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Discussion Starter · #742 ·
The gap between the two brakets is just what happens with the 18S+- configuration... when I designed that bracket, we didn't yet know the 18S+ module existed. I have QTY750 brackets and they're $9/each... so I'm not ordering more just to fix this minor inconvenience.

However, it does look like the torx heads on these tab-welded modules don't line up with the bracket holes. Again, I don't intend to order more brackets to fix this. One workaround might be to remove the torx bolts, install the brackets (following instructions at linsight.org), then reinstall the torx bolts (that secure the modules together).
 

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For those with the Blue Energy modules, there is an additional difference that requires material removal to the bracket that secures the battery to the IMA enclosure. Without modifications, I've found the bracket does not seat nicely against the battery's surface and only gives the stud about one thread of engagement to the nut with a washer. Fortunately for me, I have a buddy who has a "mill", and he enlarged the three bolt clearance holes and cut three slots. The bracket now fits nicely.

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Yea drilling out the brackets seems to be the POG move.
 

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Hi John-

Thanks for directing me on the cure for my frozen screws. The acetone worked like a charm, but using just a cotton swab I couldn't seem to get enough onto the screws to free things up (note that the board was installed on my battery pack, so it was vertical, and the screws horizontal...), so I injected some acetone into the wire wells with a syringe so I would be sure to dissolve all the acrylic coating. Then I flushed the screw threads and wells with 100% IPA (isopropyl alcohol) using another syringe--several times. Now all eight screws spin easily.

Thank you again for all the engineering expertise and logistical effort you have put into producing this LiBCM kit, and all the (nearly) idiot-proof how-to videos!

Michael


On 7/29/2022 8:06 PM, John Sullivan wrote:

Hey Michael,
I haven't seen this issue before, but my guess is that somehow the conformal coating got sucked up into the connector's screw threads.

FYI: During final electrical verification, I attach wires to each screw terminal on each PCB... but that happens prior to applying the conformal coating.

If you're up for troubleshooting:

The conformal coating is acrylic, which dissolves in acetone (e.g. 100% acetone nail polish remover).
If you dip a q-tip in acetone and then hold that q-tip on the screw head, it should dissolve the conformal coating. The acetone won't affect the connector in any way, but do try to keep it off the PCB (it will dissolve the conformal coating there, too).

Once you get all eight screws rotating, I recommend cleaning the connector with 91% (or higher) rubbing alcohol. The rubbing alcohol won't affect anything on the PCB.
Here's a video showing the process:

If that doesn't work - or you're not interested in troubleshooting - I can send you another LiBCM PCB.

Let me know how this goes, or if you'd just rather me send you a replacement PCB.-John
I also thought these screw terminals were difficult to tighten. I was careful and found the correct size screwdriver which helped. Nice to see this as an option, I'd hate to strip one, although once it is together it should never have to be taken apart except for replacement with a new PCB>
 

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Videos: Recommend liberal use of fast forward. No, you don't see me talking to myself, son is in garage with me. iCloud.
 

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Discussion Starter · #748 ·
Videos: Recommend liberal use of fast forward. No, you don't see me talking to myself, son is in garage with me. iCloud.
Humble brag: I downloaded this video in ~20 seconds.

Thoughts on the videos:

IMG_1284
FYI: You're not measuring the entire pack voltage... just the two 18S modules. You need to measure from the bottom of the contactor (HVDC+, which used to be a bus bar); to the 10 mm bolt closest to the IMA switch (that the PDU plugs into). Regardless, 10 volts is too low wherever you measure it. I agree: these batteries are toast!

Make sure you troubleshoot the 12 volt system to make sure 12V_ignition is turning off when the key is off (and that the downstream 12V_IMA is also turning off. You can verify both of these conditions by checking for 12 volts between any PNK/BLU (12V_IMA) and BRN/YEL (GND_ENG) wires in the IMA bay (there are QTY2 each going to both the MCM and BCM).

If the 12V_IMA rail remains at 12 volts when the key is off, then LiBCM will NOT turn off if the IMA battery gets low.

When your old LiBCM comes back, I'll make sure it's working correctly, too.

...

