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We all know the Pinz was designed for the cold weather, with that being said.

Does anyone know how long or how many hours you can run the BN4 heater for before it runs the batteries dead or to low to start the engine?

Can it be ran all night?

The stock wet cell batteries in the chassis are perhaps as much as 100 "Amp Hours" which is amps times hours; this means in theory that perfect batteries can supply 100 amps draw for an hour, 10 amps draw for 10 hours, or 5 amps draw for 20 hours. No battery is perfect and there are other factors involved, including temperature, so for safety sake you might want to plan for not using more than 40-50 amp hours through the night. Assuming a 10 hour night, this means that the heater should not draw more than 4-5 amps to meet this goal (and less current is better).

So you would want to measure the current that the heater draws; I do not know what the expected current would be. I'd guess that if it draws less than that 4-5 amp value then you can probably start the engine in the morning, assuming that your engine starts easily. Of course the whole assumption is that it is cold outside, meaning that the batteries will have less capacity and the engine will be harder to start; this may mean that an even greater safety factor (less than 4-5 amp draw) is important.

IIRC your BN4 will draw ~50 watts when running.

My BN4 draws 3 amps when running.

50 watts down to 3 watts, that's a huge difference.

I was hoping someone knew the basic run time in hours from past experiences.

I guess its down to testing it, run it for 3 hrs, and try to start the car, then 4 hrs and so on.

I was informed I should run it for a long period of time just to clean it out, as it does smoke a bit much in my opinion, probably because it keeps being used for such a short time, as this past winter it would run for less than 15 min. each time on our short trips here and there when we had the kids with us, it was probably the same with the previous owner.

MM58 said 3 amps, not watts. equal 72 watts.. sounds like it is in the ballpark considering age, corrosion, etc.. , if 50w is correct for new

I have run mine "all night", which was about 8-9 hours a couple of times. Engine started fine the next morning. Batteries were not new by any means, but still in good shape. FWIW, the back of my K is very insulated and I had all the blackout curtains down. My BN4 draws ~3 amps, and that's almost all from the fan, which is on continuous. (So I'm not sure if insulation affects runtime) The burner being lit adds hardly any noticable added draw. YMMV

Sorry for the misunderstanding on the watts

But thank you, that was the answer I was looking for. As I have new Batteries a 5 to 6 hrs run time should be safe.

I was thinking about going off-roading up in Big Bear and staying up there, this is the reason for my question.

I should also mention, that I prefer to use my "Mr. Heater/Little Buddy" propane heater when I have it. Don't have to listen to that obnoxious BN4 fan all night! I also have a batt powered CO detector/alarm mounted in the truck just in case.