Capacitance balancing BMS connection

[velowatt]

I am repairing a 36V LiFePO4 (12 Headway 10 Ah cells in series) which was damaged by a failed BMS (took 6 of the cells down to zero volts without cutoff, the others remained above 2.8V and appear undamaged). I have replaced damaged cells, and bought a BMS board from evassemble. I want be be *sure* not to goof up connections to the BMS. No documentation came with the board, but diagram publlished here on the forum shows the load (controller (-) lead AND the charger (-) lead connected to the P- terminal, and the battery (-) lead to the B- terminal, with third terminal labelled "OUT-" not used.

I am used to seeing B-, C- (for charger negative) and P-. The circuit board is stamped AE-LMD17 REV A1. I emailed evassemble to get info, and also Googled the number on the circi\uit board. This brought up a German EV site, where users had posted the same question and were advised that the OUT- terminal was for the charger negative, and connecting the BMS this way would prevent its balancing function from working.

I am pretty sure that the following diagram is correct- but I want to be sure and not damage the board during assembly.


Any recommendations?

 

[velowatt]

Forgive me for replying to my own post- Michael Cheung of EV Assemble emailed this diagram to connect my BMS. Looks correct, but different than others I seen on the Forums.



Update:
Connected as above, pack seems to charge up. Interesting that the latter cells (7-12) in the string hit 3.7-3.81V early without the first cells (counting from (-) moving much. Once the charger hit its cut-off voltage, it started to "pulse", coming on for a few seconds at a time. After about 2 hours, cells were all balanced at 3.48V.

 

[Spacey]

I've just been given one of those BMS's and I am unsure if it is working or not as it either does not have 'charged cell' lights or they are not working.

The charger is turning off but I can detect no heat from balancing (probably because it is capacitor based) but I can not tell if LED indicators are on this board like the other BMS of this type?

Can anyone clear this up for me? Model is: AE-LMD17 REV A1

 

[Spacey]

Figured it out.... no LED's (helpful). Odd way of balancing, puts the highest voltage in the last cell and bleeds the energy to the lower cells until all are 3.3 volts. Balances without the charger connected.

 

[Gow864]

I had one of these BMS's from EVARSEMBLE. First charge something in the BMS died and it drained one cell to 0. I replaced it with a BMS from headway (plus a replacement cell), it's a big ugly BMS but it works....

Good luck,
Gow.

 

[Spacey]

Now that is worrying, I could see how a BMS based on capacitors could do that.

Checking the voltages of the 16 cells after a night connected up to the BMS, all the cells are at 3.3v except cell 16 which is at a high 3.6v which is odd.

Wish the large Headway BMS had led indicators like the ping ones do.

 

[Spacey]

Yep looks like mine died as well before I even got to ride the bike grrr

 

[gge5]

I just received an 8-cell BMS from EVAssemble (after waiting over a month for them to ship it). I have 8 of the Headway 16Ah cells in series that I'm using in a lawn mower conversion. I connected pack negative first, and then wired up the harness from negative towards positive. On my very last connection, the pack positive, there was a high-pitched squeal and then the magic smoke was released. It managed to burn its way through the double-sided foam tape that I had used to secure the BMS in a matter of seconds. I've contacted Michael for a refund, and we'll see what happens.



I've also had a Goodrum-Fechter BMS go bad on my motorcycle, bringing two cells to 0V and killing them completely. At this point I'm starting to agree with Jack Rickard - an active BMS is a bad thing. That said, I have a CellLog 8S that I'm going to use. No capacitors or resistors to catch fire or fail in a way that kills my cells. It was about $5 from HobbyKing and it has an alarm port that triggers when any cell goes over or under a user-definable voltage. I'll use that alarm port to disengage the contactor on my lawn mower during discharge and flip an AC relay during charge.

 

[Spacey]

Can I ask which wiring diagram he gave you?

I have sent so many requests for the wiring diagram and now he has gone silent....unless he is a practising Christian and gone on a Chinese Christmas vacation.

Given up on the amount of very simple requests from him to give me the correct wiring! Sorry to see that yours blew straight away, I need to give these bikes to people who are not ebike geeks like us in the knowledge that the BMS will function safely and reliably.

Evessemble can go to hell for any future orders from me. The service has been that of a box shifter and not that of someone who actually knows his products. The battery packs cost me 4hrs of labour and £25 in parts to make good the terrible state the batteries arrive in. Taped sensor wires twisted to connectors! I mean damn....3 of them came off from gentle pulling and I mean gentle.

Also one of the cells (cell 16), was allowed by the BMS to hit 4.1volts

I just received an 8-cell BMS from EVAssemble (after waiting over a month for them to ship it). I have 8 of the Headway 16Ah cells in series that I'm using in a lawn mower conversion. I connected pack negative first, and then wired up the harness from negative towards positive. On my very last connection, the pack positive, there was a high-pitched squeal and then the magic smoke was released. It managed to burn its way through the double-sided foam tape that I had used to secure the BMS in a matter of seconds. I've contacted Michael for a refund, and we'll see what happens.



