[Electric Tire Shredder]

can an empty 12V drain the HV?

I'd still like to know if your auto-saved OBD log shows any HV damage.

My phone doesn't seem to want to open the file, & if yours won't either but you're better than me at Google Drive, the app gives you that option with just two taps (click to enlarge):

Of you can do like I did & plug the phone into a computer to open the file from there:

What you're looking for is something like this:

0% is about 3200mV, & there shouldn't be more than about 20mv difference between min & max.

 

[e500]

Ya, & a weak 12V without the U69 can't go dead, until after the HV has emptied itself trying to keep the 12V full.

I am trying to understand this better. What does the U69 do?
at what level is a 12V considered full?

 

[Electric Tire Shredder]

U69 prevents the HV drive battery pack from charging the 12V starter battery if the key is off & the car is unplugged.

A healthy 12V lead-acid battery is considered full at around 12.8V


U69 may be easier to understand as a chronological story:

Originally the car was programmed so that when it was parked unplugged, if the 12V got too low, the HV would charge it, so theoretically you wouldn't be stranded by a dead starter battery.

That makes sense until you realize that if you happen to park with the HV low, &/or leave it long enough, it will eventually damage the $6,000 HV by draining it too low. This becomes more likely as the 12V wears out.

So they created a "customer satisfaction campaign" called U69 which deletes the parked-12V-charging function.

 

[e500]

I'd still like to know if your auto-saved OBD log shows any HV damage.

My phone doesn't seem to want to open the file, & if yours won't either but you're better than me at Google Drive, the app gives you that option with just two taps (click to enlarge):
View attachment 113866 View attachment 113867

Of you can do like I did & plug the phone into a computer to open the file from there:
View attachment 113868
What you're looking for is something like this:
View attachment 113870
0% is about 3200mV, & there shouldn't be more than about 20mv difference between min & max.

U69 prevents the HV drive battery pack from charging the 12V starter battery if the key is off & the car is unplugged.

A healthy 12V lead-acid battery is considered full at around 12.8V


U69 may be easier to understand as a chronological story:

Originally the car was programmed so that when it was parked unplugged, if the 12V got too low, the HV would charge it, so theoretically you wouldn't be stranded by a dead starter battery.

That makes sense until you realize that if you happen to park with the HV low, &/or leave it long enough, it will eventually damage the $6,000 HV by draining it too low. This becomes more likely as the 12V wears out.

So they created a "customer satisfaction campaign" called U69 which deletes the parked-12V-charging function.

Hi, I just found a great video that explains how to determine if a battery is dead very well however as the presenter shows some battery brands and gadgets I am not certain if that is against posting rules and hence will not post the link here but you can find it if you look for how to test a bad battery.

What happened with my car is that I was told I had a bad battery which struck me as odd as it had been replaced recently so while I agreed to have it replaced I held on to the battery and took it home where I trickle charged it and have been testing it daily for a week now and its holding the charge nicely. So it seems like my 12 V battery is not the cause of the issue.

 

[Electric Tire Shredder]

It may not be the cause of the issue, but you did report that your 12V battery died:

When I first got back the car still turned on so it wasn't dead at that point, however it did die and I then recharged it on a drip

So when you got back from vacation it was very close to dead. A 500e can start with the 12V battery 90% drained, so "dead" can be even more drained than that.

Going back to the beginning of your situation...:

Car was running great, went on vacation, when I came back... limited power mode... wouldn't charge... two recalls one of them being U69... they said the 12V needed to be replaced even though it was just a little over a year old... no clunk sound even after the new battery had been installed.

Here are some of the relevant facts. Please correct me if I'm wrong about any that are specific to your car:

• In 23 months, a 500e can completely wear out a 12V to the point where it dies overnight.
• Your 12V was over half that age, so maybe over half worn out, taking 16 hours to die.
• Then it was parked unplugged for a vacation.
• It didn't have U69, so when the 12V went low, it would be charged by the HV, until the HV was drained.
• After the vacation, the 12V was very nearly dead, & then died completely, indicating the HV was no longer charging it, so the HV must have been fully drained before the end of the vacation.
• The only code that won't clear is for HV battery failure.

That all seems to indicate HV battery damage, however:

• A 500e will often show false error codes when its 12V is allowed to go dead.
• The code clearing attempts were done with a dead starter battery (90% drained, at 11.3V).
• You haven't tried the contactor reset in post #1 of this thread.

 

[53tmills]

Yes, that is correct. There is also a guy in Canada who did the individual cell charging after taking out the battery pack:

Fiat 500e – My Website

mandmwaddle.ca

It looks promising, but I was waiting to hear back from him on how the car performed afterwards..

Mike Waddle's approach is excellent. It looks at the basics behind all EV production vehicles (this isn't rocket science). You can buy a "programmable" charger for less than $100 Cdn. I've had good results with the Tenergy 100watt RC charger on other batteries. You can also buy new Samsung batteries to rebuild your pack, if necessary.

 

[Jiri GrandPa]

U69 prevents the HV drive battery pack from charging the 12V starter battery if the key is off & the car is unplugged. A healthy 12V lead-acid battery is considered full at around 12.8V U69 may be easier to understand as a chronological story: Originally the car was programmed so that when it was parked unplugged, if the 12V got too low, the HV would charge it, so theoretically you wouldn't be stranded by a dead starter battery. That makes sense until you realize that if you happen to park with the HV low, &/or leave it long enough, it will eventually damage the $6,000 HV by draining it too low. This becomes more likely as the 12V wears out. So they created a "customer satisfaction campaign" called U69 which deletes the parked-12V-charging function.

This is not precisely correct. HV battery will still charge 12V battery if it has enough charge. U69 will prevent it to discharge too much. not sure what the limit is ( writing this on the phone) but I think it’s certainly less than 25% of SOC.

 

[Electric Tire Shredder]

That's a nice theory, but does not match my actual measurements:

Even at 60% SOC my HV battery did not try to charge the 12V while parked unplugged.

With the car at about 60% SOC, I was testing how long a brand new tiny 3Ah 12V starter battery would take to discharge. After 6 days, it was discharged too far to start the car, so the HV had not charged the 12V.

If the HV charged the 12V, it would be impossible to get readings like these, especially with a brand new battery which was subsequently able to accept a full charge, & hold it, working fine after the test.

 

[Electric Tire Shredder]

mine show 47% not charging car 12v battery was bad any help?

Start with post #1 on page 1 of this thread (click here).

 

[Electric Tire Shredder]

If it was sitting a long time unplugged, the first thing to check is item #1 of the pre-purchase list here:

500e Pre-Purchase Checklist

Check all the standard stuff like tires, lights, wipers, locks, windows, etc. but there's no engine, transmission, clutch, fuel pump, timing belt/chain, starter or alternator to worry about, & even the brakes last over 100k since they only activate below 7mph because above that it's all...

www.fiat500owners.com