calculating electrical load/winterize tanks

[Superdawg]

I need a little help from someone with some electrical knowledge. I want to install heat tape to my tanks under my trailer for cold weather camping. I plan on using the aluminum? tape to attach it to the underside of the tank and around the first valve. The heat tape is designed to be plugged into 110v. I read online the same tape can be wired into 12v but is not as effective. I would likely be plugged into 110 v for cold weather camping but sometimes, maybe not. Here's my questions.

Can the tape be wired into 12v instead of 110v?

I have two Energizer GC2 6v golf cart batteries that are rated at 220 AH each.

I plan on using three 5' lengths of heat tape that uses 3 watts per foot, for a total of 45 watts (not including other draws such as the furnace).

Would it work on 12v?

All it has to do is not let the tank/pipe freeze.

Not including other electrical draws, how long would the batteries last?

Frostex heat tape is one of the brands I was looking at.

Thanks,

Tom

 

[LRutigliano]

I need a little help from someone with some electrical knowledge. I want to install heat tape to my tanks under my trailer for cold weather camping. I plan on using the aluminum? tape to attach it to the underside of the tank and around the first valve. The heat tape is designed to be plugged into 110v. I read online the same tape can be wired into 12v but is not as effective. I would likely be plugged into 110 v for cold weather camping but sometimes, maybe not. Here's my questions.

Can the tape be wired into 12v instead of 110v?

I have two Energizer GC2 6v golf cart batteries that are rated at 220 AH each.

I plan on using three 5' lengths of heat tape that uses 3 watts per foot, for a total of 45 watts (not including other draws such as the furnace).

Would it work on 12v?

All it has to do is not let the tank/pipe freeze.

Not including other electrical draws, how long would the batteries last?

Frostex heat tape is one of the brands I was looking at.

Thanks,

Tom

Tom,



Running on shore power (120v), you will be fine as the amp draw is very low and you have an "infinite" amount of electricity assuming you are not running the hot water heater and fridge on electric and also running electric heaters (1500 w) and hair dryers...



Running the tape on 12V, you will be drawing almost 4 amps (45w / 12v). 4 amps is a fairly large power draw, but with your 220Ah bats, you should be able to run for some time. You need to know what each 12V load is drawing, such as the furnace fan, lights, etc to really know how long the house batteries will last.



Lets assume all your 12V loads add up to 11 amps, you should be able to run them for 20 hours (220 amp-hours / 11 amps) before your batteries are considered dead. Please remember though, they will be "dead" and you run the risk of not being able to use the electric jacks or electric slide until you start your truck and start recharging them.



With the 6V batteries wired in series to provide 12V, you cannot multiply the 220 Ah x 2, you will have only 220 Ah total.



If you had 2ea 12V batteries wired in parallel, then you could multiply the Amp-hours x 2.



Here is a helpful link on RV batteries: What RVers Need to Know about Batteries



Hope this helps,

Louis

 

[Hoefler]

Are you using an inverter?? If not, it will not work. The heat tape is designed to work at 110 volts, at 12 volts you would not get any heat that is useful.

 

[Superdawg]

Thanks for the replies. Reference the inverter, I am not running one. I was wondering if the (110v) heat tape was connected to 12v if it would be effective.

I do understand it would work much better connected to 110v (shore power) but I wanted 12v for that once in a while dry camping.

By the way, the electric jacks and the slide have a manual crank function, not that I want to try it..... If I did run the trailer batteries down, I could plug into the truck, if I didn't run those down too.

 

[RCook]

One more thought on deep-cycle battery capacity: plan on drawing them down to no lower than 50% of their AH capacity at the lowest, with rare exceptions. If you go deeper, you will damage them and shorten their life considerably. If you want your batteries to last, their AH capacity should be about 3X your AH requirements between charges, since the practical operating range tends to be between 50% and 85% of capacity. That would make your practical AH capacity about 73AH, if your batteries were new.

With an inverter, you could theoretically run your 45W heat tape on 110V AC using a little over 4 amps (inverters lose about 10% to inefficiency) at 12V from your batteries. Assuming new batteries and no other electrical loads (not true, of course), you could run the heat tape for about 18 hours if you started with the batteries at 85% of fully charged and took them down to 50%. At that point you're out of juice, practically speaking.

 

[fest3er]

... I plan on using three 5' lengths of heat tape that uses 3 watts per foot, for a total of 45 watts (not including other draws such as the furnace).

Would it work on 12v? ...

To answer this specific question, it'll work, but barely. Remember: power = current X voltage, or P=IV. Were they powered at 120VAC, you'd have 45W = . 35A * 120V or . 41A * 110V. If you use 12VDC, you'll be much closer to 4. 5W, which really isn't enough to heat much. You're best off using an inverter; 80-100 W inverters don't cost all that much.



And for something slightly different, the reason you don't want to string 10 12V batteries in series to get 120VDC is mostly because if there is a short, a *tremendous* amount of power will be dissipated in a short time. Figure a battery can discharge 5,000 A for a couple seconds across a dead short:

5,000 A * 100 V = 500,000 W

That's a lot of heat for a couple seconds. Equivalent to a 660HP engine.

 

[Superdawg]

Thanks to all who added their wisdom in such a timely manner. I am constantly reminded this is probably the best $35 a year I can spend. I will wire the heat tape up to run on 110v.