Customizing a VRV

[charliem]

....... But 200 AH can run 120V 1500W heater (12.5A) for up to 16 Hrs. So running the heater on full blast all night for 8 Hrs should theoretically still leave me with 50% charge. It can be recharged in daytime via solar or generator. ....

The 12.5A current rating is at 120V, not 12V. Using an inverter running 90% conversion efficiency the current at 12V would be 137.5A. Depleting the battery to 50% would occur in less than 45 minutes. Go for the propane.

[illusha]

OK, I stand corrected, I don't know what I was thinking as I was overestimating the battery's ability.

1500W / 12V = 125A, so yes, that 200 AH battery would not last long.

There is still the generator, I am definitely not going without one, propane is still an option. A furnace is not hard to add. Deciding how to distribute weight is.

[Pinstriper]

If you have the length of your trailer from the back bumper to the hitch, and know where on that line the balance point (fulcrum) is, a little high school math will tell you what happens with the weight depending on where you put it.

Good ole Pythagorus.


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[illusha]

If there is only one fulcrum point and only two small weights on a lever, then a little high school math could get it done, but when we are talking tandem axles and weights spread over 8 foot lengths of the lever (like a quad or a water tank would), with some parts of that weight directly over the fulcrum and percentages aft and fore from it, then it becomes exponentially more difficult to calculate correctly, seems easier to just load it up and weigh it at the scale.

I do wonder why Scott designed this trailer to have 550 Lbs Tongue Weight with 2700 Lbs Curb. I am assuming that's because it's a toyhauler and that weight proportions will adjust when I load "toys" in the back of the trailer. It's interesting that both axle loads are almost the same and I wonder how that would change with the weight added in various places.

I did more research and thinking about heaters. It seems that 1 kWH of power produces about 3400 BTU of heat no matter how you slice it. To maintain a 20*F difference between outside and inside temps, a heater needs to produce 20.8 BTU per sq.ft., while for a 40*F difference it would need to produce 41.7 BTU per sq. ft. Using those numbers, my 6x15 trailer (90 sq.ft) needs 3750 BTU to stay in the 70's when it's 30's outside (with the tent pop-out closed).

Looked into the different types of heaters. Seems like 600/900/1500 Watt models are the most common for oil-filled ones. There are some that get down to 400W on low setting. I know that oil-filled heaters take a while to fully warm up. So initial warm-up could be done on high setting running off the generator. Then switch to the low setting and run off the batteries for a few hours.

Also read about "mini-split" heat pump systems. There used to be a popular one by Sanyo / Panasonic in the early oughties. Nowadays it seems that Pioneer WYS models took over. They do both heating and cooling like standard household heat pumps. In Cooling mode a 9000-BTU model ranges from 5800-10300 BTU and draws 292-1087 Watts. In Heat mode it ranges from 5400-10900 BTU and draws 335-1100 Watts. These units might be a good alternative that would also come handy in times when humidity is too high for Mochila evaporative cooler. Not the cheapest, but reasonable, seem to get good reviews and spec out well.

Someone I know often says "we are not wealthy enough to buy cheap things" and I totally agree.

Also checked out Propex and Eberspacher propane heaters and I must say they look pretty sweet. But adding propane appliances and tanks with plumbing would also add weight to the trailer. Probably about the same weight as 2 more 200 AH batteries would be. So that's still up in the air as discussed previously. Good thing is that I don't have to make any immediate decisions and have time to sit and ponder.

[Pinstriper]

A tandem axle still behaves as one fulcrum. The hangers are designed that way. The balance point is the center between the two.

Here's a page on etrailer explaining it. It is focussed on determining the distance to set when designing a trailer, but the equations are the same, just solving for a different variable.

https://www.etrailer.com/question-136065.html

You may also find the discussions over on TTNT (Tiny Trailers and Teardrops) helpful, as folks are over there either building from scratch, or converting cargo trailers to camping trailers. A lot of threads on attempting to run heaters and air conditioners on batteries from solar and generators.

It always ends the same way, however. Propane for heat. Big generator and carry lots of gasoline for air conditioning. Hope that doesn't spoil the fun. Solar and batteries just can't match petroleum for energy density.

[illusha]

Thinking about weight distribution reminded me of preschool and how seesaws work. The trailer has all those extra water tanks everywhere underneath except for the very rear section where spare tire mounts. And it certainly looks like it could take a separate 25 Gal tank there and that's just a tad over 200 Lbs of weight. Could be plumbed separately from other tanks and I bet it would be enough for many of my shorter trips. Definitely enough to counterbalance any boxes on the tongue. I'll wait to make any modifications until after I take more weight measurements with various loads. And I'll seriously need to think about reinforcing the aluminum frame and upgrading the axles at that point. Especially for any situations when one of those torsion axles might lift a wheel and shift all weight onto the other axle. Happy turkey day everyone.

[Pinstriper]

How about just getting a plastic 55gal rain barrel and a handtruck ? Bring the extra water when you want, wheel it up the ramp. Strap it to the wall and bingo.


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