I have been reading with interest the thread about building a charger to revive dead batteries.
However, the 2005-2008 FEHs come with what is essentially an onboard charger. The button on the dash end charges the HV battery using the 12V accessory battery.

Why is it that we do not re-purpose that tool to charge the battery, rather than construct a new charging circuit and charger?
Seems to me a 12-volt power source connected to the onboard charger would do much the same thing without digging into the HV battery. The carry this further, you would almost have a plug-in hybrid.
Has anyone looked into this? What am I missing?

 

I'm confused by your question. How can you re-purpose something that is not present? "Digging into the HV battery" is rarely required on an 05-08 due to the presence of the jump starter.

Jump starters are located INSIDE the 05-08 HV battery. There are substantial internal wiring differences between 05-08 and later years.

"Plug-in hybrid" folly:
HV battery capacity is 1.65kWh - less than 50% is usable in the vehicle, so 825Wh
The 12V battery is about 70Ah or 840Wh
In other words, the usable capacity of the HV battery is nearly identical to the total capacity of the 12V.
You're contemplating propelling a vehicle solely by the energy present in its 12V battery - clearly of very limited benefit.
You MUST provide means of cooling the battery while "plugged in" or you would destroy the cells - must decipher the control circuit on the fans, ensure the blend door stays open and provide power to the fans as well.
Routine charging to full as a "plug in hybrid" would dramatically shorten the life of the battery.

 

Perhaps I did not phrase that very well.
The FEH through 2008 already has a built-in charger.
When the battery drops below the threshold to start the ICE, you press the Magic Button, wait 8 minutes, repeat as required until voltage is high enough to get the ICE started, while recharging the 12V as required. .
Rather than go through that tedious repetitive process, is it not possible to wire around that switch to allow the 12V (aided by a charger) to continuously charge the HV battery until it is capable of starting the engine? Or perhaps connect a good 12V power source at the dash (wire around the switch) to run the onboard HV charger.

By sourcing an external power supply (or two) are we not roughly duplicating the equipment that came from the factory?
For that matter, would a surplus FEH charger from a pre-2009 work as well as the Mouser or similar charger?

 

Again, 05-08 rarely have need to be charged externally, so if a jump starter is present, there is no need to install a secondary unit of any kind. Substantial enhancement of HV Jump starter performance can be had by using the HV jump starter WHILE being 12V jumped by another running vehicle. The heavy load of the HV jump starter can pull the 12V down to the point that it's very ineffective. A jump vehicle's alternator can be an excellent power source for the HV jump starter.

The HV jump starter works at a 1-2A current - 3-6X the power supply.

It is a complicated piece of hardware with onboard charge control circuitry. The HV jump start switch is a momentary switch engaging the charger to "do its thing" via its own charge control function. The jump starter ALWAYS has 12V power to it; however, the unit requires the momentary closed circuit from the switch to engage the charging function. I'm sure someone with in-depth electronics knowledge could reverse engineer the unit and/or create an overriding control circuit, but we're miles past the point of diminishing returns.

You may be picturing a simple box... 12V in, switch and HV out... Nope... Here's what one looks like:






Notice the absurd number of connections. What does what?

The choices are:

1) Purchase an expensive and simple high voltage power supply and cheap components to fashion a charger.
2) Obtain and reverse-engineer a complex electronics component. Add hardware/software as needed to gain the desired function.

#1 is low effort high reward.
#2 is absurdly high effort with unknown reward.

There are other options as well. One is not limited to the above choices. There are higher current power supplies or other devices capable of supplying a lot more than 350mA. Cost goes up. One could parallel as many of the commonly used units as one cares to and can power via a single AC circuit. Spend $200 or so, and you can have a 1.4A charger that will only need 30-60 minutes of charging to be an extremely effective "jump starter." - barely more effort than a single unit.

 

I had to go through a number of HV jump starts to keep my old battery alive. A clamp-on ammeter reads 25A out of the 12v battery when the jump start is engaged. Just another data point.

 

I have a semi-related question because I was discussing it with my Dad this past weekend. Does anyone hold out hope regarding the hope that there is a possibility of an auxiliary or replacement battery pack with similar capacity and characteristics can be constructed for this vehicle for a reasonable amount of money (i.e., less than $2500 or so?)

 

No hope whatsoever. There are no options even remotely comparable to the quality of the Sanyo cells in the original pack.

 

Not sure how hard it would be to reverse engineer that jump pack. It wouldn't be so bad if it was documented anywhere, but it isn't. There would still be custom wiring, even if they kept some of the same connectors. So in the end you're doing the same thing you would be with the external supply. Considering all the parts yards around me are removing the batteries, getting one would be a worse proposition.

If you want a jump button, look for a 12v to 400v DC booster and wire that up. Sounds easier.

You can buy the cells and rebuild. It's probably way under $2500. All the 2nd battery attempts went out of business. I looked for used ones and nope. There was that guy a few months ago trying to set up the group buy for the battery controller. That's what it would take, contacting one of the companies that developed one and getting them to cough up units.

 

Source?

 

There are cells all over ebay. You'd have to charge/drain them and use the good ones. I'm cheap so that's what I'd do. There are new cells on alibaba: https://www.alibaba.com/product-deta...836136354.html