08 Tahoe hybrid
 

I have been the owner for about two years. experiencing stalls, surges and all that.
Taken it to dealer, they said replace the 300 v battery. (of course, for about $4,000)

1. Can I disconnect it without jeopardizing steering and braking?
2. Can I open it up and check and or recondition / replace the individualcells?
I have had it open and just need a bit more specific step by step instructions to follow.
I am willing to purchase some hardware that can charge / discharge the cells.
Any help or ideas would be great!
Jim

Re: 08 Tahoe hybrid
 

I can not wait to make some progress.
I just pulled the 300 v battery disconnect, then tried to start it. No starting at all, "SERVICE HYBRID SYSTEM" at the information center.
So I plugged it back in and it starts fine.

Please let me add some details from the dealers "DTC,s"
found codes: P1A88, P0BBD, P061B
The dealer, "Checked 300 volt battery cell voltage and found to have two cell groups bellow 11 volts causing concern."

I do not know how many "cell groups" are in the 300 volt battery. I think this will come into play during a reconditioning regarding balancing.

I realy need some specific details about how the battery is configured.

Is there a different way to disconnect the 300 volt battery without disabling the gas motor?
Help!

Re: 08 Tahoe hybrid
 

No. The electric/gas systems are fully integrated. Battery can not be bypassed or disabled. The hybrid battery starts the engine. There is no traditional starter.

There are 20 voltages monitored throughout the pack. 11V is horrible.

Mentally, you need to think of this as an SUV with a failed transmission. A MAJOR propulsion component has failed.

With 100% consistency in data presented on this site, reconditioning is not a viable option. The GM Hybrids and the Generation 3 Toyota hybrids have shown a frequent tendency to DAMAGE batteries with use. DAMAGE can't be fixed with reconditioning.

Your best option is to purchase $2200 worth of known good modules, because without proper testing of modules, which is a crap-ton more than just checking voltages, you'll be in the pack every 1-6 months trying to figure which module(s) is/are screwing you this time.

Terminology lesson: A battery is a collection of individual electrical cells. There are 240 individual NiMh CELLS in your battery in series. Those 240 cells are contained in 40 6-cell batteries that are replaceable. Those are frequently incorrectly referred to as "cells". They are correctly referenced as "battery module" or "module" or "subpack." Most common correct use is "module".

Since they're in series, a single cell failure takes the whole battery out.

NiMH CAN'T be wired in parallel because of the voltage drop phenomenon when a cell fills. Thus, once a cell is full, if there are other cells with it in parallel, their voltage will be higher, thus ALL the current will get dumped into the full cells... thermal runaway. Not like a Tesla catching fire at a supercharger, but a very bad day for the battery/owner.

Re: 08 Tahoe hybrid
 

Thanks for the help! Supper helpful.

Any ideas about replacing the 40 modules themselves or go after a rebuilt pack as a complete unit?

I live near Portland, Oregon. Can you recommend a vendor to get new/ rebuilt parts from?
Jim

Re: 08 Tahoe hybrid
 

Bumblebee batteries.

Re: 08 Tahoe hybrid
 

I have see bumblebees site. I will go back with more knowledge about what I need.

I have been rereading your posts.
300 v ÷ 40 modules = 7.5 v each
That matches info I have read.
each module contains 6 × 1.5 v cells = 7.5 v

Given that info I deduct that voltage measured at 20 places means ( 40 modules ÷ 20 = 2 modules that is also 7.5 × 2 = 15 v)
That is what the dealership service center was looking for (15 v ), not the 11 v found in multiple places on my defective pack.
I wonder if they could get that with a good scanner or if they had to open up the pack itself?
Just wondering.

Re: 08 Tahoe hybrid
 

Here's what you need: Call them. Tell them your make and year. Tell them you need your battery rebuilt. Tell them Steve in AZ recommended that you call them. They are in Gresham. They recently did one, and they replaced all 40 modules with known good modules from Prius batteries. Most of the GM

Correct, 20 block voltages will each be 2X module voltages. However, they are not looking for 15V. They are looking for outliers outside a tight range (more on that below).

7.5V is expected after a lengthy sit (multiple weeks/months), or if the car is parked with the battery at a VERY low state of charge. I have a Prius pack that has sat for 18 months. Voltages were 7.47-7.50V. Resting voltage is usually notably higher than 7.5V. Resting module voltages of a healthy battery are RARELY outside a 0.05V range.

The GM scan tool can see the block voltages as reported by the battery ECU along with lots of other battery data - SoC, current flow and direction, etc.

There are custom PIDs to enable Torque Pro for Android to see those blocks as well. Short version: get a bluetooth OBDII reader ($10-20), install Torque Pro ($5), enter the extended PIDs, configure the display to show them, configure the logger to record them. Search this site for more. One caution is the data rate of logging. Sampling of the block voltages can be so slow that it's hard to compare them unless you're under a relatively constant current.

While resting voltage tells you almost nothing, active voltages tell you MUCH. "Active" voltage means voltage response to discharge/charge current. A healthy battery will show very little deviation between the 20 blocks as the battery charges and discharges. Generally speaking, for light loads of 20-40A or so, they will not be outside a 0.20V range. For higher loads, they will rarely be outside a 0.30V range except for momentary bumps to 0.60V or so.

Re: 08 Tahoe hybrid
 

Making progress.
Following your advice I got a obd2 Bluetooth. Tourqe pro app. Love how they work, very fun.

Now trying to get serious about gaining the ability to read the twenty voltages the dealership charged me $120 to do.

My goal is to establishe a base before I remove the battery from the vehicle. Tear it down. Try to find the two bad module blocks (dealership info) and replace them with the four matched/ balanced modules I ordered online.

Note: I did contact bumblebee batteries as you recommend. I just can't afford to spend $2300-$3400 right now. (Price to rebuild my battery pack is dependent on the length of the warranty).

I was looking around this site to get more specific instructions on how to get Torque Pro to display voltage and current info and came across a thread that blew me away!

You and Hillbilly Hybrid were going very deep. I was able to keep up with the info presented. As I read on for hours I learned a great deal. Thanks to both of you.

Back to my current task.
Can you please direct me to specific instructions on how set up/ program the Pig's into tourqe pro so I can monitor my HV battery?
Jim Fleck

Re: 08 Tahoe hybrid
 

Re: 08 Tahoe hybrid
 

Your assumptions with your current course of action:

1) Everything I've told you is wrong.
2) The data presented on this site doesn't apply to your vehicle.
3) The dealer competently diagnosed the issue
4) the four "matched/balanced" modules you ordered "online" are:
a) matched
b) balanced
c) even suitable for installation in any vehicle.

Per post #7, I said you had to search this site for the PIDs.

Good luck,

Steve