I have a very basic question regarding how to make a non-plugin hybrid into a plug in hybrid. Lets say you have a hybrid Tahoe, Prius or whatever, couldn't you add an auxilliary battery pack that you connect in parallel with the existing battery back and hook it up with diodes so that it does not get charged by the vehicle? You would then charge this battery pack only at home with a charger. Doing this would allow the auxilliary pack to run the motors/charge the original pack without the ICE running but yet the ICE would never charge the auxilliary pack. Voila - cheap, down and dirty plug in conversion. What is the down side?

The electronics are the least of your worries. The main problem is that the electric motor wasn't designed to power the vehicle without an assist from the ICE. You could do what you want, but you'd end up with a really expensive NEV (neighborhood electric vehicle).

IMO, the YukoBurbaHoe hybrid is a waste of time, money, and technology.

The electronics are the least of your worries. The main problem is that the electric motor wasn't designed to power the vehicle without an assist from the ICE. You could do what you want, but you'd end up with a really expensive NEV (neighborhood electric vehicle).

IMO, the YukoBurbaHoe hybrid is a waste of time, money, and technology.

Well, for the small group of people who actually need a vehicle that size, it's a great truck. They get to have their truck functionality and get 75% better fuel mileage while doing it, they just don't get relatively great fuel mileage as a 2- or 4- passenger vehicle not hauling anything, when compared to other vehicles that can do THAT task well (at half the price.)

In retrospect, it was a dumb play to focus on the 2-mode hybrid tech for the big trucks, but it makes a little sense when you consider it's one size down from the system they made for buses, and it's a GREAT system for buses with their constant start-stop operation. They got caught out with nothing competitive in the "small nice efficient car" market, and it's costing them, but the hybrid trucks aren't worthless, they're just for special applications.

You have the basic idea for the conversion. It's a little more complicated than that, but your basic idea has been done and is being done for $10,000/unit by a Colorado company. They have converted a number of Prius' and Escapes for the electric coop industry. Besides adding the LION battery pack they also have to add an on-board charger and change the vehicle computers programs so that the ICE does not come on until the battery is down to a preset level. They had at least one Prius burn up because of a short in the LION batter pack they were using, but it seems that was a fluke and not the norm.

Our local electric coop has a plug-in Ford Escape and it gets a fairly consistent 100 MPG in daily city driving.

So what you want to do can work and is working today, but it's not something that I attempt in my garage. Just buy the Prius or Escape, find the company to convert it for you (for $10,000), and start enjoying not buying much gas.

In retrospect, it was a dumb play to focus on the 2-mode hybrid tech for the big trucks
It would have been a great play if the price difference was $2K rather than $10K. As it is the spread is too great, though in truth it might still be a good deal if you do a lot of "city" driving.

IMO, the YukoBurbaHoe hybrid is a waste of time, money, and technology.As compared to WHAT exactly (besides the Volt)
FYI the 2-mode utilizes more "electric only" and electric assist THAN ANY OTHER HYBRID!
So what HEV or PHEV are you comparing it to that has any more capability?

WopOnTour

To the OP:
What you're proposing COULD work, as it pretty much would create a plug-in hybrid. However integrating that into the system without being able to modify the software of the battery energy and hybrid power control modules would be difficult, if not impossible. Otherwise you would just trigger a myriad of DTCs and they system would shut down the HV operation completely. Maybe once the the 2-Mode plugin VUE is out there would be someway to mesh the firmware from it onto the Tahoe/Yukon, then add a battery pack somewhere...

It would have been a great play if the price difference was $2K rather than $10K. As it is the spread is too great, though in truth it might still be a good deal if you do a lot of "city" driving.Your numbers are incorrect is all. Your $10K is basically comparing a lower level LS or LT Tahoe to the Hybrid model. Try compring apples to apples for an equally equipped Tahoe or Yukon. i.e. add the "upgrade" costs of the items optional items the Tahoe/Yukon Hybrid INCLUDES as standard equipment such as:

3rd row seating,6-way power leather bucket front seats (both) with center console, DVD/GPS based navigation system with LCD screen, 9 speaker Bose RDS audio system with XM, subwoofer, Bluetooth voice control and 2nd row controls with headphone jacks, Tri-zone automatic climate controls with 2nd row controls, rear A/C and heater, rear view camera system, ultrasonic rear park assist, intermittent rear wiper/washer system, overhead console with universal programmable home remote, electrcally adjustable pedals,leather wrapped steering wheel with radio controls,automatic locking rear differential, 18" wheels and tires, real time active suspension system, HD trailering package with 2" receiver hitch, 7-way Bargman plug and electronic brake control harness, rear 110V accessory inverter outlet, electric tire pump and inflator kit, remote vehicle start system, as well as 37HP and 62 more LB/FT of engine...

Whether you agree with the way GM has chosen to "package" the 2-mode hybrid or not, the real difference in price FOR THE HYBRID SYSTEM is actually closer to $4K.
WopOnTour

Your numbers are incorrect is all. Your $10K is basically comparing a lower level LS or LT Tahoe to the Hybrid model. Try compring apples to apples for an equally equipped Tahoe or Yukon. i.e. add the "upgrade" costs of the items optional items the Tahoe/Yukon Hybrid INCLUDES as standard equipment such as:

Whether you agree with the way GM has chosen to "package" the 2-mode hybrid or not, the real difference in price FOR THE HYBRID SYSTEM is actually closer to $4K.
WopOnTour
However you want to look at it, you have to pay way more for the hybrid. GM did the same thing with the Escalade. To me this is similar to when, to get the option you want for $1000 you have to buy two options you don't really want for $4000. In my mind the option I want costs $5000 though you'd say $1000.

Just a different way of looking at it.

