Dash cam and 12v battery

[tchavei]

Hi

I have a stupid question. How does the 12v system work on a Taycan in terms of charging / discharging?

On ICE cars, the alternator will charge the 12V battery during normal operation so if one is to hardwire a dashcam, in Park mode, it will slowly discharge the battery until either the battery is dead or, if the dashcam comes with a voltage limiter, until the defined threshold is reached.

How is it on the Taycan? I've read contradicting statements.

Someone on this forum mentioned that the main battery will recharge the 12V whenever it's needed (even with the car turned off? Aka parked?) while I've seen others stating the 12V battery can fully discharge leaving the car inoperable until you kick-start it (which is a cumbersome process)

So I'm kinda confused right now.

Last year, someone backed into my MB while parked and I really wished I had a dashcam back then as it ended being a quite costly repair. I also had my Z3's paint job scratched with a key, 15 years ago at a supermarket. I really want to have a dashcam for the taycan (even if probably illegal here) but I'm worried about those rare, seldom moments when I have to leave my car parked for a week (maybe once or twice a year).

Of course I'm probably rushing things as I shouldn't have the car before late summer but I'm meticulous plan this kind of stuff months ahead.

Thanks for reading

Tony

Sponsored

 

[W1NGE]

Hi

I have a stupid question. How does the 12v system work on a Taycan in terms of charging / discharging?

On ICE cars, the alternator will charge the 12V battery during normal operation so if one is to hardwire a dashcam, in Park mode, it will slowly discharge the battery until either the battery is dead or, if the dashcam comes with a voltage limiter, until the defined threshold is reached.

How is it on the Taycan? I've read contradicting statements.

Someone on this forum mentioned that the main battery will recharge the 12V whenever it's needed (even with the car turned off? Aka parked?) while I've seen others stating the 12V battery can fully discharge leaving the car inoperable until you kick-start it (which is a cumbersome process)

So I'm kinda confused right now.

Last year, someone backed into my MB while parked and I really wished I had a dashcam back then as it ended being a quite costly repair. I also had my Z3's paint job scratched with a key, 15 years ago at a supermarket. I really want to have a dashcam for the taycan (even if probably illegal here) but I'm worried about those rare, seldom moments when I have to leave my car parked for a week (maybe once or twice a year).

Of course I'm probably rushing things as I shouldn't have the car before late summer but I'm meticulous plan this kind of stuff months ahead.

Thanks for reading

Tony

The 800v HV battery (the main battery) charges the 12v Lithium battery.

Porsche provide a Dashcam so clearly not an issue and so any 3rd party dashcam should work the same if wired the same.

 

[tchavei]

The 800v HV battery (the main battery) charges the 12v Lithium battery.

Porsche provide a Dashcam so clearly not an issue and so any 3rd party dashcam should work the same if wired the same.

Thank you for the information. So the whole "dead 12v battery" that surfaced around here a while ago, isn't a problem anymore?

Like I said, I'm pretty sure I only will leave the care once or twice a year for about a week. Good to know the battery should hold even with a 0.4Ah constant drain.

Maybe I'll still limit it to 12.4V just in case the small battery starts depleting.

Thank you

 

[tigerbalm]

I believe if the HV battery state of charge is less then 10% then the 12V battery may not be recharged from it and risks being depleted. Not an issue if your HV charge is higher.

 

[tchavei]

I believe if the HV battery state of charge is less then 10% then the 12V battery may not be recharged from it and risks being depleted. Not an issue if your HV charge is higher.

That's great to know. Thank you. Yeah, I don't intend on leaving the car at 10% even less if it will be at the airport for a week.

I guess that's one less issue to worry about.

Tony

 

[W1NGE]

Thank you for the information. So the whole "dead 12v battery" that surfaced around here a while ago, isn't a problem anymore?

Like I said, I'm pretty sure I only will leave the care once or twice a year for about a week. Good to know the battery should hold even with a 0.4Ah constant drain.

Maybe I'll still limit it to 12.4V just in case the small battery starts depleting.

Thank you

I believe so - bad software (again) which led to the original issue.

 

[800v]

The high voltage (HV) battery should recharge the 12V battery even when the car is off -- this used to be an issue but it should be no longer the case on updated and 2022+ models.
(however, I cannot find a specific mention of this from Porsche, it seems not to be in the manual as far as I can see; does anyone have a link to a conclusive source?).

But then, there is this:
- The HV battery will probably not maintain the 12V battery once the HV battery drops to 10% charge. This is unconfirmed though, and the source is from the Audi e-tron manual. It makes sense though, and I thought I once saw a mention of this in the manual but I cannot find it anymore.
- There is this recent thread (Nov 2022) where the battery discharged from a tracker where the dealer said that the HV battery will recharge the 12V battery at most 7 or 8 times. (again, unconfirmed).

