Portable solar for limited current draw

gemsworld wrote:

westend wrote:
I'd suggest to just buy a 100W panel and a cheap controller. If it's not enough, you can always get another panel.

X2

I have been using a folding 120-watt portable system for years and it has been more than enough to let me run a 15" laptop, TV and satellite receiver for much of the day.

Same here.....120 watt folding with 30 foot of cord lets you park in shade and put panel in the sun.

Hi there, I'm not too up on solar and I guess I should pay closer attention to these discussions, there is however, one thing I will suggest. If and when you do get a portable system, I suggest that you make sure your battery clamps and the posts are clean and bright and that you clean the chassis ground point.

I didn't think that it was to important to add this to the routine maintenance for every spring but I found out I was wrong. I was having multiple problems with the batteries receiving and maintaining a charge. When I finally, with a lot of help here found the biggest problem and decided to pull my batteries, I had to replace the latching disconnect relay and I washed and cleaned the battery box and shined up the cable clamps and wire brushed the ground spot and cable terminal. When put back together and before charging the batteries, I had about a .5 volt increase in battery voltage. Everything looked good, but, obviously it wasn't. Now my batteries read 13.7 or so when we stop and set up camp, before replacing that relay and cleaning everything I was getting 12.4 at best.

I now have Cleaning the Batteries and all their Connections on the spring cleaning list.

westend wrote:
I'd suggest to just buy a 100W panel and a cheap controller. If it's not enough, you can always get another panel.

X2

I have been using a folding 120-watt portable system for years and it has been more than enough to let me run a 15" laptop, TV and satellite receiver for much of the day.

I'd suggest to just buy a 100W panel and a cheap controller. If it's not enough, you can always get another panel.
Answers:
1)Depends on use of electrical devices. LED lights and the water pump are trivial.
2)A portable solar charging system is easiest to connect directly to the RV's battery.
3)See answer #2, above. I may do this and will have a connection installed so that I can just plug in the portable panel.

FWIW, I have a single 235W panel installed on the roof of my TT. It powers everything 12V and a 120V fridge, along with 120V entertainment devices (TV, DVD, Stereo receiver). My laptop is charged by the inverter and it's stock power supply.

Isaac-1 wrote:
There is not nearly enough information here, what type of laptop, some newer ones draw 20 watts or less while running, others draw 75 watts or more. How many hours per day do you want to run the notebook computer, is this just to check email or do you spend 16 hours per day in front of the keyboard? Either way charging a deep cycle battery with the solar panel/panels and using an inverter to power the notebook computer is probably the best way to go. You could get a DC-DC power adapter for the notebook computer, however the efficiency difference vs using a modern inverter will be trivial, as DC-DC converters are basically a DC-AC inverter coupled to an AC-DC switch mode power supply.

Having said all of this a good rule of thumb on solar panels is that on average you will get about the equivalent of 5 hours of rated output out of a panel per day, and that you will loose about 25-30 percent by storing it in a battery.

To put that another way expect to get about 500 watts per day out of a 100 watt solar panel, then expect to loose about 150 watts of that storing it in a battery leaving you with about 350 watts of power on a sunny day to use out from a 100 watt panel. Which would be enough to power a notebook computer that draws 35 watts for 10 hours per day, or enough to power a notebook computer that draws 70 watts for about 5 hours per day. This does not count power for a water pump, interior lights, furnace blower, etc.

p.s. I have 400 watts of solar panels on the roof of my coach, and would not want to try to survive with anything less, this lets me use low power LED lights when I want, power water pump, and furnace blower on cold nights, charge my cell phone, use my notebook computer a few hours per day, maybe watch tv for an hour or two, etc.

You have 400 watts of solar panels charging what? What is your battery bank?

Thanks

ohhell10339 wrote:
What's the easiest way to use the DC output of the panel(s) to light the interior of the rig (and maybe run things like a fan and/or the water pump)?

Likewise, what would be the mechanism I would use to charge the house batteries with the panels' output? Keeping in mind I want all this to be portable, so no permanent hard wiring.

I'm getting the impression you don't understand that it's not the solar panel that will be powering your 12 vdc devices but the trailer battery itself, with the solar panel used to restore depleted capacity to the battery. You haven't told us just which battery or batteries your trailer has but if it's just one then I'd choose a 100 watt - 130 watt folding, portable panel with a built in controller, the output of which can just be clipped to the battery terminals for use. For travel just fold it up and toss it on the bed. We don't normally dry camp ourselves but I may just do exactly this next season for those few times each season we find ourselves without shore power and I'd like to put some reserve back into the G31 AGM I'll be installing to replace my aging G27 flooded. :)

ohhell10339, got a fridge with a 12v brain or CO/Propane detectors that are constant draws on your battery? These things operate 24/7 so consider these loads.

100 watts makes a nice maintainer in storage (single battery) with those loads disconnected, camping it may be enough to cover those loads so your battery can be used to charge a laptop (12v adapter) and operate a few LED lights for a long weekend.

Consider
https://www.solarblvd.com/products/solar-cynergy-160-watt-foldable-12-volt-solar-panel-2/
and a grape solar charge controller
https://www.homedepot.com/p/Grape-Solar-40-Amp-PWM-Solar-Charge-Controller-with-Bluetooth-GS-PWM-40BT/207100856

If you have the newest MacBook it can charge on as little as 27 watts via the thunderbolt port. So that's possible using a simple cigarette lighter outlet style usb-c adapter. To use the computer at the same time I believe you need 54 or 60 watts minimum, 100 watts maximum. I have not found a certified 12v usb-c charger with more than 27w output. Using a non certified charger is a gamble I won't take with a $3000 computer.

To the OP: You will need at least 1,000 watts to keep your laptop charged and run a couple of lights. That is about what you are going to hear. I have done exactly what you want to do with a single 100 watt portable panel, by the way.

The RV lights and water pump are almost certainly 12 volt and will be powered by your RV battery. I like to keep things simple. Therefore, I connect the output from my panel controller directly to the RV battery with battery clips. Charging things like a laptop can be done with a small inverter or better yet, a 12 volt adapter.

Solar can be as simple as my setup or as complicated, and expensive, as you want to make it.

There is not nearly enough information here, what type of laptop, some newer ones draw 20 watts or less while running, others draw 75 watts or more. How many hours per day do you want to run the notebook computer, is this just to check email or do you spend 16 hours per day in front of the keyboard? Either way charging a deep cycle battery with the solar panel/panels and using an inverter to power the notebook computer is probably the best way to go. You could get a DC-DC power adapter for the notebook computer, however the efficiency difference vs using a modern inverter will be trivial, as DC-DC converters are basically a DC-AC inverter coupled to an AC-DC switch mode power supply.

Having said all of this a good rule of thumb on solar panels is that on average you will get about the equivalent of 5 hours of rated output out of a panel per day, and that you will loose about 25-30 percent by storing it in a battery.

To put that another way expect to get about 500 watts per day out of a 100 watt solar panel, then expect to loose about 150 watts of that storing it in a battery leaving you with about 350 watts of power on a sunny day to use out from a 100 watt panel. Which would be enough to power a notebook computer that draws 35 watts for 10 hours per day, or enough to power a notebook computer that draws 70 watts for about 5 hours per day. This does not count power for a water pump, interior lights, furnace blower, etc.

p.s. I have 400 watts of solar panels on the roof of my coach, and would not want to try to survive with anything less, this lets me use low power LED lights when I want, power water pump, and furnace blower on cold nights, charge my cell phone, use my notebook computer a few hours per day, maybe watch tv for an hour or two, etc.