We test EVERY 26650 LIFEPO cell on  

do you used a ACTIVE BALANCER

@@suleijman228 No balance, 3 years hava passed using in car (almost no in winter). Did not touch it, yet they are balanced at 1/1000 Volt!

I can not agree with you more, 26650-2500mah is quite perfect compared with other cylinder cells, we are the original 18650 and 26650 manufacturer in China, if you have interests, welcome to discuss on battery field.

Some people just use a small magnet, I use 6mm diameter 3mm tall magnets on 18650's and 21700's. You would probably want to use an 8mm diameter and up to 4mm tall magnet to give you a fake button top. There are some people concerned with using these in high discharge applications as the resistance of the magnets will add a fair bit of resistance. I believe this is true but am not sure. I don't use my method in high discharge applications and NEVER in a multi cell configuration. Single cell only, like single cell flashlights. You can buy the button tops, its literally just a cap that goes over the top of the cell but you need a welder for that specifically. Some people just put a blob of solder on the positive of the cell. After watching Ebike Battery School test soldering vs spot welding and seeing 200 Celsius on the outside of the cell I would have to say DO NOT do any soldering on the cell. He was going as fast as possible only spending 3 seconds on each solder which was just barely enough time to get a half decent solder joint. You see a lot of people on RU-vid spending 15, 20 or 30 seconds on each terminal. Fucking madness and one day we will get footage of someone soldering a cell and probably 2-3 minutes later it will explode as they are trying to solder another cell (this is of course if they don't notice the cell heating up as it goes through thermal runaway) So long story short, I do not know of any simple cap you can place on the top of the cell but a magnet works for some situations only.