braebyrn
Gold Member
Posts: 97
Joined: Thu Nov 14, 2013 5:20 pm
Delivery Date: 08 Nov 2013
Leaf Number: 024521
Location: Seattle, WA

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Thu Jul 12, 2018 2:09 pm

I inquired about upgrading my account to be able to post the picture of the service diagram, but haven't gotten a reply.

After finally getting up the nerve to turn on the heat and A/C to check if the precharge resistor would blow again, I heard the A/C compressor struggling and making a slight squealing sound, not similar to my 2012 Leaf. It turned off by itself after about 10 seconds. Worried I blew it again, I checked and the car still turns off, and on, goes into drive and reverse unlike when the precharge resistor was blown.

So putting the puzzle together, the previous owner was using the A/C defroster to clear the window this last winter. She came out to the car after 20 minutes had passed and the car would not go into drive or reverse, charge, or heat or defrost the car. Did all of the diagnostic flow charts from the service manual and upon advice from Mux, tested the precharge resistor in the battery junction box in the traction battery and verified the precharge resistor was fried. By the way, Thanks Mux for helping from long distance!

Maybe the FAILING High Voltage A/C compressor had put a large load on the precharge resistor and caused it to burn out? Would the HV compressor come on if it didn't have enough refrigerant? I wouldn't think so. Also, I read that these electric compressors must use a different oil than a regular conventional PAG compressor oil or it will cause it to fail. It calls for ND-11 ester oil made for electric compressors.

I will have my brother put some gauges to the A/C lines to verify refrigerant, but I suspect the compressor was the culprit. Anybody concur?
Should I have the compressor oil tested? As soon as my upgrade to Gold is active, I will post the wiring diagram.

goldbrick
Posts: 1253
Joined: Tue Aug 01, 2017 3:33 pm
Delivery Date: 01 Aug 2017
Leaf Number: 311806
Location: Boulder, CO

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Thu Jul 12, 2018 2:16 pm

Based on my very limited knowledge of AC systems, I think the compressor's only feedback is pressure (high side, low side or delta between the 2). I don't know of any way it could be made aware of the amount of refrigerant in the system until it was trying to pressurize it.

It's possible a seized compressor would overload the pre-load resistor but that depends on a lot of factors. It certainly is suspicious and without a detailed understanding of all the circuits and firmware involved, is a good suspect.

lorenfb
Posts: 2509
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Thu Jul 12, 2018 5:51 pm

Since no schematic has been posted, I'll surmise what occurs:

1. Since the power rating of the pre-charge resistor is 40W, the max continuous current is about 1.15 amps (30 ohms).
2. Transient suppressor/integrator capacitors (10s of ufs - 500-600V) are used across (parallel) the down inverter and motor/motor ECU.
3. The 30 ohm resistor is used to pre-charge the suppressor capacitors (Cx) before the HV battery relay is switched on to the
elements of #2 above to avoid excessive battery transient currents. The time to charge the capacitors is less than a few seconds;
3 TCs (3 X 30 ohms X Cx)
4. If any continuous load (> 1.15 amps) exists while the pre-charge relay connects the pre-charge resistor between the HV battery
and the load (#2), the pre-charge resistor is destroyed.
5. There most likely exists a test to determine if the pre-charge voltage of #3 equals approximately the HV of the battery.
If not, the system fails to allow the vehicle to enter the start mode, i.e. the Cx wasn't pre-charged and the HV main relay
is not activated.

Hopefully others will provide a schematic and/or correct/supplement the above.
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 10.3K miles, SOH 109Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F

User avatar
JeremyW
Posts: 1563
Joined: Sun Nov 13, 2011 12:53 am
Delivery Date: 23 Jun 2012
Leaf Number: 19136
Location: San Gabriel, CA

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Thu Jul 12, 2018 9:09 pm

lorenfb wrote:There most likely exists a test to determine if the pre-charge voltage of #3 equals approximately the HV of the battery.
If not, the system fails to allow the vehicle to enter the start mode, i.e. the Cx wasn't pre-charged and the HV main relay
is not activated.
Yes, there is. The motor inverter monitors the voltage of the main caps and permits startup when they start. From page 37 of the "EVC" manual for 2012's:
CONTROL FLOW
To connect the high voltage circuit, VCM first activates the system main relay 2 and pre-charge relay. As a result, the high voltage power is supplied to the respective systems via the pre-charge resistor in the pre-charge circuit. When the condenser inside the traction motor inverter is fully charged by the applied power, the traction motor inverter transmits a high voltage power supply preparation completion signal to VCM. Receiving the signal, VCM activates the system main relay 1 and deactivates the pre-charge relay. Then, normal power is supplied to the respective systems.
Former 2012 SL leasee (6/23/12 - 9/23/15)
Former Honda Fit EV leasee
Former Chevy Spark EV owner
Now driving Tesla Model 3

lorenfb
Posts: 2509
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Thu Jul 12, 2018 9:45 pm

