? size solar panel

[dtappy3353]

Folks:

We would like to use a 12v deep cycle battery for topping off our 2 laptops, 2 kindles and cell phones.

What size solar panel would be needed to keep the 12v battery charged/topped off.

Thanks much!

[pianotuna]

Hi

Run the entire RV via the kill-a-watt. Do not exceed 1800 watts. Measure for 24 hours.

[DrewE]

Simulate what you expect to be doing with your solar/battery setup. I assume that would probably be to run the laptop on battery power for awhile, then plug it in (and maybe continue to use it) while it charges up again.

Sitting doing nothing with a full battery is not going to use much power, as you've demonstrated.

[red31]

hooked up kill a watt,

Do I let it go 24 hrs or do I unplug till the batt is low and recharge?

0.05 kwh @ 7:25 am cst

[pianotuna]

red31,

What are you trying to tell us?

[red31]

using 2 pair (one 2.5 and one 3.) readers I've determine my dell 45w charger, 2.31A @19.5v rated output, currently using 0.14a, 05w, 17va, 0.00kwh, Do I let it go 24 hrs or do I unplug till the batt is low and recharge?

Start time was 6:50 pm CST

home usage would likely be a factor of 10 compared to boondocking.

At this rate 120wh a day while a flat 100w panel ought to generate 300+wh/day.

An hr in and watts go up to 14 or so when changing websites, 0.00kwh.

[RJsfishin]

Even w/ 1/2 day sun, a 100 watt panel will be more than enuff for what you stated.
We support our whole RV on 300 watts.

[Lwiddis]

“for topping off our 2 laptops, 2 kindles and cell phones.L

Why think small? Charge all RV batteries with a real solar system....250 to 300 watts.

[MEXICOWANDERER]

And I wish I could refuel using a



But reality is reality. Watts are watts and it's all about using watt hours. After the refrigerator the electronics in my temporary rental home and far and away the biggest consumption of power. Not even close. Like 5 to 1 more than the LED lighting. And this have been derived using meters not guesswork.

I see few econo laptops out there with tiny power supplies that sip juice. The I5 models with enough RAM to barge through a castle portcullis use power.


This is what I encourage you to do, using 120 volt power pedestal recharging power.



One device at a time or all ganged together. This will give you watt hour total and absolutely nail your energy usage hard and fast

[doughere]

You can find a 50 watt panel for $50 add a $10 ebay controller. Will do what you want with power to spare.

Doug

[pianotuna]

No one can answer the question until we know how many watt-hours it takes to recharge the devices. So, do an energy audit, and get back to us.

I would use a Kill-a-watt meter to measure the consumption for 24 hours on the devices you wish to charge/use.

[dtappy3353]

WOW....

I have 120 watts of solar feeding 2 12v deep cycle batteries on the fifth wheel which seem to maintain a 55-60%. We only use LED light bulbs with only one light on for the entire evening till we go to bed.

I'm hoping I'm clear and forgive me if I'm not.

We ONLY wish to recharge laptop battery with a 12v that has a trickle charge on it. How many watt solar panel would it take? We spend most of the time in AZ. Oregon doesn't factor in on this equation.

[ctilsie242]

If a laptop draws about 50 watts on average, that would be 100 watts.
iPads use 2.1 amps, so on a five volt system, that would be 10.5 watts, or 21 watts for two.
iPhones, on average charge on 500mA, but can fast charge on 2.1 amps, so will use the 500mA value, or 2.5 watts. Thus five watts for both.

So, doing guesstimatory math, (2 x 2.5) + (2 x 10.5) + (2 x 50 ) gets you 126 watts of power consumption.

Just as Mexicowanderer said, go with at least 250 watts, and a MPPT charge controller. This is a minimum setup.

A decent setup would be to go with two 12 volt batteries in parallel (or two six volt golf cart batteries in series), so you have ~400 ampere-hours. This way, you have ~200 amp-hours, because drawing down below 50% causes battery damage. For the panels, I'd go with at least 400 watts, preferably 500, and a MPPT charge controller. This will give you enough power for your electronics (including being able to charge power tool batteries, electric shavers, and other stuff.)

[MEXICOWANDERER]

I wouldn't even consider anything less than 250 watts. Unless you live on the east side of the perpetual overcast 250 watts will end up being taxed.

Why so big? AGM cannot be used and flooded batteries must be charged to 100% more often than occasionally if you want them to live.

Use direct DC to DC converters for this purpose. Laptops, ebooks, cellphones, everything.

This isn't something that additions and subtractions work well at. Batteries are fussy -- like Koala bears -- about their diet. Mistreat them and they die. It's a chemical not an electrical thing.

Lithium would be ideal. So would an Aston Martin be giving the battery a ride home. Oregon in Winter solstice is not a solar powerhouse. Keep it in mind.

[time2roll]

For the effort I would go one 12v panel 100 to 160 watts.
Oregon... you may want two.