[Caevlist] EV gathering tomorrow, Wed Aug 1st @ 7PM

Gary Graunke gary at whitecape.org
Tue Jul 31 22:05:06 PDT 2018

I could use a bit of the brain power in the group to help solve a mystery. Tesla has replaced a hardware module twice now, and the next time will cost me $500. (Plus we all want to solve this so I can continue camping with model X and trailer and they don’t have any warranty issues). 


I towed my trailer with the refrigerator on to Roseburg (on purpose, I thought I had 200AH of Calb cells connected in parallel, but the wire was too thin). By the time I got to Springfield to charge, the trailer battery was dead. The Calb cells were only somewhat discharged. But the left turn signal/brake light was on constantly, even while the car was charging and not “on” (later I found it had 13V even when the car was off). 


At Roseburg, plugged into shore power, I noticed my current draw was 9A at 120VAC. Turning off all other current drains, I opened up the trailer battery box. It was very hot (and very dead—6V). I pulled the fuses connecting the dead battery.  


I had to come back to Portland for the EV Roadmap conference, but left my wife and trailer in Roseburg—I would return the evening after the conference and continue the campout. When I started home, it went into blue (normal) trailer mode, even though no trailer was attached! Turning it off from the touch screen, it went still displayed an orange trailer mode, but auto-steer worked. 


Tesla replace the part in amazingly short time while I attended the last day of the conference, and I headed back to Roseburg on schedule. 

At the end of the first campout, I towed the trailer a short distance to a second campout in Sutherlin, about 11 miles away. No problems.


Getting ready to return home from Sutherlin, we checked the trailer signals—all were working. However, by the time we got to Springfield to charge, it had failed again!  This time the fuses were pulled on the battery (and the refrigerator was OFF). 


With the battery disconnected, I connected a lab supply to each of the six non-ground trailer connections to measure the current it draws at 12.7 V. 

The tail and running lights drew .53 A, Right turn/stop light .16 A, backup lights 0 (no backup lights—no connection), trailer brakes >3.15 A, Left turn/stop light .2 A, and the aux draws .29 A. Chassis ground to plug ground measured .1 ohms with the multimeter.  With the dead battery installed, the aux started at .16A and increased steadily (odd, it started at .16 with the dead battery installed).


I took the trailer and model X into Tesla last week early Monday morning. They didn’t have the part, and it finally came late Thursday. 

On Monday they had me replace the dead battery with a good 17AH AGM 12V battery I brought. By Friday, it was down to 7 V, so the technician charged it, and they asked me to bring a new battery. (I was going to replace it with the CALB cells, but bought lead to keep things simple).  

They fixed the model X on Friday morning and also replaced a blown 30A fuse on the aux line to the trailer that provides 12V. They and wanted to keep both to continue investigating, but I insisted that I had a camping commitment for the weekend. I connected a brand new 80A 12V trailer battery and drove it home. Since it made it a short distance from Roseburg to Sutherlin in the past without breaking,  I later changed my mind and left the trailer at home. So far, both model X and trailer are still working, but I only drove it 19 miles home from the shop.


Monday I redid the low voltage wiring. It was a single glob of wire and wire nuts all wrapped in electrical tape. I connected all the grounds to a home ground bus bar, a split bolt for the +12V, connected the 6 hot tow vehicle harness wires to a terminal strip, and the wires to which they were connected to a second terminal strip, and put zip lines around each of the remaining wire nuts and taped them individually. ATC fuses now connect the two terminal strips.


I’ve installed 3A fuses for the turn lights, 5A for the tail/running lights, 30 A for the brakes, and 20A for the aux 12V. 


My neighbor suggested that the .29 A phantom load is too high, and may be the indicator of an intermittent wiring fault. I’ll try to trace it tomorrow morning.


So that’s it. I’d still like to understand what the trailer is doing after 1.5 years of happy camping to kill the Tesla part. Was it the dead battery (the Tesla tech says the aux circuit is separate from the dying part)?  Or are both victims of the same common cause?





From: caevlist-bounces at rdrop.com [mailto:caevlist-bounces at rdrop.com] On Behalf Of Kirk Swaney - SHIFT Electric Vehicles LLC
Sent: Tuesday, July 31, 2018 6:22 PM
To: Corvallis EV CLub
Subject: [Caevlist] EV gathering tomorrow, Wed Aug 1st @ 7PM



It's time for the monthly Corvallis-Area Electric Vehicle gathering.  Newcomers & friends are always welcome.

Meeting location for this month is Otmar's shop, the big red garage with white doors.
2255 SE Crystal Lake Dr <geo:0,0?q=2255%20SE%20Crystal%20Lake%20Dr%20Corvallis%20OR%2097333> 
Corvallis, OR 97333

If you'd like to let us know beforehand about a project you'd like to share, something interesting you're bringing, or any help that you need, feel free to Reply-to-all and tell us about it!

If you have an unusual EV, please park inside the shop if there is room for show and tell.

Plenty of overflow parking for the non-electric vehicles is available in the main driveway and the next two driveways to the south.

Charging is available: 115V, 14-50's and J1772 at 32A. Also two Tesla wall connectors.

Hope to see you there!


Kirk Swaney

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