Solar Basics: Understanding Batteries

IMG_1916I recently announced that I am now selling a 90 watt Suitcase Solar Power system. Quite a few people wrote in asking just what that much solar could do for them, and that is a very important question. Before you put down your hard-earned money you want to know if it will meet your needs! Rather than try to give a detailed answer in a comment, I thought it deserved its own Post, so here we are.

Most people find learning about electricity very confusing, I know I did! The problem is it uses completely foreign words that we are unfamiliar with. When I started learning about it for the first time the idea of amps, watts, volts and amp-hours confused me for a long time! So in explaining it I am going to avoid the terminology and approach it in terms all of us can relate to: money. (While this is an analogy, if you changed the phrase “dollar per hour” to the technical term “amp-hour” it would still be completely accurate.)

I want you to think of your solar panel as a tiny factory full of elves that make money. How much money it makes depends on a lot of things like how much sun there is and how big the solar panel is. Solar panel elves only make money in daylight, and the sunnier it is the happier they are and the more money they make. Our little 90 watt solar panel makes about $5 an hour during the brightest part of the day. But if it’s cloudy out, the elves in the panel may only make 50 cents an hour, or even less depending how cloudy it is. So on an average sunny day it makes $35 total.

So our happy little solar panel is busy making us money, but, what are we going to do with that money? We can buy electricity and the pleasure and usefulness electricity provides. For example, at night it can buy me light so I can see, or it can power my portable DVD player so I can watch a movie. On a hot day it can power a fan so I can stay cool. It can charge my cell phone, laptop, iPad, Kindle, and all my other personal electronic devices.

thumb_piggy_bankSo you can see that our busy, hard-working little solar panel can greatly improve our life. But how do I use the money to buy those things? It’s simple, as your solar panel makes the money it very thoughtfully deposits the money into your piggy bank so you can buy things. Where is the piggy bank? It is your battery. The busy little elves in the solar panel make the electricity and then put it in a wheel barrow and carry it down to the battery which is the piggy bank. Piggy banks come in different sizes, but the one we have only holds $90. We can’t put more in it. And, we must always leave $45 in the bank. It gives the piggy an upset tummy if we take out more than $45 and we do not want to make our piggy bank sick so we always have to have a $45 balance in the bank.

The wonderful thing about our bank is that even during the night, I can keep buying electricity even though the elves are asleep and not making money. But, I must never let the bank balance fall below $45 and the closer it stays to $90 the happier and healthier our little piggy is. In fact if the balance were to always stay at $90, the piggy would probably live forever, and if it drops down to $45 every day he will get sick and die much earlier. If we let it drop below $45 every night, he will get sick and die very, very soon. Poor little piggy, we don’t want to do that to him do we?!!

This is my solar controller. It has a digital readout and I have it set here to show how much "money" (amps) is coming out of the panel. Right now it is 7.8 "dollars."

This is my solar controller(not the one on the Portable Suitcase System). It has a digital readout and I have it set here to show how much “money” (amps) is coming out of the panel. Right now it is 7.8 “dollars.”

During a sunny day the elves in our 90 watt Suitcase Solar Power System are making about $5 an hour. So if we buy $5 worth of electricity every hour, and they are making $5 an hour, the bank balance remains the same. If I spend more than $5 an hour, the bank balance will fall during the day, if I use less, it will rise during the day. We want to be careful to let the bank balance build until it is full at $90. That way we can spend up to $45 at night to buy electricity.

But we know that since our solar panel only makes $35 per day that is all we can practically spend. If we spend the whole $45 and the next day we only make $35, we will steadily run out of money until we are flat broke and in bankruptcy. The federal government can print money when they need it but we can’t. Our elves can only make $35 so that is all we can spend; we have to live in our budget.

What can we buy with $35? Everything we buy has a price per hour. So to know how much something will cost us we must know how much it costs per hour, and for how many hours we use it. For example, I have a fan that costs $2 an hour to use it. If I use it for one hour, it takes $2 out of the piggy bank. If I use it for two hours it takes $4 out of the piggy bank. So all we have to do is find out how much something costs per hour and multiply it by the number of hours I will use it. Here are some average prices per hour for some common devices:

  • Fan: $2 per hour
  • LED light: $1per 2 hours
  • Laptop: $4
  • Energy Star 19 inch LED TV: $2 per hour
  • Personal devices (cell phone, tablet, camera, Kindle, etc.) $1 for 2 hours
  • Roadpro 12 volt Oven: $10 per hour ( but it rarely is on for more than ½ an hour=$5 per 30 minutes of use)
  • Microwave: $100 per hour (But that is only $1.66 per minute or $8.50 for 5 minutes)

So what is the bottom line? A 90 watt solar panel should be able to let you run this realistic scenario:

  • LED light 4 hours a day ($2)
  • Laptop: 4 hours a day ($16)
  • Fan 2 hours a day ($4)
  • 12 volt Refrigerator ($11)
  • Various Personal devices ($2)

That is $35 total spent overnight, all that we are allowed to use overnight out of our piggy bank. There are so many variables, that you may or may not be able to do exactly all this, but you can do something close to it. In the winter you won’t use the fan at all and the Refrigerator will come on less, but there is less sun to generate power. You can also probably find much more efficient items than I have listed. I have a friend who switched from her laptop and mainly used a tablet and that saved her so much electricity that she was able to power a C-Pap machine overnight with just the 90 watt Suitcase Solar Power System.

