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Fixing the AEG CX8-50EB, battery powered vacuum cleaner
#11
(02-09-2019, 12:06 PM)LEDSchlucker Wrote: Maybe you have to connect the new cells before disconnecting the old ones. Sometimes on newer PCB's this is the case, some sort of "safety" feature.

It seems I have fallen foul of the "safety feature" too, while re-populating an AEG 25.2V battery with new cells.

I'm assuming this is why the BMS is now kaput since I can find 25.2V entering the board but not leaving it to power the motor?

Does anyone know a source for a replacement BMS? (the QR code on the PCB gives me nothing).
I can get a generic 7s  BMS on eBay but I think its form-factor is too big to fit into the orange battery-housing.

Best,
Marc
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#12
(02-25-2019, 02:13 AM)Oramen Wrote: [...]
Does anyone know a source for a replacement BMS? (the QR code on the PCB gives me nothing).
I can get a generic 7s  BMS on eBay but I think its form-factor is too big to fit into the orange battery-housing.
[...]

There are also some small ones out there:
https://www.aliexpress.com/item/7S-10A-B...st=ae803_5
https://www.aliexpress.com/item/Brand-7S...st=ae803_5
https://www.aliexpress.com/item/29-4V-7S...st=ae803_5

Just some examples...
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#13
I don't think you can replace the original BMS with one of these. Actually, I don't just think, I know that you can't do that. At least if your model is made like mine. There are communication connections between the battery and the BMS counterpart in the device. The vacuum cleaner will not work and just go into an error state. You'd have to remove the control electronics from the vacuum cleaner, just like I did, to directly attach the battery to the motor.
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#14
(03-02-2018, 05:11 PM)DarkRaven Wrote: Technically it isn't broken, so fixing means actually modifying. Enhancing the unit and getting rid of some stupid issues (from my point of view) that AEG has built into this model.
Oh, and when I say AEG I mean Electrolux. AEG used to be a german company but has been bought by swedish company Electrolux and is now one of their brands. You will see some part numbers below, maybe you'll find that this particular model is available under different trade names:


I bought one of these some time ago because I'm lazy and didn't want to get out the corded vacuum cleaner all the time. It does its job very well. I have no carpets and no pets so I don't need a super high power vacuum cleaner to get the job done. And the battery powered one can be charged from my solar setup so that's a win-win.
Researching about vacuum cleaners leaves you with the usual results: Lot of cheap and nasty stuff, small handheld ones and low power units 10.8V/12V (3S), 14.4V (4S), non lithium 9.6V and weird stuff like 13.5V lithium, whatever that is. Then there is the 18V (5S) and 21.6V (6S) in the middle and 25.2V (7S) and more at the top. And the "high end" stuff like Dysons which are overpriced at all sizes and voltages. The AEG CX8-50EB is a midrange 21.6V model, based on reviews it's a decent machine so I got that one. There are also 25.2V models in the CX8 range which is important later on.

AEG screwed up the battery a bit, I knew that from other reviews and AEG actually acknowledged battery issues. Usually DOA batteries (the ones that come with the unit as well as spare ones) or batteries that just die after a few cycles. I wasn't overly bothered with that, replacing cells and building/rebuilding batteries is what we do anyways. AEG used probably old stock of Samsung INR18650-15L cells or had the assembled batteries lying around for a long time, the issues are likely caused by long term storage.

But I knew that I had to fiddle with the battery at some point anyway, so to make easier I've chosen the CX8 series. I bought a second CX8-50EB with a dead battery for cheap on eBay so I didn't have to play around with my fully functional vacuum cleaner on the first try. All units from this series have a removeable battery as you can see:


Unfortunately AEG didn't think this through. The battery can only be charged inside the unit. There is no external charger bundled with the vacuum cleaner. It's not even available as an option. So what is the point? The battery is easily user-replaceable, sure, but spare parts are overpriced and low quality so I'm not sure what the idea behind this was. On the chassis there are two metal contact pads on the back. When putting the machine on it's charging station it makes a connection with the power supply which then puts 35V across the pads, 500mA max. Charging takes quite a while, even though it is just a 1500mAh battery.


The power supply is, according to its label, the same for the 21.6V and 25.2V models. When I saw this the first time I thought about whether they share more parts. Turns out they do, here is the 21.6V / 6S battery I have:



It's a 7S BMS, two wires are joined together on the same cell. On the 7S models there is just one more cell in there. The cells are hold in place by cell holders (not pictured) and there is actually an empty slot for the seventh cell.

And this is what the inside of the vacuum cleaner looks like after you've removed its chassis:


It's really not much. The white cable that runs down the side of the table has a PCB with two buttons on the end, power on/off and the speed selector. When starting it it automatically runs on full power and you can turn it down to save energy and increase the runtime but I never found this to be very useful. On the right there is the battery connector together with my remaining original battery. The small PCB with the white wires attached to the main PCB has the charging and error LEDs on it. The motor is wired directly to the main PCB. The other red/black wires with the big connector in the middle is the connection for the powered brush. Not sure why there is a connector on these wires. There is also the blue and green wires going down to the brush, have yet to work out what they are for. The red connctor on the PCB is the input, I've unplugged the wires, you can seem them on the top between the screwdrivers.

The idea is now to remove the main PCB. Apart from low voltage cutoff it provides no feature that I want or need. The motor will be powered directly from the battery, controlled by an old fashioned switch. Still have to measure the current the motor draws to properly size the switch. Low voltage warning will be done by a standard LiPo beeper from the RC world and charging will be done using a balance charger, I'll add balance wires to the battery. Not using the crappy battery BMS board anymore obviously.
Also I want to find out if this is actually the same motor as in the 25.2V models. If it is then I'll make a 7S battery for free extra power, otherwise I'll stay at 6S.


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(02-25-2019, 06:58 PM)DarkRaven Wrote: I don't think you can replace the original BMS with one of these. Actually, I don't just think, I know that you can't do that. At least if your model is made like mine. There are communication connections between the battery and the BMS counterpart in the device. The vacuum cleaner will not work and just go into an error state. You'd have to remove the control electronics from the vacuum cleaner, just like I did, to directly attach the battery to the motor.

I could see myself having to do a complete tear-down as you did, and implement some 
"custom wiring".

I have provided AEG whitegoods with the QR for the BMS but I'll be astonished if I even get an acknowledgement, never mind a replacement part.

I have had one attempt at removing the motor, but it's housing won't budge in spite of removing all visible torx screws.  I guess I will need to get in there if re-wiring.


I have the 25.2V vacuum but assuming its design is the same as yours in this regard - do you have any dis-assembly tips?

Best,
Marc



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(02-25-2019, 05:42 PM)LEDSchlucker Wrote:
(02-25-2019, 02:13 AM)Oramen Wrote: [...]
Does anyone know a source for a replacement BMS? (the QR code on the PCB gives me nothing).
I can get a generic 7s  BMS on eBay but I think its form-factor is too big to fit into the orange battery-housing.
[...]

There are also some small ones out there:
https://www.aliexpress.com/item/7S-10A-B...st=ae803_5
https://www.aliexpress.com/item/Brand-7S...st=ae803_5
https://www.aliexpress.com/item/29-4V-7S...st=ae803_5

Just some examples...

Thanks so much for the info on the 7S BMS offerings!
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#15
To be honest, the best tip is probably don't do it, but that's hardly a valid solution.

There are a lot of screws and the whole thing is rather low quality. There is some mechanical stress / tension on some parts and you'll have a hard time putting them back together properly once they came apart. The fact that you need force to get it apart in the first place just makes it worse.
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#16
(02-25-2019, 09:54 PM)DarkRaven Wrote: To be honest, the best tip is probably don't do it, but that's hardly a valid solution.

There are a lot of screws and the whole thing is rather low quality. There is some mechanical stress / tension on some parts and you'll have a hard time putting them back together properly once they came apart. The fact that you need force to get it apart in the first place just makes it worse.

Hi - thanks for the feedback on my question.  In some respects I NEED to continue with the teardown. 
Due to illness I need to re-animate this very lightweight vacuum.  Also, if I can learn some Electronics along the way, great.

That said - I had hoped I'd found an easy solution by aiming to dispense with the battery altogether, and power the motor directly from the charger 34V (this model as you know has a separate charger).  In other words - make it a 'corded-device'.  
You I'm sure will not be surprised that all this achieved was a slowly turning motor - useless for vacuuming! 

At the risk of revealing my ignorance of electronics could I ask you/the group the following:
1. Did it not work because the charger is likely NOT to be supplying enough current?
2. What is the likely function of the PCB that sits on the motor (in the step 1 test, the charger wires were connected to the posts on this PCB).
3. Is the solution to making a 'corded-vacuum' to get an upgraded power-supply and connect it directly to the motor (somehow, by-passing the integral PCB).

Thinking longer term, I have the parts to build a 'battery-pack' based on 18650 cells and a 7s BMS.  It sounds like this is your plan too and I'd appreciate any correspondence based on your efforts?

Best Wishes,
Marc
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#17
You are right, I'm not surprised Smile

The charger isn't actually a charger by the way, it's just a power supply. The charger is built-in, so to say. The necessary charging circuitry is part of the onboard electronics. One PCB in the battery, one in the vacuum itself, and together they provide the functionality of a BMS, a charger, a motor controller, together with the switch on the handle, and a controller for the LEDs.

The power supply is rated for 35V and 0.5A if I remember correctly. There are two problems:
1. Voltage, the whole system might run on 35V, but maybe it won't. You could potentially fry it by applying 35V to it. Just the charging part of the electronics will accept 35V input voltage. It's unlikely that the whole system will be able to run on 35V.
2. Amps/Power, 35V at 0.5A is 17.5W and that's nowhere near enough to actually power the vacuum.

The output voltage of the power supply will just collapse under the load. I've measured the motor (actually motors, there are two), at 22.2V (6s nomimal voltage) it draws around 10A. That's 220W at least. Yours runs on 25.9V nominal and maybe it uses another motor, not sure. It will probably also need more power.

So I guess that covered your questions #1 and #2. The solution to make it corded is indeed a more powerful ~25-30V power supply (7s fully charged is 29.4V) capable of at least 10A. I'd go for 12A, better 15A.

You are right, I want to make my own battery for it, but because of a whole lot of other projects I still never came back to this project to actually do it. I planned to do 6s just like the original battery but I assume that they are all the same and that my one would run on 7s as well. I got the cells for that ages ago but, as I said, never found the time to actually do it. I got some new Sanyo NCR20700B cells, 4.2Ah and capable of 15A. Today I would most likely get some 21700 cells.

You're saying that you have the parts and the cells, what kind of 18650s do you have? Be advised that this won't work with reclaimed laptop cells, they aren't powerful enough. You'd need a lot of them in parallel so that they are able to handle the current.
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#18
(02-26-2019, 06:00 PM)DarkRaven Wrote: You are right, I'm not surprised Smile

The charger isn't actually a charger by the way, it's just a power supply. The charger is built-in, so to say. The necessary charging circuitry is part of the onboard electronics. One PCB in the battery, one in the vacuum itself, and together they provide the functionality of a BMS, a charger, a motor controller, together with the switch on the handle, and a controller for the LEDs.

The power supply is rated for 35V and 0.5A if I remember correctly. There are two problems:
1. Voltage, the whole system might run on 35V, but maybe it won't. You could potentially fry it by applying 35V to it. Just the charging part of the electronics will accept 35V input voltage. It's unlikely that the whole system will be able to run on 35V.
2. Amps/Power, 35V at 0.5A is 17.5W and that's nowhere near enough to actually power the vacuum.

The output voltage of the power supply will just collapse under the load. I've measured the motor (actually motors, there are two), at 22.2V (6s nomimal voltage) it draws around 10A. That's 220W at least. Yours runs on 25.9V nominal and maybe it uses another motor, not sure. It will probably also need more power.

So I guess that covered your questions #1 and #2. The solution to make it corded is indeed a more powerful ~25-30V power supply (7s fully charged is 29.4V) capable of at least 10A. I'd go for 12A, better 15A.

You are right, I want to make my own battery for it, but because of a whole lot of other projects I still never came back to this project to actually do it. I planned to do 6s just like the original battery but I assume that they are all the same and that my one would run on 7s as well. I got the cells for that ages ago but, as I said, never found the time to actually do it. I got some new Sanyo NCR20700B cells, 4.2Ah and capable of 15A. Today I would most likely get some 21700 cells.

You're saying that you have the parts and the cells, what kind of 18650s do you have? Be advised that this won't work with reclaimed laptop cells, they aren't powerful enough. You'd need a lot of them in parallel so that they are able to handle the current.

Hi - really appreciate you taking the time to respond and to give such a full answer.   I think the 'corded' solution will meet my immediate requirement of getting up and going.  So my checklist (taking on-board your input) for the two activities are:

1. Corded-Vacuum: An up-rated power-supply capable of 15A and around 29V (which I would directly connect to the Motor - I assume I would remove the integral PCB?). Some sort of switch.  An in-line fuse?  
I'd been thinking about buying a 'bench power-supply' to begin 'projects', so maybe one of those could serve a dual-purpose here?  Any recommendations? Could I adapt a PC ATX psu and somehow step-up the voltage to 29V?


2. Battery-Project: the Samsung 18650's are new 3000mAh -15A.  I have a 7S 24v 20A BMS and some ***** battery-holders so far.  If you decide to complete your own, do let me know how you got on?

