Nissan Leaf BMS

Topics concerning OEM and open source BMSes
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Re: Nissan Leaf BMS

Post by johu »

Success! or rather: one step forward, one back.
I've changed the interlock return to pin 21 now and finally I get a "1" on the interlock bit. But now I'm back to the 4.5kW discharge and 0W charge limit with DTC 0x254d or 0x4d25. I have removed my special resistor on pin 6, will put it back in.

I was hoping it always balances. At least it stays on for a while after pin 5 and 6 are disconnected.
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Re: Nissan Leaf BMS

Post by johu »

I realized the old BMS had 4 current sensors, the new one has only 3. I'm lacking one. Could that be the problem? What kind of sensors are they? Maybe I can just put in a constant resistor
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Re: Nissan Leaf BMS

Post by prensel »

The grey version has just one sensor left out, nr 3. It is not connected.
Not sure what they are, i have to measure them.
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Re: Nissan Leaf BMS

Post by prensel »

I'm lost, just to be sure what are you trying to accomplish:
A white wiring loom on a grey LBC or a grey wiring loom on the white LBC ?

I can try a setup with both versions (white on white and grey on grey) and do a CANlog this weekend to see what the packets tell us..
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Re: Nissan Leaf BMS

Post by johu »

Thanks for your help!
It's a grey wiring loom with a white BMS
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Re: Nissan Leaf BMS

Post by evcar »

johu wrote: Fri Jan 17, 2020 4:40 pm I realized the old BMS had 4 current sensors, the new one has only 3. I'm lacking one. Could that be the problem? What kind of sensors are they? Maybe I can just put in a constant resistor
Are you referring to the temperature sensors? If so, they should be 4kohm nominal NTC thermistors.
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Re: Nissan Leaf BMS

Post by prensel »

johu wrote: Fri Jan 17, 2020 12:56 pm Oh you're right! That is really strange. When I remove the connection between 6 and 8 the BMS sets the discharge limit to 4.5kW and I think it displays some error. But now I see they just tie pin 6 to 12V - permanently or on ignition? When is pin 5 activated?
White loom:
Pin 6 is only +12V when IGNition on, pin 12 is constant +12V.
Pin5 is only +12V when charging
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Re: Nissan Leaf BMS

Post by johu »

Ok, nice. I will put a 4k7 resistor in place of the missing temperature sensor
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Re: Nissan Leaf BMS

Post by johu »

I did a bit of checking. So supposedly on the "all white" BMS the current sensors ground lead is connected to Pin 7 as opposed to pin 15 on the grey BMS. But all components that pin 7 goes to are unpopulated and the pin is floating. So I left the sensor on pin 15 which is solid GND.
Concerning the 3rd temp sensor I think I've found the place where it forks off to the processor via a series resistor (R59). So I will remove that and bridge it over to the 4th channel behind R62. Now I hope the 4th channel is just copied onto the 3rd.
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Re: Nissan Leaf BMS

Post by johu »

Ok, tried that but no real luck. DTC had different values. one byte is always 77 (0x4d) and one had different values on different attempts: 37 (0x25), 10 (0xa) and 93 (0x5D). None of the combinations show up in the service manual. I wonder if there is some encoding.
I'm also rather surprised the DTCs changed on every power up today. Yesterday it was 77 37 pretty consistently.
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Re: Nissan Leaf BMS

Post by johu »

After the BMS was now unpowered for a few days I checked again. Still errors. Discharge power limited to 4.5kW, charge power to 0. DTC reported is now 0x66 0x4 . No consistency there either. If I divide the numbers by two I'd end up with 0x3302 which is at least listed in the service manual as "Cell Overvoltage Module 1". What??

I drove around a bit hoping the BMS would "learn" that everything is fine but no luck.

The cell voltages look valid around 3.9V with the delta between high and low still being 70mV.

I'm wondering why there were no errors as long as the interlock was open. Maybe now that it is trying to balance it finds that 70mV difference is too much?
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Re: Nissan Leaf BMS

Post by johu »

It looks like the pack is actually quite well balanced. The low and high voltages that stick out are right next to each other. I'm assuming the chips work much like my BMS: they measure 4 voltages in series and arrive at cell voltages by subtraction. So if one voltage is measured too low, the one next to it will measure too high. I guess I have to check my wiring. Only the very first voltage doesn't follow that scheme, will measure it by hand to see whats happening.

