Denny. You might already know this, but i'll go over it just in case.
So the Headlights actually run directly from the 12volt battery under the front hood and not the traction battery. This means it has nearly zero impact on our range. Among the many good reasons for this is safety, Mitsubishi (and other EV manufacturers) don't want drivers turn off the Headlights to help with range.
Same thing goes for the wiper blades, radio, fans, and any accessories you plug into the cigarette lighter. All of these run from the 12volt. So use your headlights and wipers as much as you want. It's totally fine.
Now I know what your thinking "Doesn't the main LiON pack charge the 12volt, thereby reducing our range?". Yes and no. The pack doesn't have to keep the 12volt charged all the time, just when it dips too low, and even then, it takes so little current to do this that it's negligible on your range.
A big part of this is due to the Deep Cycle nature of the 12volt. It's the same kind of battery you find in RV's and Boats (no cranking amps required because it doesn't have to crank a starter like in an ICE vehicle). So it lasts forever and can run our headlights, wipers, etc.. all day with no problem, pretty much all on it's own.
If you've ever had a camper or boat with a battery like this, you know how well they work. The only trick to making them last for years and years is to remember to haul them out and keep them hooked up to a battery tender when you're done camping and boating. If they maintain a charge 24-7, they have an insane lifespan.
The good news is, our car does this for us!
Also, when you plug the car in, the 12volt gets charged right along with the LiON, further increasing it's lifespan and ensuring you have a nicely charged up, fully ready to go 12volt for all your headlight, wiper and radio needs.
It's a great system.
Golly, gee whiz - Where to start? So much mis-information all in one post
First, nothing 'runs' off the 12 volt battery. Lots of things run on 12 volts, but none of them are drawing any current out of the little 12 volt battery (none at all) unless the key is in the accessory position. That is the only time the 12 volt battery powers anything
You can prove this to yourself quite easily. Take a voltmeter and measure the voltage on the little battery with the car shut off (and the EVSE not plugged in). You will get something very close to 12.6 volts. This is the normal, 'resting' voltage of any ordinary 12 volt automotive battery, which is what we have. It's not a marine deep cycle battery BTW - It's just an ordinary flooded 'starting' battery with 33 AH's (Amp Hours) and 272 CCA's (Cold Cranking Amps)
Now, turn the key to the accessory position, turn on the headlights and measure again. You will get something very close to 12.0 volts. What does this mean? It means the 12 volt battery is powering the headlights. How do we know? The battery is seeing a load, so it's voltage went down - The bigger the load, the more it goes down . . . . the battery is powering the lights. 12.6 volts is the resting voltage - Not under charge, not powering anything. If it was charging, the voltage would be higher and if it was powering anything, the voltage would be lower. Elementary electronics
Now, turn the key to on, so you get the 'Ready' light and the first thing you will notice is . . . . the headlights just got much BRIGHTER
- Why? Measure the voltage again. You will get something close to 14.4 volts. The lights got brighter because they are now running on 14.4 volts instead of the 12.0 they were getting when the key was in the ACC position and they were running off the battery. What does this mean? Since the battery's voltage has risen nearly 2 volts from it's resting voltage, it means the battery is under charge. The headlights are no longer running off the battery. If they were, the voltage would still be 12.0 and they would still be dim
The 12 volt battery will measure above 14 volts anytime the car is operating. It's always under charge and never powering anything - With the key in the 'On' position, all 12 volt loads are transferred to the traction battery
What is charging the little 12 volt battery AND powering the headlights now? The DC to DC converter has taken all the load off the battery - Nothing coming OUT to power anything - Current is going IN, and it's coming directly from the 330 volt traction battery . . . . all the time, mile after mile. Turn on any 12 volt load (even turn signals) and the cars range gets incrementally (infinitesimally) lower. No 'free lunch'. As I mentioned earlier, the 100 watts or so the headlights use is small potatoes in the overall scheme of things - Less than 1% of the total power, but like every other electrical load, they do affect the range. If you run the headlights for an hour, they might decrease the range by half a mile or so . . . . just a guess, but the range did go down - Remember, everything is running off the traction battery and there is no free lunch
ICE vehicles work exactly the same way, BTW - Nothing 'runs' off the battery when the engine is running there either . . . . all loads are powered directly by the alternator which is holding the battery voltage up to something above 13.8 volts - The battery is charging
all the time . . . . powering NOTHING, same as in our car. Our 'alternator' is the DC to DC converter - On all the time, charging all the time, running off the traction battery all the time. Turn the steering wheel, the traction battery INSTANTLY feels the load of the electronic power steering . . . . and the range goes down a teeny, tiny bit
Long story short - Turn on ANY 12 volt accessory and the power to run it INSTANTLY is shifted to the 330 volt traction battery, via the DC to DC converter. You could prove this too by measuring the current the DC to DC converter is drawing from the traction battery. Turn on a 100 watt load (the headlights) and the converter instantly begins to draw an additional 100 watts + from the traction battery . . . . it's not 100% efficient. EVERY single electric thing in this car is running off the 330 volt traction battery all the time . . . . unless you have the key in the ACC position and you're listening to the radio - THEN, you're running something off the little 12 volt battery, but that is the ONLY time