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Discussion Starter · #1 ·
Howdy,
I am interested in adding a second OEM charger to a first-generation Volt to double the charging power from 3.3kW to 6.6kW. This is theoretically possible, according to work by EV developer mauswerkz, by creating a separate CANBUS network for the second charger. The CANBUS module would need to send info to the second charger based on what the car is telling the first charger to do.

Of course, there would be HVDC and AC wiring work to do: possible replacement of the J1772 inlet and AC wiring with higher-current-capacity hardware, and duplicate or replacement wiring for the HVDC charger output. Also, it'd be necessary to sniff the J1772 communication to see if there is adequate current from the EVSE to drive the second charger at full or partial power, or at all.

I could see this being pretty useful for me and others that want to minimize gas use during trips that go beyond EV range. I tend to stay close to my rural home most of the time, but regularly take longer errand-running trips that would benefit from higher-power opportunity charging. It's not necessary or beneficial for most, but it would be a nice option for some.

Does anyone know of any existing work on adding a second charger, OEM or otherwise?

Here are some more links from mauswerkz' project, which uses a number of Volt parts:
https://hackaday.io/project/4649/logs/sort/newest
http://www.diyelectriccar.com/forums/showthread.php/hacking-series-chevy-volt-hv-charger-133857.html
http://forums.evtv.me/?forum=403618
http://gm-volt.com/forum/archive/index.php/t-12958.html
https://hackaday.io/project/4649/log/46222-nitty-gritty-sweating-the-small-stuff
https://hackaday.io/project/4649/log/39542-finishing-up-underneath-enclosing-front-battery
https://hackaday.io/project/4649/log/37244-testing-supporting-components
 

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There have been several "tuners" on this board claiming that they can modify a Volt. Every one of them only talks about improving acceleration, particularly 0-60 time.

No "tuner" has even claimed to use more of the battery's total capacity, improve the charging rate, or do anything else involving the battery. Either they have no idea why people buy Volts in the first place or they only know how to change some tables, not code, through the bus.

I wonder if these guys offer Corvette tunes that just improve the mpg.
 

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Although this doesn't answer the OP's question, I disagree with Mike's comment.

  • A lot of "tuners" in this forum have modified their vehicles.
  • The most common modification is to make the accelerator pedal more sport like by default.
  • A few of us altered the ICE for better mileage.
  • One improved his 0-60 time, but required the ICE to be running and got a CEL during the process.
Regarding using a Corvette tune, that's not going to work. Our Volts are heavy and the ICE doesn't really idle since it's always maintaining the HV battery so a better tune would come from a high compression flex fuel V8 pickup.
 

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Although this doesn't answer the OP's question, I disagree with Mike's comment.

  • A lot of "tuners" in this forum have modified their vehicles.
  • The most common modification is to make the accelerator pedal more sport like by default.
  • A few of us altered the ICE for better mileage.
  • One improved his 0-60 time, but required the ICE to be running and got a CEL during the process.
Regarding using a Corvette tune, that's not going to work. Our Volts are heavy and the ICE doesn't really idle since it's always maintaining the HV battery so a better tune would come from a high compression flex fuel V8 pickup.
Are you personally aware of the engine MPG mods for better mileage? I'd love to hear more about how well that may have worked.
 

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Although this doesn't answer the OP's question, I disagree with Mike's comment.


  • A lot of "tuners" in this forum have modified their vehicles.
  • The most common modification is to make the accelerator pedal more sport like by default.
  • A few of us altered the ICE for better mileage.
  • One improved his 0-60 time, but required the ICE to be running and got a CEL during the process.

Regarding using a Corvette tune, that's not going to work. Our Volts are heavy and the ICE doesn't really idle since it's always maintaining the HV battery so a better tune would come from a high compression flex fuel V8 pickup.
Define "a lot". 3? 6? 24? 10,000?
None of the "modified" examples involve what the OP is asking about. All involve the ICE. 2 out of 3 seem suspiciously similar to what MikeG said: acceleration. The third kicks on the ICE.
 

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Although this doesn't answer the OP's question, I disagree with Mike's comment.

  • A lot of "tuners" in this forum have modified their vehicles.
  • The most common modification is to make the accelerator pedal more sport like by default.
  • A few of us altered the ICE for better mileage.
  • One improved his 0-60 time, but required the ICE to be running and got a CEL during the process.
Regarding using a Corvette tune, that's not going to work. Our Volts are heavy and the ICE doesn't really idle since it's always maintaining the HV battery so a better tune would come from a high compression flex fuel V8 pickup.
You're basically agreeing with me.

None of the tunes affect the battery in any way.

While the tuners have not disclosed their methods, other posters have strongly suggested that the tunes only involve table changes. I assume that GM has a standard format for these tables, so finding the right cells sounds doable. Decompiling the actual code has not been demonstrated.

My Corvette comment was meant as sarcasm - you don't buy a Corvette for superior mpg and you don't buy a Volt for red hot acceleration.
 

