Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

[AussieInSeattle]

Originally Posted by Sergio

AussieInSeattle, that will work fine, the KSI input on the controller (pin #10 tan wire) is a low current signal.

so to confirm, I can just splice into the #10 wire where it runs through the battery area? or I cannot? Do I need to run 14AWG or higher still? The need for 14AWG seems to contradict where I can splice?

[Sergio]

I had to back and see what I wrote (no need it was for an option interrupt location):

The wires on the K1 contacts are 14awg in case it is used to interrupt the KSI power instead of just the Controller KSI low current input, pin #10 on a Precedent Curtis or Alltrax XCT.

You could use 18ga wire if you want to interrupt the tan wire (controller ksi) if you locate the wire in the harness.

[AussieInSeattle]

Thanks for your help so far Sergio - I've managed to get my LifePo4 pack charging with some initial values setup in the BMS
- overvoltage set to 3.6v per cell and 57.6v for the pack
- charger voltage of 56.4v (3.525vpc)

My build is documented so far here:
https://www.buggiesgonewild.com/showthread.php?t=172654

I've only charged it for 45 minutes so far since it was late Saturday night. I just got done re-reading all 42 pages and documenting all the BMS settings suggested (for leaf packs) so I can get mine right before I finish charging (only at 70% charge at the moment) and put a load on the pack.

As a LifePo4 pack, the cell limits are 2.5V to 3.65V - I know about the flat discharge curve of this chemistry and want to stay somewhere in the 20%-90% range - I know I may need to tweak the charger settings below once I start using the pack to hit that 90% and that may in turn change the BMS settings.

My charger voltage is set to 56.4v (3.525vpc) for now - this gives me 2v of headroom for Regen and should be about 90% SOC for my chemistry.

Here are the values I plan on using for the BMS based on reading the 42 pages and the BMS related posts in detail - see any issues in numbers below?:

• Set Balance mode to Static and disable Load Detect
• Balance turn on voltage of 3.475v with precision of .01v initially then bump to 3.525v with precision of .03v after cycling pack a few times - cells are within .007v at ~70% initial charge at the moment so seem to be well balanced already - will monitor and change earlier if needed
• 3.6V Overvoltage setting with release at 3.55V after 2 second delay
• 2.8V Undervoltage setting with release at 3.55V after 2 second delay
• 57.6V - Pack Overvoltage with release at 56.8V after 2 second delay - this simply matches bullet one above x 16
• 44.8V - Pack Undervoltage with release at 45.6V after 2 second delay - this simply matches bullet two above x 16
• 3.65v Hardware overvoltage (from post #394) my BMS settings has cell level, not pack - not sure what these are for vs overvoltage settings?
• 2.5v Hardware undervoltage (from post #394) my BMS settings has cell level, not pack
• Following temp values from spec sheet attached
• 60C max discharge temp with release at 55C after 2 second delay
• -10C min discharge temp with release at -5C with 2 second delay - cart is in Seattle - will not be driven in this type of weather
• 50C max charge temp with release at 45C after 2 second delay
• 0C min charge temp with release at 5C with 2 second delay - unheated garage still in low 50s on coldest days so dont expect this to ever kick in

And AllTrax settings:

• Max amps set to 360Amps - (my batteries allow 3C/360Amps for 30s and 2C/240Amps continuous - will watch amp meter on longest and steepest hill with fattest mates on board to see if I should change to 240Amps
• Over Voltage set to 3.575vpc / 57.2V - 0.4V lower than BMS max
• Under Voltage set to 2.825vpc / 45.2V - 0.4V higher than BMS min
• Max regen armature amps of 120
• Max regen battery amps of 80

I'll repost above values in my build thread too but thought I'd ask here as not sure if you've seen it. Battery spec sheet attached in case you need it. Thanks again for your help.

PS - anyone reading this, note that the above values are for a 16S LifePo4 pack - not a leaf/volt/other pack which has a different chemistry and cell voltages.

[Sergio]

I have been following your build, it is looking pretty good.

I am not sure where you got the SOC percentage for the LifePO4 cells, but as far as I know 3.5v is 99% so I would think no more than 3.4vpc if you don't need the capacity.

Since You have an AH meter, perhaps you can monitor how many volts each cell drops in the first 5AH or 10AH you remove from the battery to decide if you can lower the max charge level.

