Newbie advice

[littleharbor]

7WayTrailerEnd.jpg

Not sure of the gauge, probably 14 and 12 or 12 and 10 but from my feeble recollection the 12 volt (charging) wire is heavier than the tail and turn signal light wires.

[Sunking]

Thank you so much Sunking, that sums it up. Are trips do last upto a week at times, most the time we are in the woods riding though. I do plan on using 1 of the extra wires in the trailer wiring to top off the batteries while driving, my concern was I think I've got something like a 190 amp or maybe a 200 amp altanator on my truck and that's a lot of amps to put through a 12-16 guage wire, I'm not for sure what the 7 wire trailer wiring is I'm just guessing, is this common and safe?
Again thanks to all for the help.

OK tap the brakes. If you want to charge the battery through your Alternator, you will not use 7-Pin Trailer Connector. I assume that includes Electric Brakes. You will run two 4 to 8 AWG wires. A Black one either directly on the Battery Negative Term Post, or on the Firewall where the heavy cable from the Battery Cable goes. Understand? Look under your hood you should have two heavy cables already on the Battery Negative Tern Post. One will go to the Engine Block, and another going to the Firewall or a Terminal. So you want to be either on the Term Post, or at the end of a heavy cable. OK?

You will want to use a Smart Electronic Battery Isolator for the Red Wire or Positive. It will have a Voltage Regulator built-in and you install it between the Alternator Output and the Truck Battery. It will also have aplug that goes to your Alternator Voltage Regulator. On the Isolator there will be two Ports. One for your Truck Battery, and one for the House Battery. They are vehicle specific meaning Ford, Dodge, or GM. No worries about the Alternator Amps, bigger is better. The resistance of the Wire and fuses will take care of the Current Regulation. Not something you have to worry about except proper fuses and wire size.

An Alternate method is the old Mechanical Isolators that use a relay wired to your ignition. You just take a #4 AWG to the Battery Positive Term Post, run it to the relay, and then to the Trailer. If you go that route look for one with a Pre-Charge Resistor as that will help in keeping you from welding the contacts on the relay.

You are going to make a 2nd plug using an Anderson Connector of the appropriate size. I will give you some links to look at to help you understand.

Cole Hersee is made by Little Fuse a good company makes a good 200 amp Mechanical Some What Smart Isolator and works with any vehicle. It will not connect the House Battery until the SLI battery is charged, and has Precharge.

Sure Power makes good Electron Isolators and they have to match vehicle alternator. Choose your group and Amps.

Anderson Power Connectors. Choose Wire to Wire

That ought to get you going.

[HITEKREDNEK]

Well.... it sure ain't as simple as I thought, that's for sure. I think I need to plan out a few things before I go and start buying stuff. Thank you all for help.

[SunEagle]

Well.... it sure ain't as simple as I thought, that's for sure. I think I need to plan out a few things before I go and start buying stuff. Thank you all for help.

Smart plan. It is not a good idea to look for cheap ways to generate power or charge batteries. Taking shortcuts can lead to equipment failures or worse like fires.

[ewarnerusa]

If you're using a 7-pin trailer connection as in the diagram, then you will likely be getting some battery charging from the alternator without having to buy anything else. But it is basically a trickle charger due to long skinny wire length between the vehicle's alternator and your camper battery. Useful for charging if you've got many hours of driving to do. If you want the alternator to dump gobs of amps into your camper batteries for fast charging, then Sunking has described the path.

[Sunking]

Do not use the 7-Pin Trailer Plug to charge batteries. Lot's of things happen and none of them are good. Beside the minor stuff like dim trailer lights and having someone rear end you, bad things are burnt wiring and electric brake failure. The Isolators tell you what gauge vs length you will need along with Fuse sizes. Most importantly the Connector must be sized for the amount of current. Anderson SB connectors go up to 450 amps with the proper sized wire. For your application an SB50 should be perfect. The SB50 is good up to 120 amps and can fit a #6 AWG wire. Make sure to use a 110 degree rated insulation like Marine Battery Cable or even this stuff will work great. You can order it with the Connector Terminated which I recommend because you do not have the tools or skill to terminate. You can buy all your wire, connectors, and fuses from Powerwerx. They even will make the cables for you.

[bcroe]

Anderson 50s and 175s are common here; beside being cheap, they have the additional advantage of being unisex.
Bruce Roe

[Wrybread]

To be honest if your trips are 3 days or less, you do not need solar. All you need is batteries, Inverter, and charger. Save the cash. Just conserve energy like turning off the Inverter when not being used. You can even run a line from the Alternator and an Anderson Connector to use the alternator to top off batteries while you drive. ! hour engine run time is 2 or 4 days of solar. Think before you jump in.

