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JeremyW
Posts: 1517
Joined: Sun Nov 13, 2011 12:53 am
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 12:59 pm

Can you sick leaf spy pro on it and see what codes pop up? I wonder if it's failing isolation tests thus failing to go into ready... I also think if the dc/dc cannot function you also won't go into ready so it just might be that, if the dc/dc fuse is blown.
Former 2012 SL leasee 6/23/12 - 9/23/15
Now driving Honda Fit EV, License plate: CHADEMO
2000 Honda Insight for long trips

miscrms
Posts: 141
Joined: Fri Sep 05, 2014 10:25 am
Location: Phoenix, AZ

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

Mon Feb 22, 2016 2:27 pm

The dc/dc junction box is not difficult to open, but doing so will require cutting through the sealant used to make it weather tight. This is what my 2012 looked like once opened up. It looks like the fuses are under the cover at the bottom right, which would require disconnecting some of the internal wiring connectors to access.

Image

I haven't found any fuses inside the the battery including the battery junction box, aside from maybe one in the battery heater if equiped. Replacing the battery junction box will require removing the battery, so I wouldn't go there unless you have to. If there is a failure indicated in the battery (such as P3373 or P30F4 Total Volt Over Discharge / Sensor) hopefully its just the fuse in the service plug. Assuming the fuse is in the plug itself it could be swapped out without dropping the battery. Note there are several different styles of plug, you'd need to get the right one to match your battery.

Rob

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?

Sat Feb 27, 2016 12:27 am

So my LEAF tech thinks there was a catostophic failure in the junction box in the battery but I'll know more when I get it back. Found the compressor and DC/DC junction box at a local junkyard which I dropped off to him and they passed his multimeter tests. Just found the battery junction box on eBay randomly sorting through Nissan LEAF parts that was listed with the BMS so will shortly have all the parts!

FWIW it appears the 2011/2012 battery junction box with battery heater could be used in a battery without a battery heater as it appears to be just an extra connector that could be left unplugged or the wiring disconnected but my tech was leary so I'm glad I found one with out it.

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JeremyW
Posts: 1517
Joined: Sun Nov 13, 2011 12:53 am
Delivery Date: 23 Jun 2012
Leaf Number: 19136
Location: San Gabriel, CA

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

Sat Feb 27, 2016 7:05 am

If there was a dead short across the battery terminals, besides potentially welding the main contactors, there's a chance the pre-charge resistor was damaged if someone just cleared the dtc's and tried to start the car again. Normally, the DTC's should have prevented inadvertent restart until a tech could take a look..

Basicly, theres a large capacitance in the inverter input and if the contactors were allowed to just connect the battery to this large capacitance, there would be a huge inrush that could actually damage the caps and cause a voltage spike. So, in every production EV, there's a pre-charge circuit that puts a fairly large resistance between the battery positive terminal and the dc components until the voltage rises to near normal levels, then the main positive contactor is switched in.

Hoping that it's just the DC/DC junction box and the AC compressor that will fix it up. Dropping the pack and opening it up can't be inexpensive. At least you have that part if it in fact failed.
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?

Sat Feb 27, 2016 4:01 pm

JeremyW wrote:If there was a dead short across the battery terminals, besides potentially welding the main contactors, there's a chance the pre-charge resistor was damaged if someone just cleared the dtc's and tried to start the car again. Normally, the DTC's should have prevented inadvertent restart until a tech could take a look..

Basicly, theres a large capacitance in the inverter input and if the contactors were allowed to just connect the battery to this large capacitance, there would be a huge inrush that could actually damage the caps and cause a voltage spike. So, in every production EV, there's a pre-charge circuit that puts a fairly large resistance between the battery positive terminal and the dc components until the voltage rises to near normal levels, then the main positive contactor is switched in.

Hoping that it's just the DC/DC junction box and the AC compressor that will fix it up. Dropping the pack and opening it up can't be inexpensive. At least you have that part if it in fact failed.


Oddly it's not as bad as you'd think. 8 hours of shop time to replace the compressor and DC/DC junction box and only 4 hours to replace the battery junction box, it's the parts that are the bad part, dealership wanted $922 for the junction box and new junction box cover (apparently it changed on the new part number). I'm not sure exactly what testing the battery junction box failed but he's a top LEAF tech so I fully trust that his diagnosis is correct.

Was just adding up my costs. I'll be into this $3,500 after all the parts and labor including sales tax. Then I can probably repair the DC/DC junction box if it's just the fuses and resell it. Though it needs a detailing and some seat covers.

The other good news is I've convinced my spouse that we can finally sell the ICE and be a fully solar powered two EV family!

LeafQC
Posts: 3
Joined: Wed May 23, 2012 8:20 am
Delivery Date: 18 May 2012

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

Wed Mar 16, 2016 9:52 am

I had a similar problem with one of my 2012 LEAF SL. The car could not move and heat. The dealer said that my AC Compressor blow my junction box. I think this faillure should be cover under warranty because the car is less than 5 years/60000 miles.

What do you think? Warranty or not?

Thanks!

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?

Wed Mar 16, 2016 10:10 am

LeafQC wrote:I had a similar problem with one of my 2012 LEAF SL. The car could not move and heat. The dealer said that my AC Compressor blow my junction box. I think this faillure should be cover under warranty because the car is less than 5 years/60000 miles.

What do you think? Warranty or not?

Thanks!

Definitely would be covered by the warranty. The car my original post was about was something like the 216th LEAF made and the warranty had just passed 5 years a few weeks prior.

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 Mar 20, 2016 10:04 pm

To follow up. I bought the DC/DC junction box/converter and the AC compressor from a local junk yard for $550. Then I bought a battery junction box from ebay for $80. It turned out to be different than the item pictured and had the connections for the battery heater. My LEAF technician at the dealership was hesitant but after poking around at it he was OK with using that one. Then I paid $1400 at the dealership for the labor to replace all three components. Was quoted 8 hours for the AC compressor + DC/DC junction box and 4 hours to drop the battery, open it up, and replace the junction box.

Now that I've got the battery junction box back it was obvious what was wrong. The resistor was cracked and was open instead of the 30 ohms it should have been.

So it's all running again!

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JeremyW
Posts: 1517
Joined: Sun Nov 13, 2011 12:53 am
Delivery Date: 23 Jun 2012
Leaf Number: 19136
Location: San Gabriel, CA

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

Sun Mar 20, 2016 11:15 pm

Awesome to hear! I guess I was right about the precharge resistor being blown.
Former 2012 SL leasee 6/23/12 - 9/23/15
Now driving Honda Fit EV, License plate: CHADEMO
2000 Honda Insight for long trips

cliff
Posts: 105
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?

Mon Mar 21, 2016 7:04 pm

Wow only 30 ohms, even with lowest battery voltage, that is potentially thousands of
watts! So the system has to really make sure things are not turned on during pre-charge.
Interesting that the resistor survived long enough for the fuse to blow.

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