Solar System Advice/Feedback for new Truck Camper

NinerBikes wrote:
Does my alternator underneath my front bonnet have a temperature sensor on the battery, despite me cycling it every day? I don't think so.

It just might - have you taken a closer look?
Of my several vehicles including the 2009 RV only my 1972 Chevy K5 Blazer does not have a battery temp sensor.

Take another look under the engine battery

This summer time 100 plus degree weather and high charging voltages can and will shorten the life of the battery - check that water level often if charging in hot weather without temp compensation

pianotuna wrote:
Hi,

It is NOT rocket science nor difficult to design an excellent system.

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT.

What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

Does my alternator underneath my front bonnet have a temperature sensor on the battery, despite me cycling it every day? I don't think so.

Unless you live full time off the grid, a temp sensor might be optional for you on your charge controller. If you get out quite a few times a year, and you top charge your batteries once the trip is completed, and as best you can during the trips, it's a non issue... the life of the battery won't be affected enough, nor the $ savings, unless you are RV'ing full time, or you have money to burn and you are a purist.

A temp sensor, for the weekend warrior, is fine, if you have more panel than you need. If you have just enough panel or are short a little bit on panel, to battery capacity, it's a non issue. I'd aim for 1 to 1.2 watts per amp of battery capacity, for solar panel, if portable, perhaps a little less, you will be sun chasing and they will give you a higher yield in amps for more hours per day, when aiming them at the sun, 3 or 4x a day. The OP is a truck camper... I am assuming he has a camper on the back of his truck. Think small, there's not a lot of power sucking devices on a camper shell.

Hi,

It is NOT rocket science nor difficult to design an excellent system.

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT.

What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

JiminDenver wrote:
The most important thing is to fill your needs and it doesn't matter what it takes to do it. The person that requires more features on a expensive controller has nothing more than the one that can get away with a ebay special. Each has a system that takes care of them and that's all that matters.

Mike
I think you can see by now the inexpensive portable are a good way to get started. To truly design a system requires a lot more than slapping some parts together. The portable will give you power now while you figure it all out. Believe me that one trip seeing how the solar deals with your needs, in your conditions will make you see these discussions differently. Use it for a season and give yourself time to understand more and you will tell us what will fill your needs. I'm on my second season and I'm getting there.

/\ This... jump in, gently, get a portable, get your feet wet, and from there, with some camping trips, a few meters, and some reading logs, you'll know your needs like a pro in a season or two. While I have only a 21 foot travel trailer and a single Trojan T1275 150 amp battery good for only 75 amps use to 50% discharge, the starting point for me was a portable folding 120W mono crystalline "kit" from Solar Blvd. It works fabulous for me. I recommended them here, and Solar Blvd was sold out of them by early spring, all of them... 80w, 120w and 160w versions.

They will get your feet wet. They are kits, they are jack of all trade, they are not perfect, but you will learn a lot once you get one. You'll learn about how important it is to keep the controller close to the battery, and with fat wire that last run from controller to battery. If you are inquisitive and want to monitor things, you'll learn just how cr*ppy a cheap charge controller is that does NOT have an adjustable charging voltage is. So you'll get an adjustable V charge controller. Then, perhaps, you'll buy some fatter wire and make your own cable and connections at the terminals. Because sooner or later, you'll learn from very smart engineers here that a 50 to 90% charge is throwing away 20% of your useable battery capacity, compared to 50 to 100%, or more likely 60% to 100%, or perhaps 99%, and then foregoing equalizing your batteries as frequently with 16.0V charge rates and the batteries being completely disconnected being needed while doing this routine...

You'll want the capability of charging batteries at adjustable higher voltages in colder temperatures, because that is what it takes to get them charged in late fall, winter and early spring, due to battery chemistry, or dropping voltages in the heat of summer. Me? I want 14.8v minimum at the battery on a big jar like a Trojan T-1275, 15.0v is better. I get by with a 7 amp charge rate, and I can chase the sun with a portable, that really increases my charging efficiency in any season, just by getting close to aiming it at the sun.

25 amps in 24 hours with LED lights and being careful, just me... 40 amps in 24 hour when I throw in 4 hours of TV. I charge my chromebook and smart phone in the afternoon, once the battery is closed to topped off. Spare amps then, that the battery has a hard time taking. Dark weather and no sun? Hit the Honda generator and a 33 amp power supply unit for 45 minutes to an hour with a little Honda EU1000 to give the battery a good jump start charge so the panels can likely finish off topping the battery the rest of the day. I usually turn the water heater on first thing in the morning, then fire the generator up. Run it for 15 to 20 minutes to get the charger load off the generator, by then, my hot water heater has water hot enough to shower with.
Take a shower with water pump on while generator is running... it really seems to suck the amps and the battery down if you run it for a 3 or 4 minute shower instead of a Navy shower.

crcr wrote:

BFL13 wrote:
I disagree with Almot on using an Eco-W with the 12v set-up. I would use a Solar30 PWM controller as previously mentioned. I have used both and am familiar with their features and performances.

IMO the $35 Solar30 would do as well or even better than the $108 Eco-W. You must use MPPT with a 24v set-up, so I would use one Eco-W per 24v panel like JiminDenver is doing now (and me too with one panel) rather than spend big bucks on a fancy MPPT controller that has enough amps room to run a whole array and/or has a bunch of features that I don't need like being able to attach it to my laptop. That is based only on the money difference. The expensive fancy one does no better getting the same amps to the battery.

It is all very personal and situational. Also there is a lot of snobbery among controller owners like a guy who has a Buick to go to the store to buy a loaf of bread will sneer at the mere Chev owner who does the same thing. Each gets his loaf of bread ok, but the Buick guy gets to feel smug too! :)

BFL, does the Solar30 controller have temperature compensation?

