QueenBee
Posts: 1564
Joined: Sun Aug 08, 2010 5:14 pm
Delivery Date: 20 Jun 2011
Leaf Number: 2062
Location: Bellevue (Seattle), WA

Replacing fuse in DC/DC Junction box and battery junction box?

Sat Feb 20, 2016 11:48 am

A local 2011 LEAF had the AC compressor short to ground which blew the fuse in the DC/DC junction box and the battery junction box. They aren't getting it repaired by the dealer as it'll cost as much/more as the car is worth. So looking through the service manual sounds like a fun enough project. What I'm curious about is if anyone has attempted to repair these two fuses? It's not dealership serviceable but it'd be a little disappointing if these really weren't replaceable by someone with a bit of electronics skill.

ElectricEddy
Posts: 323
Joined: Tue Feb 25, 2014 1:42 pm
Delivery Date: 31 Oct 2016
Leaf Number: 313506
Location: Nanaimo, B.C.

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Sat Feb 20, 2016 10:19 pm

QueenBee wrote:A local 2011 LEAF had the AC compressor short to ground which blew the fuse in the DC/DC junction box and the battery junction box. They aren't getting it repaired by the dealer as it'll cost as much/more as the car is worth. So looking through the service manual sounds like a fun enough project. What I'm curious about is if anyone has attempted to repair these two fuses? It's not dealership serviceable but it'd be a little disappointing if these really weren't replaceable by someone with a bit of electronics skill.

I have looked in the '13 manual and can as of yet not find the type of fuses that are required. I agree these fuses should be accessible without the removal of the battery pack. I would guess they would be bolt on 60A HRC (24KW/400V for the feeder but may be sub fed by independent fuses for HVAC). Because of the possibility of the high ampere inrush current with a bolted fault it is a good idea that they would be difficult to access but should be replaceable with proper troubleshooting by qualified personnel ( without the removal of the pack)...IMHO.
Pearl White Sl
mfd date 09/16

cliff
Posts: 96
Joined: Mon May 13, 2013 10:36 am
Delivery Date: 15 Sep 2012
Leaf Number: 022673
Location: Federal Way, WA

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Sun Feb 21, 2016 2:48 am

QueenBee wrote: What I'm curious about is if anyone has attempted to repair these two fuses? I

I have not, however here is a link to a picture of the fuses in the DC/DC junction box.
http://www.marklines.com/img/report/en/ ... _014_l.jpg
I see there is a 4th fuse in the picture in addition to the 3 that are clearly tied
to high voltage.

QueenBee
Posts: 1564
Joined: Sun Aug 08, 2010 5:14 pm
Delivery Date: 20 Jun 2011
Leaf Number: 2062
Location: Bellevue (Seattle), WA

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Sun Feb 21, 2016 3:22 am

cliff wrote:
QueenBee wrote: What I'm curious about is if anyone has attempted to repair these two fuses? I

I have not, however here is a link to a picture of the fuses in the DC/DC junction box.
http://www.marklines.com/img/report/en/ ... _014_l.jpg
I see there is a 4th fuse in the picture in addition to the 3 that are clearly tied
to high voltage.


Wow, I had not seen this site before!

Here's the junction box in the battery. Don't see fuses. http://www.marklines.com/img/report/rep1049_031.jpg

http://www.marklines.com/en/report/rep1049_201202

So I bought the LEAF!

Found the AC compressor cheap, and the DC/DC junction box for $450. Sure seems like it should be easy replace those fuses though. I wonder why they aren't dealer serviceable? Maybe concerns about maintaining its weatherproofing?

I can't find anyone with the battery junction box but worst case is its $650 new, assuming it's stocked. If I had a way to charge and test modules it would be fun to buy an entire pack and resell the modules. Though at that point I might as well buy a rear ended totaled LEAF.

cliff
Posts: 96
Joined: Mon May 13, 2013 10:36 am
Delivery Date: 15 Sep 2012
Leaf Number: 022673
Location: Federal Way, WA

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Sun Feb 21, 2016 2:14 pm

QueenBee wrote:A local 2011 LEAF had the AC compressor short to ground which blew the fuse in the DC/DC junction box and the battery junction box.


Thinking about this, a short to ground should not have done anything. One of
the main safety features of the Leaf is that neither side of the battery is connected
to ground(somewhat like power in a hospital). So the positive must of shorted to
the negative, but only the positive had a fuse to protect the wire, so what
happened to the negative? With the fuse in the battery box going, this would
suggest to me that the negative could have taken more current than it should
before the fuse went. Is this a design error not having a fuse on the negative
side? But once the positive fuse went, then why did the other fuse go?

The 3 fuses in the DC/DC junction box are all 30 amp fuses, to the heater,
charger, and compressor. the 4th fuse is a 15 amp for the converter.

QueenBee
Posts: 1564
Joined: Sun Aug 08, 2010 5:14 pm
Delivery Date: 20 Jun 2011
Leaf Number: 2062
Location: Bellevue (Seattle), WA

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Sun Feb 21, 2016 10:29 pm

cliff wrote:
QueenBee wrote:A local 2011 LEAF had the AC compressor short to ground which blew the fuse in the DC/DC junction box and the battery junction box.


Thinking about this, a short to ground should not have done anything. One of
the main safety features of the Leaf is that neither side of the battery is connected
to ground(somewhat like power in a hospital). So the positive must of shorted to
the negative, but only the positive had a fuse to protect the wire, so what
happened to the negative? With the fuse in the battery box going, this would
suggest to me that the negative could have taken more current than it should
before the fuse went. Is this a design error not having a fuse on the negative
side? But once the positive fuse went, then why did the other fuse go?

The 3 fuses in the DC/DC junction box are all 30 amp fuses, to the heater,
charger, and compressor. the 4th fuse is a 15 amp for the converter.