I've also had a Goodrum-Fechter BMS go bad on my motorcycle, bringing two cells to 0V and killing them completely. At this point I'm starting to agree with Jack Rickard - an active BMS is a bad thing. That said, I have a CellLog 8S that I'm going to use. No capacitors or resistors to catch fire or fail in a way that kills my cells. It was about $5 from HobbyKing and it has an alarm port that triggers when any cell goes over or under a user-definable voltage. I'll use that alarm port to disengage the contactor on my lawn mower during discharge and flip an AC relay during charge.

 

[Spacey]

Well I have now waited for a few days after asking for the correct diagram for this BMS, explained that customers were waiting no answer so filed a Paypal refund of $69.00 for that item. I could wait longer but am fed up with simple requests not being listened to or even being read it would seem as if they were truly read the whole situation would have been sorted out weeks ago.

 

[gge5]

Can I ask which wiring diagram he gave you?

My BMS is version AE-LMD17 REV A1. It is the 8S BMS and is about the size of a deck of cards, although a little narrower. I've attached the wiring diagram for this model. It looks the same as the others that have been posted. The negative-most sensing wire goes on the B- side of the board. P- is for charger negative and OUT- is what would run to your motor controller's B- port.

 

[Spacey]

Ok, now I am getting really annoyed with Evessemble as that diagram you have just posted is exactly the same diagram for the resistor based BMs I bought from him (3 of them), yet Michael tells me that the resistor and capacitor BMs are wired totally differently? And still has not checked my simple wiring connections I sent him off my BMS wiring on my pack or even sent me the 'capacitor' wiring diagram.

Starting to think the guy has no idea of his own products, 3 bust resistor BMS and 1 bust capacitor BMs.......yes you could think that I wired it up wrong each and every time.....but I have also managed to build a massive analog modular synthesiser that is a lot more complex than a BMS......and also when using another brand of BMS it amazingly works first time and is still working.

Fed up of this.

 

[Gow864]

Sorry, but, I just gotta smile at this. Now I don't feel not so alone. MICHAEL CHEUNG is a dick head rip-off merchant and cares nothing for the customer.

Once again. DO NOT BUY FROM EVARSEMBLE!

Merry Christmas.....

Gow.

 

[gge5]

I provided evidence to Michael that the BMS and resulting fire was not my fault and asked for a refund of the cost of the BMS ($37) to my PayPal account. He is arguing with me that I wired it wrong and that what I'm saying needs to be "verified by his engineers". I think he's stalling for time. Luckily I installed this as soon as it arrived and it blew instantly - because it took a month and 5 days to arrive. You can only file a PayPal charge dispute for the first month and a half I believe.

I've uploaded a picture of my wiring. Can anyone spot the error?

 

[Evoforce]

To gge5: It looks right from the side I can see.

 

[dnmun]

the P- normally goes to the controller. it would really help if you guys would just show a picture of the BMS that you are talking about so we can see where the traces run to give you some advice. can you guys follow the traces to see where they go?

why would the BMS burn up if you wired it up properly or why would it drain the cell to zero? did it drain the replacement cell to zero also?

 

[Spacey]

I provided evidence to Michael that the BMS and resulting fire was not my fault and asked for a refund of the cost of the BMS ($35) to my PayPal account. He is arguing with me that I wired it wrong and that what I'm saying needs to be "verified by his engineers". I think he's stalling for time. Luckily I installed this as soon as it arrived and it blew instantly - because it took a month and 5 days to arrive. You can only file a PayPal charge dispute for the first month and a half I believe.

I've uploaded a picture of my wiring. Can anyone spot the error?

Looks exactly how I wired mine up. Dnmun.... I will try and get a photo done today of the BMS.

Thing is Michael told me that it is wired totally differently from the BMS he sends with his batteries and that he only sends the capacitor based BMS when people want a BMS on it's own otherwise if they buy a full battery off him they get a resistor based BMS. Seems odd really. But the wiring diagram people with the Capacitor based BMS is exactly the same as the wiring diagram of the resistor based BMS.

The first of the small sensor wires goes to the first cells Negative end and all the rest of the sensor wires go to the positive ends of the cells right up to the last cell.

On the diagram I was sent "P-" is for charge in, "B-" goes to main negative on pack and "Out" goes to load/controller:

 

[Gow864]

dnmun Mine WAS WIRED BY EVASRSEMBLE and still F@#$%^ng blew up!

These BMS's are a piece of shit PERIOD!

DO NOT BUY FROM EVARSEMBLE!

 

[Spacey]

Well it's been 5 days since I emailed him for at least the 3rd time to send me the correct wiring. If I did wire it wrong (he never actually said I did, just that capacitor is different to resistor BMS even though gave same instructions to other buyer that is the same for both).....if I did wire it wrong I will put my hands up on this forum and explain the correct wiring. But 5 days and no reply to my requests, paypal chargeback started for the capacitor BMS.

