Fix Ergorapido Turns Itself Off

Does your cordless vacuum turn itself off after only few minutes of vacuuming?
Does it continue few more mintues by restarting it?
Perhaps it works much longer in low power mode?

I recently obtained an Electrolux Ergorapido ZB2904X cordless vacuum from a friend of mine. He got a new vacuum since ergorapido did not function properlyanymore.

I am actually not a fan of vacuum cleaners which have the motor on the handle. They do not fit under tight spaces, they have lower power and the need to push/pull weight of motor is tiresome. Not to mention, they are often more expensive than similar traditional vacuums.

Above is a photo of the ergorapido which was not functioning properly. With full charge, it worked 1m20s on high power mode and 9m50s on low power mode. By the way, the low power mode is generally useless. After about one and half minutes of use in high power mode, the handle of the motor piece gets warm and it turns itself off.

I reckon the batteries develop a fault, either getting too hot or they lost too much of their original capacity. Therefore I proceeded by change of batteries directly. The original batteries are rated 1200mAH and the vacuum is rated to run roughly 12m at high power and 35m at low power. This tells that the vacuum is using roughly 6A at high power mode.

After the battery change, vacuum operated continuously about 28m20s on high power mode.. Meaning the vacuum now operates over twice longer than when it was new! From empty to full charge takes about 6 hours with standard 25V 0.5A electrolux adapter.

I did not test the vacuum in low power mode since I have no patience to listen to it for several hours. I reckon, in low power mode it should function longer than 1 hour. Actually, this means that this old vacuum now has longer runtime than most similar cordless vacuums in the market today since best ones seem to work up to ~45 minutes ("up to" meaning in low power mode).


Requirements:

This task require a soldering iron, solder, desoldering braid, heatshrink tubes, replacement batteries, philips head screwdriver and patience,

Getting Inside The Vacuum

It is luckily rather easy to get inside the vacuuum. It has 5 screws and 4 plastic tabs around it.

First remove the 5 screws which are shown below. Yes, the handle should be charcoal colored but it was very sticky and I used IPA (isopropyl alcohol or rubbing alcohol) to wipe the color off totally from it.

Then you can carefully pry open the 4 tabs on both sides of the handle.It does not require force if done correctly.
Once you open up the vacuul, you need to carefully unplug the cable going to the battery level indicator on top You can see the connector in the picture below. Also 3 of the batteries are visible. The circuit board is also attached to handle using two clips.

Removing The Batteries

It is quite tight inside the vacuum and it must be completely disassembled  for easy access to rest of the components. I recommend you to take a lot of pictures showing positions of the wires even if you will not desolder them. This helps putting them to same positions when assembling back.

First, there are 4 wires going down to the outside connections from the sides of the vacuum. These must be desoldered. They are shown in the pictues below. I have immediately covered the open ends with tape even though the other ends are not connected to anything. They can still touch something and close circuit and cause damage.

After desoldering the 4 wires, it would be possible to completely remove the motor, circuit board and batteries from the outer shell.

You can decouple the white battery holder from the circuit board by releasing the 4 little clips around it. After that, first remove the red wire as shown below. Immediately tape them after removal to avoid accidental shorts. The thin wire is balancing wire and red one is the main power wire.

After the removal of the red wire, it is possible to remove all the batteries from the holder. There are still several balancing wires, a power wire and a heat sensor attached to batteries.

The pack can be completely freed from the rest after removing black, blue and brown wires, as shown below. Remember to tape them right away after removal to avoid potential short circuits.

Then you can clearly see that these are 3 batteries aligned in series.

Now you have the main board and 3 battery pack seperated completely.

You have to make note of the positions of the tabs going in and out of the batteries. Because you will need to assemble the new batteries exactly same or they won't fit into the plastic. Negative and positive tabs are aligned 90 degrees to each other. Below is a picture of how the original battery looks like.

The other 2 batteries are simply connected to wires so they do not require further dissassembly. You will simply need to disconnect the wires and connect them back on new batteries. I recommend keeping the tabs long for those last 2 new batteries, because they are quite tight in their place.

The remaining 2 batteries are shown below.