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OK, thanks for the threadjacking guys. I was hoping to discuss the addition of a second 3.3kW OEM charger to a Gen 1 Volt. Any comments on that?
You have to tell the Volt to use the second charger. That means understanding and changing the computer programs that monitor and control the Volt HV battery. No one outside of GM has ever demonstrated that capability. I hope that this answers your question.
 

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I don't have a Volt but, as an EE, I see that a second charger will not work because the onboard battery monitor communicates with the EVSE to determine the charging current. 3.3 kW is about 15 A for a Level 2 EVSE and that is set at the code level. A second charger, if setup to supply the same charge current of 15 A (for a possible total of 30 A), will be working against the first EVSE. The monitor circuit will detect the higher current and tell the EVSE to drop the current, so at the end, the two EVSE and chargers will reduce their outputs to be just 15 A together (or 7.5 A each).

Someone has to break into the Volt battery monitor code to allow higher currents to charge the battery. And someone here mentioned that the regenerative braking does supply higher currents, but that is from the motor/generator. If there were a way to "spoof" the monitor to believe that the Volt is in regeneration, maybe the higher charge current can be possible.

I once thought of a third path: a direct battery attachment, bypassing the internal monitor. But that is dangerous if the new external monitor cannot measure the exact current entering the battery and its thermal conitions. This is all dangerous due to the high amounts of energy involved. No layperson, or even an EE with little knowledge or training, can do any type of external modification to increase the Volt battery charging input over the coded 3.3 kW without getting some information or help from LG Chamical of any specialized GM engineer. The gain cannot compensate the risks involved.
 

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Also, Volt components have specific ID codes that are checked each time the car is turned on. If you even attempt to substitute a different charger in place of the original one, the car will not charge or operate until the main ECU is re programmed at a dealer to recognize the new component.

So you are are going to have a lot of serious obstacles to your project. (not saying it can't be done, just that you will have major headaches trying to get it to work without cooperation from GM)
 

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Discussion Starter · #12 ·
You have to tell the Volt to use the second charger. That means understanding and changing the computer programs that monitor and control the Volt HV battery. No one outside of GM has ever demonstrated that capability. I hope that this answers your question.
Incorrect. The Volt needs to know nothing about the second charger. All it cares about (WRT a second charger) is how many coulombs are entering the battery, and it can count the extra ones along with the others. All that matters within the Volt computer system is if it produces errors when it counts more than 3.3 kW entering the battery. It probably won't, just like computers didn't care about 00 being the year instead of 99. Why would it? The Leaf doesn't.
 

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Discussion Starter · #13 · (Edited)
I don't have a Volt but, as an EE, I see that a second charger will not work because the onboard battery monitor communicates with the EVSE to determine the charging current. 3.3 kW is about 15 A for a Level 2 EVSE and that is set at the code level. A second charger, if setup to supply the same charge current of 15 A (for a possible total of 30 A), will be working against the first EVSE. The monitor circuit will detect the higher current and tell the EVSE to drop the current, so at the end, the two EVSE and chargers will reduce their outputs to be just 15 A together (or 7.5 A each).

Someone has to break into the Volt battery monitor code to allow higher currents to charge the battery. And someone here mentioned that the regenerative braking does supply higher currents, but that is from the motor/generator. If there were a way to "spoof" the monitor to believe that the Volt is in regeneration, maybe the higher charge current can be possible.

I once thought of a third path: a direct battery attachment, bypassing the internal monitor. But that is dangerous if the new external monitor cannot measure the exact current entering the battery and its thermal conitions. This is all dangerous due to the high amounts of energy involved. No layperson, or even an EE with little knowledge or training, can do any type of external modification to increase the Volt battery charging input over the coded 3.3 kW without getting some information or help from LG Chamical of any specialized GM engineer. The gain cannot compensate the risks involved.
Also an engineer here.

I don't think we need to worry about the BMS. You're positing that the BMS will tell the original charger to scale back because it will detect extra AC input current flowing, right? I think that can be managed simply. Since the J1772 inlet and wiring will need to be replaced anyway, any monitoring hardware that the BMS may or may not monitor simply remains on the AC lines feeding the original charger, and nothing is wrong. For the second charger, a separate microcontroller handles EVSE-facing J1772 communications and feeds translated inputs to the onboard J1772 logic. Not too hard. Upstream from this, the second charger taps the incoming AC power.

On the topic of the BMS, I think the primary legitimate concern is if the BMS will produce and error when it sees more DC current coming in than usual. This may well be a problem, but I tend to think it won't. The BMS isn't sentient, and will only error out if GM programmed it to do so. And why would they? It'd be a waste of code. The charger likely has overcurrent protection, and that is sufficient for charging. The battery handles much higher currents regularly and there is no common AC charging overcurrent fault that GM engineers would create an error code for. Still possible, but I doubt it.
 

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Discussion Starter · #14 ·
Also, Volt components have specific ID codes that are checked each time the car is turned on. If you even attempt to substitute a different charger in place of the original one, the car will not charge or operate until the main ECU is re programmed at a dealer to recognize the new component.