Since you're going to need the batteries with or without the solar (having lights is nice!), you might as well add the solar. The solar part is dirt cheap compared to batteries, is easy to install, it keeps your batteries topped off, and is generally a good thing to learn how to work with. And there's a *really* good chance you'll run your batteries low after your first day on the road given that you're still learning about what's practical to power off of batteries (as others have said, that compressor fridge is out). This way no matter what you do you'll be charged back up the next day. And no need to drive anywhere or run your engine if you don't want to.

One issue you'll find on this particular forum is that people will only recommend top of the line equipment, and scream bloody murder if you diverge from the absolute perfect setup. That's a bit silly when installing in an RV, especially given that you describe your rig as a "hillbilly toy hauler". Furthermore they vastly over complicate things, and a specialty of this forum is either talking people out of installing solar or talking them into building vastly over priced and over spec'd setups. I'm of course not saying you shouldn't do everything to keep your setup safe, but you don't need top of the line equipment to be safe.

I just did a similar build to what you're contemplating and couldn't be happier with it. Here's my equipment list:

- Pick up one or two big 60 cell panels, which are in the 250 to 300 watt range. You could also get 72-cell panels, but then your voltage might go over 100 watts on cold mornings, which could fry your charge controller. Sticking with 60 cell panels keeps you safe there.

If you shop around a bit you should be able to find 60-cell 250 watt panels for about $150 each if they're demos or cosmetic defects or $210 or so new. Wire them in series unless you anticipate having one of the panels shaded occasionally, in which case you'll want to wire them in parallel (a bit less efficient but hey it's an RV).

- I have and highly recommend this charge controller. Its a few hundred dollars cheaper than the Morningstar and works beautifully.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

One thing to note is that it's 100 volts, so if you're planning on possibly using 3 solar panels in series now or in the future you might consider getting the 150 volt version:

https://www.amazon.com/SolarEpic-Cha.../dp/B00YCI48F4

But you can easily run two 250 watt @ 36 volt solar panels with the cheaper version.

I recommend getting the external monitor box at the above link too, it's only $30 and is very handy for seeing the status of your panels.

- get some 10 or 12 gauge wire to run from your panels to your charge controller.

https://www.amazon.com/Black-Gauge-S...ICM/ref=sr_1_4

For batteries, as recommended above get 2 6-volt batteries. You can't go wrong with Trojan T105's. Wire the batteries in series for 12 volts. If you want more capacity get 4 of them. Personally I still wire them for 12 volts to keep things simple, but there's good reasons to wire them for 24 volts. But keeping it 12 volts means you can use your existing 12 volt inverter, removes the need to step up the voltage from your alternator, removes the need to step down the voltage for your cabin etc, and 12 volts works just fine.

For your fridge, as others have recommended get a propane fridge. They work fantastically well and are available cheaply used. They still take a tiny amount of 12 volt power to run the brain but it's negligable.

And if you wire your panels in parallel, get some of these fuses (or a combiner box if you want to spend 10 times as much on the Cadillac route):

https://www.amazon.com/dp/B019YP0HQ8..._Y1oezbEV0ZKE0

And if you're wiring your panels in parallel you'll also need these or these.

And for flat mounting your panels to the roof of your RV, these work well.

[Carv]

Thanks for the post wrybread.

I'm putting together a similar system and was wondering why you say no compressor fridge?


I've done the math and a used propane 2 way (propane/dc) is $500 or more plus it's 60" tall and you have to run propane if you don't already have it.

A small mini fridge is rated at 1.1 to 1.7 amps and at 115 volts it's only drawing 127 to 196 watts when running and I can buy one for $50 and take the other $450 and build my solar system to run it.

[Wrybread]

If you want to avoid propane another option is these trucker style coolers. They've come a long way and now have dorm-fridge sized units:

https://www.amazon.com/dp/B0012EGZ9S

They're very low power (60 watts) and work well. I've never owned one but I know lots of people who swear by that particular model, mostly because of the Danfoss compressor. Further reading including some mods to improve them:

http://www.cheaprvliving.com/forums/...y-usage-please

http://forum.expeditionportal.com/th...light=edgestar

I don't know how well the other trucker style units compare, but I'm guessing favorably.