Replacing The Batteries

The original batteries were marked SE US18650VT, T 2B12XTF01C. Unfortunately there was no datasheet on Sony site but I believe the information below should be accurate:

 18650 1340mAh - li-ion battery cell 3.6V US18650VT 2B Sony

Nominal Capacity: 1340mAh(0.2C discharge)
Rated Capacity: 1300mAh(0.2C discharge)
Capacity at 1C: 1280mAh(average capacity)
Capacity at 10A: 1200mAh(average capacity)
Nominal Voltage: 3.6V
Internal Impedance:25mΩ  Typ.(measured by AC1kHz)
Cycle Performance: 60% Min. of Initial capacity at 500 cycles(10A discharge)
Charge Method: constant current constant voltage
Charge Up Voltage: 4.1±0.05V
Charge Current: 1.2A
Charge Time: 100mACut
Ambiance Temperature: 23°C
Dimensions: 18.35mm(D)*65.10mm(H)
Weight: Max.44g

I got new LG HG2 (with tabs) batteries from an online seller the specs are as follows:

18650 3000mAh - li-ion battery cell LG 18650 HG2

Nominal Capacity: 3000mah
Nominal Voltage: 3.6V
Initial Internal Impedance: <20mΩ (measured at 1kHz)
Cycle Performance: >=70% after 300 cycles(10A) and 200 cycles(20A)
Charging Voltage: 4.2v
Standard Charge: 1.5A
Fast Charge: 4A
Discharge Cut-Off Voltage: 2.5V
Max. Charging Voltage: 4.20V +-0.05V
Max. Continuous Discharge Current: 20A
Operating Temperature Charge: 0 - 45C
Operating Temperature Discharge: -20 - 60C
Dimensions: 18.2mm(D)*65.0 mm(H)
Weight: Max 48g

As can be seen from the specifications, the HG2 batteries are superior, should work cooler and run longer. They can be charged to higher voltage. I checked the vacuum battery voltage at full charge and they were charged up to 4.10V. Not charging the HG2 up to maximum 4.2V will further increase their lifespan on the long run!

In addition, HG2 are safer due to INR chemistry. Meanwhile the original Sony batteries use ICR chemistry with Lithium Cobalt Oxide which is more unstable and require protection circuits.

While I needed only 5 cells, I ordered 6 cells for roughly 10€ total cost. I ordered 6, for in case one of the cells have any problems and/or also to be able to keep one extra for a reference point.

Yes, I could get 2500mAh batteries cheaper, but with a total price difference of about 2€, I figure it is best to go with highest capacity.

Important Note:
I highly recommend obtaining equipment to test the new cells before installation. Unfortunately there are many fake cells going around and it would be useful to test every battery to ensure quality.

Even cheap chargers such as Opus BT - C3100 v2.2+ provide really nice battery test programs. It is a great investment if you have any re-chargeable batteries. As you can test the remaining capacity of your cells and determine the wear amount. This charger supports multiple chemistries.

The 1A maximum discharge current of Opus BT-C3100 is only enough for testing capacity of the cells. If you want to make sure that your cell's do not overheat or does not have voltage sag, you should use a tester which supports 5A+ discharge currents. For example ZKE Tech EBD-M05 can manage up to 5A and also can create a discharge graph in PC. Only costs about 15€

Building The Pack:

First of all, you have to be 100% sure that you are not attaching the batteries upside down. Mixing up the polarities can have catastrophic results. So, check it several times while building the pack. 

I ordered batteries with tabs attached, because it is often difficult to solder battery terminals fast enough. With pre-attached tabs, it is easier to protect the battery from heat damage. However the tabs normally do not have holes, so I had to make holes to few of them using a nail.

The hole was big enough for attaching all the cables. I highly recommend this because it makes soldering much easier.

First start with attaching 3 batteries which form the pack going into the white plastic holder. I used the soft rubber pieces from original batteries while building the pack. Then attached the tabs to each other to form pack as tightly as possible.

Remember to use heatshrink to isolate the endpoints as it was on the original batteries. Then attach the heat sensor between the last 2 batteries and tape it. Also attach the blue and brown cables and the black cable

Do NOT attach the thin/thick red cable yet!! You will first need to insert the batteries inside the white plastic holder. Remember, red cable was routed from the other side of the plastic holder. See the removal picture above at removing batteries section.

Now, put the white plastic back by sliding batteries in and then you can solder the red wires. After this, you can attach the white plastic holder to the main board. All the wires go under the white plastic and there should not be any left outside.

You can now change the remaining 2 batteries which is a much easier task. Simply desolder the connections and solder to new batteries.

Putting It Back Together

Putting everything back is reverse of removal. Use the photos you have taken to figure out exactly how the cables were originally and put them back the same as before. It require some attention to fit everything back correctly. If you put parts in wrong order or at wrong orientation, they simply won't fit back.

Testing Of The Batteries

I have tested the original batteries using my LiitoKala Lii-500 charger and they all resulted in a perfectly reasonable 1000-1100mAh result with 500mA discharge current. However they perform rather badly when tested with 5A discharge current. Perhaps the batteries had too much voltage sag which triggered the vacuum to stop prematurely.

Below is the test result of all 5 batteries using the EBD-M05 tester. The results show the battery power range between 120mA to 350mA only.

Below is test result of one of the LiitoKala LG HG2 battery. As you can see, it does a nice 2500mA with 5A discharge current. This cell is suppose to be 3000mA however LG tests them with 600mA till 2.5V threshold. I believe I could get 3000mA if I followed the same protocol.