[Jiminy]

I'm starting this thread as a guide for those whose 2011-2015 Chevrolet Volt battery is in need of replacement outside of the 8 year/100k mile powertrain warranty. I just performed my first Volt battery swap over the weekend on my 2011 Volt and I wanted to document what I learned. My goal with this thread is to make it progressively better based on the questions asked in this thread and by the experiences of everyone who performs the procedure themselves. I'd like to see this become a knowledge base on the Gen 1 HV battery home-style garage swap.

My car is a 2011 Chevy Volt that had roughly 174,000 miles on it when I bought it in February, 2018. I knew it was a risk to buy a car with so many miles but this would be my third Volt and the general consensus was that Volt batteries just don't go bad. I am very experienced in messing around with cars so I didn't think I was getting myself into something I couldn't get back out of.

When I first test drove the Volt it only had a few miles of range left yet it had been running on gasoline. I asked the owner about that and he said sometimes the ICE would run before the HV battery was depleted. I should have known right then that I was barking up the wrong tree. I did have the Torque app and I scanned it and got a P0C36 code which is a cold temp sensor 6 issue. This means that the sensor saw full cold at one point or that it was an open circuit. I cleared the code and it never came back. This was a mistake in hindsight as the local dealer couldn't start a ticket with Chevrolet without a current fault code stored in the hybrid system. My opinion on that code is that it was generated by the low resting voltage of a 7 year old OE 12v battery. The car sat for a couple of months before the previous owner decided to sell it and I think it was just a spurious code generated by a tired 12v battery. I used to see all kinds of electrical anomalies with cars that sat around with weak 12v batteries. I replaced the 12v battery with a new OE battery shortly after buying the car.

Long story short I ended up buying the car for $3800 which I thought was a pretty good deal. As it turns out wasn't a great deal. That said, I wouldn't do it differently if I could though. I learned so much.

 

[Jiminy]

Diagnosis and Rationale for Swap

Well I got the car home and immediately started trying to figure out what was going on with it. The weather was coldish (for south Texas) and so what it would do was run for about 24 miles on electricity alone and then switch over to gasoline with 8-10 miles left of AER. It would run the gas motor for 2-4 miles and then switch back to EV mode. It would run a few miles in EV mode and if there were any rises in the road it would switch back to gasoline so it seemed load dependent. On one cold (40F) morning it started the ICE as soon as I started it and ran for a few minutes and then switched back to EV mode. As I mentioned before, I replaced the 12V battery to preclude that causing any issues of its own. I was shocked to find a date code on the original battery that said 2010. It was the original battery! Needless to say, putting a GM battery back in seemed like a no brainer.

I dropped the car off at my local dealer to see if they could figure it out. They had never worked on a car with such high mileage and were a little lost in diagnosing an issue that presented no codes. When they couldn't find anything concrete they did the triple honk update and replaced my hatch struts for free and said they could do nothing about the issue of uncommanded ICE running since there were no codes present. If I had left the P0C36 code in there they would have had something to start a dialogue with TAC with.

The first thing I thought was wrong was that the pack had a bad temp sensor which was forcing the ICE ON to protect the battery. When the car was at the dealer they let me look at the screen in GDS2 showing the voltages of the individual cell groups. They were all the same (at that higher state of charge) which led me to think it must be a bad temp sensor alone causing this issue. I got on ebay and looked at all of the Volt modules for sale and asked several sellers if they could locate a temp sensor in a used pack and sell me one. Not one seller could do that for me as the sensors are buried in the module and can only be accessed by destructive means. The most important thing I learned from the first visit to the dealer is that if I was going to have a chance to fix this car I was gonna have to get my hands on a GDS2 setup. So I bought a VCX NANO setup and installed it onto an old laptop running Windows 7. Below is a GDS2 screenshot showing the temp sensors. The difference between high and low readings is 4C so I guessed that it still *could* be the issue.

