BMS card warning

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Zen
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BMS card warning

Post by Zen » Mon, 18 Dec 2017, 07:35

Hi
Has anyone had experience with these BMS cards? They are available from ebay or amazon for about $15, yet have manufacture errors in alignment of the chip sets. If the uploaded images come through, I've highlighted a 1 mm chip that is 1 mm out of alignment in the exact same spot across all 4 cards. The engineer who built the battery recons it doesn't make a difference. But the battery pack doesn't discharge properly.

What are your thoughts? Defect or not defective?
Attachments
IMG_20171217_075723.jpg
BMS PCB
IMG_20171217_075723.jpg (1.65 MiB) Viewed 894 times
IMG_20171216_201756 (1).jpg
chip alignment error
IMG_20171216_201756 (1).jpg (224.85 KiB) Viewed 894 times

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Johny
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Re: BMS card warning

Post by Johny » Mon, 18 Dec 2017, 08:43

I've edited my previous post - yes it's wrong. It look like a capacitor so may be more prone to RF Interference or EMI than if it was correctly placed.
Can you elaborate on "doesn't discharge properly"?.

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Re: BMS card warning

Post by Zen » Mon, 18 Dec 2017, 09:02

Hi. Thanks for the reply. I had the battery pack made by a supposedly reputable electric engineer near Newcastle. The battery pack only ever discharged one series of cells. I took the pack back and he recharged one cell and said all was OK. It wasn't as the battery pack only worked once for a short 1 min, then stopped and never achieved 56 V again. I looked myself and found this error.
I can only guess that one column has discharged completely and the card error means it wont charge and balance, and it follows, has now damaged the cells. Compounding errors.

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Richo
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Re: BMS card warning

Post by Richo » Mon, 18 Dec 2017, 12:55

I doubt the part you have highlighted is an assembly problem.
You'll notice the silkscreen is also different to allow for the odd placement.
The tracking appears to go to the same place as the others.
The only way it could be wrong is if the engineer didn't make the schematic correctly.
Unlikely.

It's more likely that one BMS wire going to the actual battery is swapped with it's neighbor.

The other issue could be a wrong FET or one has blown.
This is the problem with multi BMS boards is it's easy to short one of the balance wires out.
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Richo
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Re: BMS card warning

Post by Richo » Mon, 18 Dec 2017, 13:03

What on the other side of the board?
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Re: BMS card warning

Post by Zen » Mon, 18 Dec 2017, 14:01

Good question. I'll post a pic tonight.

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Re: BMS card warning

Post by Zen » Mon, 18 Dec 2017, 18:22

Looks like I don't get a chance to add images. The back is very regular with the mosfet chips on the flip side of where the manufacture name plate is. Nothing irregular.

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Re: BMS card warning

Post by Zen » Mon, 18 Dec 2017, 19:45

Looking at the manufacturers website. Don't see many mystery floating objects across the PCB's they're proud of.

http://www.gzlspcb.com/col.jsp?id=103

What questions do you think I should ask the manufacturer?

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Adverse Effects
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Re: BMS card warning

Post by Adverse Effects » Tue, 19 Dec 2017, 11:00

i would be sending the pic's and asking if this is correct

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Re: BMS card warning

Post by Richo » Tue, 19 Dec 2017, 12:41

He could - but the answer wont change.
Electrically it is the same as the section above it.
Even I can tell that from the blurry photo's above.
The reason this particular resistor is different is because the C- track comes in past it.
They could have turned it 180 and tracked it the same so it looks consistent but that really comes down to the designer on the day.

The BMS module was either installed incorrectly (swapped BMS wires), damaged during install (blown FET) or is connected to a faulty battery.
Given the engineer charged one cell and sent you on your way would suggest a faulty cell in the pack.

Double check the wiring - test the voltage at each B##+ point to see it go up 3,6,9...
OR for the sake of $15 buy another one.
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Re: BMS card warning

Post by Adverse Effects » Tue, 19 Dec 2017, 14:55

the 2 pic's are of the same card 1 is just zoomed in

1 of these things is not like the other

Image

they are a 13 channel BMS so there has to be 13 channels the same

oww and i am not an EE in anyway

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Re: BMS card warning

Post by Zen » Tue, 19 Dec 2017, 17:54

Thanks for the feedback. All good comments. I emailed the manufacturer and asked the question and will keep you posted. I somewhat doubt a timely response. That's the reason for the 'warning'.

I think a lot of EE's and battery builder out there will be taking a collective gulp! as they realise they've trashed their businesses due to bad quality control. It's not the $15 quid, its 6 months delays trying to trouble shoot, stuffed battery, and purchased a second new Kelly controller. About $6-10K damages.

How many of these do you think are in circulation? 60K -100K?!!

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Re: BMS card warning

Post by Adverse Effects » Tue, 19 Dec 2017, 18:10

Zen wrote:
Tue, 19 Dec 2017, 17:54
How many of these do you think are in circulation? 60K -100K?!!
if the Ebike blokes started using them i would guess alot

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Re: BMS card warning

Post by Richo » Wed, 20 Dec 2017, 13:04

Adverse Effects wrote:
Tue, 19 Dec 2017, 14:55
1 of these things is not like the other
You are correct it doesn't LOOK the same.

