Solar Power: Baby Steps Questions - Fiberglass RV


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Old 10-15-2014, 11:38 PM   #1
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Solar Power: Baby Steps Questions

I have a Casita I am wanting to augment with solar power. I recently purchased a briefcase-style solar panel unit from Harbor Freight. It's only rated at 13 Watts output (on sale + coupon it was $60, I couldn't pass it up). I am hoping I can dry camp a few days or more and run my laptop computer for 8 or more hours a day, and recharge my cell phone as needed, once every other day perhaps (I don't talk on it much). And also maybe run and/or recharge my portable bluetooth speaker. Here is the data I have available for these devices:

laptop 65 watts, 3.34A
phone Li-Ion 3.7V, 1900 mAh battery
speaker 12VDC, 2A

I'm traveling solo (just me and my dog) and won't be using the water pump, as I have just winterized. I have LED bulbs in the light fixtures. I might run the roof fan for a few minutes now and then.

The 12V battery is a EverStart marine battery. A label on it says it has 115 Amp hours at 1 amp. I am the 3rd owner of this camper and who knows why that battery is there, but so far is has served my minimal needs just fine.

I have several questions. :

1) The solar unit came with several adapters (car, m+f, battery clamp, barrel plug) for the end of the cable. Where (or to what) should I connect the cable:
a) directly to the battery terminals, from the exterior battery compartment hatch, using supplied clamp adapter
b) to the Casita's converter panel battery terminals (doubling up on top of where the battery cables are already connected, either by using supplied clamp adapter, or by creating wire leads with terminal ends and placing them under the lugs on top of/with the existing battery cables)
c) directly to the laptop computer (the supplied barrel plug does not fit the laptop's power input though).

2) Do I need a controller for such a small power supply? If so, would an inexpensive PWM type be okay? What about an inline fuse?

3) I have a PowerBright 1100 watt inverter spec'd at 90% efficiency. Should I also attach this to the Casita's converter panel battery terminals? Seems like it might get crowded there if I've also attached the solar panel to those terminals plus the original battery cables are still there.

4) Say I have my laptop computer plugged into the inverter, and I am drawing 65 watts. Does the inverter still draw 1100 watts from the battery? It seems like the fan runs constantly on the inverter. Also, will the modified sine wave harm my laptop computer?


Thanks for your help.
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Old 10-16-2014, 05:44 AM   #2
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I doubt that 13 watts will be sufficient for what you're hoping to do. Typically 13 watts only provides trickle charging to offset no-load discharge as when a battery is in storage. If the panel were operating at peak efficiency (which it doesn't), it would only put out a bit more than 1 amp. If your laptop spec is correct, the panel won't even handle its 3.34 amp draw.

Also, inverters will drain a battery in a very short time.
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Old 10-16-2014, 08:06 AM   #3
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Hi Julie. Solar power is an interesting but somewhat difficult thing to nail down. My best suggestion is for you to do a lot of research, the internet is a wonderful source of information, some of it actually helpful. I suggest starting with a somewhat standard resource; "The 12V Side of Life". I found it very enlightening. I hesitate to give advice but would wager, and I am not a betting man, that the 13w panel will not even begin to satisfy your needs.

Here is a link to some info I just found; http://www.amsolar.com/home/amr/page_19 Kind of introductory but written in easy to understand language.
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Old 10-16-2014, 08:38 AM   #4
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Yeah 13 watt's might be ok to keep your batteries topped off while it is being stored it just isn't going to cut it for keeping your battery topped off while camping. I added a 100 watt panel to my roof (typically around $200 for the kit with mounting hardware and charge controller and cables) After having my rooftop unit for a few months I am seeing how a portable briefcase style might be a better deal because if you park in the shade you only get so much sun hitting the panel. I think this winter if I work enough overtime I want to pick up 2 60watt panels and make my own briefcase and have them to move around to keep the sun on it. If you do any cooler weather camping and are running your furnace it might be able to extend your camping experience.
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Old 10-16-2014, 12:46 PM   #5
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My first solar venture was with the HF panels.
I ended up selling them at a yard sale.
I have added solar to 3 eggs and 2 slide in Campers over the last few years.
I've found that a 50W panel is more than adequate for boon docking if you have all LED lighting.
I even run my furnace when it's cold.

Complete 50W solar kits are available on eBay for less than $125.00.
That includes the wiring from the panel to the included controller and the mounting brackets for attaching the panel to the roof.

Solar is not a difficult project.
Mount the panel to the roof, mount the controller in a convenient location, run the wire to the controller and from the controller to the battery.
Very easy, if you are the least bit handy with tools.

