[kgundbolt]

I leased a brand new Bolt on 09/14 and on 12/7 it stalled. There was 143 miles battery power left and when I went to go home in the evening, it did not respond to my remote. Called the customer service and we did some troubleshooting (after opening the door with the key). Later it was towed to a nearby dealership (Fremont, CA).

As of today, 12/12, I have no clue on what is going on?

I called the customer care and as usual the call went to their call center in Philippines. I spent about 30 minutes explaining the agent to document the issue. It was escalated to their US counterparts and I got call from them this afternoon. I needed to explain everything again. I was told that they will reach out to the dealership and update me. They chorus with the dealership words on the loaner.

Later I got a call from the dealership and they said that the computer battery is dead and they ordered a replacement battery that would, perhaps, arrive tomorrow and they will start the troubleshooting after they install this battery. Until then they can not think of even offering me a loaner. When asked if I can expect the car by the end of this week, I was given a NO.

I am really disappointed. Not sure what other issues I need to go through until the lease ends in August 2021.

 

[NY-Rob]

The "computer battery" is the 12v AGM battery under the hood.

 

[drrjv]

Not what I like to hear :-(

 

[devbolt]

There’s been a rash of 12V battery failures with later production Bolts. Either it’s a faulty module that controls the 12V charging, or a batch of bad 12V batteries. Both cases are more or less easily fixed, but oh so annoying. A regular ICE vehicle can have the same problem, so it’s not necessarily restricted to the Bolt.

 

[just frank]

Or it could be a rash of bad 12V battery charge controllers in the Bolt.

Or it could be a marginal design of said controller that reveals weakness in the AGM batts.

 

[BlackBolt]

When I was doing my testing for the "camping mode" and long duration inverter backup power testing, the APU often dropped down to 12.6V, well below float voltage for AGM. I believe it does this to conserve energy from the main pack (ask any off-grid solar guy how much energy is burned keeping batteries at float voltage), but the trade off is less time spent truly conditioning and preventing sulfation of the lead acid battery - which is not good news for one that has been allowed to run low while sitting in inventory. After being drained heavily (below 12.3V), AGMs can do with 12+ hours at steady high voltage charge to recover what's left of the battery at that point. Unfortunately they can't truly be equalized to recover specific gravity like a flooded battery can.

The battery in my car is sitting at 12.59V at rest. If it was being fully charged, because it is only a few months old, 12.8V would be the expected resting voltage. Currently, I believe it is being chronically undercharged, and sits daily at about 75% state of charge best-case, which is a death sentence coming due, sooner or later.

I'd pick up one of those small $30 lithium jump start battery packs, they take up very little space and you can limp along until you can get a new battery. I have a few battery tenders, I'm thinking of putting one of the pigtails on the Bolt so I can check voltage on the fly with my DMM and give it a top up to keep the AGM kicking for a few years.

 

[ibboltin]

Or it could be a rash of bad 12V battery charge controllers in the Bolt.

Or it could be a marginal design of said controller that reveals weakness in the AGM batts.

I think the latter is an assumtion that leads to fake news

Let not conflate possible multiple issues into a design flaw. There could be a batch of bad batteries, and bad controllers at the same time. There also could be drained batteries, most modern cars very much misbehave when battery voltage is not at its best.

But then again if on month 3 i get a failure like the OP then ill be here stating my issue too!

 

[surgeonFWW]

I would think that any dealer who is prepping an EV for pickup would charge not only the HVB, but also clamp a charger to the 12V and make sure it has (and holds) a full charge!

 

[wonderbolt]

I would think that any dealer who is prepping an EV for pickup would charge not only the HVB, but also clamp a charger to the 12V and make sure it has (and holds) a full charge!

Should not be required if the system is operating as designed. HV battery should maintain 12V battery, charging the vehicle should be all that is required.

 

[surgeonFWW]

Should not be required if the system is operating as designed. HV battery should maintain 12V battery, charging the vehicle should be all that is required.

