My Yukon hybrid was been awesome for 185K miles, but recently repeatedly has coded P0AC4 Hybrid Powertrain CM Requested MIL, P0A80) Replace Hybrid Battery Pack, and P0BBD Hybrid Battery Pack Voltage Variation Exceeded Limit (Current). It also did the various crazy lurching and other funny issues. I have unplugged Hybrid Battery, replaced 12V battery, but still get repeated codes although seemingly driving "ok". I was confident the battery pack was going bad, and ordered a new GM one, which has come in today.
Since inquiring minds want to know, and as I am an industrial electrician and qualified (and worked for 40 years at the Delco Electronics plant where and in the department that a lot of the research on these and the Impact were done), I opened the battery pack and to my surprise recorded 318 VDC across the pack. Now I am wondering if I actually have battery issues or a control issue. Is 318 VDC higher or at normal levels? I don't have the equipment at home to do full testing and discharging, but want to feel ok to pick up the new battery.

 

Not sure why you started another thread. Did you just not like my response?

As you likely know, a battery or a cell's voltage tells you almost nothing except confirming that you don't have a COMPLETELY dead cell. An old worn-out 12V battery may show a very healthy 12.6V just sitting there, but the moment you hit it with a 100A load tester (or try to start a car with it), it falls flat on its face with massive voltage drop due to one or more nearly dead cells... that still hold SOME charge at rest.

All it takes is a single cell to render a pack unusable. A single cell failure of a 240 cell pack will make a difference of about 1.2V... that's a 0.4% difference at the nominal voltage. You'll never spot it at the pack level (resting voltage can easily be anywhere between 304 and 324V). You have to measure all 40 modules or 20 blocks directly to confirm you don't have a dead cell. Most meaningful results are obtained after at least 24 hours of sitting... preferably 48.

The cells are rated for 6500mAh. The voltage only tells you their approximate State of Charge (SoC), but it tells you nothing about their actual capacity or ability to deliver/receive current. With 100% consistency of data presented on this site, every GM 2-mode hybrid has experienced a progressive and massive capacity loss. This is likely what's happened to you... your 6500mAh battery is only able to deliver less than 500mAh of usable capacity due to massive AND consistent deterioration.

You can use Android phone/Torque Pro and OBDII bluetooth reader to test it in a manner similar to what I described in your other thread:

https://www.greenhybrid.com/forums/f...results-31736/

You can look at the deep dive into this battery:

https://www.greenhybrid.com/forums/f...ry-pack-31796/

Alternatively, you can connect 3X light bulbs in series to the pack. Use the safety plug for on/off. Discharge the battery with 100W light bulbs until the pack measures about 264V. Record all module voltages UNDER LOAD at that level. You will likely see substantial voltage variation, which confirms your battery is shot (they should all be within 0.1V of one another if the pack is at least semi-healthy).

 

Thank you for your knowledgeable and quick reply. I started this thread because I was not sure anyone would notice my question at the end of another thread, and I needed a quick response since I am taking my old battery in tomorrow morning to get my new one and not have to pay the core charge. I hadn't seen anywhere that the battery voltage could be over 300 V so that was why I was asking for clarification. Thank you again.

 

NOMINAL is 288V, but you never actually see one that low in the resting state unless they are completely and truly depleted of ALL usable (and unusable) charge - true 0% SoC.

Assuming:
1) healthy battery
2) parked with the SoC very near the bottom limit
3) sat for MONTHS/YEARS

A battery MIGHT read as low as 296V.

Given your high mileage, and the consistency in the nature of the failures, it's likely that you're vehicle isn't unique. It has likely failed in a highly similar fashion. It's possible that I'm wrong, but the data supports a high probability of failure.

 

Installed my new GM battery pack yesterday and WOW! I thought my battery was ok since it would Autostop, run on electric, and average 19.4 mpg all the time in city. The new battery has me in Autostop all the time and in electric a lot more in town. The guys here are right about the battery pack is pretty much gone before you start getting codes. Looking forward to seeing if mileage average goes up, gotta pay for that $3150 some way. Actually, was a no-brainer since it is such a nice truck and everything works.
Thanks to everyone on this forum that shares information, especially S Keith, Jaime, and others.
Dealer told me this battery pack was the only one available in the country excepting dealers who may had one on the shelf. Is there anyway to determine date of manufacture from serial number or nameplate? Since GM requires a $1000 core charge I was afraid I was going to get a rebuilt unit but I can tell you this one is brand new.

PS: This can be a one man job, used a 3' x 4' piece of 3/4" plywood slid in the back to the battery pack and lifted each end up onto it one end at a time. Then slid it to the back, and directly onto the folded down tailgate of my pickup truck.

 

The bar code on the pack should read "Primearth EV Energy" with the 5th digit of the serial number being a year code. "V" is 2018.

If you can remove the cover or see the serial number on the end module, the first 4 digits of the serial yield the DDMY of manufacture. M is 1-9, X, Y, Z and "Y" would be "T" for 2018.

In the Toyota world, modules are made generally 1-3 months before a pack is purchased, e.g., the new Prius pack I bought last week had modules made 11/12/2018. This can be skewed due to manufacturing surges. Toyota had a supply issue last year, and they supplied enough packs to catch up to the point that it wasn't uncommon to see packs as old as 4-5 months before purchase.

With the lower volume of the GM hybrids, I wouldn't be surprised if the "new" pack was made > 6 months ago.

Glad to hear you got it sorted. Glad to hear you got it $1K below MSRP. Glad the dealer didn't give you a ration of **** about selling it to you.

EDIT: Would LOVE for you to go through the exercise of using Torque Pro to log a discharge and post it here...

 

It1GMC that was a good move to buy a NEW pack. I sure wish that I had held out and bought a Brand New battery myself. I bought a rebuilt pack that I have installed and I am not seeing the huge drive-ability improvement that I expected...................I have done some testing on the old pack and it is at less than 25% of original capacity. If this rebuilt one actually has New modules (like they told me it does) then it should be noticeably better? My idea was that I wanted the truck to drive like it did when it was new. My dream is completely shattered.............................

 

a good benchmark is to run it at 25mph and see how many miles it will go??
make sure you warm up the batteries first.

there is a mod to run it to 29mph before the engine turns on maybe mine was modified to start at 29mph ???
two miles in EV mode is the Baseline for a new battery

so if you only go:
2 miles = 100% capacity
1.5miles = 75% capacity
1 mile = 50% capacity
0.5 mile 25% capacity
0.1 miles 5% capacity

 

I have the perfect test spot with a big hill going down to the local dam recreation area. The road by the river is at least a mile long (maybe more) / 25mph speed limit and perfectly flat. I will try that this weekend if I get out that way. I understand that there are a lot of factors such as if it is completely warmed up, the heated seats/heat/AC is being used etc etc I might try a couple of passes to see if it is fairly consistent though with everything turned off and completely warmed up................ It would be pretty cool to try to establish a way for people to see how their GM Two Mode compares to others.I have a feeling that my oversize wheels and tires may affect my EV mode duration negatively but we will see. All you guys out there find an equivalent spot with a long hill to charge and then a long slow speed flat stretch and report back with results? Who is good a doing spreadsheets? We will need to do a data base for the other poor souls that drive these dinosaurs.....Haha

 

On what do you base this? There are too many variables to consider and too many unknowns to make this consistent, let alone meaningful.