My first permanent installation was on a 16' Scamp.
I bought a 50 W $90.00 panel and a $30.00 controller from ebay.
I gave the Scamp to my son 3 years ago and he has NEVER run out of power, even with 3 boys who insist on their DVDs in the evening.
It's been 5 years and the group 29 deep cycle battery still going strong.

Some here try to make Solar into a complicated addition.
It's NOT.
You don't need $200.00 fancy controllers or super expensive panels to have a serviceable system.

A roof mount system eliminates the theft problem and charges your battery as long as their is ANY light.

John
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Old 10-16-2014, 12:56 PM   #6
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John is exactly right. We have two 20 watt panels on our CompactII. Don't try to over think it. Like you, we are all LED lights and small computer fans for ventilation. We can keep a swarm of cell phones and iPads all charged up and never plug in. Make sure you get a panel with a controller and mounts in your kit and you are good to go. It will wire directly to your battery, which should be a deep cycle, not starting type.

Let the sun shine


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Old 10-16-2014, 01:03 PM   #7
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My suggestion would be to do a use audit to determine you needs. While camping, keep track of what you use, how long, and how much power each device uses. The math to convert this to amp hours is not too complex, and adding everything up will give you your overall average use per day.

While many can get by with a 60 watt panel, others need more. For example. I want to be able to run an inverter to make a pot of drip coffee. I process a large number of digital photographs every day on a power hungry laptop as well as run a 3 watt cell phone amplifier to provide internet service. While I have all LED lighting & a fairly low power (1.8 amps) furnace, my average use is between 25 & 30 amp hours per day, depending on whether I make a pot of coffee or not, and peak usage as high as 55 amp hours.

While a single 95 watt panel will keep a pair of 6V 232 amp hour batteries reasonably well charged in bright, summer sun, I found that more than a couple days of heavy shade or low angle winter sun (the panel is roof mounted) will run the batteries down more than I'd like.

Since most of my trips are long (the last 305 days) and as much as a month of dry camping at a time, I now carry a folding 160 watt panel that I add to the trailer's built in panel when solar conditions are poor.

Again, these are my needs; yours may be less (or even more) but the only way to find out is to do an audit of your use.
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Old 10-16-2014, 01:27 PM   #8
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To answer your specific questions -

Quote:
Originally Posted by bluesail20 View Post
I have a Casita I am wanting to augment with solar power. I recently purchased a briefcase-style solar panel unit from Harbor Freight. It's only rated at 13 Watts output (on sale + coupon it was $60, I couldn't pass it up). I am hoping I can dry camp a few days or more and run my laptop computer for 8 or more hours a day, and recharge my cell phone as needed, once every other day perhaps (I don't talk on it much). And also maybe run and/or recharge my portable bluetooth speaker. Here is the data I have available for these devices:

laptop 65 watts, 3.34A
phone Li-Ion 3.7V, 1900 mAh battery
speaker 12VDC, 2A

I'm traveling solo (just me and my dog) and won't be using the water pump, as I have just winterized. I have LED bulbs in the light fixtures. I might run the roof fan for a few minutes now and then.

The 12V battery is a EverStart marine battery. A label on it says it has 115 Amp hours at 1 amp. I am the 3rd owner of this camper and who knows why that battery is there, but so far is has served my minimal needs just fine.

I have several questions. :

1) The solar unit came with several adapters (car, m+f, battery clamp, barrel plug) for the end of the cable. Where (or to what) should I connect the cable:
a) directly to the battery terminals, from the exterior battery compartment hatch, using supplied clamp adapter
b) to the Casita's converter panel battery terminals (doubling up on top of where the battery cables are already connected, either by using supplied clamp adapter, or by creating wire leads with terminal ends and placing them under the lugs on top of/with the existing battery cables)
c) directly to the laptop computer (the supplied barrel plug does not fit the laptop's power input though).

It would be best to keep the trailer battery as a buffer for the panel - I'd connect the panel to the battery terminals. To avoid the chance that a spark from making the connection cause an explosion of the battery, I'd first connect the clamps to the battery then plug the adapter into the panel cable. If you have a 12v receptacle in the trailer, you could plug the panel into it if it is easier to get to than the battery terminals.

Since the panel will not supply enough power to run your laptop, plugging it directly into it won't work. Again, using the battery as a buffer makes the most sense.


2) Do I need a controller for such a small power supply? If so, would an inexpensive PWM type be okay? What about an inline fuse? As others have mentioned, this panel is too small to provide much more than battery maintenance power. In any case, it does not need a controller.
3) I have a PowerBright 1100 watt inverter spec'd at 90% efficiency. Should I also attach this to the Casita's converter panel battery terminals? Seems like it might get crowded there if I've also attached the solar panel to those terminals plus the original battery cables are still there.The inverter should be connected directly to the battery if you plan to use it at any near its rated output.