Next, I charged the battery all of the way up and looked at the voltages. I definitely got an interesting reading on cell group 2:

I then drove the car all of the way down to zero remaining range and found the issue:

If you let the car sit with no range left, cell group 2 just sinks further and further. I saw less than 3 volts once. Pretty clear to me that the battery pack was compromised by one bad cell group. All of the rest of the cell groups were more or less the same voltage both fully charged and with a depleted pack. Bear in mind that the car could still do 30 miles AER in warmer weather. I knew I could continue driving the car around for the summer at least but the bad cell could ruin my day if it decided enough was enough.

There were no codes thrown for the low cell group. I took it back to the dealer to try to get Chevy to help seeing that this car could suffer a complete failure at any time but the car was giving no warnings at all. This was right when the recall/service bulletin came out on the 2017 Bolt EV in regards to adding the ability for the car to warn you that it had a bad cell. This would preclude having a cell group failure with no prior warning. I argued my point but Chevrolet was unimpressed. It was the same exact thing as the '17 Bolt but since my car had 175k by then they weren't interested in doing anything for me.

The car was purchased so that I could fix it up and sell it to my 20 year old daughter, albeit with a "family discount". I'm not one to give a kid a car but I want to help. She's an engineering student and is about half way done with her degree. She's doing well at her studies. Now, I couldn't let my daughter drive a car that might suffer a battery pack failure, now could I? Dang it. I had to change the pack.

 

[Jiminy]

LOGISTICS

Logistics for buying and then getting battery to your garage

I used www.car-part.com to find a battery for my Volt. If I lived in a more EV-friendly place I would try to find a local salvage yard with a 2013 or newer pack since it would be better to see what you are getting before it gets shipped across the country. Buying a used Volt pack is a little leap of faith but remember that as soon as the car gets hit the airbag controller tells the Hybrid Powertrain Control Module 2 to open the HV battery contacts. The battery just sits there disconnected to anything until it is put back into a car. My second Volt sat wrecked for over 2 years before I bought it and resurrected it. The battery is in perfect shape as confirmed by a scan with my GDS2 setup. Don't be too afraid of a battery that has sat around since they are usually kept at or near storage voltage during normal operation. The battery I bought just happened to be a 2013 pack that was still fully charged at 4.05v per cell. Most salvage packs will have anywhere from 3.65v to 4.0v per cell. 3.85v per cell is textbook storage voltage.

The battery I ended up buying was the third one I considered. The first one was a 2014 battery that had a VIN past the 166,xxx mark so it was the bigger capacity 17 kWh 2015 battery. I was ready to pay $1500 shipped but the salvage yard came back to me and said that they decided that they were not going to ship the battery. Blah. So, I found another one in a different yard and I asked the salesperson what the delivered price was. He told me $1400 delivered to a UPS freight terminal in San Antonio. All I wanted to finish the deal was some pictures of the pack so I could judge condition. It took them three days to get around to send me pics and the pics showed the battery to be acceptable. I called them up to pay and he told me that there was a refundable $200 core deposit on top of the $1400. I told him that I had asked about a core fee initially and asked for a delivered price. He never mentioned the core fee until I was ready to whip out my credit card. I argued with him for a while and asked him to check with his superiors whether he would honor the $1400 all-inclusive shipped price. He never got back to me. The deal felt a little wrong anyway.

Fast forward a few weeks. I thought of phoning LKQ which has a yard about 35 miles from me and a giant warehouse about 15 miles away. LKQ is a giant salvage yard operation with yards and warehouses all over the country. The salesperson, Gary, that I got on the phone was very helpful and found a pack out of a freshly dead 2013 Volt. It was up in Colorado but no worries. He transferred the pack to my local warehouse for a grand total out the door price of $1500 plus tax. So, we had the battery pack transferred and he even let me go look at the pack before committing to buy it:

The pack had a crunched electrical plug (see next post) so I negotiated $150 off of the price. I knew my original pack had a good plug and I figured I could swap it out without too much trouble. (It was easy) I have a friend with a truck with liftgate and I paid him $70 to meet me at the LKQ warehouse to pick up the pack. The forklift driver put it in my friend's truck and he drove it over to my house, offloaded it and wheeled it into my garage. This is a step that was easy for me but if you call around in your city you will be able to find a freelance trucker with a liftgate that will do the delivery for a reasonable sum of cash(only).

