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Front Collision TESLA P85. Repair and Troubleshooting Help Needed.
- Thread starter Yauheni
- Start date
Otmar
EV Modder
I agree charging the 12V battery would be a good idea. It takes a substantial 12V charger to stay ahead of the loads when the car is on. I used a 55 Amp unit. Don't use the "start" function of a charger! The voltage may be too high. I think my 6 Amp charger was too small to keep up with the car loads.
The light bulb in the fuse's place shouldn't burn out since it will have no more than 15V from one terminal to the other and the bulb won't allow more than a couple amps of current to flow. The key here is that for the DC-DC to supply current the current has to be drawn by a load. In this case the light bulb limits the load.
Maybe I wasn't clear, the light replaces the fuse so the light is in series with the battery to DC-DC connection. The light is only there to try to get the DC to DC to supply charging voltage by waking it up with a little current from the 12V battery. Once it does that then we know that the DC-DC is not internally shorted and if it wakes up it would indicate the fuse should be replaced. Only with the fuse replaced (and no more light bulb) would useful charging current flow into the battery from the DC-DC converter.
Update, I just saw the new posts. It looks like the DC-DC is at least not shorted and may be trying to wake up. At this point I'd risk replacing the fuse and give it a try.
4-8V is interesting. It may be the DC-DC detecting the high resistance link to the 12V system through the bulb and responding accordingly. You may want to try a low amperage fuse in place of the bulb to test further. Maybe a 30A inline or similar. I'm still concerned as to how the heck that 225A fuse popped, but, have to start somewhere. It at least appears that the DC-DC is trying to do something anyway.
Otmar
EV Modder
If the terminal was shorted to the car body in the accident, that could have blown the fuse. IIRC he has (Edit, "had") a damaged connector on the DC-DC converter, indicating physical damage in the area.
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I'm curious, will the car charge the battery now if you disconnect the jumper cables to the truck? I'm guessing the DC-DC may be working.
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Keep in mind that the 12V load of the "running" vehicle can be pretty substantial. I've not tested this, but I've heard figures anywhere between 500-1000W (~35-75A, depending on voltage). If you look at how quickly most people lose 12V power once their DC-DC is disabled in other disabled Model S situations this would seem to fit. The 12V battery generally won't run the car for more than a short time (~10 minutes?) without the DC-DC or an external charger.
Ok, so i connected jumper cables to the car, the connected 12v battery with approx 12.4V on it. Car starts all good. No messages. Voltage on the battery side is 13.5V on the DC-DC 4-9V. Then i disconnected the jumper cables. The lighbulb started to blink about twice faster!!! Voltage on battery side is 12.2V on DC-DC 4-7 V. I sat in the car it started, no messages, after about 10 seconds i got message that 12v battery is low, unable to drive.
Otmar
EV Modder
I'd suggest shutting it down, disconnecting the 12V battery and then replacing the 225A fuse and powering it all up again.
Yeah, the car's DC-DC won't be able to charge the 12V battery through the light bulb since it will limit the current far too much for that. You'll need a replacement fuse first. But it looks like you'll probably be good to go as soon as you get that 225A fuse replaced.
spaceballs
Member
Do you have a bench power supply? or another 12v battery? I would connect the output of the DC-DC to 12v bench power supply (or another battery) keeping it isolated from the other 12v battery.. just to see what the voltages would be when you power the car on.
Question! I got that new 12V Red Battery, it has no contacts, so I had to buy kit, which is silly, few little things, for like $150, but anyways, I think i put it right, but my how to connect a positive terminal if there is basically NO TERMINAL. The negative looks ok thou. Am I missing something? Any idea???
I just received the 225amp fuse. So i installed it with the fully charged battery. After i connected the voltage reading was like 11.85V for some reason, even thou the battery was at around 12.5V. Car didnt start, i had a message that battery is low. But then i noticed that voltage started to go up, after its been connected now for about 20-30 min the voltage shows 12.4 V. Car still doesnt start because of the low battery message
Kalud
Active Member
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