Spare battery for block heater?, 1982 300D - PeachParts Mercedes-Benz Forum

300DPETE · #1 11-06-2005, 09:36 PM

1982 300D
I
've been thinking about carrying a spare battery during the winter so that I could run the block heater even though I was not near a source of electricity (I often camp in the winter).

My question is, how long would you be able to run the block heater on the spare battery before the battery could no longer put out enough juice to run the block heater propery? If I could get at least an hour out of it, I figure it would be worth it.

Thanks,

Pete.

#2 11-06-2005, 09:40 PM

Is there any such thing as a 12V block heater? If you connect a battery to a 120V heater, it will operate at 10% capacity.

boneheaddoctor · #3 11-06-2005, 09:41 PM

Quote:

Originally Posted by 300DPETE

1982 300D
I
've been thinking about carrying a spare battery during the winter so that I could run the block heater even though I was not near a source of electricity (I often camp in the winter).

My question is, how long would you be able to run the block heater on the spare battery before the battery could no longer put out enough juice to run the block heater propery? If I could get at least an hour out of it, I figure it would be worth it.

Thanks,

Pete.

you need to find out the amp hour capacity of a DEEP CYCLE battery...figure out the efficiancy of a 500 watt inverter (many block heaters are 400 watt)

and see how long it would work figuring reduced output due to low temps.....

Not sure how long you would have but I doubt it would be measured in hours...

Deep cycle battery is critical....you will kill a normal battery trying this.

300DPETE · #4 11-06-2005, 09:46 PM

Quote:

Originally Posted by Craig

Is there any such thing as a 12V block heater? If you connect a battery to a 120V heater, it will operate at 10% capacity.

I was going to use my power inverter.

boneheaddoctor · #5 11-06-2005, 09:47 PM

Quote:

Originally Posted by 300DPETE

I was going to use my power inverter.

YOu need to know its efficency to do any math as to actual current drain....or try it and hook an ammeter to find out....on the other end no I have not heard of a 12 volt block heater.

300DPETE · #6 11-06-2005, 10:05 PM

Thanks, BHD, I'll look into it.

Has anyone actually tried this before?

Palangi · #7 11-06-2005, 10:11 PM

You're gonna need a battery the size of a Volkswagen.

Whiskeydan · #8 11-06-2005, 10:17 PM

Quote:

Originally Posted by boneheaddoctor

you need to find out the amp hour capacity of a DEEP CYCLE battery...figure out the efficiancy of a 500 watt inverter (many block heaters are 400 watt)

and see how long it would work figuring reduced output due to low temps.....

Not sure how long you would have but I doubt it would be measured in hours...

Deep cycle battery is critical....you will kill a normal battery trying this.

Bear in mind also, the amp hr rating is not at max output. For example a 45AH rated batt will not do 45 amps for 1 hr but it may do 5 amps at 9 hrs.

I wonder how much heat you would get from the glow plugs if they were cycled on intermitantly? Simple re-wire to another batt and a timer then switch to the start batt in the normal "glow" mode prior to start.

boneheaddoctor · #9 11-06-2005, 10:20 PM

Quote:

Originally Posted by Whiskeydan

Bear in mind also, the amp hr rating is not at max output. For example a 45AH rated batt will not do 45 amps for 1 hr but it may do 5 amps at 9 hrs.

I wonder how much heat you would get from the glow plugs if they were cycled on intermitantly? Simple re-wire to another batt and a timer then switch to the start batt in the normal "glow" mode prior to start.

and that figure is reduced at very low tempratures.....the very sort where you need a block heater.....

you will kill glow plugs pretty quick doing that however....

Whiskeydan · #10 11-06-2005, 10:24 PM

Quote:

Originally Posted by boneheaddoctor

and that figure is reduced at very low tempratures.....the very sort where you need a block heater.....

you will kill glow plugs pretty quick doing that however....

I was thinking PWM on the GPs. Not full on +12VDC...11...10...8...

boneheaddoctor · #11 11-06-2005, 10:27 PM

Quote:

Originally Posted by Whiskeydan

I was thinking PWM on the GPs. Not full on +12VDC...11...10...8...

IMHO glowplugs life is highly related to amount of time in use...

I would manually do a double glow cycle in extreme weather...looking at your watch for time....

But checking your vavle clearances before real cold weather may save you a lot of grief........tight valves make for a harder starting engine.

300DPETE · #12 11-06-2005, 10:39 PM

What about this puppy:
http://www.amazon.com/exec/obidos/tg/detail/-/B0006I4M6O/ref=olp_product_details/103-8640509-9747822?%5Fencoding=UTF8&v=glance

boneheaddoctor · #13 11-06-2005, 10:42 PM

First question is whats the draw in amps for a 500 watt inverter at near full load?

300DPETE · #14 11-06-2005, 10:43 PM

Quote:

Originally Posted by boneheaddoctor

First question is whats the draw in amps for a 500 watt inverter at near full load?

Okay, okay, I'll do some research

Thanks, BHD.

Palangi · #15 11-06-2005, 10:47 PM

I'm thinking one of those batteries like the phone company uses to operate the ringer circuits during power outages.

Seriously, for cold weather camping, just wake up and start the car every 2 hours and let it run for 5 minutes. Normally a block heater would not be needed except for well below freezing anyway, unless the engine is really clapped out.