I did some checking, with the info from Gary being a good start.

The regular FE/MM, with either the 4 or 6, get a BXT-40R, 590CCA, 60Ah, battery. The FEH/MMH, get a smaller BXT-96R, 500CCA, 52Ah, battery. My reference was the Motorcraft battery catalog.

I guess that weight is more important than how often the ICE has to run to just charge the 12v battery????

 

Energy in = Energy out. Just because the battery is bigger or smaller shouldn't make much of a difference as to how much the ICE has to run to recharge it. Its just like a gas tank.... Doesn't matter if its 10 gallons or 100 gallons... If I use 5 gallons, I have to put 5 gallons back in capacity is rather irrelevant in this case. The only difference would be internal resistance and frankly the FEH probably pulls so little current from the battery at all, even that doesn't matter. While going down the road the 12V battery isn't supposed to be doing anything anyway. Everything should be being provided by the 330V (to drive) and I imagine even the 12V comes from the 330V-12V charging system at that point. I believe the FEH doesn't have a separate alternator. I thought I read that somewhere... but I can't remember for sure.

 

Hi,

Just top get back to the topic for a moment , there is a difference between daytime running lights, which are always on in Canada, and the lights you want to use at night. At night, you need to turn on the "manual" lights (unless you have th enew fangled auto lights) because the daytime running lights only turn on the front headlamps. At night, you also want your tail-lamps on so people see you from behind. I'm not sure (it was mentioned in other threads) but the headlight intensity might be different as well. So when we are driving at night, and can't see the instruments, it is a reminder turn on the lights.

So, you were either driving a car with automatic lights in the past, or this may answer why so many people behind you were flashing their headlights at you over the years .

I remember when daytime lights came in. Whenever we visited the US, we'd get people flashing their headlights all the time or yelling "your lights are on!". "I know! We're from Canada!".

Cheers,

rcomeau

 

The 12 v battery is just there for the conventional electrical system. The starter is powered off of the high voltage battery (the one behind the backseat) and the 12 volt battey's charge state is maintained by the High voltage system also. The 300+ volts are stepped down by the DC/DC converter to keep the 12 v battery charged. There is no need for a deep cycle battery.

 

See, that is part of my confusion.

If the 12v battery is used for the conventional electrical system, would it not be better if it had a larger capacity, and had a deeper cycle, battery? At least to me, that would mean that the 12v battery could run the 12v electrical system (radio, lights, etc) for a longer time before needing the ICE to run just to re-charge it.

 

True.... however that just delays things. It doesn't change them. The engine would just have to run longer to charge the larger battery loss, making up for the less frequent charging times.

And, in the end, I'm pretty sure automotive systems don't work that way. They don't discharge the battery to a point and then turn on the charger.... they pretty much just keep the battery topped off all the time. With lead-acid cells this is fine. After all in a conventional engine that battery has to start the ICE... Something that is much harder with a half discharged battery.

 

The short of it is (in my opinion).... I guess on this system they could delay charging until necessary and let the battery drain more.... but I doubt it makes enough difference for the designers to worry about it. I doubt it ever gets to the point where the engine fires for just charging the 12V system.... it probably will have to come on for added drive power or to heat up the catalytic converter long before that.

 

The high voltage battery's state of charge is the sole determinant of when the engine runs or does not run other than high load modes of operation. In other words, if you floor the accelerator the engine is going to come on regardless of the state of charge. Conversely, if you drive real easy so that the engine never comes on when accelerating it will eventually come on when the HV battery SOC drops below a certain level, probably in the neighborhood of 40% from what I have read. That would happen even if you were coasting down a hill at say 20 mph or so. The state of charge of the 12v battery has no bearing on the engine operation whatsoever.


The energy stored in the HV battery is substantial compared to the 12v. It has to be since it may be called upon to propel the vehicle down the road. Hope this helps.

 

This is a common fallacy. Yes, your hybrid battery has a lot of voltage ( so does the static in your sweater ) but it's really pretty small in capacity, 1900 watt-hours.

The HV battery and 12v underhood battery have nearly the same amount of stored energy. The 330v battery will provide a higher number of watts for a shorter period of time than the 12v battery, and vice-versa.

Since the HV battery is "protected" from over discharge, and the 12v isn't....
You could actually pull more energy out of your 12v battery than your 330v one in an hour if you wanted to.

 

Right! Which is why it's possible to "jump start" the HV battery with teh 12V... it just takes a while.