Now, a 900x Plus + rear camera uses about 0.42A * 12V = 5w. So, it can run about 1000/(5*24) = 8.3 days on 1 KWh; a year of parking would be about 41 KWh so if you charge the HV to the recommended 80% you'll be good for a long time

The 12V battery in the Taycan seems to be 528Wh, and it would take about 4 days to discharge a full 12V battery. If the HV battery only recharges the 12V battery about 7 times, that would still be 28 days before the 12V battery might no longer be recharged.

So, if you drive enough it should be fine to hardwire a dashcam; and if you think you won't drive it for a longer time just disconnect the dashcam or make sure to hook up the car to a charger every month for a while (which is recommended anyways).

Someone should really test this and measure the 12V voltage over time and see how often it gets recharged; Wish Porsche would be more clear about this.

 

[tchavei]

The high voltage (HV) battery should recharge the 12V battery even when the car is off -- this used to be an issue but it should be no longer the case on updated and 2022+ models.
(however, I cannot find a specific mention of this from Porsche, it seems not to be in the manual as far as I can see; does anyone have a link to a conclusive source?).

But then, there is this:
- The HV battery will probably not maintain the 12V battery once the HV battery drops to 10% charge. This is unconfirmed though, and the source is from the Audi e-tron manual. It makes sense though, and I thought I once saw a mention of this in the manual but I cannot find it anymore.
- There is this recent thread (Nov 2022) where the battery discharged from a tracker where the dealer said that the HV battery will recharge the 12V battery at most 7 or 8 times. (again, unconfirmed).

Now, a 900x Plus + rear camera uses about 0.42A * 12V = 5.2w. So, it can run about 1000/(5.2*24) = 8.2 days on 1 KWh; a year of parking would be about 41 KWh so if you charge the HV to the recommended 80% you'll be good for a long time

The 12V battery in the Taycan seems to be 528Wh, and it would take about 4 days to discharge a full 12V battery. If the HV battery only recharges the 12V battery about 7 times, that would still be 28 days before the 12V battery might no longer be recharged.

So, if you drive enough it should be fine to hardwire a dashcam; and if you think you won't drive it for a longer time just disconnect the dashcam or make sure to hook up the car to a charger every month for a while (which is recommended anyways).

Someone should really test this and measure the 12V voltage over time and see how often it gets recharged; Wish Porsche would be more clear about this.

Very informative! Thank you. I guess I'll test it in some months if I get my allocation slot.

Now find a way to visually hide a viofo A139 Pro. Why did they place the lens on the right side of the body (and not the left side?)

Regards
Tony

 

[800v]

But then, there is this:
- The HV battery will probably not maintain the 12V battery once the HV battery drops to 10% charge. This is unconfirmed though, and the source is from the Audi e-tron manual. It makes sense though, and I thought I once saw a mention of this in the manual but I cannot find it anymore.
- There is this recent thread (Nov 2022) where the battery discharged from a tracker where the dealer said that the HV battery will recharge the 12V battery at most 7 or 8 times. (again, unconfirmed).

Answering myself , in the Audi e-tron documentation (which uses esssentially the same platform as the Porsche Taycan), it is explained how the 12V battery is recharged: see
https://static.nhtsa.gov/odi/tsbs/2021/MC-10190946-0001.pdf, page 127.

Assuming it is indeed the same on the Taycan:

- The 12V battery is indeed LiFePO4, nominal 13.2V at 40Ah (= 528Wh, as shown here). At 80% the voltage is 13.4V and at 100% it is 13.8V. The battery can operate beween 11V and 14.8V before a relay disengages it from the system (temporarily).

- If the car is "off", and the HV battery is above 10% and the 12V battery falls below 8Ah, it will be recharged from the HV battery. (and the car HV network is active)

- The recharging from the HV stops if either the battery becomes 20Ah (half-full) or 30 minutes have passed. (and the car HV network is off again)

- This happens at most 8 times (!) (while the car is "off", i.e. terminal 15 is off).

For a 900x plus with rear camera which uses about 0.42A*12V = 5w, if we start parking with a "half-full" battery, we get (20-8) = 12Ah before the first recharge to 20Ah again, so a total of 9*12Ah*13.2V = 1425KWh, and thus about 1425/(5*24h) = 11.8 days before the 12V battery will no longer be recharged.

