26 replies to this topic

[Vic Harder]

two 75AH batteries means you have about 70AH of capacity before draining the batteries to about 50%.  Packrate is right, 4A is pretty heavy draw.  So, assuming worst case, and 4A draw for 18 hour or so thats 72AH.  Batteries dead after one day with no charging going on.

 

160W of solar on the roof, with no obstructions, gets you about 8A tops.  Assuming good sunshine for 10 hours, you MIGHT be able to get 80AH back into the batteries.   Not likely on most days.  That's why you want about 2x the AH of the batteries in Solar to replenish them, so 300W of panels.  Your 260 plan is pretty close.  

 

The controllers won't "fight" with each other.  Plug both in as planned and see what the Trimetric tells you, then with all the stars aligning, you will be happy and drinking your bourbon on ice.   

 

Me, I prefer to drink my hard liquor straight up 

[PackRat]

This may be a valuable thread for those contemplating going with a 12-volt only fridge. You are then stuck with somehow providing enough batteries and enough solar panels to feed "The Beast" (your 4A power devouring fridge.). I'm not up on the solar angle so Vic's post is the one to take notes on, but this might be a moment to ask those contemplating what type of refrigeration to install or order in their  camper to listen up.

 

While solar is great, free and non-polluting...it requires the participation of Mr. Sun and in a forested area you don't get 12 hours of sunlight on the camper roof. My old Lance had a 3-way Dometic in it but I only used the 120-volt or the propane options as I had no solar or batteries to charge up on board. I plugged it in at home for 24 hours and when we arrived at camp 4 hours or so later, fired up the propane and the ice cube tray had not even melted.

 

However if you are only going solar you need more generation and storage capacity to feed that fridge of yours and anything else you have on board.

[rando]

Most of the current crop of compressor fridges draw far less than 4A over 24h average.    My 60L isotherm draws 3.x amps while the compressor is running, but only runs about 30% of the time over a 24hr average.   It runs more during the day when it is hot out, and less when it is cool or at night - but 1 - 1.5 A average current is reasonable and seems to be in line with what others are seeing.     So the 4A is either the peak current or is a bit of an anomaly. 

[BillTheHiker]

I have been thinking about alternative power sources when not enough solar energy. I plan to boondock 3-4 months at a time.

1. Drive the truck. Do a resupply run, sightseeing, etc. I do one or the other at least every 7-10 days anyway. Problem is my alternator never
gets my battery over 13.3 volts. Could be the alternator or wiring. Boise Spring Works installed the camper and connected the Blue Sea Isolator to the existing wiring harness for the OEM towing package that came with the Tacoma and I do not know what gauge wire that is, but plan to ask Toyota. I also read on the Optima? website that an alternator is not capable of topping off a deep cycle battery.

2. If #1 doe not work, drive to a campground with hookups and use my smart battery charger.

3. Bring the smallest gas generator I can find capable of running my smart battery charger. I already carry a 5 gallon gas jerry can when "out there."
The highly regarded solarbob [https://handybobsolar.wordpress.com/] said someplace on his website that a generator is a must for successful, long term off-grid  living. I fear it would tempt me to bring more heavy stuff that I could run off it.

[rando]

The OEM towing harness is definitely NOT the place to wire your camper into - it is probably 12 AWG at best, and is much longer than needs to be.    You should definitely replace this with some dedicated heavier wire.    However even this won't totally fix your issue - the alternator output on Tacoma's tends to be on the low side, and at least on the 3rd generation Tacoma's it is an ECU controlled alternator and throttles back once the starting battery is charged.      You could consider a DC-DC charger, which would allow you to get a decent charge from your alternator while driving.  I don't have one of these, but others with experience will likely chime in, and this would really help with option 1. 

 

Option 2 is always a possibility - with the bonus of coming with a shower!

 

Personal opinion, but option 3 would be WAY down on my list.   I can't think of much more miserable than sitting out in the wilderness listening to my generator (well it would be even more miserable to listen to your neighbors generator).   With a combination of fixed and portable solar (and occasional driving) you should be OK.  Many folks (myself included) run this way indefinitely with no issues. 

 

Finally, I wouldn't put much stock in 'HandyBob', not only is he rather bloviated, his recommendations are majorly out of date.

[BillTheHiker]

rando,

 

Thanks. I had asked the installer, which is an FWC authorized shop, to run a dedicated wire and it was on the install instructions from FWC so I plan to go back to them and have it done right. I am still under FWC warranty. I ordered a fridge and when that gets here will wire it up and measure. I have not ordered any solar yet.  I want to see what my amp demands are first. But I am looking close at the roof top kits from AMSOLAR because they have the no rooftop screw holes system that elevates the panel for airflow. I could get one or two of their 100 watt kits plus a portable.

Edited by BillTheHiker, 06 April 2018 - 01:57 AM.

[rando]

Sounds like a good plan.  Seeing the dealer screwed this up the first time, I would get confirmation from them about exactly what gauge wire they plan to use. You could even order some heavier gauge wire ahead of time (say 4-6AWG) and ask then to use that. 

 

200W  +  ~100W of portable would probably be plenty, but it all depends on your usage.   If you are thinking of smaller portable fridge (like an ARB or Truckfridge) you may be fine with 100W on the roof plus a portable.  

[BillTheHiker]

It is the tiny Truckfridge TB18 and is only 18 liters but meets my needs.  50 watts so about 4+ amps. I called mfg and they said it  will draw a bit higher when compressor first kicks in then drop. It has DC only via a 6 foot cigarette plug. I can set it up in the camper which has the DC outlet. I like the flexibility to also put it in the truck and run off truck battery while driving.  the compressor is smaller than any of their other units. I hope it does not use more than 20 amps per 24 hours but like I said I will measure it with a Victron BMV 702. Only other consumers are the LED lights and fantastic fan.

[rando]

If your camper is correctly wired to the truck, the fridge WILL be powered off the truck while driving without having to move it.   I agree that your tiny little fridge will likely use less than 20Ah per 24 hrs.  The LEDs use next to nothing, and if you add a PWM speed control (plenty of threads here on this) to your fantastic fan you can get the power on that down too.   You will probably be fine with 100W of solar. 

[BillTheHiker]

rando,

 

So are you saying the alternator, wired correctly, should be able to fully charge the camper battery(if driven long enough)?

 

If I plug the fridge to the truck battery while driving, would that not reduce the draw on the camper battery, thereby allowing it to get a better charge from the rooftop solar?

 

Regarding a pwm controller, some of them have the LVD feature. Is that a good thing? there is a thread somewhere on WTW where it appears the LVD was  working against the alternator when the truck was being driven.