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Discussion Starter · #1 ·
I have a crazy repair story I want to share because it may be useful, and I thought it would be great if we all keep each other up to date by posting repair stories (carzy or normal). I am still a happy Volt owner and I still recommened the car.

Here's my story:
The night before last I forgot to plug in my volt. It was the first time. I drove yesterday and used up the battery and drove on gas for 30 miles. Many day's I don't. This is probably not relevant but I include it just in case. The only other time that my car didn't get charged was when it spent a week in the LAX parking lot. (LAX has free parking for EV's which is great! but only 2 compatible chargers)

This morning the charger (the standard 120v charger that came with the car) was dark. The green lights were off. I checked the circuit breaker and the plug and they were good, so I assumeed the charger had burned out.

The car had charged from empty to 19 miles available on battery - so it had cut out in the middle of the night.

I called my Chevy dealer and told them and they said to bring it in and they would take care of it.

So I drove to the Chevy dealer with my charger. I guess I was thinking that they would just take my charger in back and check it out and then give me a new one. But they wanted the car too. I questioned it but then I let them take it and went off to the waiting room.

After waiting longer than I expected in the waiting room, I went out to find out what was going on. They said that the car had put out some error codes and they were looking at it. Then they said that the car would not charge because the 12V battery had a problem. They decided to get a replacement 12v battery, and arranged for a loaner for me (thank you!). But they were able to get the battery today and called me back. So I picked up my Volt and brought it home and now it's on the new charger.

I sure am glad that I let them check out the car when I only wanted them to replace the charger. I do wonder what happened in the middle of the night, and like I said I can't see how my forgetting to charge the night before can be related.

I have a 2012 Volt, #422C

By the way, the loaner car had a gas engine. It sure feels different. I am use to the smooth quiet feel of the Volt.
 

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Glad to see that your car got fixed. Forgetting to charge is not an issue. When I got my volt, I had a problem with my outside outlet and could not charge the car for about a week. Recently, I decided to see how the car works in cold (10-20 deg F) weather with the main battery discharged. I had no problems with the car after it was idle for 3 days.
 

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I am also spoiled by the Volt's super quiet ride. I have a 1999 Aurora (350 V8 with the rare "Autobahn" transmission), which has fallen into disuse since the Volt arrived. I've been worried about the gasoline going stale, so I drove it to work a couple days this past week, as my wife ran errands with the Volt.

WOW, does it ever sound loud. Also, I squeeled the Aurora's tires a couple of times at a freeway traffic light as the light went green, but the first three seconds of acceleration nonetheless seemed slow.
 

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What were the error codes and what was defective about the the battery? Why would you need a new charge cord if it was a defective 12v battery?
 

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Actually, what scares me a bit about this is how complicated it seems to be to replace a defective 12V battery. My father had to replace the 12V battery of his 1997 Opel Astra once, and this went much differently than told here...

One day, my father couldn't start his car anymore. He called the ARBÖ (one of the Austrian automobile associations he's a member of), and they sent a service technician (NOT a tow truck!). The technician did a few checks and found the 12V battery to be defective. For that case, since my father had already said on the telephone that he couldn't start his car, and what his car type was, the service technician had a new spare battery with him which he sold to my father and replaced in the car, on the spot, taking the old battery with him. Of course the battery wasn't exactly a great deal at about EUR 75,-, but the whole process went pretty quick... my father had a new battery, no tow truck needed, no multiple dealer visits, no rental car, my father's car was up and running again in a matter of 1-2 hours at most.
 

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Is the 12V battery an off the shelf type car battery? There seems to be a problem with this battery going dead on occasion, therefore preventing someone from starting their Volt. Has anyone jumped their Volt from another car or from a spare battery?
 

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Is the 12V battery an off the shelf type car battery? There seems to be a problem with this battery going dead on occasion, therefore preventing someone from starting their Volt. Has anyone jumped their Volt from another car or from a spare battery?
It's a 12v AGM (Absorbent Glass Mat) battery, not lead acid like other cars use. My understanding this type is used because it is inside the cabin and is sealed to not release fumes. In theory, it should be more durable because the plates are held in place by the glass mat.
 

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Is the 12V battery an off the shelf type car battery? There seems to be a problem with this battery going dead on occasion, therefore preventing someone from starting their Volt. Has anyone jumped their Volt from another car or from a spare battery?
A drained 12v battery can be jumped by following the Owner manual instructions. A discharged battery does not need to be replaced. That's why I am curious what the error codes were in this case, and what specifically was wrong with the battery. I suspect there was nothing wrong with the battery and it's replacement an unneeded exercise but await further details.
 

