2008 Tahoe Hybrid sitting for months...

[bbOOmm]

My 2008 HyHoe was running just find although I think the original 2008 hybrid battery was starting to go. I was not getting much distance running on just the battery... far shorter than usual. I parked it in the fall, I didn't disconnect the batteries expecting my wife to run the engine once a month to charge up everything. Well, she forgot..... 4 months later and after several periods of below zero weather, she went to start it.... its completely discharged. Not even the electric locks work, not even a dim dome light.

I'm not home yet - I'm still out of the country for another 2 months, still lots of winter left back at home, so I'm going to assume that the brand new $200+ AGM battery is now frozen and trashed. What about the NiMH hybrid batteries.... can they freeze and be damaged if they are discharged and then exposed to freezing temperatures? I'm assuming the hybrid battery pack will be discharged since from what I understand, the hybrid system maintains the charge on the 12v system. So if the 12V is dead, the 300V must be dead.... and frozen.

Lastly, I did a search in the forum but I didn't find an answer. Maybe I used the wrong search words.

Since the engine is started off the hybrid battery pack, is there a way to put a charge in the hybrid battery from a charger. I'm sure I could figure out something going the reverse engineering route taking the lid off the battery pack and build a 300V+ charger... but really before going that route, I'd like to see if there is a proper way, like what the dealer would do if a hybrid Tahoe came in with dead batteries. It would be a real stup!d design if the engine uses the hybrid battery pack, and the engine is the only way to charge the hybrid battery pack. There's gotta be a way of charging the hybrid pack to get the engine started.

I had plans to replace the hybrid pack.... now it looks like this spring/summer will be that job. But till I get to it, the Tahoe needs to be moved, so I need to get it started when I get home. In the mean time, I want to think about the options I have.

Any ideas on charging the 300V hybrid pack?

Thanks

 

[swathdiver]

My 2008 HyHoe was running just find although I think the original 2008 hybrid battery was starting to go. I was not getting much distance running on just the battery... far shorter than usual. I parked it in the fall, I didn't disconnect the batteries expecting my wife to run the engine once a month to charge up everything. Well, she forgot..... 4 months later and after several periods of below zero weather, she went to start it.... its completely discharged. Not even the electric locks work, not even a dim dome light.

I'm not home yet - I'm still out of the country for another 2 months, still lots of winter left back at home, so I'm going to assume that the brand new $200+ AGM battery is now frozen and trashed. What about the NiMH hybrid batteries.... can they freeze and be damaged if they are discharged and then exposed to freezing temperatures? I'm assuming the hybrid battery pack will be discharged since from what I understand, the hybrid system maintains the charge on the 12v system. So if the 12V is dead, the 300V must be dead.... and frozen.

Lastly, I did a search in the forum but I didn't find an answer. Maybe I used the wrong search words.

Since the engine is started off the hybrid battery pack, is there a way to put a charge in the hybrid battery from a charger. I'm sure I could figure out something going the reverse engineering route taking the lid off the battery pack and build a 300V+ charger... but really before going that route, I'd like to see if there is a proper way, like what the dealer would do if a hybrid Tahoe came in with dead batteries. It would be a real stup!d design if the engine uses the hybrid battery pack, and the engine is the only way to charge the hybrid battery pack. There's gotta be a way of charging the hybrid pack to get the engine started.

I had plans to replace the hybrid pack.... now it looks like this spring/summer will be that job. But till I get to it, the Tahoe needs to be moved, so I need to get it started when I get home. In the mean time, I want to think about the options I have.

Any ideas on charging the 300V hybrid pack?

Thanks

@RebelBelle

Could your wife put a charger on the under the hood battery or put it on a tender to rejuvenate it?

