Dyson 18650 battery pack: re-use cells in flashlight?

I have a Dyson SV03 vacuum cleaner. Recently stopped holding full charge, so I bought a new battery pack from Dyson and replaced the battery unit.

The old pack probably contains 6 x 18650 cells (21.6V 2100mAh 46Wh 350W on the label, made in Malaysia). From Youtube I see people opening the pack and the cells are green (maybe Panasonic or Sanyo?). The cells are connected in series and contacts may be soldered.

Can I reuse the cells for flashlights? I have an XTAR VC4 charger. Will this let me refresh the cells?

I can probably remove the outer casing fairly easily. But I’m concerned about the possible soldering on the cells themselves. Given that these cells cost ~£5 new is it worthwhile trying to salvage the used ones?

Thanks in advance for any advice. :THUMBS-UP:

I’ve taken apart and salvaged cells from Ryobi battery packs. Be careful when cutting the solder points as it may damage the casing and vent the cell in your face (ask me how I know). I use flat wire cutters to shear the contact points. I also sand down the points so it won’t grind against the spring or contact surface for the flashlight when turned. Each cell also needs to be tested to see if it holds a charge. I charge with a hobby RC charger while the cell sits on a fire resistant surface. After a full charge, the cell is disconnected and sits for several days and then I take a voltage reading. If there is no sign of significant voltage loss, then I might reuse it.

If the salvaged cell reads very low or no voltage, the charger might not even recognize it. There are ways to jump start it, but usually it’s not worth putting a fatigued/failed cell back to work.

I’ve taken them apart and have some dyson cells in storage for later projects. If you go ahead and remove them, post their capacity, resistance, and self-discharge results here. I can tell you what I would do with them based on that.

My old Dyson stick vacuum had Sony VTC5’s in it

My dyson battery packs for V6 say VTC4 on them and 2100mah, so probably Sony VTC4 cells. Might be some use, but would probably have low capacity as they are worn out.

some have 20700 or 21700 too.

I’ve had the dyson V6 for about a year and the battery life has degraded a lot. It has a 2 year warranty but I doubt they will replace the battery for me from what I’ve read online. I plan to pull the cells out and attach an adapter for kobalt power tool batteries. I can get 4ah batteries for $50 and charge them separate from the vacuum. Love the vacuum but they went cheap on the batteries and way overcharge for replacements.

This was an interesting post. It’s too bad we haven’t hear back from the OP in almost 2 weeks.

Most warranties don’t cover batteries because they are identified as consumables.
I’ve tried in the past with Dyson to no avail

They claim to cover the battery but I’m pretty sure they’ll only cover a total failure, not shortened battery life. The battery barely lasts long enough to be useful when it’s new, once it’s degraded 30 or 40 percent it’s useless, but not totally failed so they don’t have to cover it. I wouldn’t buy a dyson again.

I’ll do a tear-down of the battery pack and post pics :slight_smile:
(Maybe this weekend)

Yep I have harvested some 21700s from an old Dyson battery pack, don't know which model of Dyson since I took it out from a batteries recycle bin.
The cells were branded as Dyson. no Idea who is the real manufacturer.


Here is the old Dyson battery pack. I put the new one from Dyson into the vacuum and it works much better now.

I’ve seen Youtube videos where its possible to open up without damaging the case, but since I am not that good and was not saving the case I was a little more brutal. There are 6 clips that need to be pried apart.

In the end I chewed up the plastic to release the clips

It finally came apart, and needed a T8 screw removed before the pack could be released

There was a clear plastic piece and this was again hard to release, and I chewed up the case to help it release. It’s a good thing I bought a full replacement unit from Dyson, instead of trying to change the cells

Here is the pack

And fianlly a freed cell

The text reads
“SE US18650VTC4 C4”
“G 1798043XI13F”

I tried the cell in my Emisar D4, and it works.

Here is the cell in my XTAR VC4: it reads 4.1V

Now what do I do?

PS: I have larger pictures, but did not want to post them here. Anyone interested to see them please contact me.

That damage makes me nervous. It’s best to junk that one.

Here’s what I do:

  1. Compare the voltages of each cell from the pack against each other. If one is significantly lower, flag it with an X.
  2. Charge them all to 4.2v at a 1amp charge rate. Any that get hot during this are junk.
  3. Rest them 1 week. Record the 7 day voltage. Any that are below 4.120v are junk.
  4. Rest them 24 hours more. Record that voltage. Any that lost more than 0.002v from yesterday are junk.
  5. Resistance test each one. Any greater than 150ohm get a second chance. If it fails again, it’s junk.
  6. Discharge them at 1amp on a capacity tester. Any that get hot during this are junk.
  7. If the capacity test showed less than 1000mah, it’s not worth keeping. Junk it.

And passing these test doesn’t mean it’s healthy enough to hot rod. I would recommend a resistance below 90ohm for higher demand applications.
Six steps might sound like a lot the first time you do it, but it’s not very labor intensive at all.
One final bit of advice, it if doubt, junk it.

+1^ awesome those are some vtc4’s, 2100mah and 20A cdr. You need to rest them for a few days before condemning them. Do you have a way to discharge test them?

It’s going to be hard for me to cleanly remove the contacts from the rest of the cells. Given the price of buying new 18650s I think I am going to junk them. But thanks to everyone for advice —- I hope the thread is useful for others who may be in a similar situation.

Not sure what the point is here. If they are dead why put them in a light. Also, 18650/21700 cells are in the $4-$5 range which makes what you are doing pointless.

Some packs fail soon after manufacture because of a defect in only 1 of the cells. Sometimes people replace battery packs that are almost like new. That’s often the case with laptops. Or maybe the laptop was junked because Windows was slow. At any rate, thousands of people consider it a fun hobby to seek out those nearly new cells that were destined for a scrap bin. Hundreds of people have amassed so many good cells they build powerwalls for their house.

I would not trust a bunch of used batteries that are all different condition from all different sources with all different capacities to power my home.