I'm Lost!!

[cerenatee]

I have read, and taken notes, and read some more and I'm still lost.

I'm trying to determine how many watts or amps I need, so I can determine the size of the battery I need, so I can determine the number of solar panels I need.

I started trying to figure it with my dell laptop. The adapter label reads Input - 100-240V ~ 2.5A 50-60 Hz and Output - 19.5V ~7.7A . Assuming I use it for 14 hours a day (which is possible if I have a writing assignment and can't come up to breath), what would my amps/watts be?

And once I know my total amps/watts/whatever it is you're suppose to figure out, does that translate to the battery size I need? Because at first I was thinking that determined the size of my panels but then I realized I'm drawing from my battery so as long as the panels keep my batteries charged, I should be ok.

Uggh. I HATE asking questions that have been asked before but I tried reading through the old questions but everyone is speaking Chinese and I can't access Bob's solar power blog post.

Thanks for ANY help you can give me.

 

[cerenatee]

Ok. I ordered a Kill-a-watt meter. This is just too hard for me.

That being said, once I know how many watts I'm using, how do I figure out my battery needs?

 

[greybeard23]

I have always heard you should have batteries with the amp hours total close to the watts of the solar panel.
So if you have a 180 watt panel, you should have about 180 amp hours of batteries.

I am running a 245 watt panel but only have 210 amp hours of batteries. I have more than enough power to run my 12v fridge, fans, 12v tv, computer, printer (when I need it), magic buttet, radio and lights.

 

[Willy]

You gotta remember that the power adapter for a laptop shows the MAXIMUM power draw. Often, your laptop would be drawing much less. You've also got to take into account various 'inefficiencies' in your system (copper losses, inverter, etc).
I have abt. 180W of solar, and that runs my lights, laptop, fridge/cooler, and charges whatever else I have sitting around. ..Willy.

 

[peacetara]

Hi cerenatee,

There are a few ways to figure out what's right for you:
1) list all the things you want to power, figure out how long you will use each one per day, and then figure out how much each item uses. Go build/buy an electrical system that can sustain that usage.

2) Figure out how much you can afford, buy it, install it and hope it's enough. If it's not, add more at your earliest convenience.

3) Copy someone else that hopefully uses about the same amount of electricity as you do. (The general consensus around here seems to be a 200W solar panel and a pair of AGM deep cycle batteries)

Sounds like you are going down option 1, which is totally fine. The meter you bought will help you down that path greatly. If you are going to continue down option 1, come back with a list of all the stuff you want to use, and what the back of each one says for usage, and how long you want to run each item for, and someone around here can help you with the creepy Electrical math to help you figure out how much input power you need.

With Love,
Tara

 

[caseyc]

Without trying to figure out any math, I would simply get the largest battery that can fit in your vehicle, including the largest solar panel(s) that can fit on your rooftop, and the biggest inverter that you can get your hands on. Instead of figuring out the least you can get away with, just get everything as large as possible. That way you won't say to yourself later that you should have gotten something more powerful. Your power needs will most likely grow in the future, so getting things larger the first time around will actually save you money from having to do it over again. Just a thought.

 

[gadgetMe]

We built our system in stages, I started with a good battery bank ( two deep cycle 6 volt batteries ) then purchased a single solar panel (130 watt) and a small 15 amp charge controller, also a modified sine wave inverter (1200 watt)

This worked pretty good for the first year, but, I knew I needed to have more.
As Casey mentioned get as much as you can afford, and have room for.

All of the theory and math works good on paper, until the weather stays cloudy for 3 days to 2 weeks straight. Or you are stayin' in the northern latitudes where the sun is low in the southern sky.

If you are building a solar system over time, purchase a large charge controller in the beginning, to anticipate more additional solar panels. 50 amps is not too big.

Use your kill-a-watt meter to determine how big of one to purchase.
plug it into a wall outlet add a power strip and plug into it everything you may run at the same time and read the meter, add 25% and get one around that wattage.
Purchasing a very large one will waste precious energy even when idling with no load.

Good luck and have fun

 

[caseyc]

Good point about the weather. I'm in an environment where it gets overcast to foggy half the time. For myself, relying strictly on solar panels would be impractical.

 

[Willy]

I'm in the 'more is more' crowd when it comes to solar. Also, especially during a Canadian winter, one has to be crafty. For instance, I keep my Waeco cooler in the cab of my truck. This means that I'm not usin' a lotta juice to keep it cool vs having it in my camper and heating it up with my furnace.. then having to cool it down again. 12v LED lights are another fine power saver. Above my table, I have a 'warm white' LED and a 'cool white' beside it. Also above my bed and wherever else I can stick the lousy things.
Right now I'm debating picking up another 120W polycrystalline panel. It would be great for the winter, but 300W would kinda be gilding the Lilly for summer use. I find that 180W leaves me with a considerable excess of power during the summer. ..Willy.

 

[Zil]

Remember when checking your energy use, you don't have to operate every thing a one time. Turn off "something" while you operate 'somethingelse".
I would run my laptop until it asked for more power, then check to see how much it takes to recharge while running. Add the lights, radio, and see the minimum you will need. You can get the inverter to power what you need now, and add a second inverter as you expand your system. I would start with two six volt golf cart batteries wired for 12 volts. With a just big-enough-inverter for what I need to operate my office. I would plan a system to recharge 4 six volt batteries. I do have a 2000 watt generator and a 50 amp charger for use on shore line. Solar is coming soon. But solar is not enough to maintain deep cycle batteries on its own.

 

[Mac J]

Solar is enough to maintain 2 six volt deep cycle batteries IF you have continuous sun. Partial sun is a problem with solar.

