High and Low Voltage Battery Issues

[bigjoefatz]

My 2017 Model X P100D HV battery went dead with 4% (9 miles) SOC displaying on the dash. Couldn't move the car, nothing (even though, there was supposedly 4% of charge in the car)

Called the tow truck, they flatbedded the car to the supercharger a mile away.

Got the car hooked up to a supercharger, but the Low Voltage battery immediately displayed the "schedule service message - low voltage battery needs to be replaced" message. FWIW, I replaced the low voltage battery 11 months ago (my first low voltage battery lasted for 4 years). I've driven the car for about 100 miles now since the low voltage message warning and the message is still displaying (my high voltage pack is now at 70%)

1. Do you think there is an issue with my HV battery/battery management system?

2. Do you think I need a new low voltage battery or is it possible that the low voltage error just needs to be hard reset?

Thanks all.

 

[Tam]

My 2017 Model X P100D HV battery went dead with 4% (9 miles) SOC displaying on the dash. Couldn't move the car, nothing (even though, there was supposedly 4% of charge in the car)

Called the tow truck, they flatbedded the car to the supercharger a mile away.

Got the car hooked up to a supercharger, but the Low Voltage battery immediately displayed the "schedule service message - low voltage battery needs to be replaced" message. FWIW, I replaced the low voltage battery 11 months ago (my first low voltage battery lasted for 4 years). I've driven the car for about 100 miles now since the low voltage message warning and the message is still displaying (my high voltage pack is now at 70%)

1. Do you think there is an issue with my HV battery/battery management system?

2. Do you think I need a new low voltage battery or is it possible that the low voltage error just needs to be hard reset?

Thanks all.

It's a process of elimination.

When your main battery is low, it no longer charges your 12V battery, so that doesn't mean your 12 battery is bad. Thus, you must charge your main battery up to see if your 12V battery recovers.

When your 12V battery is bad, it would usually throw numerous errors then the car dies even though you have plenty of range left in your main battery. In this case, you need to change your 12V battery.

 

[bigjoefatz]

Tesla thinks the 12v is causing the HV to crap out early. They replaced the 12v under a 1 year warranty for repairs (I had 21 days left in the warranty period - so I guess I was fortunate?)

Is there anyway to figure out if this is going to be a continual problem or do I need to get stuck in the Mojave desert again ? Do I need to measure my battery life every so often?

 

[DCGOO]

Tesla thinks the 12v is causing the HV to crap out early. They replaced the 12v under a 1 year warranty for repairs (I had 21 days left in the warranty period - so I guess I was fortunate?)

Is there anyway to figure out if this is going to be a continual problem or do I need to get stuck in the Mojave desert again ? Do I need to measure my battery life every so often?

It will likely be a continuing problem. Every couple of years count on replacing the 12v battery. In my 2018, I replaced it twice in the four years I had the vehicle. Some folks have managed to get three years out of it, but I wouldn’t count on it.

OTOH, my Model 3 is coming up on four years with the original 12v battery.

 

[bigjoefatz]

I got 5 years out of my first 12v.

They also told me that supercharging affects the 12v life. Is that really true?

 

[henderrj]

supercharging affects the 12v life. Is that really true?

Not a chance.

By the way, I had the original Ohmu battery (when Sean still owned it). Worked great for 6 years, 200k miles. Battery still okay, connector went bad. The convenience might be worth the price. Although I have no experience with the company since he was bought out.

 

[bigjoefatz]

I know my HV pack is going. Supercharging takes longer. Running out of power with 3% SOC left. What's next?

 

[henderrj]

I know my HV pack is going. Supercharging takes longer. Running out of power with 3% SOC left. What's next?

Neither of these are a sign the battery is dying.

The BMS can only get close to accurate when you charge the battery to 100% and then down to 0 a few times. Since this is neither practical nor good for the health of the pack people don't (and shouldn't) do it.

The good news is that your BMS now has a better fix on where the bottom is. So, for at least a few months, it will be more accurate. Although I must ask - did you run your ice car until the needle was resting on the E pin?

As to the slower charging, there are many factors that could cause this. The cold weather is the most likely culprit. But Tesla does slow supercharging as the batteries age to increase their longevity. My S has 260K miles on the original battery - I rarely see better than 90 kw when supercharging.

 

[bigjoefatz]

Yes I did run my ice car down to E.