So, it seems pretty safe to hardwire a dashcam but it will eventually drain the 12V battery. So, it would be good to also set the parking safety on a 900X (or use a power magic pro) to, say, 12.5V, to have the camera switch off in case the 12V battery gets low. (and I think you can limit the 900X also to turn off after 48 hours).

 

[tchavei]

Answering myself , in the Audi e-tron documentation (which uses esssentially the same platform as the Porsche Taycan), it is explained how the 12V battery is recharged: see
https://static.nhtsa.gov/odi/tsbs/2021/MC-10190946-0001.pdf, page 127.

Assuming it is indeed the same on the Taycan:

- The 12V battery is indeed LiFePO4, nominal 13.2V at 40Ah (= 528Wh, as shown here). At 80% the voltage is 13.4V and at 100% it is 13.8V. The battery can operate beween 11V and 14.8V before a relay disengages it from the system (temporarily).

- If the car is "off", and the HV battery is above 10% and the 12V battery falls below 8Ah, it will be recharged from the HV battery. (and the car becomes "on", terminal 15 is active)

- The recharging from the HV stops if either the battery becomes 20Ah (half-full) or 30 minutes have passed. (and the car turns "off" again, terminal 15 is off)

- This happens at most 8 times (!)

For a 900x plus with rear camera which uses about 0.42A*12V = 5w, if we start parking with a "half-full" battery, we get (20-8) = 12Ah before the first recharge to 20Ah again, so a total of 9*12Ah*13.2V = 1425KWh, and thus about 1425/(5*24h) = 11.8 days before the 12V battery will no longer be recharged.

So, it seems pretty safe to hardwire a dashcam but it will eventually drain the 12V battery. So, it would be good to also set the parking safety on a 900X (or use a power magic pro) to, say, 12.5V, to have the camera switch off in case the 12V battery gets low. (and I think you can limit the 900X also to turn off after 48 hours).

Wow! What a deep insight into the charging/mantainance procedure. Thank you! This single post not only answers 95% of all my questions but probably also explains 99% of all other recent battery threads about discharged taycans.

This should be pinned to be honest.

Thanks!

PS: I'm very inclined to go for the Viofo A139 Pro Dual Dash Cam setup as it seems to me that the Blackvue is more cloud oriented which I have no need for. Installation wise, the Blackvue might be more appealing though. The A139 Pro has a weird footprint and will required to be installed on the left side of the mirror.

 

[sveinaan]

https://www.taycanforum.com/forum/t...a-of-the-12v-battery.1274/page-37#post-205015

 

[whitex]

Answering myself , in the Audi e-tron documentation (which uses esssentially the same platform as the Porsche Taycan), it is explained how the 12V battery is recharged: see
https://static.nhtsa.gov/odi/tsbs/2021/MC-10190946-0001.pdf, page 127.

Assuming it is indeed the same on the Taycan:

- The 12V battery is indeed LiFePO4, nominal 13.2V at 40Ah (= 528Wh, as shown here). At 80% the voltage is 13.4V and at 100% it is 13.8V. The battery can operate beween 11V and 14.8V before a relay disengages it from the system (temporarily).

- If the car is "off", and the HV battery is above 10% and the 12V battery falls below 8Ah, it will be recharged from the HV battery. (and the car HV network is active)

- The recharging from the HV stops if either the battery becomes 20Ah (half-full) or 30 minutes have passed. (and the car HV network is off again)

- This happens at most 8 times (!) (while the car is "off", i.e. terminal 15 is off).

For a 900x plus with rear camera which uses about 0.42A*12V = 5w, if we start parking with a "half-full" battery, we get (20-8) = 12Ah before the first recharge to 20Ah again, so a total of 9*12Ah*13.2V = 1425KWh, and thus about 1425/(5*24h) = 11.8 days before the 12V battery will no longer be recharged.

So, it seems pretty safe to hardwire a dashcam but it will eventually drain the 12V battery. So, it would be good to also set the parking safety on a 900X (or use a power magic pro) to, say, 12.5V, to have the camera switch off in case the 12V battery gets low. (and I think you can limit the 900X also to turn off after 48 hours).

I wonder why they would set a 30 minute and 8 times limits, vs. say an SoC limit of the HV battery (like Tesla does, they also send warnings to the phone app if 12V battery discharges too quickly). While it makes sense to limit the HV battery discharge, if the 12V battery is dead, you're likely calling a tow truck anyways, so would you rather come back to a half discharged HV battery but able to start and drive the car, or a dead car you cannot even get into? Also, if the car is plugged in and the HV SoC can be replenished, 8 times limit makes no sense at all (you leave your car plugged in, come back to a dead car because 12V battery stopped recharging).