bluetooth BMS?

Batteries, Chargers, and Battery Management Systems.
qwerkus   10 kW

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Re: bluetooth BMS?

Post by qwerkus » Mar 14 2020 4:59am

serious_sam wrote:
Mar 14 2020 4:50am
What are your cell group voltages? How old are the cells? How well is the pack assembled? Are you confident there isn't a problem with any cells?

Another thing to check is the shunt resistor value. One quick way to confirm that the set value is in the ball park: you can plug in your charger, and check the current flow on the phone app or pc software. If the current on the app matches the actual current, then it's set correctly.

If it reads high, then the BMS might be cutting out due to incorrectly thinking that you're running over the current limit.
Nice spotting! I didn't know the bms was keeping track of failures. Cells are brand new samsung 35e cells - don't think tey are the problem. Pack is spot welded with large serial connections should be ok. Here the cell monitoring page.
battery1.jpg
battery1.jpg (447.8 KiB) Viewed 1725 times
Same shunt is used for charge and discharge ?

qwerkus   10 kW

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Re: bluetooth BMS?

Post by qwerkus » Mar 14 2020 5:01am

serious_sam wrote:
Mar 14 2020 4:58am
Do you have motor temp connected to your controller? Could it be the controller that is cutting power due to motor temp?
Good point - thanks for the input. Controller is kt 12s and the motor has a built in temp sensor. Unfortunately I did not find any infos on where to solder that temp sensor wire so right now it's not connected, can't be overheating issue.

The sellers tells me I should disable overcurrent protection by setting it to 70a. Not sure if this is a good idea - I'm never going to hit those value anyway. The motor is rated for 1000w. Even if I pump 2000w into it, that's 40A max.
Last edited by qwerkus on Mar 14 2020 5:05am, edited 1 time in total.

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serious_sam   10 kW

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Re: bluetooth BMS?

Post by serious_sam » Mar 14 2020 5:05am

qwerkus wrote:
Mar 14 2020 4:59am
Here the cell monitoring page.
...
Same shunt is used for charge and discharge ?
Cells look well balanced.

Yes, same shunt for in and out.

Temp is 6.9c. Cold at your place!

qwerkus   10 kW

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Re: bluetooth BMS?

Post by qwerkus » Mar 14 2020 5:09am

serious_sam wrote:
Mar 14 2020 5:05am
qwerkus wrote:
Mar 14 2020 4:59am
Here the cell monitoring page.
...
Same shunt is used for charge and discharge ?
Cells look well balanced.

Yes, same shunt for in and out.

Temp is 6.9c. Cold at your place!
Yes, still winter. Pack was in the garage overnight and takes quite some time for 5kg to warm up. So I see 2 tests to do:

1. charge current test: compare serial dmm value with bms value to calibrate shunt. need the pc for that as i don't have the bt dongle.
2. cell under voltage test: plug battery to a load (somewhere) and check each individual parallel group - see if one drops too much.

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serious_sam   10 kW

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Re: bluetooth BMS?

Post by serious_sam » Mar 14 2020 5:34am

qwerkus wrote:
Mar 14 2020 5:09am
So I see 2 tests to do
Also:
3. Bypass the BMS completely, just to be 100% certain that it is the BMS causing problems.
4. Change the limits to far outside normal parameters (for example, cell ovp=4.4v, uvp=2.0v etc), and try and figure out if/which one of the limits is being tripped.

qwerkus   10 kW

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Re: bluetooth BMS?

Post by qwerkus » Mar 14 2020 11:12am

Did charge the battery completely, and obviously now it works. Test 1 showed a shunt off by 0.54A. Test 2 gave nothing - I don't have a setup allowing for this kind of test. I did spin the wheel in the air, but the load was not high enough to cause significant voltage drop amongs individual P groups. Bypassing the bms works fine. Didn't try changing the limits yet. I will let the battery balance-charge a few more hours and then go for a longer ride to empty it again. Let's see when the cutoff will happen again.

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Re: bluetooth BMS?

Post by 5bngr » Mar 16 2020 9:18am

ElectricGod wrote:
Feb 28 2018 5:42pm
Hi folks...

I'm NOT selling anything here...that would be for a for sale thread elsewhere, just looking for opinions and see if there's desire for an EG modded BMS.

[Deleted content for legibility..]