 

[bbOOmm]

The 12V battery under the hood is not the problematic issue - it can be easily charged and/or replaced. Its the 300V hybrid battery under the rear passenger seat that I need to charge somehow. To start the engine, one of the 300V motors in the transmission spins to crank the engine - that motor is powered by the 300V hybrid battery. On the 6.0L LFA engine on the hybrid Tahoe's, there is no typical 12V starter motor like you find on typical gassers. The 12V system is for powering the logic, controls and lighting... nothing to do with cranking the engine other than powering the ECM and other electrical stuffz like ignition coils, sensors etc.

How can I charge the 300V hybrid battery so I can get the engine started? Once the engine is started, the electric motors in the transmission switch to generator mode and charge the 300V hybrid battery.... this is where the problem lies - the engine needs to run to charge, but the battery needs to be charged to start the engine. Unless there is another way of charging the 300V hybrid battery - that is what I'm asking.

 

[wjburken]

I believe you can jump the vehicle with a 12V battery even when the 300V battery is dead. There are instructions in the manual on how to do it.

https://my.gm.com/content/dam/gmown...2008_chevrolet_tahoe_hybrid_owners.pdf#page81. I believe it’s on page 5-16.

Here is another post from electricvehicleforums.com regarding this same thing.

 

[bbOOmm]

Well, I found this using Jump-Assist as a keyword... looks like I have to get a Tech 2 Scan tool to initiate the APM to charge the 300V pack from 12V.

Now, to find a Tech 2 Scan Tool that will work.... I'm very leery of the chinese knock offs that are flooding ebay and amazon .... or are they OK?

 

[swathdiver]

Well, I found this using Jump-Assist as a keyword... looks like I have to get a Tech 2 Scan tool to initiate the APM to charge the 300V pack from 12V.

Now, to find a Tech 2 Scan Tool that will work.... I'm very leery of the chinese knock offs that are flooding ebay and amazon .... or are they OK?

Vetronix and Bosch transferred production to China over a decade ago, the original factory still makes them, while one or two people have gotten duds, the rest of us have had excellent results and even good customer service. The key is to buy from a seller with genuine reviews and lots of sales.

Is the truck in Florida, there's a couple of us around the state on here who have them.

 

[bbOOmm]

Vetronix and Bosch transferred production to China over a decade ago, the original factory still makes them, while one or two people have gotten duds, the rest of us have had excellent results and even good customer service. The key is to buy from a seller with genuine reviews and lots of sales.

Is the truck in Florida, there's a couple of us around the state on here who have them.

No the vehicle is in Wisconsin.

I'm seeing some Tech 2's for $250, some in the $350 range, some over $450.... most are shipped from China. Just wondering, what is the new price for a Tech 2 scan tool.... I know scammers with fake items like to price things really cheap.... I don't want to fall for that.

 

[swathdiver]

No the vehicle is in Wisconsin.

I'm seeing some Tech 2's for $250, some in the $350 range, some over $450.... most are shipped from China. Just wondering, what is the new price for a Tech 2 scan tool.... I know scammers with fake items like to price things really cheap.... I don't want to fall for that.

They were over $3K. GM has moved on to other types of tools. The going rate for the Chicom ones is about $300-350 last time I looked. Could be less, just make sure it comes with all the little adapters, the CANdi module and VCI module and most importantly the 33.004 version software on the PCMCIA card.

Historically, they don't take long to get here. I ordered a new CANdi module for mine from them on January 20th, should have it tomorrow.

 

[BG1988]

No the vehicle is in Wisconsin.

I'm seeing some Tech 2's for $250, some in the $350 range, some over $450.... most are shipped from China. Just wondering, what is the new price for a Tech 2 scan tool.... I know scammers with fake items like to price things really cheap.... I don't want to fall for that.

the other choice would to manually charge each battery using a regulated controller ..


remote start button is an option just tap the lock twice and the start button.. and pressing the start button again will automatically shut it off

 

[bbOOmm]

the other choice would to manually charge each battery using a regulated controller ..


remote start button is an option just tap the lock twice and the start button.. and pressing the start button again will automatically shut it off

I would have no problem making an individual cell charger or making a 300V+ charger... if I had to go that route. I'm going to try the onboard Jump-Assist first. I just need to get a Tech 2.