You will probably find out that you can drop the max battery amps to less than 300 amps without any noticeable impact in performance.

These are my current settings for complete reference:

[AussieInSeattle]

Originally Posted by Sergio

I have been following your build, it is looking pretty good.

I am not sure where you got the SOC percentage for the LifePO4 cells, but as far as I know 3.5v is 99% so I would think no more than 3.4vpc if you don't need the capacity.

Since You have an AH meter, perhaps you can monitor how many volts each cell drops in the first 5AH or 10AH you remove from the battery to decide if you can lower the max charge level.

You will probably find out that you can drop the max battery amps to less than 300 amps without any noticeable impact in performance.

These are my current settings for complete reference:

Thanks for the screenshots - a few more questions:

1.
I noticed that your overvolt for the pack is 14x you cell setting (4.18x14 = 58.52), however your undervolt for the pack is set to 37.8 but your undervolt per cell is 3.2 (x14 = 44.. Any reason for that?

2.
I set my charger to 54.4v (3.4vpc) due to your comment on 3.5vpc being closer to 99% - I've read so many articles that contradict each other that I figure I'll start low. I am charging the pack now and with my 10A charger it is only pushing 7Amps into the pack - when I was charging last night with the charger set to 56.6v (3.525vpc) it was pushing just under 10A in. I assume this is the charger (a UY600) just tapering off the current as it gets closer to the target voltage? Pack was resting at 52.9 when I put the charger on and is at 53.6v while under charging load at the moment

3.
I had in my notes to set Balance mode to Static - I think that was from an old version of the app. I had to set BOTH Charge Balance and Balance Enable to ON in order for the balance to work at my selected voltage (3.35vpc for now). I also see the amps going into the pack in the app - I assume this is due to the change in the middle of this thread for the Charger negative to the C-?

4.
I've seen you comment on the "lock icon" multiple times but cant find it - where is it in v3.1 of the app?

5.
I'm having a weird bluetooth issue using a Samsung S20 and latest android. The BMS never appears when I start up the app. I have to go into BT settings and click on the BMS to try and pair with it - it gives me a message saying to use the app and the blue light then comes on for the BT board and I can then connect to it from within the app. Are you seeing this too?

Thanks again for your help - still have to extend the thermistor wires and do some cable cleanup before I work out how I'm going to lift the 100lb pack into my cart with only a few mm of clearance either side :-)

[Sergio]

1) No reason other than a mistake, thanks for catching it!
I think I raised the cell under voltage setting and overlooked the pack setting.
I need to look at those settings this weekend and adjust them, I will upload a new "version" of those images to my google drive and that will update the previous post.

2) Correct, the charger will start to go into the "constant voltage" phase near the end of the charging cycle to allow the lithium cells to slowly saturate.

3) Correct, since the BMS is not disabling both FETs during either fault, it was necessary to move the charging current to the BMS as the relays are only activating on the "discharge" FET being disabled. I do have the parts to test my idea of allowing either condition to disable the relays but have not had time to test it.

4) Yes, that was about the first version of that app, here is a screen shot of that old app so you know what I meant:

5) I am not having issues with my Pixel phone, Are you using that latest version (3.1.1021), if so maybe try the previous one:

https://www.lithiumbatterypcb.com/sm...ware-download/

[AussieInSeattle]

Originally Posted by Sergio

1) No reason other than a mistake, thanks for catching it!
I think I raised the cell under voltage setting and overlooked the pack setting.
I need to look at those settings this weekend and adjust them, I will upload a new "version" of those images to my google drive and that will update the previous post.

2) Correct, the charger will start to go into the "constant voltage" phase near the end of the charging cycle to allow the lithium cells to slowly saturate.

3) Correct, since the BMS is not disabling both FETs during either fault, it was necessary to move the charging current to the BMS as the relays are only activating on the "discharge" FET being disabled. I do have the parts to test my idea of allowing either condition to disable the relays but have not had time to test it.

4) Yes, that was about the first version of that app, here is a screen shot of that old app so you know what I meant:

5) I am not having issues with my Pixel phone, Are you using that latest version (3.1.1021), if so maybe try the previous one:

https://www.lithiumbatterypcb.com/sm...ware-download/

As always, thanks for the response.