There are numerous threads that say the 12V battery in EVs is not kept in as good a condition (as an ICE vehicle keeps its 12V) by the usual events of starting and HVB charging, especially if the EV has sat for 1-2 months without being driven or charged. I still treat my 12V to a "trickle of love" every month for good measure. I have to think that some (not all) of these 12V failures are the result of sitting around unused for months. But I may be wrong...

 

[BlackBolt]

Right, it's pretty clear looking at the charging behavior and the different charge modes that were posted in some other thread from the service manual, that the lead acid charge profiles are designed for efficiency. This naturally comes at the expense of battery life. It's not "wrong" or "broken" behavior, it's just what they traded off in engineering. Efficiency > Lifespan, they picked one and optimized for it.

If the lead acid battery has ever been abused by letting the voltage drop, the Bolt's charging system is like third world hospice care, vs. extreme life saving measures. If the dealer tech or you don't give it a heavy long duration topping charge as soon as it's found to be low, the specific gravity in the mat layers will never fully recover - and that's the insidious nature of the progressive disease of death in (lead acid) battery world.

 

[redpoint5]

Dealers are notorious for abusing 12v batteries. Deeply discharging them even once permanently damages them.

Ever see the battery and jumper cable cart they wheel around to start dead cars? People spend a lot of time with the "engine" off and fiddling with settings with the door open and lights and radio on, draining the battery. Maybe they forget to turn a light off when they walk away.

I don't think bad batteries is unique to the Bolt, as building a charge controller is dead simple, and lead-acid battery construction is a well known process.

If I were the OP, I'd have started by checking the 12v battery voltage, as this is a common issue affecting many hybrids and all EVs, and a quick Google search would have said as much.

I expect dealers to not know anything, as their specialty is selling vehicles, not knowing how they work.

 

[Sean Nelson]

There are numerous threads that say the 12V battery in EVs is not kept in as good a condition (as an ICE vehicle keeps its 12V) by the usual events of starting and HVB charging, especially if the EV has sat for 1-2 months without being driven or charged.

My Prius C had the same kind of small AGM battery to power the electronic systems when the car was turned off, and it was required to close the main contactor for the high voltage battery which then propelled the car and started the engine. I never had a problem with it, despite leaving the car sitting in the garage for 7 weeks once.

 

[surgeonFWW]

My Prius C had the same kind of small AGM battery to power the electronic systems when the car was turned off, and it was required to close the main contactor for the high voltage battery which then propelled the car and started the engine. I never had a problem with it, despite leaving the car sitting in the garage for 7 weeks once.

Are there any cars nowadays which do NOT use AGM (absorbent glass mat {sealed}) batteries?

 

[BlackBolt]

Our '08 Prius still was on a flooded lead acid, I'm not sure when they made the change over. FYI a 26R flooded battery is almost the same size as our DIN44/H4/L1AGM spec, it's just an inch taller. Not that anyone normally would want to install a flooded battery, but they can be had for about $70 instead of $150 and they are a normally stocked battery at auto parts stores, if you need one while on the road.

 

[ibboltin]

There are numerous threads that say the 12V battery in EVs is not kept in as good a condition (as an ICE vehicle keeps its 12V) by the usual events of starting and HVB charging, especially if the EV has sat for 1-2 months without being driven or charged. I still treat my 12V to a "trickle of love" every month for good measure. I have to think that some (not all) of these 12V failures are the result of sitting around unused for months. But I may be wrong...

AGM stands for Advanced Glass Matt. Basically the Sulfuric acid of a flooded cell is embedded into a glass matt lead sheet separator. Still lead acid battery but with many advantages over a traditional flooded wet cell. Alll lead acids dies when the buildup of lead sulphate drystals on the plates become too much, or the plates short. So yes trick charging is the best thing for any LA battery tech. AGM has a slightly different charging curve though. Dont want to get into a battery discussion here per se. Here is what we use

https://www.pulsetech.net/pro-12-rp-redipulse12-station-battery-maintenance-system.html

That being said these are have not been sittin around for that long have they? I wonder what the parastitic drain on the 12v battery is when not in use. I wonder why the charge controller does not maintain the 12v battery while off from the main pack? seems kind of ...

