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Off grid trailer power
(08-21-2018, 07:37 PM)completelycharged Wrote: Like the plan. For cooling go with a fridge/freezer and make ice with excess power. I still have 10 Peltier devices in a box to play with but they are a low priority after a few hours messing with one of them.... Ice is way better than batteries for energy storage.... and way more efficient...

Humidity control - compressor dehumidifier if 20C and above, otherwise a desiccant dehumidifier for cooler conditions as they provide space heating as a bonus and perform better in colder conditions. Humidity is usually an issue in colder conditions as the windows and general air circulation should provide enough in warmer situations.

"Like if a bear is trying to steal my gas can for his dirt bike." - LOL..

I have found that leaving a remote light on outside (few watts) makes for a good way of attracting all the flies and insects away from where you dont want them to be...

"I might as well charge it off the motorcycle while I'm traveling" - extra solar panel will work out more efficent than vie the engine...

This is a solid recommendation... a good quality DC fridge/freezer is super efficient.  I have a 50 quart fridge/freezer and it uses about 50 watts when on and probably runs 50-60% duty cycle.  It really sips power and the performance is amazing.  I've held freezer temps with a 100 degree F differential.

Many are also 12-24v native which makes it even more efficient if you can exclude the DC-DC from the circuit.

I run mine directly off a 7s pack.

That from my Las Vegas trip in the summer.
completelycharged likes this post
Even better when the fridge is full of beer...
Crimp Daddy likes this post
(08-21-2018, 08:51 PM)completelycharged Wrote: Even better when the fridge is full of beer...

Absolutely... The 50 quart model can hold 72 cans... it's amazing how much you can carry when you don't need to leave room for ice.

Still, one of my favorite things is being able to run a freezer.  Being the only guy at a camp site with an ice cream cone in your hand never really gets old either.  "Uhh, where did you get that"
completelycharged likes this post
Well, all the 12V dehumidifiers I've seen that I might turn into an A/C use peltiers. I'll keep looking, but I'm not sure that idea will pan out. I'm a bit suspicious of those 12V refrigerators as well. I bet they use thermoelectric too; which means peltiers. I'll look into those, but I'm not sure how I'd use them or ice to cool the trailer. Remember, this is basically a 6' by 3' sleeping box. I don't have much room for bulky stuff, which is why I nixed the DIY evaporative cooler idea.

I do plan to use some rigid foam insulation in the walls. They're going to be quite thin though, to save space and weight. I don't plan to mount the solar panels on the trailer. I'd like to park in the shade if possible, and set the panels out in the sun. That would probably do more for keeping cool than using an A/C anyway.

Charging will primarily come from the motorcycle. It has a 40A alternator, and the bike only uses around 10-15A, so there's plenty to spare. The manufacturer designed it that way on purpose. I'm thinking maybe 5-10A. That would be 2-4A into the 25V battery I think.

The solar panels would provide a little power so the battery might drain more slowly while I'm camped for the afternoon. Or if I stay the whole day, I'll leave the panels hooked up all day. Since I haven't picked out all the charging hardware yet, I don't know how much power in I can expect yet.

Speaking of hardware, I'm wondering how I'll get power from the bike to the battery. I guess I'll need a booster that goes from 12-14V to around 30V, and then get a charge controller that can do 30V in and charge 7s Li-Ion. I wonder if it would be better to put the boost converter closer to the motorcycle and run the higher voltage back to the controller? Fewer Amps and more Volts means less loss, right? If anyone can suggest a good charge controller, that would be awesome!

Also, DC circuit breakers. I'd like to find some of those wall mounted ones I see folks using instead of the cheap inline ones I'm finding.

I appreciate the suggestions folks! I may not use them all, but I am considering them seriously. Smile
-Mike G
You should absolutely be weary of cheaper 12V fridges because there are those that are thermoelectric and the best you can get is 40 degrees below ambient. You need to spend some coin on a fridge that has a compressor and is very efficient and high performance. Being able to hold 100F below ambient and only use 50 watts isn't bad at all and it cost as much as a real home appliance.

Somehow I missed the entire fact that ur pulling this with a motorcycle. For some reason I thought this was more of a standard camper trailer than you pull with a truck or SUV. This obviously changes everything so I apologize for missing that detail.

Vents and fans are going to do a lot for you... along with the insulation, but I agree with your ideas on keeping cool. If you were worried about staying warm there are actually plenty of DC 12v heated blankets to choose from too. I have a couple and we love them for winter trips.