What do you think? Any interest in this? It would be a labor of love and my costs would get recouped, but that's about it.

I'm NOT selling anything here...that would be for a for sale thread elsewhere, just looking for opinions and see if there's desire for an EG modded BMS.
Hi ElectricGod,
New to the forum and was looking at getting a 24s or 32s BMS and I'd like to take you up on this, if you're up for it (i can cover labor/part costs). I tried to PM you first but couldn't for whatever reason. Could you PM me?
Thanks!!

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Re: bluetooth BMS?

Post by john61ct » Mar 16 2020 9:58am

I believe EG got banned

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Re: bluetooth BMS?

Post by 5bngr » Mar 16 2020 10:46am

Oh wow! too bad. wonder what happened..

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Re: bluetooth BMS?

Post by amberwolf » Mar 18 2020 4:47am

he exploded at people, apparently because he couldn't handle his incorrect / misinformation being pointed out and corrected by others. managed to get some of their posts deleted, then edited his own bad behavior out. eventually this didn't work anymore, so he then self-deleted a bunch of his own stuff, then created multiple accounts to scream at people about what they "did to" him (which he did to himself), and claim he wasn't even actually himself, and even that he had no idea who he himself was, even though it was obvious it was still him just being himself.

so...that's what happened. (read thru his last posts and you'll see; all the posts from his "alter ego" accounts were re-assigned to his original).

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Re: bluetooth BMS?

Post by thundercamel » Mar 20 2020 3:33pm

qwerkus wrote:
Mar 14 2020 4:59am
serious_sam wrote:
Mar 14 2020 4:50am
What are your cell group voltages? How old are the cells? How well is the pack assembled? Are you confident there isn't a problem with any cells?

Another thing to check is the shunt resistor value. One quick way to confirm that the set value is in the ball park: you can plug in your charger, and check the current flow on the phone app or pc software. If the current on the app matches the actual current, then it's set correctly.

If it reads high, then the BMS might be cutting out due to incorrectly thinking that you're running over the current limit.
Nice spotting! I didn't know the bms was keeping track of failures. Cells are brand new samsung 35e cells - don't think tey are the problem. Pack is spot welded with large serial connections should be ok. Here the cell monitoring page.

battery1.jpg

Same shunt is used for charge and discharge ?
Qwerkus, that estimated capacity showing 51% is just an estimation, and I believe the JBD units try to update their capacity numbers as you use them. Whatever capacity settings you have entered currently are too optimistic, and it's closer to empty than actually 51%. Try to monitor the BMS in real time with an android device as you're riding, and you can see what reasons it shuts off for. This was shown to be a case of cell undervolt protection, which is almost always the case for me as well once my battery gets empty. There's plenty of voltage sag at low state of charge levels.

I was hoping to get my JBD estimated state of charge numbers to be reliable, but after two years I have not (on two bikes), and I feel like it's because they change the capacity numbers themselves on the fly. I've just been watching voltages instead, and consider 3.7 volts no load my 50% mark for MJ1 cells. If I charge to 4.2 volts, then at 3.7 off throttle I turn around and go home :)
My Ebike builds - Existing bikes, affordable motor kits, self built 14s6p batteries - Now with more recumbent!

qwerkus   10 kW

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Re: bluetooth BMS?

Post by qwerkus » Mar 20 2020 4:55pm

thundercamel wrote:
Mar 20 2020 3:33pm
Qwerkus, that estimated capacity showing 51% is just an estimation, and I believe the JBD units try to update their capacity numbers as you use them. Whatever capacity settings you have entered currently are too optimistic, and it's closer to empty than actually 51%. Try to monitor the BMS in real time with an android device as you're riding, and you can see what reasons it shuts off for. This was shown to be a case of cell undervolt protection, which is almost always the case for me as well once my battery gets empty. There's plenty of voltage sag at low state of charge levels.

I was hoping to get my JBD estimated state of charge numbers to be reliable, but after two years I have not (on two bikes), and I feel like it's because they change the capacity numbers themselves on the fly. I've just been watching voltages instead, and consider 3.7 volts no load my 50% mark for MJ1 cells. If I charge to 4.2 volts, then at 3.7 off throttle I turn around and go home :)
I think you are pointing to a valid issue. The documentation mentions a "smart capacity calculator" that should estimate remaining capacity based on measured full and empty charge values. Never seen it actually work. I charged that battery for 24h hours, fixed a few values according to the samsung datasheet for 35e and new it seems to work. The voltage drop at full throttle still seems a bit high, but after another tour jbd software didn't show any lvc cutoffs any more.