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We are hearing more about bad 12v batteries than anything else here. AGM's ARE lead-calcium-acid, it's just that the acid is in the glass mat instead of being a loose liquid in there. They don't gas *much* but they do gas some at high input voltages. They are a lot pickier about their care and feeding than a starter battery - they are deep cycle types and need tighter control over charge and discharge profiles than a starter battery does (only takes about 1 amp hour to start a car if it's running right - this battery gets cycled, which would kill a regular starter battery in only a few cycles).

I measured mine - and in my Volt, they're running it at ~15.1 volts when the car is on - which by the way, is quick death on an AGM battery and will make it gas - and fail. I mentioned this to my VA and they basically told me to forget about it - it was causing overvolt trips on an inverter I hooked to it that they don't approve of (they don' approve of any car mods at all). I pointed out this would kill the battery as well as my inverter - no response. A VA isn't at a high enough level in GM to know this sort of thing, or even know who to talk to about it. It's just "calibrated at the factory". Yeah, well it's calibrated wrong in mine.

Maybe it's not just the bluetooth bug we hear about, but that they are overcharging the snot out of these and making them fail. Mine sure does run a too high voltage and it will surely die young due to that. AGM's have less acid, so it's easier to boil it all out gassing them.
 

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<snip>
I measured mine - and in my Volt, they're running it at ~15.1 volts when the car is on - which by the way, is quick death on an AGM battery and will make it gas - and fail.
<snip> they are overcharging the snot out of these and making them fail. Mine sure does run a too high voltage and it will surely die young due to that. AGM's have less acid, so it's easier to boil it all out gassing them.
I've seen 14.1 and looking back at this post I saw 13.6 on my ScanGuage.

So-what-will-the-Volts-OBD-show-on-a-product-like-ScanGuage
http://gm-volt.com/forum/showthread...on-a-product-like-ScanGuage&p=63472#post63472
 

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Discussion Starter · #11 ·
two thing failed

What were the error codes and what was defective about the the battery? Why would you need a new charge cord if it was a defective 12v battery?
I didn't get the error codes. Wish I had. The initial failure was the 120v charger - the lights went dark. The two failures - the 12v battery and the 120v charger seem to be part of the same problem.
 
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Sorry to hear you were without a Volt for a short period time. But that is good to hear your back in it and that your dealer took the time and was able to pull those codes up!
 

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We are hearing more about bad 12v batteries than anything else here. AGM's ARE lead-calcium-acid, it's just that the acid is in the glass mat instead of being a loose liquid in there. They don't gas *much* but they do gas some at high input voltages. Snip!

I measured mine - and in my Volt, they're running it at ~15.1 volts when the car is on - which by the way, is quick death on an AGM battery and will make it gas - and fail.
Hi, DCFusor!
Wow, 15.1Volts measered at the battery posts? This is a case of cooking/frying those AGM 12V batteries! The usual voltage is around 13.8Volts for nominal 12Volts lead-acid batteries. The battery could certainly stand up to 14.1Volts, but 15.1Volts is indeed a great recipe to gas the batteries through electrolysis. The cell that has the least acid in it will dry up first, and when this happens, you got a battery that is almost an open circuit - thus the car doesn't start or boot problem that we see around.

Excuse me if my electrical engineering basics come back, but are you sure about your measure? I had a numeric multimeter (in voltmeter function) giving me up to 20% error on the voltage measured when the intrument 9V internal battery was getting low. If you are sure that your instrument gives a reliable calibrated measure, and if this 15.1Volts battery voltage is "standard" in chevy Volts, we will certainly see many 12V battery replacements pop up some more in those forums. (We did see a few of those, and some owners seems to go equip themselves with portable booster packs)

When I will get my car, I will check this out with a voltmeter.
 

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Yes, I'm sure - I'm a pro too. Checked it with a couple known-good 4.5 digit meters and only after a well trusted inverter kept overvolt-tripping on it. I wanted to have 120v AC for various reasons, so I installed one in the back with the battery on nicely fat wire. Looks like I should have put a Shottky diode in series with it to drop the voltage a little bit (or modded the inverter internals).

