I have up and down in my life as all have
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
, and missed this video.
The biggest percentage of the reason of battery having leakage seems to be when two or more batteries are connected in series with the batteries which do not have the same remaining level left.
They suffered to find a good method of sealing electrode terminal and they used rice as one of the ingredients.
I head this when the battery was Manganese battery. The reason I remember this story is because they were talking about rise. The company was sending rise to factories in overseas. The employee of the factories were happy to have the Japanese rise for their dinner when the rise was left at the factories because it was very difficult time to find Japanese rise which is sticky short grain (which they have grown up with) in foreign countries. It is easy now, since there are many Japanese food stores now, but in 80’s and 90’s it was not the same and many places.
At least what they did was enforce tight quality control and through away of a battery which could not package in the same package from the same lot. The different lot seems to have slight variation. Having the package from all two or four batteries from the same lot for hoping to reduce the probability of different remaining level to be used in series.
This could be the reason I do not see much 3.7V soft laminated LiPo rechargeable batteries are not used in series without BMS when they want 7 or 8V.
I am not battery a person, this is purely what I have heard from who have worked at battery division long time ago