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Discussion Starter · #1 ·
I had a curious incident the other day: I came home from a 7-day trip to find my XC40 Recharge completely without power. I couldn't even use the battery-powered keys to unlock the car, and every feature of the car was not working. I had been monitoring the status of the charge using the app (as much as possible, since the app is a bit glitchy and won't always report the charge to me). Just a couple days before this incident, I was at 77 percent charge (down from 87 percent when I left). At most I've seen the car lose 5 percent of its charge overnight in the past, so I find it hard to believe that it lost all of its charge in the intervening couple of days. I'd be curious about whether people have any insight into what might have happened. Could it be the 12-volt battery went dead? Maybe, but when the tow truck came we powered the 12-volt battery and the electronics came on (with a lot of errors and glitches) and the readout said the main battery was at zero. I'm at a loss and find it hard to believe that the car could lose that much battery over such a short amount of time just sitting in the driveway.
 

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This has happened to a few people on here. You can search the board.

It had been caused by a faulty 12 volt for others.

Is you car working? Have you taken it to a dealer?

I wondering using the app slot can drain the 12 volt ….
 

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I have reported this happened to me three separate times. It had nothing to do with the 12 volt battery in my case. It was a TCAM failure caused by a leaking shark fin antenna. The TCAM allows communication of the main battery to the car system.

Even if t he battery has a charge, the system will not report the charge level. And, the system will not allow charging.

In my case the problem was intermittent. After each tow to the dealer, they "fixed" the issue with a simple software re installation. The third time they replaced the TCAM and issues a recall on the leaky shark fin antenna.

For what it's worth, since the TCAM replacement and sealing the antenna, the GPS/LTE and internet have worked without a hitch and the car is functioning.

If you want to confirm it's not the 12 volt battery, the car can be jumped. There are multiple posts on how to do this. In my case, this never worked.

This is from the manual

 

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Discussion Starter · #4 ·
This has happened to a few people on here. You can search the board.

It had been caused by a faulty 12 volt for others.

Is you car working? Have you taken it to a dealer?

I wondering using the app slot can drain the 12 volt ….
I wonder about that too--the app has always been glitchy for me, and I wonder if it got stuck with one of the requests for battery status and drained all the 12 volt battery. It must be something to do with the battery, because I am checking my app now and it says the main battery is at 74 percent. At any rate, it's down at the dealer now, so I hope I'll have some updates on what went wrong soon.
 

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Discussion Starter · #5 ·
Update: the dealer took a look at the vehicle and basically said there wasn't anything wrong with the vehicle that a total software update couldn't solve. Not a lot of specifics. They just said something drained the 12 volt battery--could have been "frequent use of the app on your phone" or the keys being located too close to the vehicle. Who knows? I was told that the battery itself was fine, but I have to wonder what kind of "good" battery drains over the course of a week. Lots of cars sit without use for a week and have no problems.

I'm having a 240V outlet installed this week so hopefully that will prevent this from happening again (the 12V is charged when the car as a whole is charging, right?). Because my car couldn't charge with the 120V (for other reasons logged in another thread), the car wasn't charging the whole time I was gone. Apparently you really have to have the car plugged in if you're not using it if you don't want this kind of failure to happen--nuts.
 

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Update: the dealer took a look at the vehicle and basically said there wasn't anything wrong with the vehicle that a total software update couldn't solve. Not a lot of specifics. They just said something drained the 12 volt battery--could have been "frequent use of the app on your phone" or the keys being located too close to the vehicle. Who knows? I was told that the battery itself was fine, but I have to wonder what kind of "good" battery drains over the course of a week. Lots of cars sit without use for a week and have no problems.

I'm having a 240V outlet installed this week so hopefully that will prevent this from happening again (the 12V is charged when the car as a whole is charging, right?). Because my car couldn't charge with the 120V (for other reasons logged in another thread), the car wasn't charging the whole time I was gone. Apparently you really have to have the car plugged in if you're not using it if you don't want this kind of failure to happen--nuts.
You had said before you checked the app a lot. What defines a lot? As a someone with ocd a lot can mean … A LOT. Curious.

Does anyone know the power drain when we fire up the app? Does the whole computer have to boot up? (Mmm would this explain why sometimes it takes a while to work …)

Someone had a remove voltage meter … does that show any effect when the remote app logs in?
 

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Update: the dealer took a look at the vehicle and basically said there wasn't anything wrong with the vehicle that a total software update couldn't solve. Not a lot of specifics. They just said something drained the 12 volt battery--could have been "frequent use of the app on your phone" or the keys being located too close to the vehicle. Who knows? I was told that the battery itself was fine, but I have to wonder what kind of "good" battery drains over the course of a week. Lots of cars sit without use for a week and have no problems.
Given how little functionality the app offers, it’s hard to believe anyone could use it enough to drain the battery. This car exhibits too much unexplainable behavior.
 

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If waking up the computer with the app caused it to use X Watts of power for Y minutes. How many times could you do that with the cars 12 volt battery before you drained it? What would we guess X and Y to be?

Anyone snuck up on their car without the remote and watched to make sure no screens turn on when you fire up the app from your phone? It would be bad if they did just curious if we know for sure they do not.
 