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Re: bluetooth BMS?

Post by john61ct » Mar 20 2020 5:22pm

Getting even within 6-8% accuracy on SoC by counting coulombs is a huge technical challenge for a device designed to work with different model cells.

Even dedicated meters costing hundreds struggle, need frequent recalibration and 100% resets. And regular CC load testing to keep up with what actual Ah capacity is as it declines…

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serious_sam   10 kW

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Re: bluetooth BMS?

Post by serious_sam » Mar 20 2020 6:12pm

In my understanding, these bluetooth BMS don't count coulombs.

From what I've experienced (extremely poor accuracy), they just use cell voltage as an indication of SOC. If you look at the PC software, there is a section for setting SOC voltages.
SOC.jpg
SOC.jpg (36.89 KiB) Viewed 1455 times
My Nucular 12F has a reasonably accurate coulomb counter. But since total cell energy available changes depending on rate of discharge, I only use it as a guide for what I've used. Not what I've got left.

Even a 100% accurate coulomb counter can't tell you 100% accurate energy remaining. It can really only tell you how much energy has passed through that device. If it has been calibrated according to a specific cell type, it can approximate remaining charge to a reasonable accuracy. But like John said, even that calibration will lose accuracy as the cell degrades.
Last edited by serious_sam on Mar 20 2020 10:26pm, edited 1 time in total.

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Re: bluetooth BMS?

Post by john61ct » Mar 20 2020 6:33pm

wow voltage-only, no wonder pretty useless

I supposed if you had a proper Ah counter to calibrate your guesstimates, and only looked at it after stopping for a cuppa, and. . .

never mind 8-)

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Re: bluetooth BMS?

Post by DogDipstick » Mar 21 2020 3:48am

john61ct wrote:
Mar 20 2020 6:33pm
wow voltage-only, no wonder pretty useless



never mind 8-)
I use it. Accurate enough. Usefull.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 85% healed..).. :? Waddyamean? You cant tell me how many amperes/Ft.^2 of the plate ?!?!? :x 1 (pound / second) Horse Power = 338.24 M^2 Kg^2 / Sec^4 ( :twisted: prove me wrong :twisted: ) :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: bluetooth BMS?

Post by serious_sam » Mar 21 2020 5:01am

DogDipstick wrote:
Mar 21 2020 3:48am
Usefull.
I agree with you to the extent that, as a tool to wirelessly give an approximate SOC for a pack sitting on the bench at home, it does the job.

But as John indicated, it's really only good for a rested pack. For real-time SOC (i.e. while riding), I wouldn't bother with it. Even if the Nuc didn't coulomb count, I still wouldn't bother. IMO, it's too inaccurate with a heavily loaded pack.

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Re: bluetooth BMS?

Post by DogDipstick » Mar 21 2020 5:45am

serious_sam wrote:
Mar 21 2020 5:01am
as a tool to wirelessly give an approximate SOC for a pack sitting on the bench at home, it does the job.

For real-time SOC (i.e. while riding),

IMO, it's too inaccurate with a heavily loaded pack.
Yeah but you know the calibration is possible, with an accurate map. Cycle life degradation deviation? My opinion is that cycles accumulate so slowly that the difference is negligible.

As for looking to see how much "gas" is in the "tank" while you are riding, sometimes, ( hills, refueling the trimmed airplane tanks, sloshing off road, most motorcycles ) you dont ever know how much gas is in the tank accurately,. Still manage to get there and back. Only time you notice is if the engine shuts down. If this happens to you personally you should invest in a "reserve" pack.

If you can accurately map you cell, and you are 50 or 150 cycles into 1000, ( or who knows how many into 1000) I dont think it is useless. I guess something that matters is how big a cycle is.. and the health of the battery in general. Build a shitty batt, and you will think it is useless based on voltage. Build a pack with thousands or tens of thousands of miles planned into its lifespan... and you can use it. No?
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 85% healed..).. :? Waddyamean? You cant tell me how many amperes/Ft.^2 of the plate ?!?!? :x 1 (pound / second) Horse Power = 338.24 M^2 Kg^2 / Sec^4 ( :twisted: prove me wrong :twisted: ) :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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serious_sam   10 kW

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Re: bluetooth BMS?

