I should mention something that nobody has yet pointed out...

Lead acid batteries like to be kept fully charged. Manufacturers still use lead-acid battery technology for car starter batteries because they get the best life expectancy based on the way these batteries are normally used -- e.g. they drain just slightly while running the 'starter' on the car, then when the car starts they immediately get charged back up. These batteries seldom ever drain below 95% full and for lead-acid technology that's a good thing.

If you never let lead-acid battery technology drain below an 80% charge then you can expect the battery to last a very long time. If you start draining it down below that you can expect to reduce the battery life (by which I mean the number of years before you have to buy a new battery). I would never let my car battery drain down to say -- 20% capacity because that just kills the life expectancy.

ALSO... should you happen to over-drain the car to a point where it wont start, make sure you read the owners manual in the section on jump starting. The FEH should not be jump started in the manner of a conventional car. However, since it has two independent battery systems it is actually capable of jump-starting itself. Down in the driver's side footwell there's a panel with a button (the owner's manual illustrates where to find it) which performs this. It's been a while since I read it, but I seem to recall that you push the button, an LED will blink for about 30 seconds (while it transfers some charge from one battery to the other via a transformer) and the light goes solid -- at which point you should attempt to start the car. I think they claim it has enough power to attempt this twice.

 

While we're on this subject, has anybody here tried using deep-cycle batteries like Optima yellow tops or Odysseys instead of the OEMs for better accessory performance? I realize that if you need to make a warranty claim, youbably want to keep everything underhood looking stock, but a stronger battery could be helpful for these situations.

 

Just to clarify...

The built-in 150 watt 110 VAC inverter does not work without the key in run.
Anytime the key is in run, the HV battery is active.
Therfore, it is the HV battery that is providing the "juice" to the inverter, the radio, the lamps, the windows, etc... AS LONG AT IT IS CAPABLE.

Only after the HV battery drops below 40%, A) the engine will kick on to recharge, and the 12v under hood battery will never be used... or B) the HV battery will be cut out ( you can hear a relay click ) and the 12v battery will take over...

A) occurs if you "start" the car and get the car icon. Engine will cycle.
B) occurs if you put the key to run without a start ( no car icon )

The 12v battery does very, very little in this car.

 

The correct answer is, all accessories draw current from the HV battery first, and only draw current from the 12v battery as back-up, if the HV battery ever drops below 40%.

The HV battery IS your "inverter". There is no under-hood inverter in this car.

 

Hmmmm.....I'm a bit confused....

At least one if not both of the 12V accessory outlets that ARE active even with no key in the ignition...the same goes with the NAV unit which can run for up to 30 minutes after the key is pulled out.....(or until you open the door). Only the 120V seems to be off and dead with the key NOT in the run position...

Now once that key is in the ignition and its in RUN its academic.... The car is ON and the whole thing is really just tapped off the HV system with a HV to 14V stepdown converter (for those that wonder I'm guessing at the 14V, I believe thats typically what the charging system for normal a car runs at, you have to have a slightly higher voltage to recharge a 12V battery and all the accessories are desgined to take it)..... I have no idea whether the 120V is created from the HV buss or the 12V buss but in reality it doesn't matter...either way with that key in run the power is coming originally from the HV system.

With the key off and the SUV sitting there I thought the HV system was off, therefore anything that still runs would have to come off the 12V wouldn't it? So in that case some of the accessories do run off the 12V.

That may be what you meant... I'm just confused.....

 

True if the HV battery is low - the 12V can boost the 330V. If the 12V battery is dead you can still jump-start the car with a donor vehicle. You can't charge a dead 12V with the HV battery the way I understand it.

 

That is pretty much what I meant. The HV battery provides all the power when possible.

-John

 

Thanks John I was checking my own "facts" to see if they were right. If you'd said different then I'd start to compare notes to see what was different.

 

This is fascinating guys. What about the Accessory position for the key -- between Off and Run? That is from the big HV battery then, right? That was the impression I got from the start of this thread.

And do I also understand correctly from what has been said, that even the starting of the engine is done from the big HV battery (thus the reason for the way the "internal jump" trick works)

Thanks from an electrical newbie.

-Christopher

 

I was just thinking.... the brakes pressure up when you open the door...

Is this being done by the 12v or 300v system???
It is for sure going on without the key!

And one would think it would tend to run via 300 volts...

FYI

One click of the key is ACC... this runs windows, lights, radio, from 12v system. YOU DO NOT have the inverter on with ACC.

Two clicks of the key is RUN... this runs windows, lights, radio, from 300v system. YOU DO have the inverter on with RUN.

Turn farther and you hit start. Release and the key rebounds to run. You do not need to start to use the inverter or activate the big 300v battery.

Turn your headlamps on, and move key to ACC. You will get 12.x volts.
Leave headlamps on, and move key to RUN. You will get 14.x volts.
Engine is off the whole time.

-John