You could easily buy/diy your own charger using a current limiting DC-DC converter. Just use it for maintenance / bulk charging at a lower than full voltage at whatever current level work for you. If you wanted a proper charger, you could look into something like a CTEK which is pretty poplar in the off-road crowd but I would keep a close eye on voltages since it is a Pb charger.

But again, Victron pretty much has something for everything you mentioned.
completelycharged likes this post
Breakers - for DC at 24V use DIN rail mounded breakers and I use these type :
They are cheap and work ok. They are type C so delay tripping a while.

Boost, use the 1500W boost version of the unit in the earlier post, has a fan and will work upto 30A depending on voltage range (check the actual spec as the 30A is only for a certain voltage range). I had a few experiments with them on this post
The boost would only provide a CC CV charge so sill balancing to sort out...

Critical : set the input limit on the boost to the float level of your bike battery, otherwise the boost unit can end up discharging your bike battery and then have no juice to start the bike... !!!!

Solar can be 3kWh per kWh of capacity, depending on location, sun rise/set, etc.

I would opt for more solar to try and avoid charging from the bike at all as this should in the long run cost less in fuel.. still prepare for options to have the bike as a backup charger.. weight may become an issue though as larger 300W panels can be 20kg each.

With alternators if they are brushed connections to the rotor using them at higher amps will burn out the brushes earlier. I had a car alternator, which they put on test after a "repair" and the brushes burnt out in seconds at full load (130A), burning the copper connection surface from the rotor.... toast. suppose the other option is to provide the ability to run the bike from the battery pack in the case of an alternator failure, use a small buck to charge the 12V bike battery..
Yeah, didn't think about that all the 12V version stuff would be peltiers. Don't recall if you would be using an inverter, but seems like that'd be the only way to get the "freon" version of the dehumidifiers.

Did some searching, and I'm either getting peltier styles, or evaporative coolers (which u don't want as it raises the humidity in the camper)
I suppose this is something you're gonna have to think about. If you go the DC route, you might as well get a full blown RV style cooler, the type that goes ontop of the camper. If you want a smaller unit, or go with modifying something, then you'll need an inverter to run it.
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I've been looking into the power input side of things. It's not as good as I'd hoped. For times when a power outlet is available, I'll have no problems, but I also want to be able to just pull off the road and camp. No power, water, anything. For those time, I'm going to have to really conserve my battery.

The folks on the Ural forum tell me that I can easily draw 10A from my alternator all day with no problems. So I can get 14V x 10A = 140W, and if I ride for, say, 4 hours, that's 560Wh minus losses.

I've decided to put 2 12V panels together instead of my original plan to have just one. Each would be 100W, so I figure if I'm lucky I can get 160W out of both in parallel. If I can set those out and get good sun for maybe 3 hours a day while camping, I could get 480Wh.

This would be 1040Wh total, which is quite a bit less than what I was planning on using. Which was around 1500Wh per day. Also, I completely forgot about my little netbook which has this cool OBDII access in case I have trouble with the bike. And also, it's just nicer to have a larger screen and a real keyboard if I want to do any computer stuff along the way.

So I plan to work on this from both ends.

On the consumption end, I think I will completely eliminate the A/C, and just live with the fans for ventilation. Also, I'm going to do away with the 12V outlet. I've been trying to think of what it would be good for, and I just can't come up with anything. Other than an electric tire pump. But that would be better suited for the starter battery, as it uses high Amps, but for a short time. I've already got a 12V outlet on the bike anyway. I can also disable the heater and humidifier functions on my CPAP. I don't use the humidifier anyway. This should greatly reduce the Amps that the machine will need. I'll have to put it on a power meter and see what the real difference is. With all that, It looks like I can get the power down to 1200Wh per day.

On the production side, I'm thinking of doing something like mounting the panels to the trailer while I ride, and then be able to detach them while camping so I can have the trailer in the shade and the panels in the sun. Still have to think on that, but then I could get 4 hours of solar while I ride, in addition to the 3 while I'm camping. That would put me at 1680Whr if conditions are good.

Even so, the sun is not always going to be out, and I may not want to ride 4 hours every day. In fact, if the weather is crappy, I'm less likely to want to ride anyway, and I might generate no power at all for a day. I'm going to have to figure out a minimum power usage plan! Or find a campsite with power.

The 7s battery has allowed me to clean up the wiring diagram quite a bit.
-Mike G
I don't know about the towing services either.
But definitely pick the trailer that will suit your needs first, then modify it for off-grid, or whatever you want to do. Smile
-Mike G
Why the unnecessary complex shape of the trailer ?

All you get from that is a lot more work, lower structural integrity, less usable space and the probability of it ending up looking like undesired objects.

I'd do that as simple as possible, like a cube.

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