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If using the app really places a significant load on the 12-volt, it should come with a gigantic, flashing warning every time you open it.
Ha!!! That would be good. I have left my car for a week a few times due to health issues and have used the app a bit obsessively to see if it was still working and never had a battery problem.

I suspect faulty battery or faulty, circuits or software.
 
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Discussion Starter · #12 ·
You had said before you checked the app a lot. What defines a lot? As a someone with ocd a lot can mean … A LOT. Curious.

Does anyone know the power drain when we fire up the app? Does the whole computer have to boot up? (Mmm would this explain why sometimes it takes a while to work …)

Someone had a remove voltage meter … does that show any effect when the remote app logs in?
Like once a day. I did leave it open on my phone (I'm bad at closing apps). Wonder if that matters...
 

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Like once a day. I did leave it open on my phone (I'm bad at closing apps). Wonder if that matters...
There is no way the app drains the battery - - I have had the app on and in the garage and there is no extra noises from the car on any indications on the screens that anything is on using power.
 

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Discussion Starter · #14 ·
There is no way the app drains the battery - - I have had the app on and in the garage and there is no extra noises from the car on any indications on the screens that anything is on using power.
Yeah, I wouldn't think so, but that's what they insisted. I'm getting really frustrated with the responses I've gotten from Volvo dealers on this issue and others. It seems like they just throw out hypotheses and pray that a software update will solve everything. IMO it's just unacceptable to spend $60k on something that is this faulty.
 

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I had a curious incident the other day: I came home from a 7-day trip to find my XC40 Recharge completely without power. I couldn't even use the battery-powered keys to unlock the car, and every feature of the car was not working. I had been monitoring the status of the charge using the app (as much as possible, since the app is a bit glitchy and won't always report the charge to me). Just a couple days before this incident, I was at 77 percent charge (down from 87 percent when I left). At most I've seen the car lose 5 percent of its charge overnight in the past, so I find it hard to believe that it lost all of its charge in the intervening couple of days. I'd be curious about whether people have any insight into what might have happened. Could it be the 12-volt battery went dead? Maybe, but when the tow truck came we powered the 12-volt battery and the electronics came on (with a lot of errors and glitches) and the readout said the main battery was at zero. I'm at a loss and find it hard to believe that the car could lose that much battery over such a short amount of time just sitting in the driveway.
The same thing happened to my XC 40. I was away for 10 days and the car went into “sleep mode” as the Volvo “on call” person called it. No power whatsoever, dash was blank, remote didn’t work and I could not even set the “tow mode”. Took car to dealer using proper tow system and waiting for a diagnose. I was not aware there is a 12 volt battery on board. I would be very interested in knowing if other owners received feedback from dealer? In similar cases? I am getting very worried about battery reliability and performance. I only get about 185 usable miles as compared to the 220 miles claimed by Volvo. Any comments?
Oscar
 

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I don't even fully understand why there is a need for a 12v battery either. I get many of the legacy car systems are designed to run off 12v, but surely they could just use an inverter and step down part of the high voltage battery to 12v to run these systems. That would save having to carry around a heavy lead acid (or whatever) battery up the front and would prevent anybody from having a "flat 12v battery" every again.
 

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I don't even fully understand why there is a need for a 12v battery either....surely they could just use an inverter and step down part of the high voltage battery to 12v to run these systems....
The consensus is that an EV's12V battery allows the car's HV battery to be completely disconnected from the car as needed for safety, etc with some of the vehicle's systems still operating. But I haven't read any direct info from an actual EV engineer.
 

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I don't even fully understand why there is a need for a 12v battery either. I get many of the legacy car systems are designed to run off 12v, but surely they could just use an inverter and step down part of the high voltage battery to 12v to run these systems. That would save having to carry around a heavy lead acid (or whatever) battery up the front and would prevent anybody from having a "flat 12v battery" every again.
Google is your friend
 

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I don't even fully understand why there is a need for a 12v battery either. I get many of the legacy car systems are designed to run off 12v, but surely they could just use an inverter and step down part of the high voltage battery to 12v to run these systems.
I think there's a couple reasons - first is safety, always keeping the high-voltage battery disconnected from the rest of the car except when needed for driving, running AC/heat pump, or periodically charging the 12V battery. And that connect/disconnect system is a big relay, which requires power from (you guessed it) a 12V battery.

Second is protecting the big expensive battery from power drain & faults in the low-voltage system. Obviously this should never happen - but if it does, better to drain the cheap 12V battery first. It's my understanding the first-gen Tesla Roadsters did exactly what you suggest - no 12V battery, run everything off main traction battery with step-down transformer, etc - and they had lots of main battery failures. Resulting in a 12V battery being added to the second-gen Roadsters, and pretty much every EV since.

Also there's no reason our 12V batteries have to be lead-acid or AGM - except cost. Tesla is now using 12V Lithium-Ion in their high end Model S and Model X.
 

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Google is your friend
I sure like this idea and hope it catches on.

From caranddriver.com:
Hyundai, for instance, considered the absurdity of jump-starting an electric car or hybrid and connected its low-voltage systems to the large traction battery, allowing electrified Hyundais to jump-start themselves when you push the "12V Batt Reset" button on the dash. And while that button conjures an image of your standard AC Delco lead-acid, the low-voltage systems are actually run by a 14-volt lithium-ion battery that sits inside the high-voltage battery pack. You won't find that at the local auto-parts store.

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