FlexiBMS Lite - Flexible Configuration BMS w/ CAN-bus

https://uk.farnell.com/stmicroelectronics/stm32l433ccy6tr/mcu-arm-cortex-m4-80mhz-wlcsp/dp/2855695?st=STM32L433C

Those STM32L433CCY6TR have different soldering technic but aren’t they basically the same ? - I imagine it would not be too hard to change pcb to take this instead ?

There are over 250pcs stock now and the price is a lot cheaper than 3.5 vs like 6 for cc6

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What does the state report show for the charger voltage when the charger is not connected? You can also reset the faults with $G, to get rid of that magenta color.

It’s a very involved PCB redesign and I’m pretty sure the place where I’m currently getting the PCBs made doesn’t have good enough production tolerances for the requirements for that tiny, dense package.

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@SimosMCmuffin

$2 alows me to set a static charge termination current witch is ok if you only ever use 1 charger. If I want to use a fast charge occasionally and still follow manufactures advice I would need to charge the settings on the fly that is possible through the metr pro but not ideal.

Is it possible for the flexi to calculate a table from 2 different charge amp and mA cut off and work out it’s cut off from the max charg ampage of that charge cycle?

Eg for a 4p q30 pack
Standard charge 1.5A X P group = 6A
Charge cut off 150mA X P group = 600mA

Fast charge 4A X P group = 16A
charge cut off 100mA X P group =400ma

So if you plugged in a 10a charger (max the flexi is rated for) it would set the cut off at 520mA automatically for that charge

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So it´s not showing any faults with battery minus and balance cable connected. As soon as i connect battery plus, it´s blinking all colors like it should be and then goes into green green violett.
I connected the Flexi through USB and logged that behavior:

State:5374:5374:5374:5374:5374:5374:5374:5374:5374:5374:5374:5374:0-0-0:0-0-0:0-3-6:298:671:0:notCharging:
State:3586:3585:3586:3586:3586:3585:3586:3586:3586:3585:3585:3585:0-43057-43076:0-42476-42516:0-0-3:297:299:0:faultState:
State:3585:3585:3585:3586:3586:3585:3585:3586:3586:3585:3585:3585:42997-42997-43057:42455-42455-42496:0-0-0:297:299:0:faultState:
State:3585:3585:3585:3586:3586:3585:3585:3586:3586:3585:3585:3585:42997-43017-43037:42455-42455-42476:0-0-0:298:299:0:faultState:
State:3586:3585:3586:3586:3585:3586:3586:3585:3586:3586:3585:3585:42997-43017-43037:42435-42455-42476:0-0-0:298:299:0:faultState:
State:3586:3585:3585:3586:3586:3585:3586:3585:3586:3585:3586:3585:42978-42997-43017:42435-42455-42476:0-0-0:298:299:0:faultState:

The flexi does nothing in this stage, so no charging when i hook up some voltage, no displaying in the Metr App, nothing just blinking.
When i reset the fault with $G it stops blinking, but still not possible to do something.
I then disconnected everything, then connected batt minus, balance, batt plus and starting all over with the light show, then again green green violett.

sucks :frowning: so we are all stuck without good small charge only bms for VESC for now. :weary::weary: at least those that need 16-18s :sob::sob:

get in this thread, 16s charge only bms. no canbus or anything tough.

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There is something weird going on as the BMS shows the battery voltage on the charger port. This would indicate that the charger FETs are likely damaged, because when the BMS goes into faultState it should shutoff the charging Fets and therefore shouldn’t show any voltage there, especially with no charger connected. This is also the reason for the double green chargingEnd blink, as the BMS detects a voltage on the charger port, but finishes immediately, as there is no current flow.

Assembly is currently underway.

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Nice. :star_struck:

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Hi, I’m wiring my Flexi and my sensor wires looks like this:

Connector 0 goes to negative terminal, next balanse wires, up to positive battery terminal. I have a question regarding balance wires. Let me explain my picture… connection between those 2 batteries (thin black) is spot welded, bent nickel strip. there is additional nickel strip coming from that connection (green) but from negative side (safer, no short). Does it matter if balance wire goes from positive or negative terminal ? They are connected in series so it should not make a difference.

Since they’re electrically connected (same voltage) anyway, it does not matter.

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No; like you said, it’s safer on the negative side because if something vibrates/rubs through the cell’s wrap then it’s not a short.

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Is there a 3d model of the OG flexi? Or an enclosure other than the one with the cable holes on top?

So I have put in the work and designed my own case, here is the link to thingiverse. Feel free to use this.

Link

Pics:

Cheers

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I really love this case, is there a way you could edit it just slightly (or post the .step/.ipt) so it would work with both vertical and horizontal plugs? I have a mix of both and it should be as simple as making the lid cutouts deeper by 2mm on the balance side and 3.5mm on the CAN side.

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Sure, updated the thingiverse page with an updated lid version, now supports both horizontal and vertical ports. Could be a while till it shows up though, so check back later if it processed.

Edit: fuck it, takes to long. here’s the .stl.
Flexi BMS lid vert. + hor. ports v6.stl (83.9 KB)

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Awesome thank you so much! I’ll print it off now and let you know if it works.

Could you also make a version with a thermistor plug cutout. That would greatly be appreciated.

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You guys seriously need to learn how to alter .stl files, its not that difficult. :rofl:

But seriously, just thread the wires through the cooling slots.

Yeah yeah, still sucks working with them :joy:

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