Yes, and I agree with your assessment as well and I absolutely don't agree with how they are currently packaging the 2-mode utilities. I just don't like to see people paint it with a big broad add $10,000 dollar brush for the hybrid version, when you "get" (albeit force fed?) so much more for that 10K.

Certainly some people want a "luxury" 2-mode hybrid, but I believe they'd sell more of them if they'd dress them down a little. I'm really against the navigation display. That's a near $3000 option alone, and just to watch the pretty hybrid drive pictures (and be potentially ditracted because of it) that has no real functional purpose. The "double-edged" economy gage on the cluster is all one needs to learn how to optimize your driving habits.
JMO
WopOnTour

The parallel hybrid motor is way too small. It can never be a true series hybrid. End of story.

On the other topic, the 2-mode truck hybrid is brilliant. It just needs to be way cheaper for this market. They need to create striped down models and attempt to make them more accessible. The days of big profits on big vehicles is over for now. Just like the housing market, without all kinds of "free" money and debt schemes, the seller has to work much harder to meet the buyers actual needs and budget.

Here's an idea for GM, build a fleet of 2 Mode hybrids designed for the contractor. You know, plain white trucks meant to work. Install the system in your cargo vans and you can finally knock Ford from the king of the vans like they have been for the last 30 years At the same time, take some of the wind out of the emerging Dodge Sprinter van. Offer it in cab only and cut-away versions so body companies can build special utility bodies.

The parallel hybrid motor is way too small. It can never be a true series hybrid. End of story.I think one of us is confused. I was assuming the OP was considering adding a "plug-in" charging system and an additional isolated, depletion battery in order to convert a 2-mode Yukon/Tahoe into a PHEV. i.e. More akin to the upcoming 2-mode hybrid VUE, not actually attempting to turn it into a pure series hybrid (or EREV like the Volt)
WopOnTour

Here's an idea for GM, build a fleet of 2 Mode hybrids designed for the contractor. You know, plain white trucks meant to work. Install the system in your cargo vans and you can finally knock Ford from the king of the vans like they have been for the last 30 years At the same time, take some of the wind out of the emerging Dodge Sprinter van. Offer it in cab only and cut-away versions so body companies can build special utility bodies.I think we WILL see the "stripped down" 2-mode pickup in the not-too-distant future. However for 2009 MY (Q:1 2009) apparently it will only be available in a crew-cab short-box with a "package" of fixed options similar to the Yuk-Tah hybrids.
WopOnTour

Yes, it cold be done but you'd also have to re-program the computer that controls the battery charging. The extra battries would 'confuse' it. If the computer cannot control the charging you may siginficantly reduce the life of the batteries.

Ned23, Why? The ICE/regen braking would only charge the original battery. I believe the cpu would be unaware of why or where the extra power is coming from. When the voltage of the original battery was lower than the aux battery then power flow would come from the aux battery either to the original battery or to the motor, most likely the latter because that is what would be pulling down the voltage of the original battery. Remember with diodes in place the vehicle would not be able to charge the aux battery only the original battery. Once the aux battery is drained to the lowest voltage that the original battery is allowed to drop to then the aux battery voltage would never be higher than the original so from then on it would be just extra weight until you charged it at home again.

The parallel hybrid motor is way too small. It can never be a true series hybrid. End of story.


I agree.
Adding an additional battery only increases the range of that really slow speed that Priuses can do before the motor kicks on.
If your upgrade includes a motor power increase you need to make sure that your battery architecture can support it.

As for changing software, I bet that would have to be upgraded. At least your fault detection thresholds will need to be changed to accommodate different system response. That being said that type of change is not difficult especially if your software is built well.

The last I saw, upgrading your Prius cost more like $30k not $10k. But I was only browsing and not investigating. If someone can point me in the direction of a company that does that work cheap, my family would be interested in a conversion.

I think one of us is confused. I was assuming the OP was considering adding a "plug-in" charging system and an additional isolated, depletion battery in order to convert a 2-mode Yukon/Tahoe into a PHEV. i.e. More akin to the upcoming 2-mode hybrid VUE, not actually attempting to turn it into a pure series hybrid (or EREV like the Volt)
WopOnTour

Yeah, you're right. I was confused. The OP is just talking about building a plug in parallel hybrid. So I'm not sure now what he is asking. Isn't what he is talking about pretty much what all these after market companies are doing right now for big piles of cash?

Yeah, you're right. I was confused. The OP is just talking about building a plug in parallel hybrid. So I'm not sure now what he is asking. Isn't what he is talking about pretty much what all these after market companies are doing right now for big piles of cash?Yea, I question some of the current PHEV strategies as well. Unless I'm missing something it I can't see it having a huge fuel-savings impact over and above the existing seies-parallel hybrids. Perhaps only extending the initial ICE start-up "set" speed somewhat due to near 100% initial SOC of the depletion battery (and possibly higher initial battery temps as well?) and therefore reducing the ICE run frequency up until depletion.
I personally think products like the Prius and VUE plug-ins are just a ploy to satisfy the PHEV lobby group.
WopOnTour

Ned23, Why? The ICE/regen braking would only charge the original battery. I believe the cpu would be unaware of why or where the extra power is coming from. When the voltage of the original battery was lower than the aux battery then power flow would come from the aux battery either to the original battery or to the motor, most likely the latter because that is what would be pulling down the voltage of the original battery. Remember with diodes in place the vehicle would not be able to charge the aux battery only the original battery. Once the aux battery is drained to the lowest voltage that the original battery is allowed to drop to then the aux battery voltage would never be higher than the original so from then on it would be just extra weight until you charged it at home again.


That might work. Don't forget that the extra battery is adding extra weight to the car, though. That will reduce your gas mileage. Use lithium cells.