It's obviously going to cook these babies fairly quick. I'm not sure if the chemistry in the Ultima deep cycles is enough different to overcome that either if you try and put in a "better" battery instead of the one in there.

I tried to warn GM, evidently to no avail. It seems they want to assume the guy on the other end is an idiot till proved otherwise (often a good call, sadly - I've done support in my day.). They'll find out if they're all like this, though. At any rate, all I really got from them is "don't put an inverter in there, we don't approve of any mods at all".


Do check it - I only have this one data point on mine (this is only with the car "on" BTW, and yes, at the posts). But since we're seeing all these issues, well, this might be at least a part of it. For medium life/some cycling, you can run these around 14.5-14.8v (in the cold, batteries have a tempco too), but his is just flat out too high - and I measured it on a 65F day when it was middling warm. For long term float, yes, the 13.8 you quote is the right number. Wonder if they just wanted the incandescents in there to be extra white? Top_Speed1's mods for leds would take care of that one (have done some of them myself, nice, especially the HID headlights, they are pure killer good).
 

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It would be nice to know the voltage of the 12V battery of a couple of Volts around, to differentiate between a widespread characteristic or a fewer (but problematic?) higher 15Volts cars. If some "talented" owners could post their Volt's battery voltage when ON, we would learn about it rapidly.

I bought a boat that came brand new with the internal voltage regulator of the alternator driving the battery to 15Volts too. I asked right away to have that fixed, and found on the net the Mercury's service bulletin stating the alternator output should be between 13.6 and 14.1 Volts. I did not take delivery of the boat until this was fixed. I had to argument a bit, since the dealer did not believe that the problem was present on a brand new machine. The Service Bulletin made him understand. After a little hour ride, the battery was hotter than normal because of the higher charge current.

Thanks also for clarifying that we can rely on your voltage measurement, DC! . A simple mod could also be to install two normal silicon diodes back to back in parallel, so they create a 0.7V voltage drop to / from the battery. 15.1V - 0.7V = 14.4 V - a bit better.
 

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Yeah but - this thing can charge at up to 175 amps! Think how hot those diodes are going to get, now you really do have a fire hazard! 0.7 (or more under big loads, most spec around a volt at ratings) times 175 = 122 watts - now that's some heat in a small place. The tempco is the wrong way, and you'd lose the "filtering" of the battery acting like a big bypass capacitor as well.
That's big heat-sink and fan turf - imagine a desert environment on top. Ouch. I might have used a diode in series with the inverter (or just its low level electronics) but I looked at that calculation for the whole shebang and instantly said "no way".

The right way is to get the APM module to put out the right voltage in the first place, which is why I whined to GM about it.
And the right voltage is a function of temperature of the battery (my solar system have temperature sensors on the batteries for that) and the intended use. 13.8v as you quote is ideal for things like UPS and burgler alarms where they're not really cycling much at all, and you can stand a long recharge time. In part-cycling use (what we have here), you use a little higher - mid 14's or so, for best overall performance. But never 15+ when it's warm, jeeez, this is going to eat these batteries fairly quick as they don't have as much electrolyte to boil out before going bad - that glass mat takes up some of the room for that.

How about some other members go measure theirs and report? I found this bouncing 15-15.2 more or less even with another 500w load on the inverter and the car on.
 

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Hmmm, 175 amps? drained or charged to the 12V battery? Since there is no starter to crank, what load can get 175 Amps drain from the 12V battery?

I agree the 2 back to back diodes are merely a patch that would help lower the charging voltage of 0.7Volts, and that the best solution is to have a proper voltage regulator fixed at 13.8Volts. I also understand that in normal use, the battery of the Volt is not designed to be used in a deep discharge / charge cycles. When the 12V battery discharges, it is an unintentionnal cause that's the root cause.

I'd like to see other owners come up with their 12V battery voltages when the Volt is powered on.
 

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Yes, we need more data - one data point might just be one bad setting resistor, D/A value (or reference voltage supply), or a bad pot - however they did it.

The reason for the high current is that a few things that are normally belt driven run off the 12v system instead in a Volt - power steering, hydraulic pump for the brakes, AC...and on and on - and it might all want to run at once. That is the rating of the charger at any rate. And remember, a kilowatt is about 80 amps at 12v, so it's not that outlandish when you're running all those motors. I've tested it to a kilowatt myself, and it holds the silly high voltage even then, with the car on. With it off, that little battery can only take that for a few seconds at most.