Post by serious_sam » Mar 22 2020 5:31am

So, I went for a ride today. I used just about 55% from a fully charged (20S5P, 15Ah) pack. Coulomb counting from Nuc 12F agrees with rested voltage (indicating about 45% remaining).

But the BMS thinks I've only got 10% left. It should be reading around 50%, based on the pack voltage (~3.69V per cell) and the BMS settings (60% SOC @ 3.82V, 40% SOC @ 3.64V). But it thinks 10%. It's usually pretty bad, but never been this bad.

I'm thinking that it read the lowest voltage during my ride (probably about 64V due to ~10V sag), and once it took that reading, it didn't recalculate once the voltage bounced back up to 74V resting. 64V does equate to about 10% SOC. Maybe it can count down, but not up, and it needs to be fully recharged to reset back to 100%.
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Discharge curve.jpg
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john61ct   100 GW

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Re: bluetooth BMS?

Post by john61ct » Mar 22 2020 7:46am

Are you sure the BMS is even counting coulombs at all?

Personally I would just ignore that feature and use the known-reasonable coulometer

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Re: bluetooth BMS?

Post by marka-ee » Mar 24 2020 5:46pm

Hello,
I have an 'Ant' bluetooth bms that I got maybe a year ago from ebay but only tried to use it this week. It's the 2 PC board version with the balance connectors along the long side, up to 24s and 100 amp. I tried about 4 different android apps that I found here on the forum but have no luck connecting to it except for the 'VBMS' app which kinda worked on an older phone running kit-kat os version. It connected but seemed to give rather mixed up results on the parameter fields. Not usable. Android ver. 7 didn't connect at all.
So in my quest, a couple of questions : The 'blue elephant' iconed app, is it for the Ant bms ? There seems to be 2 or 3 different brands of these types of BMS but it is so unclear what APP goes with what BMS. Are they all rebranded and actually the same firmware in all of them ?
The 'blue elephant' app shows several bluetooth devices of local TV's etc. What a joke. Shouldn't it filter only BMS to connect to ?
The VBMS APP which did connect has absolute garbage english wordings for items on the screen. I am usually pretty good at 2nd guessing the meanings but these were on another level. Is VBMS app even supposed to work with Ant BMS's ?
The MAC address detected by VBMS was a bogus AA:BB:CC;D..... type, but it did connect. The 'blue elephant' app did not even list that MAC.
All attempts were with already paired Bluetooth BMS. ( not sure why 'elephant' app listed other non-paired devices...)
All attempts were with freshly powered on Ant BMS with it's LCD attatched.
Sorry for ranting a bit, I am so frustrated. Any hints or guidance much appreciated.

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Re: bluetooth BMS?

Post by dragon-fly » Mar 29 2020 10:24pm

i have the 24S BMS ANT BMS from ICGOGOGO,

has anyone tried/purchassed the VBMS on google play? Does it work?

this one here
https://play.google.com/store/apps/deta ... tecks.vbms

Thanks

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Re: bluetooth BMS?

Post by Manna » Mar 31 2020 7:52am

Hi Everyone

Does anyone have the firmware for ANT bms ?
I would like to customize the data displayed.

https://a.aliexpress.com/_B0RWb3

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Re: bluetooth BMS?

Post by tavsanist » Apr 02 2020 6:28pm

Hi everyone,
Can anyone help me about correct settings and hardware mod(balance wiring) for a JBD BMS.
I do have SP15S020 BMS, it is 14S BMS but i want to use it on 12S battery,
How should i wire the balance cables ?
And there some balance ports are shorted each other intentioally by manufacturer. i assume it is for making it as a 14S BMS. There are also other pads that i can short with soldering but i dont know which ones.. and i didnt test it because didnt wanted to damage it.

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Re: bluetooth BMS?

Post by quamau » Apr 04 2020 11:43am

There is a post back in this very thread where schematics for every number of series connections are drawn (pictures too, if memory serves). Simple soldering job if you know what to connect and where to desolder.

I did something similar to modify 16s in 17s. What is not that evident is that, if BMS is already set up, you need to re-calibrate it. AFAIK this is it possible via the UART box, phone app does not work. There is *one* message in this thread mentioning this, but I am unable to find it right away

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