Killer Amps

its camper shell ? on a pickup truck, no furnace, nothing, not anything on the inside, except what ever portable gear he brings along

unless i mis-understood his OP

A Camper Shell, for those who do not know about them, is simply a fiberglass shell that fits over the bed of a pickup. Mine creates a box approximately 6.5' X 5' X 4' which can easily be warmed with any kind of small heater. I am not talking freezing temperatures, just a little warmth on a cool Spring morning. Very practical. No furnace, no fireplace. The problem is actually to find a heater that is small enough. Typical 1,500 watt units or a Little Buddy is way overkill for the application. I carry a small AGM battery which proved incapable of operating the 250 watt electric heater. A 20 amp load slammed on a 35 ah battery pulled down the available juice to under 10 volts. Inverter disconnected the load. I would not have even tried the test had I remembered that the heater was 250 watts instead of 100.

I think a better option would be to buy a 12 volt heater. They are typically 150 watt. A search on Amazon found these:
12 volt heaters on Amazon

Tom_M wrote:
I think a better option would be to buy a 12 volt heater. They are typically 150 watt. A search on Amazon found these:
12 volt heaters on Amazon

My old TV heater core started leaking so I bypassed it. Now no heat. I bought one of these at a truck stop to heat my cab while driving to work. I placed it on the floorboard to blow on my feet. I could feel it on my feet but after a 40 minute drive it did not heat up the cab one degree. Granted, it was about 40 degrees outside, moving vehicle, heat leaks, etc..

It may work for your application. Or get a bigger battery and 2 12V heaters. Start with both on and then turn one off after 10 minutes or so.

The experiment failed, "Nothing ventured, nothing learned". Some may be missing the whole point of camper shell camping and that is Simplicity. I have owned all kinds of RV's including motorhomes and trailers. I still have a thirty foot travel trailer.

The shell is my "Mini Mini Motorhome". Something I use for quick trips in mild weather. I don't want two or three batteries. I don't want a generator. It has a bed, a porta potti, and a cooler. Lots of fun, as long as I keep it simple. 23 mpg isn't bad either.

OK, if it's just a camper shell, we are talking about a drastically smaller space than even most truck campers. 250w might do the trick if it's just a little chilly.

As others have mentioned, a 12v heater probably makes more sense but still need a bigger battery. That or some higher wattage 12v bulbs as most of the energy turns to heat anyway.

Hi,

The "rule of thumb" for heating is 1.25 watts per cubic foot.

So 163 watts would be the minimum. I would stick with the 250 watt heater myself since you wish to take the chill off--quicker is better! There is also a contribution of waste heat from the inverter.

250 watt-hours =~ 21 amp-hours @ 12 volts.

To run the heater for one hour a 100 amp-hour flooded battery would be a good fit.

https://www.batterystuff.com/kb/tools/calculator-sizing-a-battery-to-a-load.html

TomG2 wrote:
A Camper Shell, for those who do not know about them, is simply a fiberglass shell that fits over the bed of a pickup. Mine creates a box approximately 6.5' X 5' X 4' which can easily be warmed with any kind of small heater.

TomG2 wrote:
The experiment failed, "Nothing ventured, nothing learned".

How did it fail? The battery fell flat or lacked enough heat output?

Some may be missing the whole point of camper shell camping

I 'camper shell' camped years ago down in Mexico quite often. We had a blast.

2112 wrote:
How did it fail? The battery fell flat or lacked enough heat output?

Bingo. The battery voltage immediately dropped below 10 volts and the inverter disconnected the load. Too much load or too little battery. Take your pick.

pianotuna wrote:
...snip.....
To run the heater for one our a 100 amp-hour flooded battery would be a good fit.

Not sure that I want to charge and discharge a flooded cell battery in the small confines of a camper shell. Good idea?