[Steverino]

You understand what he was talking about? Lost me. Did the conversation shift from 12v to traction battery?

Given they were talking about a DC charging issue, yes, I'm going with he's referring to the traction battery. If the 12V battery had a problem, it takes about 15 minutes to put in a new one and they are readily available. There'd be no need to leave the car at a dealer unless it was a weekend maybe. Even then, it's a simple maintenance replacement.

 

[Duke Woolworth]

If GM wants you to follow a

The 12v system powered by a regular 12v lead-acid AGM battery. I'd expect 4-6 years for most situations, variable based on use, environmental conditions, etc, with some only getting 3 years, others stretching to 8. The AGM battery on my truck is 6 years old, and it has had a far less than optimal use: hot summers and cold winters, sitting for long stretches not used, driven for short distances for some periods, and lots of towing for others.

The 12V batteries in our '19 Bolts are still fine. In the Korean EV forums, there have been many complaints about their 12Vs, often caused by faulty ICCUs. GM has not had that problem. In olden days, a 12V battery at rest was used mainly to wind the clock.

 

[Steverino]

12V battery issues are being reported by Rivian, VW, Hyundai, Kia, Genesis, Tesla and Toyota EV owner's depending on model and year according to InsideEV's

Automakers use several different methods to keep the 12v battery in an EV topped off. Some, like the ICCU approach used by the Koreans seem more problematic than others, but each approach has pros and cons. Even the trouble Hyundai is having is said to affect only 1% of the cars. Automakers are responding with fixes in both hardware and software and in some cases redesigns.

Like this dead 12v battery report by Davef, while the issue seems rare, if it happens to you it can be a real PITA.

 

[lvriesling]

@Steverino Interesting article, but it doesn’t say exactly which method Equinox EV uses…

Most companies use a simple approach—when the vehicle is on, the high voltage (HV) system charges the low-voltage (LV) 12-volt battery. Other designs use more power when switched off, and therefore have an automatic power control logic that will flip on the HV battery to top off the LV system when it gets low.

Automakers are getting more experienced not just with EV technology, but also managing the workload on 12-volt batteries. Some have moved towards dual-battery setups or, in the case of Tesla's Cybertruck, a primarily 48-volt system.

Automakers are also getting more intentional about choosing low-voltage batteries better suited to EVs. Many are switching toward deep-cycle batteries, which are worse at handling the high-current demand of starting an internal combustion vehicle, but better suited to being depleted more often.

Should a (pricier) new deep-cycle 12V battery should be used to replace the Equinox EV’s AGM battery when it dies?

 

[Steverino]

it doesn’t say exactly which method Equinox EV uses

You are correct.

Should a (pricier) new deep-cycle 12V battery should be used to replace the Equinox EV’s AGM battery when it dies?

The OEM 12v battery is an AGM (Absorbed Glass Mat) battery, These are generally considered as deep cycle. So you already have a deep cycle in the car. GM started using AGM batteries in the 2011 Volt and later with the 2017 Bolt EV.

My basement sump pump backup system uses a ADM battery. There are basically two types of batteries that are deep cycle: Sealed or Flooded. Sealed are a maintenance-free or a valve-regulated lead acid battery. IOW, unlike a Flooded deep cycle battery you don't need to add water to the cells over time. The AGM battery charges faster than a gel or flooded battery but have lower tolerance to overcharging. This is where the software and hardware used to maintain the 12v battery come into play.

 

[coastalcruiser]

The OEM 12v battery is an AGM (All Glass Mat) battery

Small nit. It is Absorbed Glass Mat. ;>

And it appears that some AGM designs are tuned for deeper recycling than others. As we learn about how often the 12v ☰ battery is being exercised, if I was replacing mine outside of warranty I would lean toward a battery heavily tuned for deep cycle -like maybe a Trojan or Optima Blue top- as the battery seems to experience few if any high current discharges.

 

[martinjlm]

Even though it appears to be a simple issue, "How do you keep the 12V charged?" is a big deal with all EVs. Remember, ICE vehicles have an alternator that is turned by a belt that is turned by the engine crankshaft. No engine means no crankshaft and no accessory belt. A lot of EVs are shifting to lithium ion 12V batteries. I know Tesla has made that shift. The lithium ion 12V is about a quarter the size and mass of the AGM it replaced and their complaints about 12V dying for no apparent reason seem to have reduced significantly. Not sure if their motivation for making the change was mass reduction or reliability. The silver box with the orange tape on it is the lithium ion battery, right next to the replaced AGM battery. Photos taken at and with courtesy and permission of CareSoft Global.