In this use, you really do want a voltage around middle 14's. I could take a picture of a nice AGM battery charging on my bench right now that shows 13.8 for long term float, but 14.5-14.8 for cycling - it's picky enough they printed the data right on the side!

The battery just won't draw enough current at 13.8v to get to a full charge again on a short drive, which is kind of a requirement here, and if you're going to cycle these (so they last 3-5 years instead of forever) that's OK. But the 15.1 and up - that'll just split the electrolyte into hydrogen and oxygen in short order - perhaps under a year if that voltage is maintained in the warm. Batteries have a tempco just like diodes - same direction, lower "forward volts" when hot.

The car design really needs this battery to be fully charged at turn off time, even for short runs - there's some drain for the onstar and so on all the time, so it wouldn't be good to be "too gentle" on it - but you don't want to brutalize it either. For whatever reason, GM doesn't allow the APM to charge the 12v off the 360v when the car is off - probably too much quiescent drain from it and any controller that tells it what to do that way.

It's about the same kind of service my home batteries are exposed to, actually. I'm running a large lead acid pack, about the same electrical size as the Volt main battery (16kwh or so) here, and have been for over 30 years now - I've been completely off the grid all that time. Needless to say, I know my batteries by now - you don't make many mistakes as this means you've gotta buy new ones, and they aren't cheap either. There are only slight differences in the electrochemistry of lead acid batteries. The "maintenance proof" ones use calcium in the plate alloy which reduces the gassing at high volts - but the AGMs can't use that as you can't cycle the calcium alloy plates - they fall apart in short order. So they're really just a wet lead acid chemistry and alloys, with fiberglass to keep the electrolyte from sloshing around in there - and to make a feeble attempt to recombine the H2 and O2 back into water, but they can't keep up with much of that. For home installs, they sell a palladium catalyst battery cap for this, but it's real expensive and still doesn't really fix all the badness that happens in extended overcharging - eventually the plates fall apart and the paste all falls out when you do that too much.

Well, I guess a zillion warranty claims will get GM the religion if nothing else, but they way they are doing such good service on these, it's going to be a real expensive lesson if they don't pick up on it real quick, sigh.
 

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If there are very large variations on the load asked from the 12V battery, it could be understandable that a large charging current be furnished. But the 12V battery cannot sustain 175amps (2kW) of power for very long time (less than 60 seconds).

Normally the usual charging scenario for lead acid is at constant voltage, and for usual ICE cars, it's at 13.8 Volts.
If in the Volt case, a large transient load depletes the battery, then lets go with a high charging voltage (15.1 Volts) BUT not forever!
There must be more "intelligence" or feedback put into the charger controller: temperature of the battery is certainly a nice parameter to monitor, and if the battery heats up, then this indicates an overcharge and the charge controller should lower the charging voltage to go back to 14Volts. Better, there could be a pressure switch: when the battery is starting to gas up because of overcharging, a pressure switch could signal this to the charge controller to lower the charging voltage. When high loads are being drained from the battery, a constant time higher voltage could be applied before returning back to nominal 13.8V charging.

I would be pretty confident that if all Volts charge their 12V batteries at 15.1Volts constant voltage, GM and Volt owners will get to see quite a few of those 12V batteries going dead.
 

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I believe the high output available from the APM is just so the battery really won't have to take the big peaks when the car is on and they can happen - it's just a "bypass capacitor" when the car is on - the APM delivers all demand in real time it seems.

When the car is off, the battery runs standby things - the auto-on for the computers, the remote fob listener, the OnStar radio, junk like that. Which is why they have to be real serious about getting it to full charge even in a short on-time - there's more of what we solar guys call "vampire loads" when the car is off than in most other cars - it might be much more run down than it would be in a more normal car because of them when you start it up the next time. I remember when cars first got computers and not running one for a week would result in a dead battery almost every time if the battery was over a year old - you had to drive the car at least an hour a week to overcome that one, preferably more than that.

I have good hope GM and others are learning that a battery symbol on a schematic (like most other electrical components) isn't completely described by that symbol - they have little issue and quirks, just like all capacitors have parasitic series R and L, and maybe some leakage (parallel R), which you can usually ignore, but not always - with batteries, not so much - all those quirks define the thing. They'd have to be learning that from the main battery with all it's quirks and special conditions it needs to stay healthy after all.

They'll learn of course, money talks. But it'd be nice if they could learn from the mistakes of others, rather than having to repeat them.
 
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