Frustrated by EV 12v battery issues!

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Mark W

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I have been an owner of various EVs and PHEVs for 4 years now.

I started my "EV" life by buying a 2003? Gen 1 Prius for my daughter, then a Gen 2. Then about 4 years ago I bought a Leaf, then a Clarity, then a Hyundai Ioniq Electric, and recently a 2017 Bolt. My main reason for driving EVs is I like the way they drive and I like the low cost of ownership and less maintenance and things to go wrong. At this point, I do have to admit that 12v battery issues have been a huge PITA with all my EVs.

12v batteries on all cars wear out and have to be replaced. With ICE vehicles, it is very clear when that is the case. Engine becomes slower to turn over. If you ignore it long enough, the car doesn't start one day, and you know it's time to replace it. With my EVs however, issues with the 12v battery present themselves in other ways. You start seeing maybe weird messages that sound ominous.

Leaf - I don't remember what the specific messages I got were, but I know in my two years of ownership I had to replace the 12v once.
Inoniq Electric - Was seeing some strange serious sounding messages. I was not able to drive it one day. Dealer installed new 12v under warranty. A few months ago, had strange screen issues, car would not go into gear. Had to disconnect the battery. Problem has not returned to this point.
Bolt - (Yesterday, have owned it for two months) Got Propulsion Power Reduced message and then car would not drive at all. Yellow light on dash. After several hours parked, was able to get it home, still with yellow light. Searching on Bolt forum, current theory is 12v needs to be replaced. Not proven yet.

My apologies for not remembering all of the details, but in all cases with the EV, there was no way to know the 12v battery was the issue, and you could not just jump start the car to get where you needed.

Do I have to do something to maintain my 12v batteries better in my EVs? Do I have to buy a battery tester? I'm just frustrated right now. I keep telling my family that EVs are more reliable, but keep having problems related to the battery. Thanks for listening and any suggestions.
 
The MINI Cooper SE automatically takes care of the 12 V battery via the high-voltage batteries, and warns when the 12 V battery discharges when the car is off (something I have personal experience with, turned out to be a button on the remote being pushed keeping the car from going to sleep). The SE will not move without a working 12 V battery.

MINIs use AGM batteries, which handle deep cycling better. But I've still had them fail over time. I would like to switch to a lithium-ion 12 V battery, not sure why car manufacturers aren't using them in BEVs. They're about in the same price range as AGM batteries now.
 
The 12V battery health in an EV can be a problem. Once the car 'starts,' the traction battery-to-12V inverter drives the battery voltage, not the battery itself. So I'm going to suggest trying to read the car off, unloaded voltage:
  • below 12V with no load - time to replace. 12.85V is a new battery
  • find access to the 12V terminals and leave access open
  • park car and give it 15-30 minutes to shutoff
  • measure 12V battery voltage
You may want to raise the same question in vehicle specific forums as they may recommended practices.

Bob Wilson
 
But yeah this needs to be fixed industry wide. Nearly every manufacture suffers from it, so I assume it's not as simple as one would assume (I have a fair few ideas how to handle it better, but I doubt they're better than the engineers around the world).

Teslas solution seems to be to move to lithium ion 12v battery plus my assumed software diagnosis.
 
Counterpoint, my Prius never had 12V problems without a clear cause, such as a friend [?] leaving the
dome light on half the night. The rail from the DC/DC would always come right up to 14V or so, and
car-off quiescent current once housekeeping settled down was about 11 mA. There was no funny
stuff trying to run in the background, like bluelink attempting to phone home. The Yellowtop I put
in it after the stock flooded-cell bulged lasted a solid 8 years.

_H*
 
hobbit said:
Counterpoint, my Prius never had 12V problems without a clear cause
Click to expand...
Different climates lead to different experiences. Boston (I believe that's your location) is a somewhat mild climate. Where I live our winters are extremely cold, and there's a lot of hard starting in subzero temperatures that can really take a toll on batteries (not true with BEVs, of course, since there's no cranking the engine). And I have family in Albuquerque, where battery problems are really common because of the constant strong sun.
 
You would think having an always on battery maintainer powered from the traction battery and an AGM would prevent most of the 12V battery issues outside of age. The battery would always be fully charged and ready until it finally sulfates up from age. The amount of juice pulled off the traction battery would be minimal to keep the 12V topped off especially on a full EV.


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Tesla is going to LiON for the 12 V battery and one of the Korean EV makers built the 12 V battery source into their traction battery pack.

Bob Wilson
 
Uggghhh.... OP checking back in. My situation has gotten worse. The problem with the Bolt has been diagnosed as a bad wiring harness. Bad news is they say that is not covered under the powertain or battery warranty. $1000.00. Worse news... the harness is on back order with no ETA. Been that way since December 29th. And now, the electrical problems with my Ioniq Electric have returned. Screen is blank multiple lights on the dash. Both EVs are out of commission. This is very frustrating.
 
I don’t understand how a Bolt you owned for two months is not covered under a powertrain warranty. Was it used? There was a battery recall for fire issues, I wonder if a shoddy repair damaged your harness. I would call Chevrolet and elevate the issue.


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Mad_River said:
I don’t understand how a Bolt you owned for two months is not covered under a powertrain warranty. Was it used? There was a battery recall for fire issues, I wonder if a shoddy repair damaged your harness. I would call Chevrolet and elevate the issue.


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Click to expand...
Yes, I should have been clearer above, it is a 2017 Bolt that I just bought two months ago. The battery has not been replaced yet. I tried the GM EV Concierge line, they were no help. I did talk to the dealer this morning, and they are going to try something else with GM supposedly. I am just desperate to get it back at this point. I may need to rent a car.
 
The Chevy dealership agreed to replace the harness under warranty, and the part will be in tomorrow. So, at least I will get that back soon. I got an appointment for the Ioniq at a dealer that's kind of far away and no loaner, but at least it will get looked at.
 
When we travel (used to travel) for several months, we would put a smart charger on our garaged 2017 Bolt. Works well. Recently we were looking at a phev Hyundai Tucson for our other car. They use a Li battery system. Manual requires it be started and driven every couple of weeks. No smart charger workaround. Too bad it didn't fit our lifestyle. There is something to be said for lead acid batteries.
 
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