Ah good point, the tech specifically said ground but yeah he must have really meant the negative. A short to ground would have actually been easier to fix as it would have detected this happening and shut the car down, then it would just be the compressor being replaced.

I'm not very familiar with fuses but it's common enough with breakers/GFCI that a fault can successfully trip more than one so it seems plausible that this could happen with fusses?

It's my understanding that the isolated ground like in a hospital isn't helping much with regards to safety but is just trying to keep the ground reference used in hospital equipment cleaner by connecting the equipment directly to the panel and then bonding all of the metal junction boxes, conduit, etc. back to the panel separately vs using all of these being connected. So back at the main service panel neutral, EGC and isolated grounds would all be bonded.

GerryAZ
Gold Member
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Delivery Date: 12 Jun 2011
Location: Phoenix, AZ

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Mon Feb 22, 2016 2:55 am

If the compressor circuit failed one leg to ground and then the other leg to ground, the other fuses could see short circuits and blow (depending upon where the grounds were in relation to the fuses and main contactor). The DC ground detection system would try to open the main contactor to isolate the battery as soon as it detected the first ground, but fuses would blow if the grounds became short circuits quickly. Have you checked the main contactor and insulation to ground of all high-voltage wiring? Good luck with your repairs.

Gerry
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015

QueenBee
Posts: 1564
Joined: Sun Aug 08, 2010 5:14 pm
Delivery Date: 20 Jun 2011
Leaf Number: 2062
Location: Bellevue (Seattle), WA

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Mon Feb 22, 2016 11:49 am

GerryAZ wrote:If the compressor circuit failed one leg to ground and then the other leg to ground, the other fuses could see short circuits and blow (depending upon where the grounds were in relation to the fuses and main contactor). The DC ground detection system would try to open the main contactor to isolate the battery as soon as it detected the first ground, but fuses would blow if the grounds became short circuits quickly. Have you checked the main contactor and insulation to ground of all high-voltage wiring? Good luck with your repairs.

Gerry

Ah, true, seems possible that both legs could fail to ground. I'll know more when I talk to our local LEAF tech when he's back tomorrow. More good news: He's optimistic that they he'll be able to get approval to install used parts and I made it clear that I would not expect any warranties of the parts and any additional diagnostic/rework time as a result of the use used parts/defective parts/etc. would be on me. He said the time to replace the compressor and DC/DC junction box is 8 hours and 4 hours to replace the junction box in the battery. So add $200 for a used compressor and the labor bill will be about what I was expecting it was going to cost just to have them replace the compressor!

Our local LEAF tech is pretty good and has been working on them since the beginning so I'm pretty confident in his diagnostic. The original owner had actually first had the dealership that is closest to us diagnosis it but then decided to have it towed over to him.

I'm thinking I'll just buy a DC/DC junction box then have him give me the old one so I can look at repairing it and then reselling. That way the timing if he's doing all the work doesn't get in the way. Found a local junk yard which has it and the compressor.

Then late last night I heard back from hybridautocenter.com I assumed that anyone who was tearing apart packs would have the a bunch of the battery junction boxes. They do and they are cheap! Need to ensure I get the correct revision which I'm having trouble reading the parts diagram but should be easy to get sorted out today when I get a copy of the repair quote.

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JeremyW
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Delivery Date: 23 Jun 2012
Leaf Number: 19136
Location: San Gabriel, CA

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Mon Feb 22, 2016 12:18 pm

Looks like you got it all settled before I wandered in, QueenBee. I would do the same thing, swap the dc/dc junction box and then teardown the dead one.

It's not clear to me, but I suspect the only the fuses in the dc/dc junction box are blown. In the 2011-2012 cars, the main pack fuse is in the orange disconnect that is in the backseat footwell. Does the car otherwise start and drive without AC?

The 2013+ cars have a different "HV junction" setup, and thus the 2013 service manual wouldn't be much help, Electric Eddy. At any rate, Nissan does module swaps and wouldn't have a normal tech replace fuses in the dc/dc. For example, we've seen the same with 2011-2012 chargers and diode issues: they always just replace the entire charger.
Former 2012 SL leasee 6/23/12 - 9/23/15
Now driving Honda Fit EV, License plate: CHADEMO
2000 Honda Insight for long trips

QueenBee
Posts: 1564
Joined: Sun Aug 08, 2010 5:14 pm
Delivery Date: 20 Jun 2011
Leaf Number: 2062
Location: Bellevue (Seattle), WA

Re: Replacing fuse in DC/DC Junction box and battery junction box?

Mon Feb 22, 2016 12:53 pm

JeremyW wrote:Looks like you got it all settled before I wandered in, QueenBee. I would do the same thing, swap the dc/dc junction box and then teardown the dead one.

It's not clear to me, but I suspect the only the fuses in the dc/dc junction box are blown. In the 2011-2012 cars, the main pack fuse is in the orange disconnect that is in the backseat footwell. Does the car otherwise start and drive without AC?

The 2013+ cars have a different "HV junction" setup, and thus the 2013 service manual wouldn't be much help, Electric Eddy. At any rate, Nissan does module swaps and wouldn't have a normal tech replace fuses in the dc/dc. For example, we've seen the same with 2011-2012 chargers and diode issues: they always just replace the entire charger.


I've been trying not to bug the tech on his days off so haven't started pestering him with questions. I believe I'll get a copy of the quote this evening when I get the title but this is what he said was wrong so I've been looking around based on that information.

The high voltage side of the A/C compressor shorted to ground and blew the fuse in both the junction box internal to the battery and the fuse inside the DC/DC converter.


The car isn't driveable right now. It will be interesting to figure out exactly what is wrong with the battery junction box. Maybe it has fuses as well as the fuses in the service plug?

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