Some tips for recelling battery packs extracted from my posts in various places.
A. Buying cells
1. Always buy new cells from renowned sellers. You may pay a bit more, but it's always a good guarantee.
2. Beware of the overstated capacity. As far as I know, even the large brands (Panasonic, Sony, Sanyo, Nitecore, etc.) are making cells capped at around 3,400 to 3,600 mAh. Do not be tempted to get those boosting 4xxx mAh. I'm not sure whether they even really exist.
3. Just as 2 implies, always buy cells made by good brands. Sanyo (like the ones shown in my blog post) is often recommened.
4. Stay away from dubious brands, such as "Ultrafire", which are infamous of having so many fakes all over the place. Super cheap, but you may get half the stated capacity at best, and poorly made explosives at worst.
5. Don't buy cells which are overly (and suspiciously) cheap. My impression is on average a 18650 sells for around USD$4-6.
6. Some cells are manufactured with a small protection board built on top of the positive terminal, making these cells longer than those found in the battery packs. Don't buy these cells because they just won't fit in the original battery pack casing. In general the charging circuits should already have certain builtin protection mechanisms.
7. Check the appearance of the cells:
- Positive terminal (top): Each (large) brand has their own different tops (see the pic). They should be clean, no marks or dents.
- Negative terminal (bottom): Should be all flat without bump/ring/plate/etc, and clean. Many scratches and marks may suggest that the cells have some hidden secrets that don't want you to know.
- Rust means the cells are very old.
- Tabs can be helpful for you to make the connection. But I'd prefer not to buy ones with them because the tabs may cover the top or the bottom so you may not be able to examine the terminals closely enough. The tabs may also add to the length of the connected cells. Sometimes the space within some casing can be so tight that even 1mm matters. And if you are careful enough when removing the old cells, you should be able to reuse the original tabs and wires without doing any extra work.
8. eBay sellers can be hit or miss, even more so for AliExpress. My personal opinion is that (actual) shops which sell many genuine brand products, professional equipment and torches, etc. (and with customers frequenting regularly), would be signs of a reliable seller.
9. My shopping tactics: Examine the appearance of cells carefully, ask the seller some "dumb" questions to see how much they can tell you, then before paying ask the seller to do some simple testing with a multimeter on the spot, perhaps even buy a quality and reasonably priced charger/discharger for yourself to do more home testing.
10. To tell fakes from genuine cells, weight is the least reliable (unless the cells are clearly over/underweight). Looks can be deceiving from time to time (esp. online images). Usually except for expensive professional products (like those for very strong lights and torches), generally the wrapping of these cells is very dull looking and contains nothing more than a model number (or a QR code for some models).
11. To begin, buy just a couple of cells for one battery pack first. If the result is great after recelling that pack, then you know where to get more next time.
B. Recelling
13. Tools particularly userful for recelling: Sculpting knife, masking tape, clamps, phone opener/flat tip screwdriver, cell charger-discharger, powerful fingers, focused eyes.
14. To minimize cosmetic damage to the casing, start scoring on the connector side.
15. Do not ever cut or pierce the cells, which can lead to disastrous consequences.
16. Do not rush. Always use patience and gentle force.
17. Keep the original wiring and connections as undamaged as possible.
18. NEVER apply regular soldering on the cells! Use low heat solder or a dedicated spot welder. Masking tape is a good alternative. Be careful when using cable/wire/duct tapes because they can grow sticky and rather hard to remove over time.
19. Tape or hotglue the casings after recelling to ease further repair work in the future.
20. After recelling the battery packs for the handhelds, it is always useful to test the capacity of those old cells with a charger-discharger. In fact, very often when a battery pack seems to be dead, it would turn out that only one or two of the cells inside the pack are depleted, while the rest are still functional. These old cells, even though not ideal on the handhelds anymore, can still be put to good use to charge up other devices. One ideal solution is to put these cells in a cheap/DIY empty powerbank box.
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