So you are are going to have a lot of serious obstacles to your project. (not saying it can't be done, just that you will have major headaches trying to get it to work without cooperation from GM)
You are right about that, and that's why a second CANBUS network is needed. The OEM chargers are only happy to work, according to mauswerkz, as the only charger on their particular CANBUS network. So we have a second CANBUS network via a microcontroller, with some custom work mentioned previously to translate J1772 inputs and decide when and how much to run the second charger.
 

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OK, thanks for the threadjacking guys. I was hoping to discuss the addition of a second 3.3kW OEM charger to a Gen 1 Volt. Any comments on that?
Agreed - don't you just love the internet :)
It does sound interesting, however it's way above my paygrade. Hopefully this becomes a useful discussion.
 

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Also an engineer here.

I don't think we need to worry about the BMS. You're positing that the BMS will tell the original charger to scale back because it will detect extra AC input current flowing, right? I think that can be managed simply. Since the J1772 inlet and wiring will need to be replaced anyway, any monitoring hardware that the BMS may or may not monitor simply remains on the AC lines feeding the original charger, and nothing is wrong. For the second charger, a separate microcontroller handles EVSE-facing J1772 communications and feeds translated inputs to the onboard J1772 logic. Not too hard. Upstream from this, the second charger taps the incoming AC power.

On the topic of the BMS, I think the primary legitimate concern is if the BMS will produce and error when it sees more DC current coming in than usual. This may well be a problem, but I tend to think it won't. The BMS isn't sentient, and will only error out if GM programmed it to do so. And why would they? It'd be a waste of code. The charger likely has overcurrent protection, and that is sufficient for charging. The battery handles much higher currents regularly and there is no common AC charging overcurrent fault that GM engineers would create an error code for. Still possible, but I doubt it.
I think doubling the current coming into the volt with two separate EVSEs will likely fry the batteries or at a minimum shorten the lifespan of the battery. But you'd have to hack into a bunch of code that nobody really has cracked AFAIK. A few years back someone found a higher capacity charger online and was wondering if they could upgrade the onboard charger with this higher capacity one. That became a dead end.

To date, I think the only solution for charging faster is to trade the volt in for a different vehicle. I personally don't need faster charging as much as I would love a 100 mile battery with my range extender. More cargo space is also pretty high on my list as the volt is the smallest vehicles I've ever purchased for myself (I did have a Toyota Supra which was about the same size, yet 2 doors, but my Dad gave that to me).
 

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@nedfunnell:

It seems pretty obvious (to me at any rate) that you've given this much more thought, and have better comprehension of your intents and proposed implementation, than most if not all of the other contributors to this point in the thread.

Unless user WopOnTour joins the discussion, I think you may well be the most knowledgeable person on this subject who's posting here.

So while this is a good place to ask your question, I don't expect you to get very high-quality responses that go beyond what you've already gleaned on your own (unless and until WOT joins the discussion).

Personally, although this mod definitely isn't for me, I am curious to hear more about your efforts. The Volt has been available for almost 7 years now, it's about time we get some competent tinkerers who are willing and able to push the car beyond it's design limitations.
 

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There have been several "tuners" on this board claiming that they can modify a Volt. Every one of them only talks about improving acceleration, particularly 0-60 time.

No "tuner" has even claimed to use more of the battery's total capacity, improve the charging rate, or do anything else involving the battery. Either they have no idea why people buy Volts in the first place or they only know how to change some tables, not code, through the bus.

I wonder if these guys offer Corvette tunes that just improve the mpg.
Don't conflate why YOU purchased a Volt with why "people" buy Volts. This anti "tuner" attitude is infuriating.

And yes, tuners DO offer Corvette tunes specifically to improve the mpg... why on earth wouldn't they do this? Oh, right... tuners are neanderthals that are hell bent on destroying the earth, I forgot!

I purchased the Volt for 2 reasons. I love the quiet comfortable driving experience of an electric drivetrain, and because I hate waste of any kind. Driving a high powered aftermarket tuned turbocharged 300 HP Miata on the weekends is a blast, driving it as a daily driver commuter car is a waste...

Now back on topic, I don't know of anyone working on the Volt to increase battery charge rate, but twright is probably on the right track pointing you towards people that have used the Volt charger in a custom configuration on different vehicles. Good luck finding a tuner who knows Volt code that hasn't left this forum in disgust due to the bad attitude of the many "enlightened" volt owners here.

Keith
 

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I would think the simplest route would be to find a higher powered charger that fits in the space of the existing 3.3 unit (they probably exist by now as electronics get smaller over time) and build the aforementioned translation unit to make the car thing it is talking to the original lear unit (serial # 123467) and everything is A-OK

From what I can gather of the 240V charging process, the car just says "Hey, charge time" to the lear unit, it does it's job and then sends a message back to the main computer "I'm done". I know this because it always defaults to 83.5% SOC when charge complete happens. This means it's a programmed response vs a measurement. It will update to a measured/calculated SOC at a later time.
There is likely no monitoring of kW rate or anything of that sort.
The computer is only involved in 120V charging as part of the 8A/12A limiting process.
 
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