 

[Sean Nelson]

Are there any cars nowadays which do NOT use AGM (absorbent glass mat {sealed}) batteries?

It was my understanding that the Prius C used an AGM battery because the battery was located under the rear seat - that precluded the use of a standard battery which can vent hydrogen while charging. Hydrogen inside the passenger compartment is a big no-no.

 

[Mike Brigham]

It may or not be obvious here, but an AGM battery doesn't have the spillable electrolyte (acid) that a flooded battery has, so is much safer to handle and also doesn't ever need watering.

 

[TotaledJetta]

I have had a similar experience. It is described in an earlier thread "12 V battery trouble". After a few failures, the dealer found the transmission module was telling the charging system that when the car was in ON and in gear, it was in service mode, which doesn't charge the 12 V. After this was corrected my 12 V failed again. I have since measured its state of charge and also watched how the system charges the Bolt on the road. My conclusion is if you get the battery significantly discharged, just driving around and even putting it on the EVSE doesn't properly return the battery to a near full state of charge. I bought an AGM charger and it ran a charging voltage of about 14.7 volts for a couple of hours. Since then the SOC has been reading about 12.56 to 12.59, which according the the service manual section posted by Drdiesel1 is close to full charge. To monitor while driving, I use a auxiliary jack in the "cigarette" plug and a dvm. On start up it charges up to 14.8 V momentarily, then at about 14.6 V for about 2 minutes, then drops to 12.68-12.72 V for at least 15 minutes. Haven't driven longer to test that. So, I agree they are being very stingy with charging the 12 V system and that may not be enough if for some reason your battery gets significantly discharged. I think my charging system is working as designed, but that is marginal. After I used the AGM charger the SOC was still about 12.7 V a day later. So if you are having this problem, an $80 AGM charger might help. Mine is a BatteryMinder 2000 for AGM batteries.:nerd:

When I was doing my testing for the "camping mode" and long duration inverter backup power testing, the APU often dropped down to 12.6V, well below float voltage for AGM. I believe it does this to conserve energy from the main pack (ask any off-grid solar guy how much energy is burned keeping batteries at float voltage), but the trade off is less time spent truly conditioning and preventing sulfation of the lead acid battery - which is not good news for one that has been allowed to run low while sitting in inventory. After being drained heavily (below 12.3V), AGMs can do with 12+ hours at steady high voltage charge to recover what's left of the battery at that point. Unfortunately they can't truly be equalized to recover specific gravity like a flooded battery can.

The battery in my car is sitting at 12.59V at rest. If it was being fully charged, because it is only a few months old, 12.8V would be the expected resting voltage. Currently, I believe it is being chronically undercharged, and sits daily at about 75% state of charge best-case, which is a death sentence coming due, sooner or later.

I'd pick up one of those small $30 lithium jump start battery packs, they take up very little space and you can limp along until you can get a new battery. I have a few battery tenders, I'm thinking of putting one of the pigtails on the Bolt so I can check voltage on the fly with my DMM and give it a top up to keep the AGM kicking for a few years.

 

[kendallg]

I would think that any dealer who is prepping an EV for pickup would charge not only the HVB, but also clamp a charger to the 12V and make sure it has (and holds) a full charge!

When I purchased my Bolt it was covered in dust and debris, which the detailing didn't even entirely fix, and the tires were 7 PSI below the manufacturer recommended level. Clearly my car had been sitting on their lot for quite some time. Considering they couldn't be bothered to check the tires, is it a big leap to think they wouldn't bother checking the battery status? I don't think so... They just want to move the car.