Ep. 37 | Batteries? I can’t repair them, but I can build them
Creator’s own settings as stated in the video (timestamps link to the moment). Not official values — test on scrap first.
Bill of materials
Welder, accessories, consumables and parts used in this build; quantities and specs are editable Download BOMDescription
Blind Tool Repair ep. 37, ‘batteries — can’t repair them but can build them’: a hot-glue gun that won’t heat is a loose wire; a customer asks original or home-made battery — a 15-cell tool pack built on the spot, 3.95V per cell, ¥130; then a stripped screw, worn carbon brushes, a tripped breaker, 607/608 bearings, ¥40 housing; 320k likes
A customer’s hot-glue gun lights up but won’t heat; open it, a wire has come off, stick it back, nothing wrong. Another wants a battery ‘delivered to Hanlin Huafu’ and asks whether to use an original or have me build one — ‘whichever works’; take 15 cells, open the cover, beautiful; measure a single cell at 395 (3.95V); pack assembled, done, ¥130. Then: a stripped screw inside a drill, apply some tricks (scorching hot; I have a way to fix it, done in the open, no secrets); an angle grinder won’t turn, the carbon brushes are worn, and the breaker tripped again (protecting the motor); another one also brushes and a broken wire, brushes are aftermarket not original; bearings are all gone, housing ¥40, bearings ¥10, swap in 607 and 608 bearings; ¥10 each. 9339 comments: top comment ‘original battery or one I make’ at 240k; ‘original isn’t as good as hand-built’; experienced viewers advise not to stick paper on the cell sides (absorbs water), use PET; someone asks whether the assembled pack can be recharged.
Outcome
| Goal | Shop day: build a power-tool battery pack on the spot + several tool repairs |
| Build | 15-cell battery pack (¥130), hot-glue gun, drill, angle grinder brushes / bearings |
| Result | Pack built; the rest repaired and charged item by item · verified on camera: 100–103s ‘done, 130’; 145s ‘that’s that’ |
Steps6 steps · click a frame to jump
1. Hot-glue gun won’t heat: a loose wireThe light is on for ages but it won’t heat; open it, a wire came off, stick it back, nothing wrong.
00:01 – 00:20
2. ‘Original or shall I build you one’Build me a whole battery, deliver to Hanlin Huafu; original or shall I build you one; whichever works; 15 cells.
00:19 – 00:47
3. Build the pack on the spot: open the cover, measure 3.95V, done, ¥130Open the cover, beautiful; call the courier; done; measure 395; sorted; 130.
00:47 – 01:43
4. Stripped drill screw: scorching hot, apply the trick, no secretsA screw inside is stripped, apply some tricks; scorching hot; most people keep the trick to themselves, I do it in the open; done.
01:45 – 02:30
5. Angle grinder brushes worn, breaker tripped; aftermarket brushes; broken wireBrushes worn and the breaker tripped again, it protects the motor; another one also brushes and a broken wire; aftermarket brushes; ten yuan.
02:31 – 03:15
6. Bearings and housing all replaced: housing ¥40, bearings ¥10, 607/608Bearings and housing are all gone, in stock; housing 40, bearings 10; grab a 607; the neck bearing is gone too, swap it; grab a 608, also worn out; ten yuan.
03:17 – 04:42
Bill of materials
| Cells ×15 | Battery pack |
| Spot welder (AWithZ, per title) ×1 | Spot welding |
| Hot-glue gun ×1 | Being repaired |
| Carbon brushes (aftermarket) / 607, 608 bearings / housing | Angle grinder repair |
Measured on camera
| Cell voltage | 3.95 V 01:25 |
Creator’s tips
- Worn brushes often come with a tripped breaker; it is protecting the motor 02:31
- Comment: don’t stick absorbent paper on the cell sides, use PET or nothing
Pitfalls
- The hot-glue gun not heating was just a loose wire 00:19
- A stripped screw needs a ‘trick’ 01:45
Li-ion safety
- Disassembled parts are scorching hot 02:03
Quotes
Cost & time
| Battery pack | ¥130 |
| Housing | ¥40 |
| Bearing | ¥10 |
| Minor repair | ¥10 |
Comment insightsanswered 0 · open 2 · corrections 2
Open questions
Corrections from viewers
I used to be in Jiangsu, and what I replaced most was carbon brushes on grinders — 100, 125, 150, three sizes of grinder, sitting on a stool made from an electrode reel swapping brushes from morning till night. Thanks for reminding me of the lean years
Reply @南宫同学:
From work experience and my own battery DIY: better not to stick paper on the sides of the cells, it fails easily once wet, and this paper absorbs water — it gets soggy even in humid weather. If you must, use PET; honestly not sticking anything is fine, the housing's protection and insulation is more than enough, and it's ventilated so it dries easily. @BiyanXiuGongju
Reply @里昂:
From work experience and my own battery DIY: better not to stick paper on the sides of the cells, it fails easily once wet, and this paper absorbs water — it gets soggy even in humid weather. If you must, use PET; honestly not sticking anything is fine, the housing's protection and insulation is more than enough, and it's ventilated so it dries easily. @BiyanXiuGongju
Reply @里昂:
I used to be in Jiangsu, and what I replaced most was carbon brushes on grinders — 100, 125, 150, three sizes of grinder, sitting on a stool made from an electrode reel swapping brushes from morning till night. Thanks for reminding me of the lean years
Reply @南宫同学:
I used to be in Jiangsu, and what I replaced most was carbon brushes on grinders — 100, 125, 150, three sizes of grinder, sitting on a stool made from an electrode reel swapping brushes from morning till night. Thanks for reminding me of the lean years
Reply @南宫同学:
From work experience and my own battery DIY: better not to stick paper on the sides of the cells, it fails easily once wet, and this paper absorbs water — it gets soggy even in humid weather. If you must, use PET; honestly not sticking anything is fine, the housing's protection and insulation is more than enough, and it's ventilated so it dries easily. @BiyanXiuGongju
Reply @里昂: