Cheap(ish) BMS from Aliexpress

Topics concerning OEM and open source BMSes
Alibro
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Re: Cheap(ish) BMS from Aliexpress

Post by Alibro »

zippy500 wrote: Fri Aug 20, 2021 5:36 pm
Pity he hasn't installed and tested it yet.
Have you watched his Leaf upgrade video? I wouldn't want to be in a crash in that car. :o
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arber333
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

Right!
Yesterday i have measured my battery modules when i had to put them back in the car (after A/C system cleaning). I was really carefull with measuring voltage. I had 16S capacity active balancer connected for 3 weeks now. Some mixed results...
1. All cells within the 16S module were within 0.03V difference! That is a real plus.
2. Cells in modules not under active balancers had less than 0.1V difference with one or two exceptions that sank below 0.2V difference.
3. I noticed complete module that was actively balanced had lower voltage with 62.5V than not balanced which were around 62.8Vdc throughout the pack.

I can draw conclusion that within some margin active balancer draws some energy from module overtime although it keeps it aligned.
I bet using 6x active balancers for complete battery of 96S will rectify that.
Even if i will have each module balanced i will still use my BMS to show individual cell votages.

Does anyone know any BMS systems which would work directly with 16S modules and output CAN telegrams out? Only for information?
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Re: Cheap(ish) BMS from Aliexpress

Post by Alibro »

arber333 wrote: Thu Sep 02, 2021 11:05 am Right!
Yesterday i have measured my battery modules when i had to put them back in the car (after A/C system cleaning). I was really carefull with measuring voltage. I had 16S capacity active balancer connected for 3 weeks now. Some mixed results...
1. All cells within the 16S module were within 0.03V difference! That is a real plus.
2. Cells in modules not under active balancers had less than 0.1V difference with one or two exceptions that sank below 0.2V difference.
3. I noticed complete module that was actively balanced had lower voltage with 62.5V than not balanced which were around 62.8Vdc throughout the pack.

I can draw conclusion that within some margin active balancer draws some energy from module overtime although it keeps it aligned.
I bet using 6x active balancers for complete battery of 96S will rectify that.
Even if i will have each module balanced i will still use my BMS to show individual cell votages.

Does anyone know any BMS systems which would work directly with 16S modules and output CAN telegrams out? Only for information?
There are loads of ANT BMS that will work with 16S, have bluetooth connection to an Android device to show voltages and could have the balancing turned off but they are expensive (especially if multiplied by 5 or 6) and would be overkill as they still have all the normal BMS options.
Also it is difficult or impossible to have them all work on the one Android device.

It would be great if we could use an Arduino or mini PC of some kind to show the voltages of each cell and use some of these balancers to keep the pack balanced.
The one caveat about active balancers is they will mask the issue if a cell starts to go bad so it would be better if the balancing was only done once a week or maybe once a month.
I'm still living in hope I can use the Leaf BMS to monitor my system but haven't done anything about it yet.
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

Alibro wrote: Thu Sep 02, 2021 3:19 pm There are loads of ANT BMS that will work with 16S, have bluetooth connection to an Android device to show voltages and could have the balancing turned off but they are expensive (especially if multiplied by 5 or 6) and would be overkill as they still have all the normal BMS options.
Also it is difficult or impossible to have them all work on the one Android device.

It would be great if we could use an Arduino or mini PC of some kind to show the voltages of each cell and use some of these balancers to keep the pack balanced.
The one caveat about active balancers is they will mask the issue if a cell starts to go bad so it would be better if the balancing was only done once a week or maybe once a month.
I'm still living in hope I can use the Leaf BMS to monitor my system but haven't done anything about it yet.
Hm... i am thinking of using Volt Gen1 BMS for 96S cells. Just like that. It is CAN bus controlled and it can transmitt cell voltages over CAN. With those active circuit i dont need other balancing.
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Re: Cheap(ish) BMS from Aliexpress

Post by Alibro »

arber333 wrote: Thu Sep 02, 2021 3:33 pm
Alibro wrote: Thu Sep 02, 2021 3:19 pm There are loads of ANT BMS that will work with 16S, have bluetooth connection to an Android device to show voltages and could have the balancing turned off but they are expensive (especially if multiplied by 5 or 6) and would be overkill as they still have all the normal BMS options.
Also it is difficult or impossible to have them all work on the one Android device.

It would be great if we could use an Arduino or mini PC of some kind to show the voltages of each cell and use some of these balancers to keep the pack balanced.
The one caveat about active balancers is they will mask the issue if a cell starts to go bad so it would be better if the balancing was only done once a week or maybe once a month.
I'm still living in hope I can use the Leaf BMS to monitor my system but haven't done anything about it yet.
Hm... i am thinking of using Volt Gen1 BMS for 96S cells. Just like that. It is CAN bus controlled and it can transmitt cell voltages over CAN. With those active circuit i dont need other balancing.
If you are able to decipher the CAN signals and produce a display to show voltages then you are on a winner.
But if you can use a Volt BMS that way why would you need the active balancing? Couldn't you use the BMS to do that as I'm not sure active would give much advantage.
Or am I missing something?
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

I like active balansers very much. But i dont trust them fully. I need to have a system that can detect individual cell voltages and display that over CAN. Then i can teach my car controler (charging, DCDC.. ) to gather cell values and report anomalies. As a kind of monitor.

I could make another module BMS board with 16S cell module sensing and CAN bus, but i really dont have the energy to design another BMS type. It was all done already.
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Re: Cheap(ish) BMS from Aliexpress

Post by MattsAwesomeStuff »

arber333 wrote: Thu Sep 02, 2021 4:06 pmI like active balansers very much. But i dont trust them fully. I need to have a system that can detect individual cell voltages and display that over CAN. Then i can teach my car controler (charging, DCDC.. ) to gather cell values and report anomalies. As a kind of monitor.
This is my philosophy too. In OEM use and under warranty, I trust a BMS. In a cheap chinese BMS, or my own DIY efforts, I do not. Especially considering the alternative.

If my pack capacities are matched, then balancing is more of an information issue than it is a charging issue. If my pack becomes poorly capacity-matched, the solution isn't to lean on the BMS to force a square peg into a round hole, it's to address the capacity-mismatch.

Beyond that, any balancing issue should be extremely rare. And, when it does occur, it should be minor, and, if it is, I have no problem manually balancing things on occasion, I don't need a system to do it for me, especially not constantly.

But, I don't know of a BMS that is reporting-based only. I don't need CAN, as I'm not likely to have a central CAN system anyway, but, I'm not opposed to it. I would ideally just like something cheap as possible that gives me the information I need and lets me decide what to do about it.

I've even considered hooking up a grid of 96 tiny voltmeters on a panel and a cannon plug that I shove in once in a while to check voltages. (Or a 5x2 grid I move to 10 different terminals).
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

MattsAwesomeStuff wrote: Fri Sep 03, 2021 12:09 am But, I don't know of a BMS that is reporting-based only. I don't need CAN, as I'm not likely to have a central CAN system anyway, but, I'm not opposed to it. I would ideally just like something cheap as possible that gives me the information I need and lets me decide what to do about it.

I've even considered hooking up a grid of 96 tiny voltmeters on a panel and a cannon plug that I shove in once in a while to check voltages. (Or a 5x2 grid I move to 10 different terminals).
I allready made my share of tiny voltmeters. I put them here viewtopic.php?f=13&t=61
I think its twisted pair comms are getting crowded at 9600baud speed. But it is really insensitive to EMI. Because of this it works really well as a monitor, but it can cause harmonics issue while balancing.
Now that i know i want active balancers i can make my diyBMS as is and adapt the master unit.
Master unit now uses Pic16f chip. I could go and design a new master using Pic18f chip with CAN bus. Hm...
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

I got those remaining 5 boards from Aliexpress. That was fast shipping.
For now i reconfigured my existing BMS so it is connected to active balancers by 16S connection. I left 1.6mm holes for testing and measuring cell voltages and they accepted the new balancer cables.
20210904_192301.jpg
I didnt want to shorten the cables so i kept the lenght and i sorted them out along the circuit.
20210904_192314.jpg
20210904_192332.jpg
What i found out when i measured my cells was the small but consistent drag from those balancers. In the pack that was connected to the first 16S balancer couple of weeks before i noticed voltage 4.02V per cell in all cells! While others were varying at 4.02 to 4.08...
I think rest of cells will come in line when they accept balancers.

So for me those capacitive active balancers are a real deal!
The only think left to experiment with is the small pads on the balancers which are soldered by default. If i cut ithis connection balancer stops. I am thinking of connecting those pads with opto couplers and a signal from my BMS. This will operate balancers only above certain voltage where Ri is high enough that balancing (charg or drain) actually matters.
20210904_192327.jpg
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Re: Cheap(ish) BMS from Aliexpress

Post by Alibro »

arber333 wrote: Sun Sep 05, 2021 11:34 am I got those remaining 5 boards from Aliexpress. That was fast shipping.
For now i reconfigured my existing BMS so it is connected to active balancers by 16S connection. I left 1.6mm holes for testing and measuring cell voltages and they accepted the new balancer cables.
20210904_192301.jpg

I didnt want to shorten the cables so i kept the lenght and i sorted them out along the circuit.
20210904_192314.jpg20210904_192332.jpg

What i found out when i measured my cells was the small but consistent drag from those balancers. In the pack that was connected to the first 16S balancer couple of weeks before i noticed voltage 4.02V per cell in all cells! While others were varying at 4.02 to 4.08...
I think rest of cells will come in line when they accept balancers.

So for me those capacitive active balancers are a real deal!
The only think left to experiment with is the small pads on the balancers which are soldered by default. If i cut ithis connection balancer stops. I am thinking of connecting those pads with opto couplers and a signal from my BMS. This will operate balancers only above certain voltage where Ri is high enough that balancing (charg or drain) actually matters.
20210904_192327.jpg
I like this a lot.
I plan to bring all my balance leads to a single location in the car so that I can balance them manually from time to time. Maybe someday I'll sort out a proper system but for now my priority is getting the damn thing going. ;)
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

Alibro wrote: Fri Sep 10, 2021 8:03 am I like this a lot.
I plan to bring all my balance leads to a single location in the car so that I can balance them manually from time to time. Maybe someday I'll sort out a proper system but for now my priority is getting the damn thing going. ;)
The idea is to have a central system which would transmitt cell values to compare on a single LCD or similar. I am inclined to use Ampera/Volt BICMs since they are already designed for this application and they work using SimpBMS with LCD.
I would only need to make an interface board to connect battery modules with BICM.

Also BICM are 12S per side and i would need to work some magic to use correct cell numbers.
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

I have found another active BMS/Balancer system. I couldnt help myself and i ordered it for testing.
https://www.aliexpress.com/item/1005002 ... 4c4dNpYkyI

This is a 24S active balancer with 1A balancing capability and voltage measurement. And the difference from previous balancers it can pass power directly to the cell which is low. In theory this should balance really fast. It works using supercap to store energy before passing it on.
It works with various ways of communication bluetooth, CAN or RS485. Multiple instances of 24S can be connected with CAN or RS485 option. Address is determined by DIP switches on the back.
I decided on CAN communication since i got to know it better than RS485.
CAN system operates with 250kbaud. There would be an option for 500kbaud but one would need to order at least 100 pieces 8-).
Protocol is described in the file attached.
I also made some testing boards for 4x 16S cells to connect my pack to the balancers.
Will keep you updated...

I see someone already tested ordinary bluetooth version...
Attachments
Balancer-CAN-Communication Protocol (1).pdf
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

OK... I connected the new balancer and connect it to the first battery from negative side inside the pack.
I had some trouble connecting to the CAN. It should be 250kbd, but i just cant get it to run...
Next i searched for bluetooth signal and lo and behold i got it immediately!
I set the cell numbers and watched the values. I could select balance command and it would start.

It is a nice UI. I just need to get the CAN to work. Will get back...
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Screenshot_20211124-205338.jpg
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Re: Cheap(ish) BMS from Aliexpress

Post by chentron »

This bms is the one I have in a solar battery. It has been working perfectly for almost 2 years. the pity is that it is not possible to show more than 24 cells on the screen of my phone.
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Re: Cheap(ish) BMS from Aliexpress

Post by Alibro »

After a lot of time spent adapting wiring looms and faffing about I managed to get my Leaf BMS working with the eGolf modules.
IMG_20220503_213915077.jpg
This is the setup at the moment as I'm trying to get the charger working but the BMS only needs 12V and CAN connections for the OBD2 port, Getting the DC-DC working was very simple in the end.

This is the output on Leafspy
Screenshot_20220502-001220.png
It seems to be trying to balance the pack but it's a very slow process. When I get it charging and discharging I'll know better if it's going to be able to balance these cells but at least it is showing their voltage.
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

I have fiddled some with my batteries and its balancer modules.
I took my 65V 16S charger and clip it to individual packs to correct them a bit according to 4V per cell reference on other modules.

FYI inside balancer app settings menu i found ADC position which declared voltage of a complete module. It is a setting to smooth differences with ADC sensing.
If i first measured complete module voltage with my multimeter i got 95.8V and 3.99 on individual cell modules. That module in particular was showing 94.8. When i corrected the value of complete module i immediately got correct value for individual cells.
Just saying there is more to the UI app than first impression shows.
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Re: Cheap(ish) BMS from Aliexpress

Post by arber333 »

Well now... i have discovered the first bad side of those JK 24S active balancers.
Inside the circuit there are small 0603 resistors of 0.01R value. They are somewhere at 500mW value and seem too small for 1A declared balancing.
I use those balancers actively for about a year.

This weekend i found one module in error! Bluetooth screen showed gaps between cells.
When i measured cells for error i couldnt find any. All were sitting at 3.80V.
I inspected the electronics board for obvious errors. I found several resistors burned.
I went on and contacted Hankzor BMS rep on Aliexpress. They were really forthcomming and helpfull with instructions even though i had a feeling of language barrier.

In the end they advised replacing all R01 resistors with new ones.
As i didnt have them in stock i went and soldered some thin silver wire in their place, just to try if rest of circuit was ok.
I got good contact with BT and CAN! Looks like BMS is alive.

EDIT: To clarify, BMS was not faulty from the long term use of balancing at 1A the cell fuses burned up. They are fairly easy to replace even with hand soldering. I think i will see more failed fuses in future and i intend to replace them. Another preventive measure would be to limit balancing to two scenarios:
1. When any cell would be higher than 3.90V
2. When the biggest voltage differential allowed would happen. Value would be set pragmatically.
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