bluetooth BMS?

Batteries, Chargers, and Battery Management Systems.
john61ct   1 GW

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Re: bluetooth BMS?

Post by john61ct » Sep 11 2019 9:17pm

Another thread, got this specific reco

Ant Smart BMS, aka RJXZS, Olive Leaf
300A and lower

https://www.aliexpress.com/item/32826820690.html

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cycborg   1 kW

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Re: bluetooth BMS?

Post by cycborg » Sep 23 2019 1:19pm

Frustrating mystery from this weekend. Bottom line, 5/14ths of my pack is dead, and I don't know what it could be other than some BMS malfunction, although I haven't pinned it down. BMS is this one, 14s 30 A.

I hadn't used my ebike in a couple months, although I connected via Bluetooth once per week or so. I figured that connection meant that things were probably OK, but I should have tapped over to the Battery State screen...

This weekend I wanted to fire it up, but when I connected and unlocked the FETs, I got the "IC front end error". It was reporting a pack voltage of 1.5 V. Shit.

I disconnected the battery and took it down to the workshop and cut off the shrinkwrap. The voltage at the terminals was indeed 1.5 V, but when I measured from the input side of the BMS instead of the output, I got 36 V. Whew, so not a total loss. 2.6 V/group means there's a current drain somewhere I have to track down, but the battery is still usable. Just have to charge it up and see if that resets the "IC front end error", whatever that means.

Connected the charger, no current. The FETs were still closed. Tried opening them with JBD Tools, no luck. Meanwhile, the BMS was still reporting nonsense voltages on all the groups.

Measuring the pins on the balance connector, it turned out that the pack wasn't at 2.6 V/group. Instead, the top 9 groups were at 4 V each (where I had left them when I charged last), and the lower 5 were at zero.

I did a quick visual to see if there were any shorts between the groups, but I couldn't see anything. And since I had closed the FETs while it was being stored, there shouldn't have been any external load, and if there were it should have drained the groups uniformly. The only thing connected to individual groups was the balance wires.

Not sure where to go from here in terms of diagnosis, but I have 10 GA cells with 3 cycles on them that are now useless. This is frustrating on its own terms, but I'm also concerned since I have a similar BMS on my scooter, which is a much larger pack. I have been regularly checking the cell voltages on this pack, and so far so good, but it makes me less confident about leaving the BMS attached to any pack of significant value.

Now, having vented my frustration, in 1k+ posts on this thread I think there's only been one other catastrophic failure (due to an endless balancing loop, IIRC), so I'm not recommending that anyone throw these in the bin. Just providing some anecdata and hoping it sparks some thoughts that could help me figure out what went wrong and help others to avoid a similar circumstance.

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thundercamel   1 kW

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Re: bluetooth BMS?

Post by thundercamel » Sep 23 2019 4:14pm

Probably the balance wire of group 10 broke. Did you measure the voltages directly at the cell groups, instead of at the balance wires?
My Ebike builds - Existing bikes, affordable motor kits, self built 14s6p batteries - Now with more recumbent!

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cycborg   1 kW

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Re: bluetooth BMS?

Post by cycborg » Sep 23 2019 4:50pm

thundercamel wrote:
Sep 23 2019 4:14pm
Probably the balance wire of group 10 broke. Did you measure the voltages directly at the cell groups, instead of at the balance wires?
Yep, I scratched through the Kapton and measured across 1-5 on the electrodes. Dead, dead, dead. Balance wires (and their solder connection to the electrodes) look intact. Thanks for the suggestion, though.

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flippy   1 MW

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Re: bluetooth BMS?

Post by flippy » Sep 24 2019 6:06am

the FET on a balance port fried itself. it happens on crappy bms.
Lithium beats liquid dinosaurs.

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cycborg   1 kW

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Re: bluetooth BMS?