 

[gge5]

Michael hasn't replied since I sent him the picture of my setup that I labeled. During the times he hasn't contacted you, he was contacting me. He has no excuse. He'll probably claim to be on "Chinese Holiday" or something. I'm forced to file a PayPal dispute as well then...

EVAssemble is the first negative experience I've had with Chinese vendors. I've bought from DealExtreme, Kelly Controller, and have been in contact with Thundersky and have had great service...

I see that because my order wasn't shipped for over a month from ordering I could be eligible for the %15 discount that Michael promised here on the forums, but I don't want to be an asshole about it.

 

[gge5]

I've filed a paypal dispute:

This is the worst customer service that I have ever experienced. First shipping is delayed by one month. You are very unclear on why, and all of the parts are listed as in-stock on your website. When deadlines are passed and no shipment is made, I threaten to cancel my order and only then do you reveal that the charger is still in-production. I can wait patiently for a reasonable amount of time as long as I’m informed of my order’s progress.

My order finally arrived on December 22nd (35 days after placing my order). This alone qualifies me for getting 15% of my purchase refunded due to it not being shipped for over a month. However my issue is that the BMS included in my order was undeniably faulty. Despite wiring the BMS to the battery pack correctly, its operation resulted in fire, smoke, and a truly horrible and perhaps toxic smell of burning electronics. When I politely explained the situation with the BMS and requested a refund you became argumentative in aspects that did not work towards resolving the dispute. Because you continue to argue with me, despite having provided to you clear and undeniable evidence of faulty equipment, I have no expectation that you will issue me a refund willingly. This is not how a company should behave, at least not one that continues to want to have customers. This is my notification to you that I have issued a dispute via PayPal for the value of the BMS, in the amount of 37 USD. I’m sorry that it had to come to this resolution, and I feel sorry for you and your business that I must portray this story as a warning to the electric vehicle communities.

If you wish to continue to do business I would recommend the following:
• Provide an accurate representation of an item’s stock on your website
• Provide notification on an item’s description page if it will need additional production time before it can be shipped, and an estimated time to completion.
• Provide notification on your website of potential delays in delivery due to holidays, vacations, or other planned leaves of absence.
• Provide feedback on an order’s status (Processing request, payment received, in production, order being package, order shipped).
• If a customer receives a defective part, ask for pictures or other evidence. When the customer provides that evidence, provide either a replacement free of charge, or issue a refund.

 

[splash]

I received a Capacity BMS from BMS Battery.com. It has the same wiring diagram as GGe5 shows. I think I made a wiring mistake (the BMS got quite warm). Ordered another one from them. Didn't receive it yet.
RG

 

[Spacey]

Michael hasn't replied since I sent him the picture of my setup that I labeled. During the times he hasn't contacted you, he was contacting me. He has no excuse. He'll probably claim to be on "Chinese Holiday" or something. I'm forced to file a PayPal dispute as well then...

EVAssemble is the first negative experience I've had with Chinese vendors. I've bought from DealExtreme, Kelly Controller, and have been in contact with Thundersky and have had great service...

I see that because my order wasn't shipped for over a month from ordering I could be eligible for the %15 discount that Michael promised here on the forums, but I don't want to be an asshole about it.

Well that's just not good business. I have emailed him over and over again to supply me with the "Correct" wiring to prove that I have wired this correctly. He has not responded at all to my requests for help.

Having spent a few thousand pounds with him recently you would have thought that he would look after a start-up business knowing that a looked after customer would stay loyal and order from you in the future. Should have listened to people on here.

The chargers you get from him are set for Lipo and not Lifepo4, so when the pack is charged it just turns off without allowing the BMS to slowly balance the pack. Having explained this to him in a very nice and detailed way I got no reply of thanks for taking a few hours to explain it to him, I just think the guy is a box shifter who knows nothing about his products. And to not reply to me when all I wanted were the wiring diagram for the BMS he sent me .....with a waiting customer wanting their Christmas present all waiting on the BMS is just naughty and shows total disrespect for customer.

Luckily I had a couple of other brand BMS kicking about. Guess what....they worked fine.

 

[splash]

The procedure is to wire up the BMS connector to the battery pack......... then plug the BMS board into the connector. I have lots of experience in electronics and you should never plug a cct board into a powered connector. Problem is, there is no other way to do it. Just take your chance of maybe blowing the board!
RG

 

[Spacey]

The procedure is to wire up the BMS connector to the battery pack......... then plug the BMS board into the connector. I have lots of experience in electronics and you should never plug a cct board into a powered connector. Problem is, there is no other way to do it. Just take your chance of maybe blowing the board!
RG

Without wanting to seem rude..... could you explain it in none Electronic diploma language he he.

I always connected the B- on the BMS to the Battery Pack Negative before plugging in the 16 Sensor wires interface. These are just a really crap design and the seller knows it. He says that they are wired up to the battery pack differently than the normal BMS yet WILL NOT tell me how. Looking at other instructions he has given people I know that I have wired it up 100%.

Still no email from him, even though he has been emailing others when they want to buy things from him.