 

[Steverino]

if I was replacing mine outside of warranty I would lean toward a battery heavily tuned for deep cycle

Assuming the specs and physical size matched the oem and there wasn't a large price difference, I could see that. On the other hand, if the lifespan of the 12v batteries in the Equinox EV end up being normal (5 to 10 years based on local conditions), then perhaps it's a moot point Coastal?

Not sure if their motivation for making the change was mass reduction or reliability.

The 12V issue seems to be a moving target as auto companies adjust to improve long term reliability.

 

[coastalcruiser]

On the other hand, if the lifespan of the 12v batteries in the Equinox EV end up being normal (5 to 10 years based on local conditions), then perhaps it's a moot point Coastal?

Definitely moot if it lives for 5 years +. But it's a fairly big if. I say that only from the posts indicating how much the 12v is cycling with the car off. In the current config (hardware/software) I would not expect long life.

That's just an expectation. Not a prediction. Would love to be wrong about my conjecture.

 

[Salkin]

I know Tesla has made that shift. The lithium ion 12V is about a quarter the size and mass of the AGM it replaced and their complaints about 12V dying for no apparent reason seem to have reduced significantly.

I don't know how Tesla manages a small 12v Li battery. But even though the Li battery may last longer than FLA battery, the thermal management is critical. Without 12v Li battery specific BTM, the working temperature range would be seriously reduced.

How do you keep the 12V charged?" is a big deal with all EVs. Remember, ICE vehicles have an alternator that is turned by a belt that is turned by the engine crankshaft.

Toyota have been keep charging the 12v battery without alternator in Prius HEV longer than any BEV models. None of my previous HEVs and PHEVs in the last 20 years had alternator, yet I never experienced problem with the 12v battery dying for no apparent reason. So the recent problems of the 12v battery premature demiss in many models of cars, BEVs, PHEVs, HEVs, and conventional ICEVs, are not because of the lack of alternator. I think it is related to more phantom draws while cars are off in modern cars with sensors, telemetrics, wifi, etc., in an always connected vehicle. Cars from 20 years ago could sit months without draining the 12v battery. But our EQEV's 12v battery dies within a few hours if it is not properly charged from the traction battery.

See this comment and 12V monitor graph of EQEV:

https://www.equinoxevforum.com/posts/59370/

 

[Kenny]

I don't know how Tesla manages a small 12v Li battery. But even though the Li battery may last longer than FLA battery, the thermal management is critical. Without 12v Li battery specific BTM, the working temperature range would be seriously reduced.


Toyota have been keep charging the 12v battery without alternator in Prius HEV longer than any BEV models. None of my previous HEVs and PHEVs in the last 20 years had alternator, yet I never experienced problem with the 12v battery dying for no apparent reason. So the recent problems of the 12v battery premature demiss in many models of cars, BEVs, PHEVs, HEVs, and conventional ICEVs, are not because of the lack of alternator. I think it is related to more phantom draws while cars are off in modern cars with sensors, telemetrics, wifi, etc. In an always connected vehicle. Cars from 20 years ago could sit months without draining the 12v battery. But our EQEV's 12v battery died within a few hours if it is not properly charged from the traction battery.

See this comment and 12V monitor graph of EQEV:

https://www.equinoxevforum.com/posts/59370/

This!
Things like the damn car waking up every time I walk from my living room to my kitchen past the garage door!!!!

 

[Salkin]

Just for information:

Here is an example of a 24-hour 12V battery monitor graph on EQEV. Chronologically, here is what happened to the car and the 12V battery.

1. 00:00 to ~09:30, parked, unplugged, no fobs nearby: The drain of the 12V battery is due to normal off activity of the EQEV.
2. At ~00:30 and again at ~2:50, with the car off and unplugged, the 12 V battery's voltage dropped below 12.4 V. The car then automatically started charging the 12 V battery at a normal 14.3-14.5 V charge level from the traction battery.
3. At ~09:30, the car was driven for several in-town short trips, with a total duration of about 1.5 hours. During this time, the car was stopped and parked several times. Each time the car is in READY mode, the 12 V battery is charged at a normal 14.3-14.5 V charge level from the traction battery.
4. At ~16:15, the car was briefly in READY mode to shut down the windows that were left open. It was ON only for a few seconds. The 12 V battery was not drained below 12.4 V; thus, the charge level was slightly lower than the normal 14.3-14.5 V charge level.
5. At ~20:00, I plugged in the L2 EVSE. It took only 1 hour and 10 minutes to charge from 62% to 75%, using 13.01 kWh at the wall, as reported by EVSE, which is equivalent to 11.33 kWh being charged into the traction battery, as reported by the car. During this charge session, the 12 V battery was charged at a lower "maintainer" charge level of 13.5 V.
6. At ~21:10, the charge was completed. The car remained plugged in, but continued to drain as it sat.
7. At ~23:00, the 12 V battery drained below 12.4 V. With the EVSE plugged, the 12 V battery is charged at a normal 14.3-14.5 V charge level by power supplied from the wall. The EVSE reported this as 29 min charge session using 0.20 kWh of power from the wall, but the car did not register this as a charge session, thus no power went into the battery according to the report from the car.