IMG_1285
Sorry about getting conformal coating in those screws... I will make sure that doesn't happen on future LiBCM shipments. Glad to see you're wearing high voltage gloves!

FYI: You have the honker ferrite installed in the 'wrong' place. It should be around the two thick IMA cables heading from the junction board to the PDU (the thing on the left in the IMA bay). It's a tight fit. I still haven't filmed a video showing how to do it, so my apologies. This isn't what killed your batteries, though.
FYI: Placing the ferrite here will block EMI from the HVDC+ and HVDC-, but conducted noise from the PDU will still hit LiBCM via the BMS leads. Moving the ferrite to the IMA power cables will block the IGBT noise closer to the source, before it gets to the junction board.

It's difficult to tell from the video, but it looks like the WHT/WHT wire heading to the MCM'e' connector isn't connected to the correct 8-pin position. The correct wiring (left-to-right) is:
-PRP (grid_pwm+)
-GRY (grid_pwn-)
-BLU (grid_DC-)
-RED (grid_DC+)
-RED (MCMe+)
-WHT (MCMe-) (this is the one that looks wrong)
-BLK (Pack-)
-RED (Pack+)
Please verify the above wiring.

I'm surprised how difficult removing the wires from these connectors was. Is it all due to difficult screws (from the conformal coating)? It looks like you've over-tightened them, which is causing the ferrules to deform into place. No big deal, just feedback on why it's difficult to remove them.

FYI: Once you've removed the left 18S connector, there is essentially no more high voltage on the LiBCM PCB... you're still slightly over the UL low voltage rating (60 VDC), but just barely: 72 volts or so isn't going to hurt too much if you get zapped. I'm only mentioning this because it'll make removing the temperature sensors easily without those gloves on. Certainly after you've removed both 18S modules there's no more high voltage.

...

IMG_1285
Yup, those modules are toast!

...

Thanks for taking the time to upload these videos. Apologies this happened to your pack. Obviously I have a huge interest in getting to the root cause. Based on the information I know, I strongly suspect this was an issue with the 12 volt ignition not turning off when the key was off. Please troubleshoot this to completion before you put the new modules in... the replacement 12S module is in the mail.
 

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Discussion Starter · #749 ·
For those with the Blue Energy modules, there is an additional difference that requires material removal to the bracket that secures the battery to the IMA enclosure. Without modifications, I've found the bracket does not seat nicely against the battery's surface and only gives the stud about one thread of engagement to the nut with a washer. Fortunately for me, I have a buddy who has a "mill", and he enlarged the three bolt clearance holes and cut three slots. The bracket now fits nicely.
Thanks for the feedback. I have a CNC machine and I can certainly modify my existing brackets for those that need them... that's a little ways out right now, but eventually I will do this.
 

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Thanks for the feedback. I have a CNC machine and I can certainly modify my existing brackets for those that need them... that's a little ways out right now, but eventually I will do this.
Good to hear! Also note, the necessary material removal locations on the brackets will most likely be different for the 18S- module, which I did not have to do since only my 18S+ is the welded module variant.

Also, @mudder since I'm getting close to grid charging for the first time and this is the first built pack with a welded module as the 18+, is there any information you want me to look for? I'm thinking both in terms of safety and capacity/performance.
 

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Just wanted to make a quick post saying that I've got my pack now grid charging for the night and everything looks good. I'll include some pictures.

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I had the sticky conformal coating issue, acetone and patience solved it!

One other difficulty was the HVDV- cable was not easy to pass through its drilled hole and I just barely got it into the screw terminal, due to a lack in workable length in the LiBCM side. I'm a little concerned that there is some tension on the wire. There may be a small amount of slack on the junction board side, but I couldn't get it to transfer over to the LiBCM side.
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Beginning grid charging! Looks like from post #29, the main data to look for is the pack to eventually get to 3.9v.
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Discussion Starter · #752 ·
since I'm getting close to grid charging for the first time and this is the first built pack with a welded module as the 18+, is there any information you want me to look for? I'm thinking both in terms of safety and capacity/performance.
Once the pack gets all balanced out... maybe late tomorrow:
-Go for a long assist-heavy drive (e.g. enable calpod when you would normally regen). Get the pack all the way down to maybe 30% SoC.
-Turn the key off and wait ten minutes.
-Plug a laptop into LiBCM's USB cable.
-Open an Arduino Serial Window.
-Type $DISP=CELL.
-Turn the key ON (but not started).
-LiBCM will start spitting out all the cell voltages. Log these in a text file and post it here.