[Wrybread]

As far as powering a 125 - 200 watt fridge off your batteries, you could certainly try. The worst that'll happen, assuming you use appropriate sized wiring and fuses (which you must do!), is that you'll find that your batteries can't keep up, and then you can make the appropriate upgrades and changes. A lot depends on how often the compressor in your fridge is kicking on of course.

I made a system that powers my propane/AC fridge off solar when my batteries are fully charged and the panels are putting out more than 200 watts, details here (fair warning, the thread gets pretty mindlessly hijacked):

https://www.solarpaneltalk.com/forum...my-setup/page9

It works well as a way to minimize the amount of propane use and maximize the use of the power from my panels, and for me the most important part is that if my propane runs out while I'm away my fridge stays cold and doesn't turn into a science experiment mess. I'll probably post the code to my Github page at some point, but since it runs on Linux it still takes a bit of programming skill to install.

Personally I'm surprised the ability to turn on an external load after the batteries are fully charged isn't a more common feature on charge controllers. It's so close on these Tracers (the controllers linked above), since it already has an output that you can configure to only turn on when the sun is out, or not out, etc, it would be nice if they released a firmware update that added an option to power it when the excess power is being generated.

No matter what, you might want to get a battery monitor so you can keep track of your batteries' charge and get a sense of the loads. These work well enough and are super cheap:

https://www.amazon.com/bayite-6-5-10.../dp/B013PKYILS

And personally I'd confirm what the actual power consumption of your fridge is with one of these.

[Carv]

Well I have converted a mini stand up freezer rated at 1.1A to a fridge with a digital temp controller.

I did a test run off my 2 -6Vs in series through my pure sine wave inverter (no charging source) and it ran for 72 hours and only dropped the batteries to 11.8V at rest and 11.6 under load.

Based on this I think the set up will work just fine for my needs especially when I start feeding the system with a panel or two.

and as I stated earlier for the price of a propane fridge I can set up the whole system.

I am interested in finding a charge controller that with act as a switch and once batteries are full, it'll run the fridge off the excess when it's availiable. Do you know of a 30 or 40 A mppt controller that'll do this, that's reasonablly priced?

Thanks

[SunEagle]

Well I have converted a mini stand up freezer rated at 1.1A to a fridge with a digital temp controller.

I did a test run off my 2 -6Vs in series through my pure sine wave inverter (no charging source) and it ran for 72 hours and only dropped the batteries to 11.8V at rest and 11.6 under load.

Based on this I think the set up will work just fine for my needs especially when I start feeding the system with a panel or two.

and as I stated earlier for the price of a propane fridge I can set up the whole system.

I am interested in finding a charge controller that with act as a switch and once batteries are full, it'll run the fridge off the excess when it's availiable. Do you know of a 30 or 40 A mppt controller that'll do this, that's reasonablly priced?

Thanks

Dropping the voltage of a 12volt battery to less than 12volt is a sure sign of giving it a very short life. You really should never go below 12.4volts and 11.6v is not good.

[ewarnerusa]

Well I have converted a mini stand up freezer rated at 1.1A to a fridge with a digital temp controller.

I did a test run off my 2 -6Vs in series through my pure sine wave inverter (no charging source) and it ran for 72 hours and only dropped the batteries to 11.8V at rest and 11.6 under load.

Based on this I think the set up will work just fine for my needs especially when I start feeding the system with a panel or two.

and as I stated earlier for the price of a propane fridge I can set up the whole system.

I am interested in finding a charge controller that with act as a switch and once batteries are full, it'll run the fridge off the excess when it's availiable. Do you know of a 30 or 40 A mppt controller that'll do this, that's reasonablly priced?

Thanks

Seems like you've answered your own question as to why running a compressor fridge with AC electric only is not favorable for boondocking. Although 3 days is pretty dang good, you've discharged those batteries to like 25% SOC. While you have interpreted these results as favorable, I see it as the fridge alone used more battery capacity than is available for a long weekend without even considering any other power usage that will be required. You're right that the solar will offset this, though. One answer is more battery capacity and therefore more solar to go along with more batteries. If you've got the space for more panels, the cargo capacity and space for more batteries, and the comfort of being able to make it through any long spells of poor solar harvest, then it should work.

[Wrybread]

There's a chart here showing how charged your batteries are based on their voltage at rest:

http://www.trojanbattery.com/tech-su...y-maintenance/

According to to that your batteries were about 30% charged when they were 11.8 volts. Which isn't bad for the type of use you describe. Grab a couple of ~300 watt panels and a controller and you should be fine. And if you find that you're under powered, you can make adjustments.