If it fits your budget, I would get 2 six volt Trojan T-150 batteries, a 95 watt solar panel with charger and a 1500 watt inverter. If your refrigerator runs on LP and you only use your AC when hooked to shore power you will be just fine with power as long as you have sun.

 

[cerenatee]

Thank you all for responding. I was literally driving myself nuts between trying to find a van, figuring out when to take off, and figuring out my solar needs.

Greybeard - 245 watt panel and a 210 amp battery might be right for me too. I'm running an energy hogging computer for DVDs, television, writing, editing photographs, and the internet. Plus I'll have a modem, a router, a 12v fridge, fans in the summer, lights, a 12v oven, and a magic bullet. I'll also need the system to recharge my phone, kindle, and Ipad. How much time are you on your computer? When working or bad weather, I can easily be on mine 10 hours a day for a week.

Willy - thanks for the info on the laptop. I didn't know that. I actually called a solar shop and the guy didn't mention it. He did say my amps were high at 151 when most laptops are around 60, but I have a gaming laptop so it's pretty powerful. He's the one who suggested getting the Kill-a-Watt meter.

Tara - thanks for the suggestions. I was going the "determine what you need route" but, like you said, it will be a lot easier to just copy someone else. So far I'm getting a 245 watt panel, 210 amp agm golf batteries (Trojan T-150 batteries?), 1500-2000 watt inverter, and a 50 amp charge controller.

Mac - I'll be in a van so I won't be hooked up to shore power. I'll only have solar power to charge my batteries. Right now I plan to follow the weather - North and East in the summer, South in the fall, West in the Winter - to save myself from extreme heat or extreme cold. Do you think my batteries will get enough charge or will I need more panels? I'll be in a conversion van so I really won't have a lot of room, I don't think.

 

[Mac J]

A 245 watt solar panel is 5'6"x 3"4". That is a large solar panel. You don't need one that big. For all your energy needs I would recommend 4 Trojan T150 batteries. The energy comes from your stored power and your stored power is in your batteries. Your batteries will recharge as you drive and when in sunshine. Your 12 volt fridge and your 12 volt oven (I've never heard of one of these. Is it a toaster oven?) will be your biggest drain.

 

[Willy]

Depending on the laptop, you should be able to run it with the integrated GPU rather than the discrete one for power savings; don't think you'd be pulling 151 amps tho'. ..Willy.

 

[arizonatruck]

I always plan for a at least a 10 percent error margin. But, I would suggest at least doubling your storage for your electrical needs.

I used to work full time in landscape management, including landscape installations. A general rule of thumb for installations was to add 10 percent to what is calculated, just in case your calculations are a little off.

I plan on having a few lights and possibly a monitor and a camera or two running off the battery and a few light electrical devices such as two cells phones and a tablet. I have no more than 50 amp hours. So, my goal is to have a bank of 200 amp hours so that I can power those at night.

A standard desktop computer, just the tower, is approximately 300 watts. At 12 volts that is 25 amps and 150 watts for the monitor, 12.5 amps. The kindle fire that I have is 1.8 amps, approximately 9 watts. The laptop I have consumes 65 watts at 3.25 amps at 20 volts. The two cell phones consume about 10 watts, 2 amps. I will not be using the desktop in the trailer/truck due to its high power consumption and need for an extra monitor and speaker set. The lights are going to be about 4 amps at 12 volts, 48 watts. My total power consumption using these will be less than 10 amps. With that calculation I should have at least 20 amps of available power.

If I am missing something, please let me know.

 

[Mac J]

Arizonatruck, what are you charging your batterie(s) with?

I doubt you will have all your items running off your stored energy all at the same time. It sounds like the desktop tower and monitor won't be a draw.

You haven't mentioned a furnace or any heating or refrigeration or fans, water pump, or hot water heater yet. Are you in a van or a car or an RV?

Led lights will dramatically cut down your energy draw.

I'd give the same advise to you as I gave to cerenatee .

2 Trojan T150 6 volt batteries and a 95 watt solar panel with charger.

 

[arizonatruck]

I live in AZ, so heating isn't as crucial, but I will be using a jacket to start with. I am a fairly sturdy fella when it comes to cold weather (I am fat, but when I was skinny it was the same thing). For taking the edge off, possibly just some sort of mild heating flame of some sort. In phoenix the highs are in the 80s and the lows have been in the lower 40s to mid 50s. Pretty nice weather. Up north, not as nice, but weather able. I tend to right a little warm anyway.

For both cooking and hot water a camping two burner stove will be used. I can take cold water baths/showers, doesn't bother me as much as others. Most of the hot water I use is for coffee and dish water.

Not all the usage will be at once and I am going to get at least 300 watts of solar as I get the money to do so. I am going l.e.d. as I get the money as well.

As of now I am charging the house battery that I do have off of either the truck alternator when I am driving or a charger when grid electricity is available. I only run the desktop when grid power is available. Which has been today. My laptop is down, I think I fried the motherboard. I may take it in somewhere to have it looked at.

I have a 20 foot trailer that I am converting into a workshop/house. It isn't going to be fancy, except for the size. Plus, I am possibly going to convert the bed of the tow vehicle with a camper shell, kind of like the one bob did.

 

[Mac J]

I think I'd only buy a 300 watt solar panel if it was cheaper than a 95 watt panel unless I planned on needing more power requirements. If the latter was so I'd increase my power bank with batteries. 6 volt is best. It can be very easy to over buy.

 

[Willy]

Personally, I'd rather have 3x 100W panels than a single 300W one. If one bites the biscuit, no problem cuz 2 more to provide power: a single big one being toast can really screw up your day. Also, a dispersed panel setup can help alleviate problems with shading. ..Willy.

 

[Mac J]

That's a good point Willy, If I was going to add a second 95 watt panel I'd want it to be portable for max sun.