What we're looking for is that the cells in all three modules are at the same resting voltage, which indicates the cells have the same ampacity. It's not the end of the world if they aren't the same, but it'll be nice to know.

Also, let me know which module types are in which bays (bay 1 is closest to the junction board).
 

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Discussion Starter · #753 ·
I had the sticky conformal coating issue, acetone and patience solved it!
I must have just been really sloppy applying coating on this latest batch. I thought I was being careful.

One other difficulty was the HVDV- cable was not easy to pass through its drilled hole and I just barely got it into the screw terminal, due to a lack in workable length in the LiBCM side. I'm a little concerned that there is some tension on the wire. There may be a small amount of slack on the junction board side, but I couldn't get it to transfer over to the LiBCM side.
@retepsnikrep mentioned this, too. I went back and rechecked (when he mentioned it), and while the cable could be longer (and will be the next time I make them), when properly installed it was long enough. However, I can certainly send you a longer cable if you're unable to make the one you have already work.

Beginning grid charging! Looks like from post #29, the main data to look for is the pack to eventually get to 3.9v.
FYI: Based on your pictures, the delta is increasing during this initial bulk charge... that probably means the two different cell types have different capacity. Not an issue though (but do keep watching it); as soon as LiBCM gets up to 3.9000 volts, the real balancing begins. You have a pretty large delta... it's probably going to take around 12 hours to shrink to 0.001 mV.
 

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Humble brag: I downloaded this video in ~20 seconds.

Thoughts on the videos:


It's difficult to tell from the video, but it looks like the WHT/WHT wire heading to the MCM'e' connector isn't connected to the correct 8-pin position. The correct wiring (left-to-right) is:
-PRP (grid_pwm+)
-GRY (grid_pwn-)
-BLU (grid_DC-)
-RED (grid_DC+)
-RED (MCMe+)
-WHT (MCMe-) (this is the one that looks wrong)
-BLK (Pack-)
-RED (Pack+)
Please verify the above wiring.

FYI: Once you've removed the left 18S connector, there is essentially no more high voltage on the LiBCM PCB... you're still slightly over the UL low voltage rating (60 VDC), but just barely: 72 volts or so isn't going to hurt too much if you get zapped. I'm only mentioning this because it'll make removing the temperature sensors easily without those gloves on. Certainly after you've removed both 18S modules there's no more high voltage.

Thanks for taking the time to upload these videos. Apologies this happened to your pack. Obviously I have a huge interest in getting to the root cause. Based on the information I know, I strongly suspect this was an issue with the 12 volt ignition not turning off when the key was off. Please troubleshoot this to completion before you put the new modules in... the replacement 12S module is in the mail.
No apologies needed, beta testing is to find bugs before going production. Look at the test mule Corvette that went en fuego in Germany this week :). I will test the 12v, and I'll be installing a battery isolation switch 'just in case' the switch issue is intermittent and I don't detect an issue in testing. Many of my cars have them simply because they sit for long periods of time. iCloud
 

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Discussion Starter · #755 ·
I will test the 12v, and I'll be installing a battery isolation switch 'just in case' the switch issue is intermittent and I don't detect an issue in testing. Many of my cars have them simply because they sit for long periods of time. iCloud
If you'd like, I can (eventually) add a feature to make LiBCM constantly beep if it detects 12 volts, but doesn't receive valid "engine is running" data from the MCM after a couple hours.

...

Also, keep in mind that we haven't proven my theory yet... this could very well be a different issue. So for the time being I would check your SoC at least every couple days. If that's not possible, just turn the IMA switch off... that prevents any current draw from occurring from the IMA battery. FYI: This recommendation is only for your specific car; other users don't need to do this (unless they're gonna park the car for half a year or longer).
 

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If you'd like, I can (eventually) add a feature to make LiBCM constantly beep if it detects 12 volts, but doesn't receive valid "engine is running" data from the MCM after a couple hours.

