braebyrn
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Posts: 90
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: 248
Joined: Tue Aug 01, 2017 3:33 pm
Delivery Date: 01 Aug 2017
Leaf Number: 311806
Location: Colorado front range

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: 1845
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.
Leaf SL MY 9/13: 70K miles, 49 Ahrs, 5.1 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

User avatar
JeremyW
Posts: 1540
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
Now driving Honda Fit EV, License plate: CHADEMO
2000 Honda Insight for long trips

lorenfb
Posts: 1845
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.
Leaf SL MY 9/13: 70K miles, 49 Ahrs, 5.1 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

braebyrn
Forum Supporter
Posts: 90
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: 973
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 16.25mo
2nd- 49k mi 25.5mo 51.5Ah
3rd- 73k mi 36.5mo 46.9Ah
4th- 86.5k mi 43mo 42.61Ah
5th- 101k mi 50.5mo 38.38Ah, end 36.13Ah
New Battery 9/28/15 104k mi 66.14Ah
1st- 160.5k 34mo 54.02Ah

braebyrn
Forum Supporter
Posts: 90
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.

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