Battery Surgery

I have a story to tell about todays events.

After some more manual research our team figured out how the battery management system (BMS) should be switched on in the start of its use. It was not very clearly said anywhere in the manual so thats why it took so long to figure it out. Once we got the BMS working we found something disturbing.

BMS
BMS showing battery status.

In the picture above the is one thing that is not right. The middle bar is the 4th cell of one of our batteries and that cells voltage is only 2.9 volts while others were well above 3.8 V. When we tried to charge the battery with a balancer the cell voltage dropped down right after disconnecting the charger. Because of one cell malfunctioning the whole batttery is useless. It is comparable when human has a organ that fails the human could pass away almost certainly. That is why we were already giving up on the battery and calling the time of death.

While we were looking for a replacement batteries a miracle happend. We found an old cell that could replace the broken one! But that meant that we needed to do some surgery on the battery which is dangerous and should be done carefully.

The Head of Battery Cell Surgery Dr. Vepsäläinen and the Electric Engineering Surgeon Dr. Autiosalo decided to perform an cell replacement surgery.

All along the operation it is very similar to the kids game “Operation”. You guys remember that? The only difference is that if you fail and hit the edges of metal, instead of a error light and sound there is relatively big arc of light and possibly loud explotion.

operation_the_game
The operation game from the 90’s.

With this “penalty” in mind the two first time Doctors took their job seriously and wore the appropriate safety gear. Operating while wearing those is quite hot and clumsy as some of these pictures from the operation show.

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Dr. Autiosalo’s precise and accurate manouvers.
puoli0
The skin removed to see the organs.

After the battery’s cover was removed it was time to extract the dead cell and replace it. This is was the tricky part since the cell contacts are very thin (less than 1 mm) and might rip out easy. At this part the operation had been going on for about 45 minutes.

puoli3
Critical artery cut. The stakes have never been higher.

Once we got the bad cell removed the syphtomps were validated. The cell had swelled about two times the nominal thickness from one corner. This cell was long gone.

kuolio
This bad boy was gone. Rest in pieces.

The old cell we found was in rather good shape but it didn’t have holes in the same places of the contacts as the other cell. Then Dr. Autiosalo performed a quick round of shots to the contactors.

hammering
It is not engineering if you are not using a hammer.

After the the delicate handeling of the newbie cell it was time to put the battery back into one piece. We had done good documenting of what goes where so the assembly was pretty straightforward.

loppu
Good as new!

After 2 hours and 11 minutes the operation ended succesfully. We hope that the patient is fully recovered and after some rest it should be better than ever.

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The new cell is reaching to the same potential as his new friends.
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