...

Also, keep in mind that we haven't proven my theory yet... this could very well be a different issue. So for the time being I would check your SoC at least every couple days. If that's not possible, just turn the IMA switch off... that prevents any current draw from occurring from the IMA battery. FYI: This recommendation is only for your specific car; other users don't need to do this (unless they're gonna park the car for half a year or longer).
I have an RPI mounted in a 7" touchscreen that I've been planning to put in as my apple carplay, will be running amp off of it for streaming music. Easy to connect it up and monitor the 12v IMA connection at key off. I just need to setup the delay shutoff for the RPI :). For now I'll do the simple check.
 

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FYI: Based on your pictures, the delta is increasing during this initial bulk charge... that probably means the two different cell types have different capacity. Not an issue though (but do keep watching it); as soon as LiBCM gets up to 3.9000 volts, the real balancing begins. You have a pretty large delta... it's probably going to take around 12 hours to shrink to 0.001 mV.
Quick update on charging and balancing. The delta has decreased and the SoC has increased, so we know it's trending in the right direction. Since it's been over 18 hours, I'm curious as to what each cell's voltage is. I think I'll check that next.
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Also, let me know which module types are in which bays (bay 1 is closest to the junction board).
Battery pack: 12S+/18S-/18S+
Bay 1: Bolted 12S+ (from Bumblebee)
Bay 2: Bolted 18S- (from Bumblebee)
Bay 3: Welded 18S+ (Blue Energy)
 

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Discussion Starter · #758 ·
@FlyingHood395 has posted enough data to make some predictions.
3.8800 Voc is ~75% SoC (for the bolted cells).
3.7610 Voc is ~57% SoC (for the bolted cells).
So you need to balance out 18% SoC, which is 900 mAh.
LiBCM's balance circuitry is shunting each 3.9 volt cell across a 75 Ohm resistor... which is 52 mA discharging each 'full' cell.
So it should take another 17 hours to balance the pack (900 mAh / 52 mA).
Given when you posted that picture, I would say if the pack isn't balanced by maybe 1PM Pacific Time tomorrow, then report back for further instructions.

Note that once the pack is balanced, you're not going to need to wait this long again... it's only the initial balance. Of course, if there is a notable Ah difference between the modules, then we'll need to rewrite the firmware to only balance the cells when they're full. If that's the case, then for now we can increase CELL_BALANCE_MIN_SoC (in config.h) to '70'. That'll prevent cell balancing unless the pack is fully charged. Eventually the firmware will do this more intelligently.
 

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@FlyingHood395 has posted enough data to make some predictions.
3.8800 Voc is ~75% SoC (for the bolted cells).
3.7610 Voc is ~57% SoC (for the bolted cells).
So you need to balance out 18% SoC, which is 900 mAh.
LiBCM's balance circuitry is shunting each 3.9 volt cell across a 75 Ohm resistor... which is 52 mA discharging each 'full' cell.
So it should take another 17 hours to balance the pack (900 mAh / 52 mA).
Given when you posted that picture, I would say if the pack isn't balanced by maybe 1PM Pacific Time tomorrow, then report back for further instructions.

Note that once the pack is balanced, you're not going to need to wait this long again... it's only the initial balance. Of course, if there is a notable Ah difference between the modules, then we'll need to rewrite the firmware to only balance the cells when they're full. If that's the case, then for now we can increase CELL_BALANCE_MIN_SoC (in config.h) to '70'. That'll prevent cell balancing unless the pack is fully charged. Eventually the firmware will do this more intelligently.
Yea I just completely disabled balancing in my CVT car. Even after 2 months the cells were only 0.006 out of balance. And that was when that car was my daily.
 

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Discussion Starter · #760 ·
Yea I just completely disabled balancing in my CVT car. Even after 2 months the cells were only 0.006 out of balance. And that was when that car was my daily.
You have some really well balanced cells... my pack gets 6 mV out of balance after a couple weeks of hard driving.

...

Here's my initial testing on @thibble's PCB:
-Summary: there's nothing wrong with the hardware... at least it's working the way I expect it to.
-My hunch is still that 12V_IGNITION or 12V_IMA is stuck on in @thibble's car.
 
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