I am using 3.1.1021 - will just put up with the connection issue for now since I have a workaround.

I think the reason for the lock icon removal from 3.1 is that you can individually turn off Charging and Discharging with those little button sliders instead - so just a UI/UX change.

I ended up changing my charging voltage from 54.4 (3.4vpc) to 54.8 (3.425vpc). I was finding that while charging that the voltage at the charging terminals where they connect to the battery was 53.8 when the charger was set to 54.4. After boosting the charger voltage to 54.8 the voltage at the charging terminals was 54.3 - can't seem to track down the reason for the voltage drop but 54.8v is still safely within the battery range.

In the end I pushed 48Ah (40% capacity) into the pack over about 6.5 hours. The pack was reading 54.3 while still charging at 6.6Amps when I disconnected it. The cells were at about 3.29vpc when I started and are usually shipped at around 50% capacity so I believe I am around 85%-90% charged. Pack voltage dropped after disconnecting the charger and is resting at 53.44v 12hrs after disconnecting the charger.

My vpc are 3.335-3.344 after settling overnight which is also inline with 85-90% charged according to this chart I am using which I assume is resting voltage:
https://docs.google.com/spreadsheets...#gid=968848831
It is so hard to use voltages for capacity due to the flat voltage of LifePo4 so this will be an ongoing process to work out where "my" 20% is. Seems like I should be able to work that out at the lower end of the discharge curve due to the greater voltage drop under 20% capacity. From there I can work out how many Ah to pump back into the pack to get to ~90%.

[Sergio]

The nice thing about that Renogy battery meter you got is that you only have to worry about the cell voltages one time.

After a full charge you set whatever that voltage/capacity is as "100%".

You then just have to drive and monitor the cell voltages until they get as low as you would like to go and set that voltage/capacity as your "0%".

From that point forward the meter will accurately display the percentage of capacity your have left regardless the part of the discharge curve your cells are at the moment.

It is also not affected by the pack voltage dropping during acceleration or rapidly declining near the "knee" on the curve.

[AussieInSeattle]

Originally Posted by Sergio

The nice thing about that Renogy battery meter you got is that you only have to worry about the cell voltages one time.

After a full charge you set whatever that voltage/capacity is as "100%".

You then just have to drive and monitor the cell voltages until they get as low as you would like to go and set that voltage/capacity as your "0%".

From that point forward the meter will accurately display the percentage of capacity your have left regardless the part of the discharge curve your cells are at the moment.

It is also not affected by the pack voltage dropping during acceleration or rapidly declining near the "knee" on the curve.

That's kind of the approach I was thinking but you explained it much better :-)

So to confirm, the approach would be as follows to have "my 0-100%" sit in the 20%-90% SOC range:

• drive cart until I reach 51.2 volts left in pack - this should be ~20% remaining
• reset renogy battery meter to 0% and change Ah capacity to 84Ah (70% of 120Ah)
• charge pack to 84Ah which should be close to 90% SOC
• to get charger to shut off or reduce Amps pushed at end of charge, note resting pack voltage an hour after I hit 84Ah and set charger to this voltage?
• OR could also take note of how many hours it takes to get from 0Ah - 84Ah and use a smart outlet to auto shutoff charging after x hours via home automation system and voice commands based on how much charge I want to add, whether I'm home, etc

I think I also need to ensure I do the above steps (drive pack down to 20% SOC) in slightly warmer weather than now (Seattle) as LifePo4 discharge C rates are lower in colder weather - cant find chart for my cells but I believe they like to be above 50% SOC in current weather (<10 Celsius) to get at least half (120Amps) of the 2C continuous discharge rating.

[Sergio]

You are overthinking the process, the actual AH that you initially "preset" the meter is irrelevant, it just needs to be higher than the pack capacity.

If You want to start from the bottom so You know the AH capacity that You will have:

Discharge the pack to whatever voltage will be your 0% and hold the "down" key for 3s to set the capacity to 0.

Set the preset capacity "Higher" than your actual pack, like 200AH.

Now charge the battery until the charger stops, the displayed AH capacity when the charger stops will be the actual usable capacity.

Set AH that was displayed as the new preset AH capacity.

Hold the "up" key for 3s to set the capacity to 100% if the meter did not switch to 100%.