Really? I actually put it in numbered steps for you. No. That's not what I said at all. I made no mention of 300V. 300V is nowhere near fully charged. You can see that for yourself in your own data. I can't remember the specifics, but a fully charged 40 module pack at 350mA charge current will read 336-344V when full while actively cooled to < 90°F.


A fully charged pack that has sat for a week after charging will be at about 316V.


I said charge for a time and discharge to target voltages. I even laid it out in numbered steps for you. I didn't do that for my benefit.


Follow the instructions exactly as I laid them out and provide a means for cooling the battery pack in a manner comparable to its own system, i.e., air is flowing up or down through the modules at a noteworthy rate.


The fan is likely PWM controlled, so without a PWM controller you can't run the battery fan. If you could run the battery fan while charging, then your in-truck situation would work. If you could replace the fan or even just blast air into the inlet or the exhaust with some rigged dryer hose contraption or similar - that would work as long as you're getting noteworthy flow through the pack from bottom to top or top to bottom. "noteworthy" would be enough to float or displace a piece of 8.5" x 11" copier paper placed on a pack being subjected to upward flow. More is better.


Please note that it took me about an hour (my lunch hour) to generate those graphs, research that power supply and type the post. I'm not doing any of this for my benefit. I do it because I want to be helpful, but I've dealt with too many "askholes" to be tolerant of it anymore.


I don't mind being questioned at all as I make mistakes too, but when someone takes a step by step procedure and breaks it down into something barely based on it, I kinda wonder why I bother.


askhole - someone who repeatedly asks a bunch of different people for advice and takes none of it.

 

I certainly appreciate your time and helping. I didn't mean to offend or question...just making sure I understood and you telling me it isn't 300v helps.

 

As I said, please question me as I make mistakes. If something I type doesn't make sense to you, again, please ask for clarification.


It's how you took a detailed process I presented and turned it into nothing like it. That's what makes me question how I use my time.


What is not understood by most is that NiMH voltage is a bastard. It doesn't tell you much of anything, and ratings are misleading.


NiMH cells are 1.2V nominal. Note that you will almost never see a working cell at 1.2V unless it's under load. At rest, if it has any charge, it will be notably higher than 1.2V.


Any time you see "nominal" associated with a voltage, you should think of it as the "average" voltage. if you ever actually measure a resting NiMH cell at nominal 1.2V, it is actually depleted of useful charge.


A healthy battery that has sat overnight will be at about 7.7V per module or 308V for the pack - this is when it's at about 60% charge.


For the scenario I presented, I will give two caveats to the 24/30hr charge time: 1) if the voltage hasn't risen by 0.1V in the last 8 hours, you can terminate the charge as it's close enough to full and 2) if the pack is > 20°F above ambient with active cooling, it is likely full.


Lastly... cooling. That's not negotiable. You have to provide adequate cooling, or you will make it worse.

 

NOTE to ALL.


If a GM 2-Mode throws the dreaded P061b...


YOU NEED A NEW BATTERY.


Or a real specialist like S Keith to find the bad module and replace it.

 

Finally took to dealership and explained everything. They kept it for 6 hours.

They tightened the 12V battery terminals and gave it back. So far (2 hrs) so good.

 

Dealer ticket...

 

heh... I appreciate the confidence, but I am confident that I could not find the offending module based on the provided data without full pack processing. Without a full regiment of module level testing/reconditioning to determine performance parameters, I would identify the entire pack as bad due to severe imbalance from varying rates of self-discharge and/or peculiarities with the GM battery management.


Frankly, that data looks a lot like an Arizona HCH2 pack. It's shockingly common to see an HCH2 pack fail with nearly every cell losing almost all charge in a very short period of time. The pack mostly functions as each first-drive of the day get's the battery back into a working range. Heat is hard on cylindrical cells.


I have not see prismatic modules behave this way - ever; however, it is common to have notably different SD rates, but that can be mitigated by battery management. NiMH is self-balancing to a degree at higher states of charge. As SoC increases, charge efficiency decreases. As cells get fuller, a larger portion of the charge current is lost as heat compared to what is stored as capacity. The cells at lower SoC lose less current to heat and store more as capacity. Systems that manage SoC at lower levels get less of this benefit.


Is this effect dramatic? No, but it can go a long way to keeping all cells operating within the intended range, even if not well-balanced.


This pack is an enigma in my experience with prismatic modules. That's why I have some hope that grid charging to true 100% SoC may help restore balance.

 

That would be fantastic if that fixes it. Sometimes, it's easy to get focused on the bigger problem, and we forget...


12V system MUST be in good heath for proper diagnostics.

 

Y'all will be the first to know the second I can post the next time it shudders.

Meanwhile, if anyone new to this forum is looking for answers, here's my "check this first" list that I would perform before starting anything major:

1) Have your Hybrid battery cleaned professionally. It's imperative that every corner of the battery pack gets a constant flow of cooling air. Ensure that the cooling fan is functional. My battery pack had a lot of dog hair from the previous owner all around the fan, and inside the housing. My MPG boosted from 16 to 19 with that work alone.

2) Ensure that you not only have a good 12V battery, but that the leads on the terminals are TIGHT. You may also want to get the harness system checked for opens and shorts. Sometimes, even if the 12V tests good, it may have some fluctuation in output which WILL mess with your computers.

If these two steps don't curb the stalling out, then start to get a full evaluation of the hybrid battery. Then, decide whether it's time to replace the battery or, if you're able, follow S Keith's procedures.

FWIW, Greenbeanbattery.com offers a fully reconditioned battery swapout for the 08 Tahoe for around $2500. It's only available in the East, and they come to you. That's out the door. They don't diagnose, though. So, if your 12v battery terminal is loose, it ain't gonna do you any good to replace the whole battery.

Good luck!

 

I've assembled all of the necessary tools to rebalance the battery and followed the wiring diagram by sharrq27 (image below) but something isn't quite right. I have insured all the wiring is fine and I get a tone when checking continuity.

Prior to attaching to the HV battery with the LPC-150-350, my Harbor Frieght voltmeter is reading 419 (my good meter is reading 429) and the Harbor Frieght is reading 0 amps. When I connect it all up to my HV battery and reinsert the orange plug, the volt meter is reading 419 and the amp meter is still at zero. I have confirmed that I do have the 429 volts at the hv posts. Have I wired something incorrectly and it isn't completing the circuit or does the HV battery need to charge back up after I pulled the HV orange plug? I'm starting to think this isn't as easy as connecting + to + and - to - !!

My setup is exactly like this picture (except I have the LPC-150-350 transformer)