3. Other Future Projects: Battery Welder/Bench Power-supply/Arduino robot.


Thanks again,
Marc
  
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#19
(02-26-2019, 11:24 PM)Oramen Wrote:
(02-26-2019, 06:00 PM)DarkRaven Wrote: You are right, I'm not surprised Smile

The charger isn't actually a charger by the way, it's just a power supply. The charger is built-in, so to say. The necessary charging circuitry is part of the onboard electronics. One PCB in the battery, one in the vacuum itself, and together they provide the functionality of a BMS, a charger, a motor controller, together with the switch on the handle, and a controller for the LEDs.

The power supply is rated for 35V and 0.5A if I remember correctly. There are two problems:
1. Voltage, the whole system might run on 35V, but maybe it won't. You could potentially fry it by applying 35V to it. Just the charging part of the electronics will accept 35V input voltage. It's unlikely that the whole system will be able to run on 35V.
2. Amps/Power, 35V at 0.5A is 17.5W and that's nowhere near enough to actually power the vacuum.

The output voltage of the power supply will just collapse under the load. I've measured the motor (actually motors, there are two), at 22.2V (6s nomimal voltage) it draws around 10A. That's 220W at least. Yours runs on 25.9V nominal and maybe it uses another motor, not sure. It will probably also need more power.

So I guess that covered your questions #1 and #2. The solution to make it corded is indeed a more powerful ~25-30V power supply (7s fully charged is 29.4V) capable of at least 10A. I'd go for 12A, better 15A.

You are right, I want to make my own battery for it, but because of a whole lot of other projects I still never came back to this project to actually do it. I planned to do 6s just like the original battery but I assume that they are all the same and that my one would run on 7s as well. I got the cells for that ages ago but, as I said, never found the time to actually do it. I got some new Sanyo NCR20700B cells, 4.2Ah and capable of 15A. Today I would most likely get some 21700 cells.

You're saying that you have the parts and the cells, what kind of 18650s do you have? Be advised that this won't work with reclaimed laptop cells, they aren't powerful enough. You'd need a lot of them in parallel so that they are able to handle the current.

Hi - really appreciate you taking the time to respond and to give such a full answer.   I think the 'corded' solution will meet my immediate requirement of getting up and going.  So my checklist (taking on-board your input) for the two activities are:

1. Corded-Vacuum: An up-rated power-supply capable of 15A and around 29V (which I would directly connect to the Motor - I assume I would remove the integral PCB?). Some sort of switch.  An in-line fuse?  
I'd been thinking about buying a 'bench power-supply' to begin 'projects', so maybe one of those could serve a dual-purpose here?  Any recommendations? Could I adapt a PC ATX psu and somehow step-up the voltage to 29V?


2. Battery-Project: the Samsung 18650's are new 3000mAh -15A.  I have a 7S 24v 20A BMS and some ***** battery-holders so far.  If you decide to complete your own, do let me know how you got on?

3. Other Future Projects: Battery Welder/Bench Power-supply/Arduino robot.


Thanks again,
Marc
  
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Hello again - I found this power-supply on eBay (its at the top-end of what I can afford and only 10A). It would be ludicrous to buy this just to run a Vacuum I know, but as I said, I could do with a Bench supply for projects etc.  Do you think this looks fit for purpose? 


https://www.ebay.co.uk/itm/Mini-30V-10A-...3347290930?




Thanks,
Marc

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#20
A bench power supply would work, if it's powerful enough, but don't forget that you can't (or shouldn't) run a several meters long DC wire to power the vacuum. That means you basically need to attach the PSU directly to the vacuum to keep the distances as short as possible. An ATX PSU would work as well, with a boost converter to boost the voltage from 12V to 29V.

But I wouldn't suggest either. Instead I'd get a powerful yet compact as possible PSU, like a laptop power brick or similar, and build a suitable DC-DC converter into the vacuum. The power brick can simply be strapped onto the outside of the vaccum and will supply power to the DC-DC converter. It's not pretty but would work well and you can use the AC power cord to connect it to the mains. It's certainly more practical than a bench PSU or ATX PSU.

Or you make a new battery. This sounds like you have Samsung INR18650-30Q cells, these are suitable for the job. Don't use the battery holders though, the current will be too high. You can either spotweld the cells together with nickel strip (around 8x0.2mm should be fine for 10A to 15A) or solder the cells together. I initially wanted to spotweld the cells together but I could only get 6x0.15mm nickel strip which is a bit too small for my taste. If I pick it up again at some point I'd probably solder the cells together using a solid copper wire.
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