Dont get hung up on that one resistor it's NOT the problem.
Electrically it is the same as the rest.
It's only in a different position due to the C- track.
Zen wrote:
Tue, 19 Dec 2017, 17:54
I think a lot of EE's and battery builder out there will be taking a collective gulp! as they realise they've trashed their businesses due to bad quality control.
The way I see it a lot of consumers buy electronic parts, put it together and then wonder why it goes wrong and have no clue how to fix it.
They then complain about the engineers trying to palm off the problem when really it's user error.
Engineers spend a lot of time designing and testing products before a customer touches them.
Sure there are assembly errors - it's a statistical probability.
That's why we have manufacturers warranty as part of consumer law.
Zen wrote:
Tue, 19 Dec 2017, 17:54
It's not the $15 quid, its 6 months delays trying to trouble shoot, stuffed battery, and purchased a second new Kelly controller. About $6-10K damages.
Really this is a sub 2hr problem for a skilled person.
$15 for a replacement/spare BMS is not much to ask anyway.
It would clearly show if the BMS is at fault.
If it wasn't the fault then you'd have a backup/spare.
Getting a skilled person to look at it would be $150-200 - a lot more than the $15 for the product.
This could have been done within a week with little or no damage to anything.
You should have charged, tested and balanced the pack manually if it concerned you that much.
Why you'd waste 6 months trying to solve this is just neglect.

The controller has nothing to do with it either since this BMS is a stand alone system.

Sure the principal of it does come into it but really it will slow down getting to the bottom of the problem.

You'll have to provide some more information for us to diagnose the actual problem.
Otherwise I'd be going back to your battery builder again and asking them to sort the problem out.
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Re: BMS card warning

Post by Zen » Wed, 20 Dec 2017, 15:03

Hi Yes you are right in many respects.
The EE will not admit its a problem and says he's tested it. He did do a manual rebalance and then said its my user neglect, as did you, and gave it back. It discharged once and did not recharge. As he put that it was my error, without saying what the error was and not returning my calls or emails, I then embarked on a process of elimination and reasoning, to eventually find this error.

The error shows on the volt meter, yet the EE says the dead battery is in cell 3 and not 11. I doubt a BMS can balance a pack if one domain is not resonating correctly. Its likely that the cells with the error never discharged and drained the other cells.

It is not a matter of 1 PCB. Its 4 with the exact same alignment error. As 'adverse Effects' rightly points out, if there are 14 channels then each one must be the same. In electronics, If there are 4 cards in series then, is the effect the sum of each error, or a factor, or to the power? I'm thinking its 4 to the power of 4. How would one test this? Who would I take it to to get an independent test?

Neglect and user abuse or a warranty matter. Im not sure what has been neglected. The battery or the consumer. If you build and sell a product then it must work and be fit for purpose. I purchased it because I wanted something that worked, not an experiment.

N.b. still no response from China.

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Re: BMS card warning

Post by Adverse Effects » Wed, 20 Dec 2017, 18:07

you could test it with like 13 18650's and see if it flattens just 1 cell or just dosent recharge the 1 cell

and from what i can see there 13 channel not 14

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Re: BMS card warning

Post by Richo » Thu, 21 Dec 2017, 12:48

As I mentioned in some other thread the cheapest 18650 are like $1.30 and still have some capacity - 10% of what they claim but enough for testing purposes.

The BMS is supposed to prevent over charge, over discharge and keep them "balanced".
So it would be hard to explain user error for a fault.
From what I understand you have a pack that the overall voltage drops too low and provides some kind of warning and prevents you from using it and wont recharge.
It's sounds like the BMS is doing its job.

The unfortunate part is that one cell is dead.
If the EE recharged a cell handed it back but develops the same fault on the next use then the person who sold you the cells is responsible.
Weather the cell had diminished capacity or manufacturing error makes no difference they should replace the cell.

If you have had these cells for 1-2 years then it may come under fair wear/useage.
Batteries wont last for ever.
Expect to change some at some point.
Given you haven't told us what the BMS connects to we can only provide general information.

Who you'd take it to for testing I don't know - you haven't even told us the country your in.
The other option is buy a battery charger/discharger/balancer from a RC hobby store.
You can plug in each cell individually and test each one yourself.
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Re: BMS card warning

Post by Richo » Thu, 21 Dec 2017, 12:55

Zen wrote:
Wed, 20 Dec 2017, 15:03
It is not a matter of 1 PCB.
Its 4 with the exact same alignment error.
As 'adverse Effects' rightly points out, if there are 14 channels then each one must be the same.
And I keep telling you electrically they are the same - follow the tracks.
It's not hard even a 5yo can solve those pencil in maze games from McDoodies.
Don't hold your breath for China.

You can solve this yourself.

What cells are you using and where did they come from?
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