Furthermore I found when connecting the charge input the DTC changes to 0xA 0x4
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Re: Nissan Leaf BMS

Post by johu »

Alright I took the plunge and measured all 96 voltages with a multimeter. Little surprise, the variation isn't nearly as large as the BMS suggests. Lowest voltage was 3978mV 3878mV and highest was 3904mV, so 26mV delta, not 70mV.
I'm thinking there are some weak connections in my adapter cable that cause a voltage drop. The LBCs inputs seem to be fairly low impedance, so these weak connections don't show up on the multimeter. The BMS might also notice an unusual voltage drop when trying to balance.
Will go over the adapter cable once more and see if I can get some valid numbers.
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Re: Nissan Leaf BMS

Post by boekel »

Hi Johu, can it be the low cells are balancing when measuring? this could also give such results.
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Re: Nissan Leaf BMS

Post by johu »

I read that the balancing is inhibited when you pull the service jumper (i.e. cut the interlock link). The voltages are still the same then. Also the balancing flags (provided I interpret them correctly) are all 0
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Re: Nissan Leaf BMS

Post by prensel »

johu wrote: Sun Jan 26, 2020 4:03 pm Lowest voltage was 3978mV and highest was 3904mV, so 26mV delta, not 70mV.
That should read 3878mV as lowest voltage I assume ?
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Re: Nissan Leaf BMS

Post by johu »

Oh, yes ;)
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Re: Nissan Leaf BMS

Post by johu »

Today I took a left over pin and put it into each of the "jacks". Most jacks will hold on to the pin so it doesn't just slide out. But some jacks did not hold on and the pin can just slide out. This will also cause bad contact, I suppose. I must have damaged them when I pushed them back out with a sewing needle because they were in a wrong slot.
I'm hoping when thats repaired I get valid readings and no more errors :roll:
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Re: Nissan Leaf BMS

Post by evcar »

If you need to replace the connectors, you can use this series of connectors from TE connectivity (some examples):
https://www.digikey.com/product-detail/ ... ND/2273493
https://www.digikey.com/product-detail/ ... ND/2273504

They aren't the exact replacement connector, but I'm using them and they work fine. The white ones aren't keyed, so you can plug in a white connector into a colored socket on the BMS.
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Re: Nissan Leaf BMS

Post by johu »

Yes I used these.
Finally: success!! The DTC is gone, I get a valid charge and discharge rate and I'm seeing one balancing flag :)
So the problem actually was my unconcerned way to pull wrongly populated pins from the connector. as I couldn't pull them out the back without ripping the cable out I decided to push them from the front. Which worked, but also bent the little spring that actually makes contact. So I tested each jack as described above and removed all those who were loosy-goosy. Bent the spring back, plugged back in - joy :)

Cell voltages 1 and 2 still read a bit high (3940mV instead of 3920mV) but it seems close enough for the LBC not to treat it as an implausibility. I know this derivation will cause early charge termination and mis-balancing further down the line, but for now I'm happy.
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Re: Nissan Leaf BMS

Post by johu »

Now, mostly happy with what the LBC does. Only, when I charge SoC doesn't increase. It will increase later as I drive but thats too much delay.
So I'm wondering, when charging do I need to pull Pin 5 AND 6 to 12V or just pin 5? Currently doing the latter.
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Re: Nissan Leaf BMS

Post by evcar »

johu wrote: Thu Feb 27, 2020 7:49 am Now, mostly happy with what the LBC does. Only, when I charge SoC doesn't increase. It will increase later as I drive but thats too much delay.
So I'm wondering, when charging do I need to pull Pin 5 AND 6 to 12V or just pin 5? Currently doing the latter.
In my car I'm pulling both pins to 12V, but the SoC mostly stays the same. According to the service manual, the VCM sends a can bus command to the BMS to "refresh" the SoC value (Target Li-ion battery remained energy signal) but I haven't figured it out yet.
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Re: Nissan Leaf BMS

Post by prensel »

Did you ever figure out what relates the error code from message 0x5C0 (LB_Diagnosis_Trouble_Code) to the codes in the EVB manual ?
I'm currently facing errors 0x03 and 0x60 but charge and discharge limits seem to be ok.

I have Leaf Spy Lite but neither the generic Elm327 BT device or the OBDLink MX+ I have seem to work with it.
So waiting for the LELink to arrive this friday...
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Re: Nissan Leaf BMS

Post by johu »

I see different error codes these days, don't remember which one.
The stationary SoC problem has disappeared, maybe the LBC was still "learning". Also SoH has changed from 85% to 89%
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Re: Nissan Leaf BMS

Post by prensel »

Ok, I have searched around various DBC files, websites and fora to figure out the 'translation' between the byte width errorcode in 0x5C0 and the4-digit DTC P-code that the EVB manual uses but cant find it. It must be some sort of hash because LeafSpy seems to translate them properly. Like said my LeafSpy is not working YET so have to figure out another way. The pack I'm currently working on seems to be working fine though, proper values for the charge and discharge currents, I can see the status/shunt bits in group 6 changing so now and then but most of the time they are 'silenty' zero.

Regarding the SOC there are two 'locations' that this value is available. On is 'static' and used on startup and probably a copy of the last known 'live' value which starts to be available after all cell values have been polled. LeafSpy is using these values this way.
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