24-hour 12V battery monitor graph on EQEV monitored by BM2

 

[martinjlm]

Phantom draws have been a thing ever since the first application of OnStar. In that regard EVs are no different than ICEVs. I had forgotten about Toyota's charging without an accessory belt. I remember we were looking at this at GM and just decided the cost / mass reduction of no accessory belt wasn't worth the cost of the system(s) that replace it. One of the things we were looking at was starter generator physically connected to the flywheel. I think that may be what Toyota uses. They were using that for their Stop/Start systems so maybe that's the approach. Still requires an ICE to charge the battery and that is the issue that causes EV manufacturers to look for new ways to keep the 12V charged.

 

[coastalcruiser]

When I look at all the ways 12v battery health has been addressed (of the solutions I am aware of; charging the 12v from the traction battery when car is left off, Lion battery cells, BMS optimization, mitigating vampire drain, restricting use of energy to only critical systems when car is off) it seems that Tesla's approach of migrating systems from drawing from the 12v battery to drawing from the traction battery via the DC-DC converter makes the most sense. The power to run the systems ultimately comes from the traction battery, either directly or from the process of keeping the 12v battery charged.

But I must be missing a piece of the jigsaw puzzle, otherwise everyone would be running the 12v systems directly from the traction battery.

 

[Kenny]

When I look at all the ways 12v battery health has been addressed (of the solutions I am aware of; charging the 12v from the traction battery when car is left off, Lion battery cells, BMS optimization, mitigating vampire drain, restricting use of energy to only critical systems when car is off) it seems that Tesla's approach of migrating systems from drawing from the 12v battery to drawing from the traction battery via the DC-DC converter makes the most sense. The power to run the systems comes from the traction battery, either directly or from the process keeping the 12v battery charged.

I was shocked when I learned EVs still had 12V battteries!

 

[martinjlm]

I was shocked when I learned EVs still had 12V battteries!

They operate everything except vehicle propulsion. Lights, audio, telematics. I think Hyundai has an application where they segment the large traction battery to operate the accessories off of the segmented portion, but I haven't seen anyone else try that. Tesla Cybertruck has a 48V system instead of a 12V system due to the expanded burden of onboard systems. We may see more 48V systems on the horizon.

 

[Salkin]

Toyota Prius is not unique in not using belt-driven alternator to charge the 12v battery. Use of the motor generator to charge the 12v battery is quite popular among many hybrid models. Except a very few mild hybrids I know of, most hybrid used the engine driven motor generator to charge the 12v battery. My first Honda hybrid with Integrated Motor Assist (IMA), allowed the engine to power the motor-generator, which in turn charged the battery, and also directly powered the wheels. Then Toyota and Ford hybrids I gad used the Hybrid Synergy Drive (HSD) system. The 12V auxiliary battery was primarily charged by the high-voltage (HV) hybrid battery through a DC-DC converter.

I always believed the reason that the hybrid and BEV still use the 12V auxiliary battery is to protect the expensive lithium battery from draining too low during off time. But that may not be the whole story. I am sure cost saving in designing and manufacturing must have played a role.

 

[Fred_Savage]

This!
Things like the damn car waking up every time I walk from my living room to my kitchen past the garage door!!!!

@Kenny you can always just hang up the key fob - it wakes up when it senses motion. Have your house keys separate from your keyfob using a quick release:

 

[lvriesling]

When I look at all the ways 12v battery health has been addressed (of the solutions I am aware of; charging the 12v from the traction battery when car is left off, Lion battery cells, BMS optimization, mitigating vampire drain, restricting use of energy to only critical systems when car is off) it seems that Tesla's approach of migrating systems from drawing from the 12v battery to drawing from the traction battery via the DC-DC converter makes the most sense. The power to run the systems ultimately comes from the traction battery, either directly or from the process of keeping the 12v battery charged.

But I must be missing a piece of the jigsaw puzzle, otherwise everyone would be running the 12v systems directly from the traction battery.

Consider situations in which the traction battery fails. Would you want the vehicle to be able to report that immediately via OnStar? That's what the separate 12V battery is for.

 

[coastalcruiser]

Consider situations in which the traction battery fails. Would you want the vehicle to be able to report that immediately via OnStar? That's what the separate 12V battery is for.

My statement did not argue for the elimination of the 12v battery. Just to mitigate its usage, so that its there when needed.