I'm not sure I understand your remote start button comment --- I think 2x lock then start button is to remote start procedure, not to put the system into Jump-Assist.

 

[wjburken]

I would have no problem making an individual cell charger or making a 300V+ charger... if I had to go that route. I'm going to try the onboard Jump-Assist first. I just need to get a Tech 2.


I'm not sure I understand your remote start button comment --- I think 2x lock then start button is to remote start procedure, not to put the system into Jump-Assist.

Are you sure you need a Tech-2 just to jump the vehicle using another vehicle with a 12V battery? In looking at the manual for your vehicle, it shows how to jump with a 12v vehicle but doesn’t mention anything about needing a Tech-2. The post from another forum that I shared mentions the Jump-Assist, but I’m not sure that’s the same thing as what is outlined in the manual. I’ll admit, I don’t have a Hybrid and am only going off of what I read in the owners manual for your vehicle.

 

[bbOOmm]

Are you sure you need a Tech-2 just to jump the vehicle using another vehicle with a 12V battery? In looking at the manual for your vehicle, it shows how to jump with a 12v vehicle but doesn’t mention anything about needing a Tech-2. The post from another forum that I shared mentions the Jump-Assist, but I’m not sure that’s the same thing as what is outlined in the manual. I’ll admit, I don’t have a Hybrid and am only going off of what I read in the owners manual for your vehicle.

I have the original Hybrid Tahoe owners manual for the vehicle, I read the same thing. In several other areas in the HYBRID MANUAL, it describes features, functions and procedures of the gasser Tahoe, as if GM forgot to edit the sections for the Hybrid. This jump starting section in the HYBRID MANUAL is one of those forgotten sections I'm thinking, because it does not make any sense, especially after reading the Jump Assist procedure. The controllers have to be instructed to charge the hybrid pack. In normal operation, with the engine running, the vehicle generates 300V+ from the motor/generators in the transmission, then the 12V system is charged through a controller. Not the reverse.... unless in Jump-Assist mode. There is no engine driven generation of 12V as it is with a gasser.

The errors in the HYBRID MANUAL add to the confusion to MANY issues. Like..... WHERE THE EFF is the fuses or circuit breakers for the AC compressor? The manual references a 300V electric compressor, but yet references the fuses for the gasser 12V AC system.

 

[BG1988]

I would have no problem making an individual cell charger or making a 300V+ charger... if I had to go that route. I'm going to try the onboard Jump-Assist first. I just need to get a Tech 2.


I'm not sure I understand your remote start button comment --- I think 2x lock then start button is to remote start procedure, not to put the system into Jump-Assist.

just make sure the key is off position when attaching the 12v+ or a new battery

or you set off the crash detection system, that will disable the suv from being started(it would have to be reset then )


for the a/c system
it's in the HV battery most likely since it's tied into the HVDC system i guess Fusible Links?

 

[bbOOmm]

just make sure the key is off position when attaching the 12v+ or a new battery

or you set off the crash detection system, that will disable the suv from being started(it would have to be reset then )


for the a/c system
it's in the HV battery most likely since it's tied into the HVDC system i guess Fusible Links?

I was thinking it would be in the HV battery enclosure, but looking at the exploded view of the HV system as a whole, the 300V AC compressor has a short wiring harness that goes to the hybrid controller / inverter. I remember taking the plastic cover off that unit ( Under hood, rear ,passenger side) just to see what was hiding under it, long ago, There is an aluminum box basically, bolted up tight, nothing much more and the HV wiring going in and out of it.

Has anyone opened up one of these Tahoe hybrid inverters ? Pictures? Curious to see whats in it, how its constructed and if there are any fuses, fusable links, or circuit breakers hidden in there. Gotta be something. It seems unsafe to have HV wiring going places without any sort protection devices.

