The metal shield is also connected to this circuit board, via its own wire.
A second pair of HC cables run from this board to the drone/charger connector.
I disconnected the multistrand cable and connected a charger to the HC terminals atop the block of cells. I had the 'battery' inside a deep stainless steel saucepan in case any thing went wrong. It seems to have taken a charge, 17+V, but still will not switch on.
I suspect that something in the "suspended circuit board" (SCB) needs resetting and have seen mention of this, in connection with drone batteries, on the web and it seems that this is done by disconnecting the multistrand cable from the SCB. There is a good thread concerning this and an Inspire 1 battery on another forum. However it appears that there are only 2 HC cables running to the SCB in an Inspire battery and I suspect that this means that there is no voltage ANYWHERE on the Inspire's SCB when its multistrand cable is disconnected.
The 4 HC cables running to the P3's SCB suggest to me that some part of the P3's SCB will 'always' see the battery voltage and I am wondering if, aside from disconnecting the multistrand cable, I will also have to disconnect one of the HC cables coming from the battery block it order to attempt a reset...........does anyone know ?.

I think the green staining in the attached photos is just a green coloured varnish
 

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I suspect that something in the "suspended circuit board" (SCB) needs resetting

Good thinking. Though that reset (or rather unlocking) isn't always that easy. Details:

Some people say there is a reason when the battery gets locked. Though even a battery which you can't trust is sometimes useful.
 
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I think the green staining in the attached photos is just a green coloured varnish
Where are the photos?
Be very careful as there could still be a lot of current available in there! Was there any "wetness" in the pack? Photos would be lovely :p
 
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Sorry, not sure what happened to the photos, I am reattching them as I type.
I will have a read, I disconnected at the SCB the HC +ve from the block of cells last night .
The battery was bone dry with no evidence of leakage though I must admit the green stain was disconcerting but it is very smooth, any corrosion damage I have seen before (old batteries in whatever etc.) was granular/crystalline and it doesn't look like verdigris.
Quaddamage ta, I will have a read.
Attached is a photo of the underside of the SCB, the through hole is where the +ve HC cable attaches, the hook if noticed was to balance the board for the photo.
 

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Quaddamage, that's an interesting article though most of it looks to be beyond my 'skill set', I am not capable of reading chips or any programming on them.
Those folks go 'deep'. It will take several reads to get a better grasp of it.
 
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Big mistake opening and trying to bypass the board.

Lets get to basics ....

The battery itself is a Lithium High Voltage 4 cell item. No different from any other LiHV 4S battery available for general use such as RC. It has two sets of leads ... main power leads for motor and charger ... lesser multi lead for access to each individual cell + total. This multi lead is called a Balance Lead.

On a normal LiPo / LiHV - there is no board to interfere with users access to both leads and to charge / discharge the cells. But DJI have devised a regulator board to look after charge / discharge and telemetry flow.

DJI do not use a LiPo based charger in any form. They provide a 17.5V regulated PSU that has no cut-off or programability whatsoever. It just supplies Constant Voltage with the 'Regulator Board' fitted to battery controlling the charge flow. Once it reaches 17.4V overall detected in the total pack - it shuts off the supply from the PSU charger.
The Multi Lead provides basic cell info to the chip to approximate balancing - it actually fails dismally on this task - but that's another story.

So we have in normal terms - a charged battery now with the board on front of the battery.

What then happens is the Auto-Discharge timer starts the moment you stop charging. Based on User setting - after the set time, the board starts resistive discharge of the pack - taking approx 48+ hours to arrive at about 55 - 60% charge level. At that point - the auto-discharge stops - as it it is now at DJI's level of storage.

BUT discharge does not stop completely. All batterys suffer Self Discharge. with LiPo's - the rate is extremely low but it is still there. DJI have thought about this and programmed the board with a function termed Hibernation Mode.

As the pack over next months or so discharges .. when it gets to the lowest level board allows - it drops into Hibernation Mode and you then cannot switch on the battery - it appears DEAD as a DoDo ...

There is no reset ... no magic resolution to this ... it really is a trial by luck whether you can kick it back into life again.

How ?

1. Have a simple DJI charger ready. A LiPo charger cannot work for this solution as it needs battery voltage feedback. Forget multi charge hubs etc. Just the plain single DJI charger.

2. Press the On button twice as usual - IGNORE the lights ... DO NOT press again.

3. Put the battery down and leave it alone for at least 5 minutes.

4. Now plug in charger - STILL DO NOT PRESS any button again

5. Leave it on charger .. it may spring to life in minutes - it may take all day.

IGNORE all lights ... leave it alone ...

If it springs back to life - then just let it charge up fully and you are one lucky fella !!

Trying to kick it back to life via internal leads - is doomed as the board will default out .. yes you can actually apply a jumper to a couple of points on the board to 'reset' it but I will not indicate where. Please do not ask. LiPo's are not to be played with.

About the only value you can have by opening up a DJI battery - is to revert the pack to a non board pack for other use !!

There is a good reason DJI fit that board and seal up the pack ...
 
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Ta Solent, in what follows I am not ignoring your post I had done what follows before seeing your post. I will read you post carefully later, a quick skim found some interesting points

I left the SCB disconnected over night, when I went to reconnect the HC cable the green LEDs on the board came on, all 4 of them. When I connected the multistrand cable I was able to switch the 'battery' off and on with the normal incremental number of green LEDs etc. However once switched on 3 of the green LEDs go out, there is 17+V 'in' the battrery, nor will it charge via the normal method and there seems to be no connection to the normal drone HC connector, so partial success possibly
 
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Myself and another guy in our Club dismantled a P3 battery and were able to transpose the board to another set of cells. But the act of disconnection causes the board to shut off and will not work correctly. We then found the two contacts to bridge to reset it.
It had two effects - 1 - it set cycle count to zero, 2 it allowed battery to work ...

I know other guy only used the battery in short test hops as we felt unsafe with it. It was in all honesty a trial to see if it could be done.

I will not pass on the position of the contacts to bridge - to avoid anyone having loss of drone or failure as a result. Sorry but that's my position on it.
All I will say - is according to our observations - disconnection of any lead to the board causes it to default out.

I think you would have been better following the Hibernation Routine to get battery up again ... too late now.
 

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