I used my small floor jack and got the pack transferred onto a 12" wide piece of plywood and then onto furniture dollies I bought for $10 each at Northern Tool. The pack's bottom steel plate is a lot less flimsy than I read it would be so moving it onto dollies and plywood was very easy. Anticlimactic in fact.

I immediately cleaned the outside of the case with my vacuum cleaner and a dry wash mit since it was properly filthy with a very fine dust. I was happy that the pack had a patina since it told me nobody had taken the cover off. I then performed a lift test with the pack to make sure getting it up and down would pose no serious issues. It was really so very simple. Just make sure your floor jacks are centered on the pack. Work slowly. 450 pounds sounds like a lot of weight but to a good set of floor jacks it isn't.

 

[Jiminy]

Tools required and removal of battery

The single most challenging part of this Volt battery swap is jacking the car up high enough to get the black plastic rocker panels at least 20" above the ground, both front and rear. This is just enough height to roll the battery pack out from under the car, assuming you use furniture dollies that have decks that are under 5" high. My somewhat small dollies are just 4 7/8" high. I also have 3/4" plywood under the battery pack for extra support and this adds to the overall height. I jacked the car up to 21" and supported it with two very beefy 3.5 ton jack stands in front and two 6 ton stands in back, supported at the jacking points at the pinch rails. As it turned out, I had the car an inch higher than necessary so 20" should suffice for anyone else doing the job.

I have worked on a lot of cars, mostly on jack stands while laying on my back on the ground. I am pretty comfortable doing this. What made me uncomfortable with this job is the amount of height needed to get the battery pack out. Jacking up the front is easy since there is a lot of structure there like a subframe. I first drove the front wheels up on Rhino Ramps made for trucks (they are wider). I made a laminated 2x4 beam to stretch between the rear mounting bolts for the subframe. This was just two 30" 2x4's with wood glue and nails holding it together. Once I got the car up on ramps I started working on the rear of the car. The issue I had with the rear of the car is that the pinch weld jacking point is pretty close to the ideal place to put jack stands which is inboard by eight or so inches. I decided to use big bottle jacks under the inboard jacking points to raise the rear of the car since they have a small footprint. The small footprint made it easier to get jack stands under the pinch seam as I went up with the car. The bottle jacks were a pain to use. I've never used them before and will likely never use them again. One of the ones I bought from Northern Tool has a faulty release valve and the other has a piston that just doesn't want to retract at all. The other problem I discovered after I had put the front up on jack stands. I found that if I didn't raise the car evenly in the rear then one of the front jack stands would become unloaded so the car was not being held by four points of contact. Not good. I decided to make a laminated 2x4 beam 52" long to stretch across to both rear inboard jacking points. I then would raise the rear of the car with my big floor jack placed under the center of the beam. Problem is, the beam flexed too much. I had to place a thinner piece of wood on top of the center of the beam so that when the beam flexed upwards it contacted the rear edge of the battery pack and only then would the beam start raising the rear end. The rear of the pack has a very nice steel beam bolted on top of it that makes it OK to lift. This beam goes all of the way across the car and also supports the gas tank.

Once the 52' beam was properly placed and loaded I could move the car upwards by a few inches and then place jack stands under the pinch seam on the rocker panels. Since this was my only big jack I then had to move the jack to the front of the car and go up a few inches and repeat at the rear of the car. It was time consuming and a little daunting. I finally reached the 21" height and got all of the jack stands well placed to make me confident of being underneath the car. THIS is the part of the procedure that needs the most work. Getting the car up safely and supported safely is the single most challenging part of the job. I did some research on new technology for the home garage mechanic and found two products that looked promising. I'm not able to post more than one video so if you put "Safety Jack Stands in Ruzza Torino's yellow livery" into YouTube's search box you will come up with the second idea that might make the job easier and safer.