 

[BG1988]

I have the original Hybrid Tahoe owners manual for the vehicle, I read the same thing. In several other areas in the HYBRID MANUAL, it describes features, functions and procedures of the gasser Tahoe, as if GM forgot to edit the sections for the Hybrid. This jump starting section in the HYBRID MANUAL is one of those forgotten sections I'm thinking, because it does not make any sense, especially after reading the Jump Assist procedure. The controllers have to be instructed to charge the hybrid pack. In normal operation, with the engine running, the vehicle generates 300V+ from the motor/generators in the transmission, then the 12V system is charged through a controller. Not the reverse.... unless in Jump-Assist mode. There is no engine driven generation of 12V as it is with a gasser.

The errors in the HYBRID MANUAL add to the confusion to MANY issues. Like..... WHERE THE EFF is the fuses or circuit breakers for the AC compressor? The manual references a 300V electric compressor, but yet references the fuses for the gasser 12V AC system.

this it's not inside of the inverter but it's still good information

​

 

[bbOOmm]

this it's not inside of the inverter but it's still good information

​

That video helped a bit. Now I see the cover the comes off to get access to the wiring for the two motor/generators. Towards the front of the inverter under that now removed cover, theres some device there. If I'm remembering correctly, that is about where the AC HV wiring enters the inverter, so MAYYYYYYBE, that device is the a fuse, a fuseable link or a circuit breaker for the HV AC compressor. Cool, something for me to look at when I get home. I was worried because there is a totally separate cooling system for the hybrid system, I didn't want to unbolt something and have a mess on my hands trying to seal it back up, the video showed the access cover.

 

[dnt1010]

I understand your concern about the Hybrid battery being dead but maybe it is OK? I would probably charge the 12V under the hood first before going to a lot of extra trouble and expense. The issue with the crash detection shutting down the system is REAL what I would do is disconnect the 12V battery cables and charge the 12V battery independently of the vehicle then once fully charged, remove the charger and reconnect and give it a try.
If that simple and cheap procedure fails then to me the key information is that you believe that Hybrid battery already needed to be replaced and maybe just go ahead and do that? Sometimes the simplest plan is the best?

 

[2-ModeJoe]

I understand your concern about the Hybrid battery being dead but maybe it is OK? I would probably charge the 12V under the hood first before going to a lot of extra trouble and expense. The issue with the crash detection shutting down the system is REAL what I would do is disconnect the 12V battery cables and charge the 12V battery independently of the vehicle then once fully charged, remove the charger and reconnect and give it a try.
If that simple and cheap procedure fails then to me the key information is that you believe that Hybrid battery already needed to be replaced and maybe just go ahead and do that? Sometimes the simplest plan is the best?

I am not understanding why you are looking into such complicated (and expensive) resolutions for (as of now possibly a dead 12V battery) to crank it and start charging the entire system. As you probably know,it has 2 generators,and you CAN crank the engine with adequate voltage from your 12V battery. I know this is now an ild thread,but I own a 08 Hybrid Tahoe also,and I have only had to charge (or replace) the 12V battery for a nonstart due to lack of Voltage,and I was hoping you can give us an update as to what happened when you returned to the vehicle and started working on getting it cranked?? It will likely be valuable information for us on here. Thanks

 

[2-ModeJoe]

No the vehicle is in Wisconsin.

I'm seeing some Tech 2's for $250, some in the $350 range, some over $450.... most are shipped from China. Just wondering, what is the new price for a Tech 2 scan tool.... I know scammers with fake items like to price things really cheap.... I don't want to fall for that.

Why not start with he 12v battery first,test it & charge\replace and then drive it a substantial distance with plenty of coasting and substantial time to more thoroughly charge the 300V battery before buying extra possibly unnecessary products? Can you let us know whatever happened?? Thanks

 

[SpareParts]

You realize his last post about this was in 2022.