Espar heater alternative??

[KBennett]

The idea of a warm truck on a cold morning really appeals to me but after seeing the price of an Espar heater I have sticker shock. No big deal, just plug it in right? What about in the evening when I leave work?

I may have figured out a cure. Has anyone experimented with a deep cycle marine battery and an AC inverter placed in a vented enclosure in the bed to power the heater? About an hour before I leave the office I could go out and flip a switch or use one of those 24/7 day timers to do it for me. This would give the motor a head start anyway. The battery could be charged by the truck when I start it using an isolation diode or similar circuit. Does anyone know what the wattage or current draw of the block heater is?

 

[RobertBolinger]

I think you are going to kill the battery before it gets warm. I'm no expert here, but I have seen several posts that say that you should start the timer 2-3 hours before you are leaving. Now given that, a typical deep-cycle marine battery has an AH (Amp/Hour) rating of 85 to 105. I'm not sure what the block heaters pull, but let's assume 10 amps... at 120volts. That is 100 amps at 12volts , so the block heater alone is going to kill the battery dead in less than an hour . Thats not taking into consideration losses inside the inverter-all that heat that the inverter creates during normal operation is power lost. Also most inverters are going to shut down before the battery goes completely dead because they can't make reliable 120v power-this is to protect the battery as well as sensitive electrical equipment plugged into the inverter (computers, TVs, etc. ). Granted, the block heater probably would not be harmed by low voltage, the inverter does not know this. Also, the larger inverters are several hundred dollars- example 1500watt unit at Northern Tool for $349. You could hook up several batteries in series to boost the run time, but batteries are heavy.

 

[KBennett]

You are right about the current draw if it draws 10 amps. That is why I asked on the post if anyone knew the exact draw. I have some old UPS's(Uninterruptable Power Supplies) from computers that put out 1200 watts and operate on 12V. If I could get one of these to work with the marine battery my cost for the inverter would be $0. I was also thinking of connecting the 12V battery directly to the heater. This would not harm the heater but would drop the power of the heater to about 1/10 of the wattage and it may not be enought to overcome the dissipated heat of the block.

 

[JPM]

My guess,the block heater is just a heavy resistance wire, it would work on 12v DC, not good but it would work. It would still kill the battery. Even plugged into 120v AC,the block heater will not heat up the cab, melt off the snow and ice like the Espar. I need a Espar(take out another loan!? ),anyone around the Midwest installing them? E Iowa? There is money to be made in these things,

 

[ImagesThatSing]

Our solution is when it is really cold, I start the 5500 watt Honda generator in the back of the truck and run and extention cord to the plug in heater. But then, that only works if you need the generator for boondocking or other activities.

 

[bulabula]

I thought the manual said the block heater is 750W, or about 6. 8A @ 110V. That 750W hooked to a 12V inverter works out to about 62A. An aux battery could power it for a while, but not sure if your drive home etc would keep it replenished.



I don't think a 1 hour soak before going home will make that much of a difference (from a cold start) to go through all that work of wiring it up etc. But it does sound like a fun exercise.

 

[nickleinonen]

i remember reading on the block heater cord 1200watts, or maybe that is what the cord is rated for?

 

[bulabula]

I dunno, but that would translate into 100A current for 12V; even harder on an aux battery.

 

[Cooker]

The block heater is 720 watts.