Rennstands:

View attachment 152554

 

[Jiminy]

Putting the pack back in and final words

The pack went in easily. It took about 45 minutes to go from rolling it under the car to finish bolting it up. The best news of this whole thread is that this swap required no trip to the dealer for programming or bleeding the pack's cooling system. All I had to do to avoid programming anything was to swap the BECM and the four module-level slave controllers from my old battery pack over to the new one. I also made sure that the charge on the old pack was approximately the same as the new pack (4.05v per cell group or 389v total for the pack). I used a voltmeter on the new pack to confirm voltage and then since it was fully charged (weird), I just fully charged the old battery pack before disconnecting the 12v battery. Not sure I had to do this but I wanted the original BECM to wake up to a pack that was about at the same state of charge as the battery it was just removed from. When it powered up again for the first time it didn't know anything had changed. Like a dream where you wake up a lot younger.

When you start jacking the battery pack upwards you need to line up the central cross brace in the center tunnel with the big gap in the battery's middle section. Be careful to keep it centered left to right as well.

When I got it close to the floor pan I used four, long 10mm bolts threaded into the stock holes as guides to finish raising the pack. I also checked all of the electrical plugs ahead of the pack every time I raised the jack. I didn't want to pinch anything.

Sadly, I don't have any pictures of this but as I mentioned in the last post, the hard metal coolant lines have very little give to them and so I could not get the driver side line inserted into the port without loosening the front ten or so 10mm bolts on the battery pack. This lowered the pack 1/4" so that I could get the driver side coolant line reinserted into the fitting. All of this while coolant dribbled onto my shoulder from the open port and coolant line. This won the prize for the most miserable part of the whole affair as I truly dislike the feeling of automotive coolant on my skin. anyways, I got the line reinserted, got the retaining clip back in the groove and tightened the ten bolts back up. The pack was in! If I had to do this over again, I would make sure to reinsert the coolant lines before I tightened all of the pack bolts if possible.

Reinstalling the two orange upper electrical connectors was like doing the hokey pokey. There's an order to it where only a video will suffice to show it. I have sent in a request to LKQ to get me the electrical harness for the front of the battery so that I can shoot and embed a short YouTube video. Stay tuned.

Here is a picture of the range I achieved on my first full recharge. Most of this was highway miles at 60-63 without AC. I think range will get better as the pack gets used a little more. I could perform a relearning procedure for the new pack but the car is working so well that I will likely leave it alone.

Conclusions

 

[Guest]

*grabs popcorn*

 

[Tacoma]

I looked at your picture. What do you have the battery packs resting on?
Will be interested to see how you lowered the packs in and out exactly.
Will you post any videos? or just pics?
Great thread to start by the way, thanks for starting it.

 

[Jiminy]

I used three $10 furniture dollies purchased from Northern Tool. I had planned on shooting video but the job came along slowly enough that making a proper video would require significant video editing which is definitely not my forte. I think I have enough pictures to post to convey the procedure but I will likely have to take more.

Jim

 

[Guest]

Very interested to see the rest of this, and to hear about how and where you procured the replacement battery.

 

[Loboc]

Coolness. If I were just a little younger...

 

[timoshev]

Will you be adding narrative to the last two postings that have only pictures? I am particularly interested in what was involved in replacing the end piece with the broken plastic socket. Did this break the coolant barrier? Was there a shock hazard you needed to avoid? etc. etc.

 

[Tacoma]

Diagnosis and Rationale for Swap
The weather was coldish (for south Texas) and so what it would do was run for about 24 miles on electricity alone and then switch over to gasoline with 8-10 miles left of AER. It would run the gas motor for 2-4 miles and then switch back to EV mode. It would run a few miles in EV mode and if there were any rises in the road it would switch back to gasoline so it seemed load dependent. On one cold (40F) morning it started the ICE as soon as I started it and ran for a few minutes and then switched back to EV mode.