JeremyW wrote:
lorenfb wrote:There most likely exists a test to determine if the pre-charge voltage of #3 equals approximately the HV of the battery.
If not, the system fails to allow the vehicle to enter the start mode, i.e. the Cx wasn't pre-charged and the HV main relay
is not activated.
Yes, there is. The motor inverter monitors the voltage of the main caps and permits startup when they start. From page 37 of the "EVC" manual for 2012's:
CONTROL FLOW
To connect the high voltage circuit, VCM first activates the system main relay 2 and pre-charge relay. As a result, the high voltage power is supplied to the respective systems via the pre-charge resistor in the pre-charge circuit. When the condenser inside the traction motor inverter is fully charged by the applied power, the traction motor inverter transmits a high voltage power supply preparation completion signal to VCM. Receiving the signal, VCM activates the system main relay 1 and deactivates the pre-charge relay. Then, normal power is supplied to the respective systems.
Thanks for the info. So hopefully nothing in the traction motor inverter circuitry, or any other load, can result in the pre-charge current
being greater than an amp or the pre-charge resistor will be damaged. Obviously a delay in the VCM de-activating the pre-charge
relay, or its hanging, could be problematic. You've have thought that the pre-charge resistor would have been fused, i.e. given the
complexity to replace it or a worst case failure mode analysis. Its failure, notwithstanding a DIY effort, is very costly as previously noted.
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 10.3K miles, SOH 109Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F

braebyrn
Gold Member
Posts: 97
Joined: Thu Nov 14, 2013 5:20 pm
Delivery Date: 08 Nov 2013
Leaf Number: 024521
Location: Seattle, WA

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Fri Jul 13, 2018 11:26 pm

What did you all say? Sorry, its a bit over my head. We are soon to install an a/c compressor with of coarse the appropriate ND-11 compressor oil when I get my hands on it.


I have left messages with two moderators and haven't gotten a response about updating my account to post the diagrams and pictures.

91040
Posts: 1055
Joined: Fri Mar 11, 2011 10:36 pm
Delivery Date: 06 May 2011
Location: Los Angeles, CA

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Sun Jul 15, 2018 5:45 pm

Used to be that you put your photos and diagrams on a site like shutterfly, then linked to them here. Does that not work anymore?
1st Capacity Bar loss 30k mi 16mo
2nd- 49k mi 25.5mo 51.5Ah
3rd- 73k mi 36.5mo 46.9Ah
4th- 86.5k mi 43mo 42.6Ah
5th- 101k mi 50.5mo 38.4Ah, end 36.1Ah
New Battery 9/28/15 104k mi 66.1Ah
1st- 160.5k mi 34mo 54Ah
2nd- 184.4k mi 53mo 49Ah

braebyrn
Gold Member
Posts: 97
Joined: Thu Nov 14, 2013 5:20 pm
Delivery Date: 08 Nov 2013
Leaf Number: 024521
Location: Seattle, WA

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Mon Jul 23, 2018 8:07 am

We turned the A/C on again and the sounds coming from the compressor were consistent with my 2012 parked alongside. It's unknown to us why upon initial startup it sounded different other than the air conditioning hadn't been used in 6 months.

An A/C gauge set determined the pressures were nearly identical to my 2012 running at the same time on the same fan speed and cabin temperature.

After driving the car in 90 degree temps for about a week and with the A/C on, everything is all good again.

w7gz
Posts: 3
Joined: Wed Jan 11, 2017 7:50 pm
Delivery Date: 22 Aug 2011
Leaf Number: 123456

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Fri Apr 23, 2021 7:21 am

I have another confirmation of the association of these codes with the failure of the pre-charge resistor. I bought an immobile 2011 Leaf with a 100% SOH traction battery. After dropping the battery and removing the main relay box, I determined that the resistor was open. I replaced it and the car is completely functional. The initial cause of the failure is unknown to me, but a new resistor resolved the problem. Clearly Nissan didn't anticipate this part to be a common problem or they would have located it outside the traction battery. It's a cheap fix, but certainly not in terms of the labor involved.

Now, how can a 2011 still have a perfect battery after 70K miles? I saw no evidence of it ever having been replaced when I was under the car.

Answer: After driving the car for 40 miles, I discovered an inconsistency between the battery display and regeneration behavior and the initial 100% SOH reading. While it still shows 12 battery bars, SOH is now 60% on LeafSpy. It appears that a service tech did a BMS reset in an attempt to fix the error codes the disabled car was throwing, and, of course, was unable to repair the pre-charge resistor that way. I'll swap in another traction battery in a few weeks.
Last edited by w7gz on Fri Apr 23, 2021 12:37 pm, edited 1 time in total.

alozzy
Posts: 1930
Joined: Fri Jan 20, 2017 4:25 pm
Delivery Date: 18 Jan 2017
Location: Vancouver, BC
Contact: Website

Re: Opened the traction battery and found the Pre-charge resistor was bad. What caused it to fail?

Fri Apr 23, 2021 9:27 am

If the pack isn't brand new, then there's zero chance of an SOH of 100%

Almost certainly, the BMS was reset and you won't know the real SOH unless you:
  • Road test to verify the useable range
  • Estimate the capacity by running down to 20%, L2 charging to 80%, then multiplying the kWh reported by the EVSE by 1.67 to estimate the capacity
  • Wait for the BMS to recalibrate
Vancouver, CA owner of a 2013 Ocean Blue SV + QC, purchased 01/2017 in WA
Zencar 12/20/24/30A L1/L2 portable EVSE
1-1/4" Curt #11396 hitch
After market, DIY LED DRLs
LeafSpy Pro + Konnwei KW902 ELM327 BT OBDII dongle
Loving my first BEV :D

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