Yes, it does have a temp sensor. I was one of the first to point out one of these Solar 30's, then BFL bought one, and then I bought one. It is a very nice piece. Since it has an LCD display, mounting it inside so it can be viewed is common sense. At that point, the plastic case is moot. It is almost identical to an Ecoworthy 30 amp PWM for about half the price, shipped from Hong Kong.

The most important thing is to fill your needs and it doesn't matter what it takes to do it. The person that requires more features on a expensive controller has nothing more than the one that can get away with a ebay special. Each has a system that takes care of them and that's all that matters.

Mike
I think you can see by now the inexpensive portable are a good way to get started. To truly design a system requires a lot more than slapping some parts together. The portable will give you power now while you figure it all out. Believe me that one trip seeing how the solar deals with your needs, in your conditions will make you see these discussions differently. Use it for a season and give yourself time to understand more and you will tell us what will fill your needs. I'm on my second season and I'm getting there.

Best Observation Kudos Award Goes to BFL 13:

...."It is all very personal and situational. Also there is a lot of snobbery among controller owners like a guy who has a Buick to go to the store to buy a loaf of bread will sneer at the mere Chev owner who does the same thing. Each gets his loaf of bread ok, but the Buick guy gets to feel smug too!"....


LOL on this one!! I'll gracefully refrain from adding even more to the 'highly subjective' column....!!

Best Regards,

3 tons

Hi BFL13,

Choice of controller ought to be dictated by features and price per watt (or amp for those of us who may be wattage challenged).

When I was doing my system, cost per watt for panels was $6.50. MPPT made sense. Now it is under a buck per watt for panels, so PWM makes sense. I do insist that temperature compensation be at the battery--and I'd be willing to pay extra for that.

Today MPPT makes sense if, and only if, the roof structure does not have enough room for the wattage that the owner wants to have. MPPT will harvest about 8% more per day. Some folks also say MPPT will start charging earlier and keep charging later in the day--but I've never seen documented evidence of that.

Hi Mike,

1. at 24 volts you want to move over to an MPPT controller. Xantrex is not a brand I would recommend.

2. no, a 300 watt inverter will not run a drip coffee machine. Some drip coffee machines can draw 1200 watts. The inverter should be a minimum of 125% of that value (1600 watts).

3. In best practise, it should be impossible to plug the shore power cord into a pedestal and the inverter at the same time. A simple manual system of plugs will make that possible. You can get fancy and use a transfer switch--but I don't like them. I want to KNOW the power is off, and unplugging does that for me. In addition to powering via the shore power cable, I chose to add a dedicated inverter outlet in the kitchen. When I have only 15 amp shore power that lets me draw from the battery bank while cooking. Much nicer than having to "load balance", particularly if you do not have access to the shore power breaker.

Mike@Asheville wrote:


3 more questions please.

1. What is the practical difference in 12v and 24v panels. How do they impact the user different?

2. Is a 300 watt inverter enough to run most drip coffee machines? I'm sure the other electrical needs I have will be more than covered by 300w. A few LED lights, a little TV occasionally, charging phones, and the sleep machine at night when my wife is along. When I'm alone I'm normally outside until close to bedtime so I don't use much A.C.

From 3 Tons: "What I did is wire the output of my Morningstar inverter to a 30 amp RV receptacle. Before I turn on the inverter, I turn off the converter. Then all 110V outlets are live, which is very convenient. The only caution is when doing it that way, don't try to run the microwave or AC. If I want those heavy draw items to run, I plug the 30A power cable into my genset."

3. I'm still confused on the 110 outlets. From 3 Tons post it sounds like you can make all the outlets live but you risk someone forgetting to turn converter or inverter off and causing a significant repair bill. Is that correct?

if so It sounds like it's best to have one or two NEW dedicated outlets run directly to the converter. is that right?

BFL13 wrote:
IMO the $35 Solar30 would do as well or even better than the $108 Eco-W. You must use MPPT with a 24v set-up, so I would use one Eco-W per 24v panel like JiminDenver is doing now (and me too with one panel) rather than spend big bucks on a fancy MPPT controller that has enough amps room to run a whole array and/or has a bunch of features that I don't need like being able to attach it to my laptop.

Nobody said anything about connecting controller to laptop, and, not being BFL13, I don't know why would anybody want to, when there is a perfectly functional display on controller :)

Also, in light of "expansion" idea that we somehow overlooked, I don't know why we were discussing 12V panels and PWM all those 5 pages. Arrays over 300W are easier to build with 24V panels and MPPT.

OP wanted to pay $900 for 280W 12V array, PWM C35 and 300W inverter. Here is a another scenario:

24V panel 240W Trina Solar, $218
Controller 30A Rogue MPPT, $350, display and remote temp sensor included. It can, unfortunately, be connected to laptop and has other useless features like voltage sense and ability to adjust the length of Absorb stage (sorry BFL, couldn't resist ;) .
Same $245 300W inverter (if 300W is enough of course).
Same #10 MC4 wire

Total $860.
You can go lower yet to $840, there is a cheaper 240W panel in that store, but Trina is a better brand. Less watts than 280, and less money. All good components. Expandable up to 480W by adding another 240W panel in series without changing #10 MC4 cable or adding a rooftop box.

Crcr - Solar 30 has a temp sensor, but it's on-board, not remote. Looks similar to $56 PWM by Eco. God only knows who steals from who in that China.

Well, looks like this is going to be another +11 pages thread of "what solar for us" kind. I'm out.