AliExpress replacement battery - chances of dudness.

Quite possibly relabelled e-waste cells. Or just a whole battery from the e-waste bin.

Not surprised at that price...

Tip: never go for 'higher capacity' versions. The OEM battery on these is

(Comparing the weights might be fun too... unless they've added an extra slug of steel or cement in there to make it reassuringly hefty)

Be interesting to hear how the refund process goes. I think Aliexpress is wielding a bigger stick at their sellers nowadays, but not sure if there are loopholes.

Theo

I don't know the design of the machine. Is there room inside for a battery with twice the number of cells/ cells twice as big?

Here's a '6800mAh' listing. You can have any capacity but they look identical.

Theo

I asked Co-Pilot this question, and this was the reply:

"🔍 Here’s how manufacturers boost capacity within the same volume:

Higher Tap Density Materials

Advances in cathode formulation allow more active material to be packed per unit volume.

This increases capacity without changing the battery’s external dimensions.

Cell Format Optimization

Switching from cylindrical to prismatic or pouch cells can reduce wasted space.

Pouch cells, in particular, offer better volume utilization and thermal management.

Improved Electrode Architecture

Thinner separators and optimized electrode layering reduce internal resistance and allow more active material.

Some designs use stacked electrodes instead of wound ones to maximize space efficiency.

Advanced Manufacturing Techniques

Laser welding, precision coating, and tighter tolerances help reduce dead space and improve packing density.

This is especially useful in custom battery packs for drones, medical devices, or compact appliances.

Parallel Cell Configuration

Within a fixed battery case, manufacturers may use multiple smaller cells in parallel to increase amp-hour capacity while keeping voltage constant3.

Thermal and BMS Integration

Smarter Battery Management Systems (BMS) and better heat dissipation allow cells to operate closer to their full rated capacity without overheating.

🧠 Bottom line: You don’t change the chemistry — you optimize the cell design, layout, and materials to extract more usable energy from the same footprint."

Some of that sounds plausible, so might be true.

However, I can't see you getting any clever tech for £12.99 inc P&P. :)

That comes in several different capacities, all of which look identical, apart from the paper label.

Well refund agreed.

I'll try again with the direct replacement.

Hmmm.... Read enough bad stories about cheap cells from no-names on eBay and ali-express.

So for compatible rechargeable batteries I made a point of looking for Bricks and Mortar suppliers prepared to put their names behind the items.

e.g. for Dyson, Sebo & Henry

The dynamic here is being careful with pennies, I am not going to spend that much on a replacement battery for a 3 year old device. If I *have* to spend £50, I'd rather it was as part of a new-with-guarantee unit. Possibly with better features .....

I've not used AliExpress but presumably the battery was mailed from China. In which case, who pays the return postage in this case?

I'm sure that the cheap battery was never going to deliver that claimed

Two batteries giving the same result is at least a hint that the problem could be elsewhere.

Have you considered that there might be something wrong with the base station's charging circuit? Dirty contacts?

You can buy a new robovac for £50? Or you're being careful with pennies but prefer to spend £200+ on a new vac instead of £50?

It seems that Ecovacs deliberately don't sell official replacement batteries, they expect you to send the unit for service:

Ecovacs South Africa do, maybe they have different laws?

Theo

They are. I've already got the QR code for RM postage.

Back in the day us aeromodellers used to buy 'end of line' 'reduced, must go' electric items purely for the batteries, which were worth more than eh tool was being sold for...

A typical electric screwdriver might have a £2 electric motor and a 50p gearbox with 10p switch and a £1 injection moulded base.

And £30 worth of batteries.

If your pack comes apart and contains individual cells it may be possible to replace them

Is it worth it for the vendor? I would guess the postage costs more than the goods (even at their full retail price).

The 800mAh battery scam. Nice.

Depending on the construction of the batteries, like

Maybe a Panasonic cell offers a pretty humble value. But then, it delivers that much. It meets the spec.

Whereas the Chinese cells used to get into "spec wars", where for example a product would be labeled "9999 mAh", which is of course "one better than 8888 mAh".

As a consequence of this sporting tradition, be aware that any Ultra Super High Capacity cells, are just the usual crappy

There used to be one Internet gentleman, with a battery capacity meter (automated capacity determination), and he used to buy various wonder-cells and find them to be delivering 800mAh. (About 1/4 the correct value.) That's why I recommend just knocking the lead-digit off the rating :-)

This sport is a lot like buying 2TB USB sticks for a tenner. You're delusional if you are thinking these are honest offers. The only problem is, it's now possible to get 2TB in a single (large) chip, and we're getting closer to an overlap of the fraud ones, with potential real ones. The 2TB chips are usually a bit too big to fit into traditional-dimension USB sticks. And the price of a real one, is still 10x to 20x the price of the fraud one. There is a 1TB USB stick, which is actually a legit product (runs at around 600MB/sec on SS10 interface). It gets a bit warm though.

Paul

TBF they had an automated process which offered a part refund (£3.something) which didn't require a return. But, being old I exercise my right to be a nuisance. (Not that anyone could tell :) )

Reminds me of when some SX CPUs could actually be DX.

And memory chips were made all the same and the ones that didn't fail at higher speeds were sold as faster ...

And the transistors that failed were narked as 'Sinclair' and sold at twice the price.

How he escaped jail beggars belief

Just tried them for my Dyson DC35 - the battery failed yesterday, by coincidence. No longer stocked - obsolete, they say.

Guess I'm at the mercy of Amazon etc. . . .