Post by cycborg » Sep 24 2019 9:30am

flippy wrote:
Sep 24 2019 6:06am
the FET on a balance port fried itself. it happens on crappy bms.
But could this result in the failure cascading through 5 groups?

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thundercamel   1 kW

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Re: bluetooth BMS?

Post by thundercamel » Sep 24 2019 10:00am

Bummer! I two have the same BMS in the 60A model, and no problems so far. I do check in on the cell group voltages every couple weeks, which was my main purpose in buying a smart BMS. I've read that you can try to bring the cells back to life with very low current manual charging. You'd probably need a variable voltage power supply to do so.
My Ebike builds - Existing bikes, affordable motor kits, self built 14s6p batteries - Now with more recumbent!

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Re: bluetooth BMS?

Post by john61ct » Sep 24 2019 11:56am

Doing so with LI (other than LFP or LTO) is pretty darn fire-risky.

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flippy   1 MW

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Re: bluetooth BMS?

Post by flippy » Sep 24 2019 12:38pm

cycborg wrote:
Sep 24 2019 9:30am
But could this result in the failure cascading through 5 groups?
yes, this is due to the circuit design that is used in most bms. it means that the number 7 FET is blown up.
Lithium beats liquid dinosaurs.

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cycborg   1 kW

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Re: bluetooth BMS?

Post by cycborg » Sep 24 2019 2:24pm

flippy wrote:
Sep 24 2019 12:38pm
...the number 7 FET is blown up.
Do you mean number 5? It's groups 1-5 that failed. Regardless, what's the mechanism that causes this cascade?

I think the management IC is the TI BQ76940, which is for up to 15s. These 15 are split into 3 blocks of 5, so it's plausible that a whole block failed somehow. Now to figure out the how.

plateau   1 mW

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Re: bluetooth BMS?

Post by plateau » Oct 02 2019 9:33pm

Hi, people, how are you doing?

I'm trying to repair my bluetooth BMS but I don't know which component is that marked with this blue arrow. I know it's a diode but I don't know if it is a rectifier, schottky or a zener. It fried after the 10R resistor (white arrow) has blown.

Further, I have replaced the µC (ATMEGA328P) and the 10R (white arrow).

Does anybody can help me?

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Re: bluetooth BMS?

Post by chico1 » Oct 03 2019 9:52am

Inwo wrote:
Jun 04 2017 10:21am
14s bt cell count.png
Hi i have the same problem with the pc sw. cant connect i have the ant bms got it from aliexpress
https://www.aliexpress.com/item/3299755 ... 4c4djjhFBj
have you figured out how to connect. thank you for any info you can give me.

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cycborg   1 kW

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Re: bluetooth BMS?

Post by cycborg » Oct 03 2019 10:23am

plateau wrote:
Oct 02 2019 9:33pm
I have replaced the µC
So... are you writing your own software?

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Re: bluetooth BMS?

Post by plateau » Oct 03 2019 9:50pm

cycborg wrote:
Oct 03 2019 10:23am
plateau wrote:
Oct 02 2019 9:33pm
I have replaced the µC
So... are you writing your own software?
Unfortunately no, my dear.

A month ago I have tried to update the firmware and the connection has been lost during the procedure. Mr BotoXbz has shared the stock firmware with me and I flashed it in the new µC. However, I can't go ahead because I need to replace this diode to avoid more problems.

Do you have a BMS like that? If so, could you check if there is anything marked over the component?

Regards

bramhall45   1 µW

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JDBTools V1.1 Current Calibration function.

Post by bramhall45 » Oct 10 2019 9:10am

Hi, great discussion, so glad I found this forum.

On the calibration tab, there is VoltageTemp Calibration and Current Calibration.

I had calibrated each cell and temp probes and all looked good and consistent with my multi meter.
Next I tried the current calibration.
I have to say that the current readout of the Pack Info tab was pretty close without any calibration.
The default settings, what ever they were, were good enough.
However, I proceeded to calibrate the current.
The battery was in a resting state in my system (Victron ESS), so I pressed the Idle button which I believed would set the quiescent current level.
Unfortunately, now I get no current readout in Pack Info tab - 0.0, when the battery is being discharged/charged.