4) Say I have my laptop computer plugged into the inverter, and I am drawing 65 watts. Does the inverter still draw 1100 watts from the battery? It seems like the fan runs constantly on the inverter. Also, will the modified sine wave harm my laptop computer? The inverter will draw the load you connect to it + its losses. In the case of your 65 watt laptop, that would be 65 watts + another 6-7 watts to cover the losses. While this is a little over 1/2 an amp at 120 volts, it would be 10X that at 12V (the battery voltage) or around 5-6 amps. At that current draw you could plug the inverter into a typical 12V outlet, however if you put a full load of 1100 watts on it, it would draw close to 100 amps. For that draw it would need to be connected directly to the battery.

Most laptop power supplies will work fine on a modified sine wave inverter.



Thanks for your help.
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Old 10-16-2014, 05:46 PM   #9
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Solar, is it for everybody?

Solar panels might not be necessary. There's several tricks you can do to keep power up and running for short trips (3 to 4 days).
Recharging electronic devices like computers, smart phones, etc. --- I always recharge those things from the tow vehicle. Rarely does the tow vehicle sit for more than a couple days, when sit seeing or running to the store for little bit more food is a great time to recharge those electronic devices.
LED Lights are of course a good idea.

My own experiences --- We stay in one place up to 30 days at time. It's usually 3 days before I drag out the solar panel and recharge the house battery. The only thing the house battery runs is lights (LEDs and a CCFL) and the furnace fan. If the weather is quite warm (furnace doesn't run) I don't have to recharge very often.

Solar might not be something that's needed. Campers got along for years without generators and solar. I was camped next to a couple that would have to hook up the tow vehicle power cord to have lights.

I suggest you think about your want and needs carefully before investing in solar and think about ways to conserve energy rather than way of increasing capacity and consumption.
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Old 10-16-2014, 11:04 PM   #10
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From the sound of it you would be no where near the 1100 watts. Maybe 100 or so watts. I have to agree that 13 watts is more of a maintenance item than a power supply. Sorry if that doesn't help much. Hope you get it figured out. At least yer campin.

e
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Old 10-16-2014, 11:48 PM   #11
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13W will do fine for maintaining the battery when your trailer is parked in your yard (stored, unused), but for camping it sounds like you will need quite a bit more. I would suggest 50 or 60 watts at least. A little more is better in case you can't get sun every day.

I bought a 75W panel for about $100 and a Morningstar SG-4 controller for $28, from solarblvd.com. I then bought a short extension cord and cut it in half, and wired one end of the cut cord to the panel's wires and the other end to the controller's input wires. The 3 prong plugs can be connected easily at the campsite, or I can add an extension cord of any desired length in between those plugs to get the panel into full sun. On the controller's output wires, I added a 7 pin receptacle just like the one on the back of the tow vehicle; so the trailer's pigtail plugs in there and it charges the trailer battery. It was really easy!
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Old 10-17-2014, 12:43 AM   #12
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Yes Julie, as others have said the 13 watt will only help for battery mantenance while sitting for long periods. I have the same HF unit that I've used for years in a class A. Kept it on the dashboard and connected to the battery 7/24 trickle charging. The coach sat for a month or so between trips. Never had a problem using it that way as the battery was always charged up. But that small of a panel would never make it for a daily top off in our trailers while camping. Good luck to you
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Old 10-17-2014, 09:19 AM   #13
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Quote:
Originally Posted by Mike Magee View Post
I then bought a short extension cord and cut it in half, and wired one end of the cut cord to the panel's wires and the other end to the controller's input wires. The 3 prong plugs can be connected easily at the campsite, or I can add an extension cord of any desired length in between those plugs to get the panel into full sun.
I have thought about this also, as I have many 16, 12, & even 10 gauge extension cords of various lengths. One thing I have thought about is wiring them "backwards", or male prongs "hot". Yes, you could have exposed hot plugs if you hooked stuff up in the wrong sequence, but it is “only” 12V, not 120V. And that way someone (else, not you) could not plug a hot 120V into your 12V system and wreck havoc.
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Old 10-17-2014, 12:34 PM   #14
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Julie,

You'll find a suitcase kit solar unit that lots of Casita folks have purchased which would definitely do the trick for you. It's a portable plug and play unit. Comes with everything you need, has 2 panels which add up to 90 watts. Seems to me that the price is around $400. The initial outlay for solar isn't cheap.

I've seen these units and they are quite nice. I already have a large solar panel however, if I didn't I would surely purchase the suitcase style mentioned above.

Here's the Casita site on which I've seen these suitcase panels spoken about. There is often a mention of a group sale. You might inquire with the folks on that site. Do a search for 90watt solar panel.

www.casitaforum.com
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