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Discussion Starter · #1 ·
I have a Chevy Volt with at least 1 faulty temperature sensor in the HV battery. Is it possible to filter out the data from a faulty sensor with a "man in the middle" board between the battery and HPCM2?
 

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I have a Chevy Volt with at least 1 faulty temperature sensor in the HV battery. Is it possible to filter out the data from a faulty sensor with a "man in the middle" board between the battery and HPCM2?
I'm assuming since you refer to the HPCM2 that you don't want to crack the battery case and deal with the BECM or BICMs (understandable). Otherwise if you are getting into the case, it would probably be easier to spoof the analog thermistor signal right at the BICM to battery connector. I'm not a CAN expert but it seems like it would be challenging to interleave the outgoing BECM traffic onto the HPCM2 side without tromping on frames. And vice versa.
 

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Discussion Starter · #4 ·
I'm assuming since you refer to the HPCM2 that you don't want to crack the battery case and deal with the BECM or BICMs (understandable). Otherwise if you are getting into the case, it would probably be easier to spoof the analog thermistor signal right at the BICM to battery connector. I'm not a CAN expert but it seems like it would be challenging to interleave the outgoing BECM traffic onto the HPCM2 side without tromping on frames. And vice versa.
Yes I don't want to get inside the battery - thanks for your input
 

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I'm doing something like this to try to get balancing working, so I did go inside the battery, but with different connectors you should be able to do this between the HPCM and BECM.
You can use something like this: Teensy 4.0 Triple CAN Bus Board With Two CAN 2.0B And One CAN FD Port
The code is pretty easy, packet in on port 1, check ID if it is the one you want to change, if not, send out port 2 and vice versa.
I will say I'm having a hard time making the BECM happy with my faked BICM traffic while balancing since that seems to change the packets significantly.

Anyway you can get the female and male version of the connector you want to intercept and make a harness to just brake out the can in and out and send it to the board. All of the connector types are in the Volt service manual that is available around here somewhere.
 

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Discussion Starter · #6 ·
I'm doing something like this to try to get balancing working, so I did go inside the battery, but with different connectors you should be able to do this between the HPCM and BECM.
You can use something like this: Teensy 4.0 Triple CAN Bus Board With Two CAN 2.0B And One CAN FD Port
The code is pretty easy, packet in on port 1, check ID if it is the one you want to change, if not, send out port 2 and vice versa.
I will say I'm having a hard time making the BECM happy with my faked BICM traffic while balancing since that seems to change the packets significantly.

Anyway you can get the female and male version of the connector you want to intercept and make a harness to just brake out the can in and out and send it to the board. All of the connector types are in the Volt service manual that is available around here somewhere.
I bought a cheap Chinese "man in the middle attack" board that was sold to spoof the ODO on a Mercedes, it already has the CAN interface IC's and a STM micro-controller so I plan to try using that first. If the HPCM2 to BECM traffic could be completely emulated then all sorts of things could be possible such as adding to the battery capacity or even using different batteries altogether.
Good luck with your balancing project.
 

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It’s amazing how many complete battery assemblies in the us have been replaced due to a $2 sensor but overseas it’s common practice , a simple matter and chea p to just drop the pack, remove the top and swap/clean/replace temperature sensors
 

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I'm responding to rmay635703. About a year ago, at ~160,000 miles, the battery in my 2012 Volt stopped working at temperatures below about 60 degrees. The car simply becomes an ICE vehicle. Between about 55 degree and 70 degrees, it can occasionally access the battery (which shows as fully charged on the display). Above ~70 degrees it pretty dependably accesses the battery, pretty much as normal, and I get the usual mileage from the battery before it switches to ICE. I've taken it to 2 Chevy dealers, both of whom say I need to replace the battery--for about $12,000. That is far more than the value of the car. I love this car, and would drive it forever, if not for this battery-access problem. I've told both dealers that the battery works just fine, has normal battery function and range for its age, when the temperature is right. Thus, the battery itself must be fine. There must be a faulty temperature sensor or relay or the like. Evidently, their diagnostics haven't found what sensor that might be. They keep insisting that the whole battery must be replaced. I think they just need to look harder. Does anyone have insight into this? I appreciate this forum being available.
 

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No definitive answer from me, but thoughts: I'm sure it's because the manufacturer made the decision to treat the HV battery as a black box and not train the dealer mechanics in how to do anything but remove the box and send it back to the factory (or scrap it). Probably a mix of cost-effectiveness of the training and liability issues if they messed something up while inside the battery. Even though gas systems are every bit as dangerous (if not more so), traction batteries are a new sideline to GM and complete voodoo to the average ICE mechanic.
 

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Thank you, Swoozle! It sounds like you're thinking this is not something overcome-able.
 

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Thank you, Swoozle! It sounds like you're thinking this is not something overcome-able.
your dealership gave you the F off price that indicates they don’t want to work on it.

In the US nobody will replace battery sensors

Scrap Volt/ELR Batteries are anywhere from $1000-$2500, get one with low age/miles and swap the whole thing in your driv

Brian Baptista on the Chevy Volt DIY Repair and modding Facebook page canhelp
You need to run codes yourself outside the dealership to understand the actual fault.

There are Chevy repair techs that are more competent like Jaryd Carvell also on the Facebook volt forums.

Now days you can’t take a dealers word at face value and need to do some simple checks yourself

Some have gotten an old laptop, dongle and software and just use the software to force the Volt motor on and off manually without addressing the fault, it’s up to you what level of involvement you want
But Brian can help if you will run codes yourself
 

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your dealership gave you the F off price that indicates they don’t want to work on it.

In the US nobody will replace battery sensors

Scrap Volt/ELR Batteries are anywhere from $1000-$2500, get one with low age/miles and swap the whole thing in your driv

Brian Baptista on the Chevy Volt DIY Repair and modding Facebook page canhelp
You need to run codes yourself outside the dealership to understand the actual fault.

There are Chevy repair techs that are more competent like Jaryd Carvell also on the Facebook volt forums.

Now days you can’t take a dealers word at face value and need to do some simple checks yourself

Some have gotten an old laptop, dongle and software and just use the software to force the Volt motor on and off manually without addressing the fault, it’s up to you what level of involvement you want
But Brian can help if you will run codes yourself
 

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I REALLY appreciate the thoughtful feedback I get in this community. At this point, I'm inclined to bypass the dealer and find a (hopefully) local mechanic who could replace my 2012 Volt battery (with almost 200,000 miles, and non-functioning below ~60 degrees F, with no useful solutions provided by 2 dealers). Does anyone know a mechanic who could do this? I'm in the Kansas City metro area, but would be willing to drive pretty far to get this done, if it were the right mechanic. Looking forward to ideas. Thank you
 

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I REALLY appreciate the thoughtful feedback I get in this community. At this point, I'm inclined to bypass the dealer and find a (hopefully) local mechanic who could replace my 2012 Volt battery (with almost 200,000 miles, and non-functioning below ~60 degrees F, with no useful solutions provided by 2 dealers). Does anyone know a mechanic who could do this? I'm in the Kansas City metro area, but would be willing to drive pretty far to get this done, if it were the right mechanic. Looking forward to ideas. Thank you

...and I'd be getting the used battery--presumably with a lot less use than the one I'm replacing--online or the like, per other posts on this and other threads...
 
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