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Best way to check 12V Battery?

12593 Views 53 Replies 17 Participants Last post by 240vPlug, May 12, 2020

psyflyjohn

Discussion Starter · May 23, 2019

It's becoming apparent from posts on this forum and others that the 12V battery is somewhat of an Achilles heel for the Bolt. I know that lead-acid batteries have a finite life, and it seems that when they give up the ghost on Bolts they can create a variety of problems.

My question: What's the best way to monitor the battery status besides waiting for a problem to occur (which of course, will be at an inconvenient time). A routine check with a multimeter? I know that the Bolt system tries to keep the battery charged, so a good reading may be inaccurate on a weak battery. I could "load test" the battery, but would probably have to disconnect it to do that. Your informed opinion would be appreciated.

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drdiesel1

· #41 · May 31, 2019 (Edited)

evprogress said:
The 12 volt accessory battery is problematic in all modern automobiles whether electric, hybrid or piston. The Bolt is no exception. A modern car parked at the airport or elsewhere for days at a time will experience 12 volt battery discharge due to paracidic loads.

I disagree! I don't think you understand the parasitic load factor on new cars. It's not the battery at fault.
It's the lack of USE! That's it. It's that simple. Don't blame the battery.
Control modules, radios, and other electrical components require KAM power on all cars. Like I said before,
Drive it or charge it. Those are you 2 choices. Nothing else is going to magically fix it.

The Bolt's system will work just fine as is. Lack of use will shorten the 12V batteries life, unless you supplement it.
Automakers do a fine job and the Bolt is proof. You just can't please 100% of the people, 100%.
Instead of condemning all cars, buy a simple smart charger and use it!

Reactions: 1

Edchris

· #42 · May 31, 2019

Yes there are parasitic loads, most cars have a clock, & blinking light that shows a theft system is active.
I once left my Sienna van for 4 months, & the battery ran down. Last year, it was garage parked for 5 months. I simply disconnected the negative post, & it was fine. Temperatures affect run down, a battery discharges faster in hot weather.
I left a Honda Civic parked for 4 months last winter, didn’t do anything, & it started right up this spring. The ICE vehicles have larger capacity batteries than the Bolt, but really, if I was leaving my Bolt for a month or two of vacation, I would simply disconnect the Neg terminal & leave it.
My experience with AGM batteries is that they are not fragile little flowers that need to be treated with kid gloves.
My jet ski & lawn tractor AGM are removed in winter, charged, then left sitting in the shop til spring. If I remember, I might give them a short charge midwinter. Maybe I’ve just been lucky, but my sienna battery went 11 years, corolla is now 10, Civic 8, jet ski 5...& Well the Bolt is not quite 1.

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evprogress

· #43 · May 31, 2019

drdiesel1 said:
12.4 to 12.6 if you start with a 12.6 or better SOC. I don't think you're testing your battery properly to get the reading you claim.

Good guess for moderate temperature where thermal management is not in play. Even so you ignored the SOC part of the question.

At 12.4 - 12.6 volts the 12 volt accessory battery is at 50% -75% SOC. Sulfates at this level will harden and crystalize. Once crystalized, no amount of charging caan reverse the process. Capacity will be lost.

FYI, I use a Fluke with two decimal digit of precision to test OC voltage after 8 hours of rest.

psyflyjohn

Discussion Starter · #44 · May 31, 2019

Well, after starting this thread and the vigorous discussion that followed, here's what I decided to do: Get a simple 12v meter that resides in the power outlet to continually monitor the battery status. When the standing voltage nears 12v or drops lower, it will be a sign that the battery is nearing it's life end. If I want to confirm that, I can just do a simple load test as previously described.
Simple, eh?

Reactions: 2

KeithMoon

· #45 · May 31, 2019 (Edited)

evprogress said:
The 12 volt accessory battery is problematic in all modern automobiles whether electric, hybrid or piston. The Bolt is no exception. A modern car parked at the airport or elsewhere for days at a time will experience 12 volt battery discharge due to paracidic loads.

I've left my other car (also an EV) for more than 2 weeks without any issue whatsoever, and others have left theirs for months without issue. One person for 9 months!

Reactions: 2

drdiesel1

· #46 · Jun 1, 2019

evprogress said:
Good guess for moderate temperature where thermal management is not in play. Even so you ignored the SOC part of the question.

At 12.4 - 12.6 volts the 12 volt accessory battery is at 50% -75% SOC. Sulfates at this level will harden and crystalize. Once crystalized, no amount of charging caan reverse the process. Capacity will be lost.

FYI, I use a Fluke with two decimal digit of precision to test OC voltage after 8 hours of rest.