I love this project, but silly question, this wasn't an ERDTT (Engine running due to temperature) event?

 

[Jiminy]

I love this project, but silly question, this wasn't an ERDTT (Engine running due to temperature) event?

No, the lowest temp the car saw since I have owned it was 40F, well above ERDTT territory as I understand it.

Jim

 

[Jiminy]

Will you be adding narrative to the last two postings that have only pictures? I am particularly interested in what was involved in replacing the end piece with the broken plastic socket. Did this break the coolant barrier? Was there a shock hazard you needed to avoid? etc. etc.

I am adding information to all five posts. I just uploaded photos first to make it more interesting.

Replacing the electrical plug was "plug and play". If I understand you correctly, yes, I had to open the battery pack case but I was sure to make sure the corners nearest the front relay plate were sealed with the black sticky dum-dum putty to keep the coolant inside the pack if it should ever leak internally. The case of the pack has a wide, 1/4" thick foam gasket that should make a good second sealing of the pack. I made sure the gasket surface was very clean before reinstalling the cover.

As for shock hazard, I just made sure not to wet my fingers and touch the terminals of the battery modules. The full pack voltage was 390v but that was with the orange manual service disconnect in place. I worked on the battery with the disconnect removed. I am aware of the potential danger and just kept my wits about me.

 

[Tacoma]

Thing is, if the sensor were off a bit 40 deg might trip the 35 Deg setting. Unsure of how the 2011 Volts Engine assisted heating works.

This from my 2014 Volt operator's manual, there are 2 settings to choose from:
Engine Assisted Heating
If equipped, this feature selects the outside temperature level at which the engine may run to assist heating in Electric Mode. A change in selection will not take affect until after the vehicle is first powered down. Select At Cold Outside Temperatures, for temperatures below approximately 2°C (35°F) or At Very Cold Outside Temperatures, for temperatures below approximately −10°C (15°F).


One other thought, seems like the BMS would throw some codes if it detected low cells in the main battery pack?
I am very interested in how one knows a battery pack needs replacing.
I have an EV conversion, and I can tell you what every cell in the pack is doing, and how it performs after 5 years of operation with respect to new.

Most importantly, I am interested in seeing how you did the replacement in your home garage, and I don't want to distract from that effort.

 

[Jiminy]

From what I understand, the 2011 Volts are not able to change the ERDTT threshold temperature. I always thought ERDTT was triggered at 25F.

Jim

 

[Tacoma]

This thread seems to confirm your understanding,

What the heck is ERDTT?

Again, sorry, I don't want to distract from the thread, which is a really cool project.

 

[Jiminy]

...One other thought, seems like the BMS would throw some codes if it detected low cells in the main battery pack?
I am very interested in how one knows a battery pack needs replacing...

See Post #2.

That's the thing. There were no codes thrown for the low cell group. I took it back to the dealer to try to get Chevy to help seeing that this car could suffer a complete failure at any time but the car was giving no warnings at all. This was right when the recall/service bulletin came out on the 2017 Bolt EV in regards to adding the ability for the car to warn you that it had a bad cell. This would preclude having a cell group failure with no prior warning. I argued my point but Chevrolet was unimpressed. It was the same exact thing as the '17 Bolt but since my car had 175k by then they weren't interested in doing anything for me.

Jim

 

[flyingsherpa]

Impressive, thanks for sharing! Would be interested in hearing more on how things hook back together during install... how many bolts, electrical connectors, coolant tubes did you have to mess with? Did you have to use the nano to "activate" the pack after installation? I assume you have the shop manual?

 

[Synovialbasher]

This is really cool. I've been wondering if anyone's done it yet, and I'm sure as these cars get older, batteries will fail. Good to know if mine ever goes while I still own it, I should be able to do it myself.

Like flyingsherpa asked, I'm also curious if it needs any reprogramming to get going after swapping out the battery. I'd assume you'd need to run the commands to pump the coolant through the system to eliminate air bubbles and such, along with whatever other reprogramming the computer needs.