I set the actual discharge current during discharge to the Victron ESS displayed value and pressed the Discharge current button.

This did not have any effect, still showing 0.0 current being drawn in Pack Info tab.

So I am obviously doing this calibration wrong, but can't get back to the original setting before I made changes.

Has anyone successfully done the current calibration or if possible to set the BMS back to Factory original settings.

Thanks in advance

Cliff

john61ct   1 GW

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Re: bluetooth BMS?

Post by john61ct » Oct 10 2019 9:13am

if it ain't broke, don't fix it

bramhall45   1 µW

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Re: bluetooth BMS?

Post by bramhall45 » Oct 10 2019 9:44am

John61ct “if it ain't broke, don't fix it”

True enough.

A tinker too far maybe, but the calibration function is there in the software.

Any experience in this area would be most welcome.
As a last resort is it possible to reset the BMS to factory original settings.

Thanks in advance for more practical advice.

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eee291   100 kW

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Re: bluetooth BMS?

Post by eee291 » Oct 10 2019 10:55am

I made this mistake once,
IIRC I changed the shunt value to something like 2.5mOhm and then did a current calibration at 10A discharge and 5A charge and all was good again.
It wasn't any more accurate than it was previously btw.

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flippy   1 MW

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Re: bluetooth BMS?

Post by flippy » Oct 10 2019 11:56am

john61ct wrote:
Oct 10 2019 9:13am
if it ain't broke, don't fix it
if it aint broke: mess with it until it is. :mrgreen:
Lithium beats liquid dinosaurs.

plateau   1 mW

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Re: bluetooth BMS?

Post by plateau » Oct 10 2019 12:50pm

flippy wrote:
Oct 10 2019 11:56am
john61ct wrote:
Oct 10 2019 9:13am
if it ain't broke, don't fix it
if it aint broke: mess with it until it is. :mrgreen:
HaHa I know... that's why I'm trying to find someone who can help me to figure out which component is that I mentioned.

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flippy   1 MW

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Re: bluetooth BMS?

Post by flippy » Oct 11 2019 4:35am

you need to disconnect ALL users before callibarating the shunt. ANY current flow will mess up the reading.
Lithium beats liquid dinosaurs.

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Re: bluetooth BMS?

Post by bramhall45 » Oct 11 2019 4:24pm

flippy wrote:
Oct 11 2019 4:35am
you need to disconnect ALL users before callibarating the shunt. ANY current flow will mess up the reading.
Would this be for the Idle button, you are talking about. Don’t quite understand what you mean. Can you elaborate with reference to the jdbtool software as to how the calibration is meant to be performed.

Thanks.

KarlJ   100 W

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Re: bluetooth BMS?

Post by KarlJ » Oct 12 2019 1:21am

HELP

I have the ANT 8S-24S BMS all hooked up to my 22S battery and although i've found software on the iphone in Chinese does anyone know what the app is called for android - having O luck today

https://www.aliexpress.com/snapshot/0.h ... 2856349172

Cheers Karl

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flippy   1 MW

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Re: bluetooth BMS?

Post by flippy » Oct 12 2019 2:08am

the download link is several pages back posted by me
Lithium beats liquid dinosaurs.

Zaziki   1 µW

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Re: bluetooth BMS?

Post by Zaziki » Oct 13 2019 6:32am

Hello Everybody,

i bought a ANT-BMS 16S wich seems to behaive differently from the one i read all over the pages.

My BMS has no UART header i opened it this morning and i found a Panasonic AN49503A Chip.

Does anybody know this Board ?

The Reason why i ask is beause i tried different bluetooth implementation to get the data out of the bms into linux and no one has worked for me.

Thank You!

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