Wasn't a guess! I disagree with your claims of SOC "VS" battery percentage.
12.4 is 80% and 12.6 is 100%.

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TotaledJetta

· #47 · Jun 1, 2019

drdiesel1 said:
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It won't affect anything and it's the only way to do an actual load test of the 12 volt battery
Please don't post nonsense as technically valid information. Thanks!

Does the Bolt remember all its setting after disconnecting the 12 V system? My wife's 2006 Acura is a mess after doing that. The alarm is hard to reset. The radio must be reinitialized, the GPS system needed a code, The radio forgot all its station settings. So, I assumed that something similar would happen on the Bolt. I learned a lot from drdiesel during my 12 V troubles, but never experimented with disconnecting the battery and actually don't think I will. But as a read from this thread, I guess it is fairly harmless. :nerd:

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drdiesel1

· #48 · Jun 1, 2019

TotaledJetta said:
Does the Bolt remember all its setting after disconnecting the 12 V system? My wife's 2006 Acura is a mess after doing that. The alarm is hard to reset. The radio must be reinitialized, the GPS system needed a code, The radio forgot all its station settings. So, I assumed that something similar would happen on the Bolt. I learned a lot from drdiesel during my 12 V troubles, but never experimented with disconnecting the battery and actually don't think I will. But as a read from this thread, I guess it is fairly harmless. :nerd:

To save memory in the control modules and radio, you can plug a 12V power adapter
into the cigar lighter. Have it hooked to a 12V supply and everything in the Keep Alive Memory (KAM)
will be saved.

Sean Nelson

· #49 · Jun 4, 2019 (Edited)

Edchris said:
Yes there are parasitic loads, most cars have a clock, & blinking light that shows a theft system is active.

It's worse than that, because all of the modern cars with keyless entry systems also require the associated radio transmitters and receivers to be continuously powered.

psyflyjohn said:
Well, after starting this thread and the vigorous discussion that followed, here's what I decided to do: Get a simple 12v meter that resides in the power outlet to continually monitor the battery status.

Isn't it true that the DC "cigarette lighter" outlet is only powered up when the car is turned on? If so, you're really only measuring the output of the high voltage inverter and not the 12V battery.

Reactions: 1

240vPlug

· #50 · May 11, 2020

Ok I'm digging up this thread. Mainly because my Bolt has started to me misbehave in various electronic ways and I suspect my 12v battery may be weak.

If the 12v outlet inside is only powered up when the vehicle is on then putting a 12v supply on that would not preserve any settings right? Does anyone know what exactly needs to be done after a disconnection? I think I need to try a load test on it but I would like to know what I'm signing up for before I disconnect the battery.

TIA

TotaledJetta

· #51 · May 11, 2020

One way is to connect wires across the battery, run them out the hood, close the hood and connect a good quality voltmeter. Then leave your fob far away and check the voltage after some hours of rest. This will give you a good state of charge reading without the Bolt waking up and messing with the readings. The state of charge should be about 12.6 volts. At less than 12 you may be in trouble. I also used a plug that fit in the 12 v accessory port and a voltmeter to monitor the charging system, when driving. My Bolt's initial problem was the software in the transmission module was faulty and the charging system didn't charge when it was in drive. This eventually damaged the 12 V battery, took me three trips to the dealer before the battery failed their cold start cranking number and they replaced it for free. If you try to start the Bolt with about 10 V out of the battery, all kinds of bizarre messages come up. I know because my 12 V system would occasionally drop to under 10 V when I was away from home and it left me stranded several times because one cell would randomly short out. That was all in the first year (2017) , I have had smooth sailing since.

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redpoint5

· #52 · May 11, 2020

I've maintained 12v supply while swapping a battery before, but it's a little cumbersome, at least the way I did it using alligator clips and a spare 12v battery.

Reactions: 1

240vPlug

· #53 · May 11, 2020

Well I stuck the 1a trickle charger on there and after an hour or so it was fully charged so it doesn't look like it was discharged in my case. I still want to load test it though...because the past month or two it has done some strange things on a couple different occasions. Examples are refusing to detect the fob, locking infotainment screen, and just last night refusing to charge (it eventually started charging on its own about an hour later). These incidents were weeks apart but it just strange.

240vPlug

· #54 · May 12, 2020

What do you all think about these conductance testers for checking the health of the 12v battery?

smile.amazon.com

Amazon.com: SOLAR BA7 100-1200 CCA Electronic Battery and System Tester : Everything Else

Amazon.com: SOLAR BA7 100-1200 CCA Electronic Battery and System Tester : Everything Else

smile.amazon.com

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