Solar_Power_Basics_3_-505x399The important thing is you understand the idea of a $90 bank and you can NOT spend more than $35 overnight. You will just have to play with all your devices and see what combination will work for you. My friend had to have her C-Pap so she had to sacrifice the fan and get a more energy efficient computing device. After doing that she has been entirely satisfied with the 90 watts she has. I have another friend with the 45 watt Harbor Freight system and she was so frugal with electricity that it met all her needs quite well. Think how much happier she would have been with double the power of this system! Also, be aware that you can hook your piggy bank up to the starting battery of your van and the squirrels inside your engine will also make money/electricity for your piggy bank while you drive, increasing your power all the more.

I know this is a silly analogy, but you just learned the basics of solar power. If you change dollars to amp-hours, and piggy bank to battery bank, you will sound very wise and not at all silly!

Bob
About

I've been a full-time VanDweller for 12 years and I love it. I hope to never live in a house again!

Posted in Solar Power
75 comments on “Solar Basics: Understanding Batteries
  1. stan watkins says:

    Everyone should remenber. You can have more than 1 piggy bank ( battery) . Thanks Bob as always.

    • Bob Bob says:

      Very good point Stan. You can have as many solar panels, elves and piggy banks as you can afford!
      Bob

    • Mr Bob Wells I don’t know if you are aware of these panels but there are panels that provide 300 watts costing under $140. You have to buy min 4 of them but they are huge and I would call that a bonus. They are so large they can be used to form the roof of a structure proving not only rain protection but much needed power 2 birds theory. (BUT I DON’T NEED 300 WATTS.) Sure you don’t but I rather have a panel that can provide too much power than not enough. You can always expand your system in the future. Correct me if I am wrong if you have too much power you can always burn the extra with appliances during production periods? Most use it for heating water. Or of you have a window unit you could power that and expand your range of places to dwell in. Sure one 300 watt panel will not provide enough to power a 450 watt AC but 4 of them clearly will 1200 watts of panels is a lot of space but here is where having cab and trailer can pay off. Sure wind will prohibit travel on some days but the trade off is probably worth the effort to have this set. Thanks Mr. Wells for all you do.

      • I forgot to add this. There are more than solar panels to harvest the suns energy you want to use as much passive solar devices you can to keep from having to pay for the generation of solar electric. Solar ovens, solar water heating, also proper insulation and shading if you plan to park in the sun? Remember you don’t make cold you remove heat the important thing is you don’t allow the heat to get into the structure or your vehicle. Insulation is one thing but other smart ways to prevent heating like when you park find a spot that is in shade or was shaded by a vehicle parked there prior. That black top will build up heat. Also travel when it is cooler early morning runs to put most of your trip in your back pocket when the sun comes up it is much easier to get parking in a truck stop they need parking most when the sun goes down. Where you are in the country makes commercial parking very desireable. TN KY NY IN OH all are trucker hotspots they are there to service the over populated NE states.

  2. Greg says:

    Hey Bob, great way to explain the solar system! I mounted two 90 watt panels on my rig and have two 6V batteries for about 220 AH piggy bank. I can spend spend spend!!!

    • Bob Bob says:

      Greg, you are rich!!!!! I have pretty close to that on my trailer with 190 watts and 2, 6 volt batteries. I have been very happy with it. It’s nice to haves such happy, healthy little piggies!!
      Bob

  3. Rob says:

    That was a fine job of explaining how it all works!

    • Bob Bob says:

      Thanks Rob, I know I have bored and irritated lots of people with a traditional explanation of the whole thing. When their eyes glaze over and they stare blankly off into space I know it was too much. Hopefully that didn’t happen this way!
      Bob

  4. Page says:

    Thank you for the analogy.

    • Bob Bob says:

      You are welcome Page! I know to a bunch of my readers this is very elementary stuff, but hopefully they will find it entertaining or at least be tolerant of people who are just learning about solar. Thanks again!
      Bob

  5. m.a. says:

    Great post for us ‘non-left-brainers’, Bob. Thanks.

  6. cozygirl says:

    PERFECT – I’m finally getting it through my thick skull. While I only have a couple piggy banks…I’ll remember to spend my money wisely :O)
    cozygirl recently posted…My Spring Break Week off …My Profile

    • Bob Bob says:

      cozygirl, very well said! I checked out your blog and liked it. If you get out this way be sure to stop by and say hello!
      Bob

    • Bob Bob says:

      I wanted to add one more thing. I’ve been doing this for awhile but I am still learning. Your boyfriends idea of running the wiring under the trailer in a black garden hose was brilliant! I am going to have to start doing that!
      Bob

  7. Karen says:

    One of the best posts on using solar polar I have seen! I just bought a 130 watt suitcase solar system. I went with the bigger system as it allows me to withdraw from the bank during the day and still deposit to the bank at the same time. Next I will add a second battery which will also allow more in the bank for rainy days. At the cost of campground fees, it just took days to pay off the solar panel. Great post!! Well done!!

    • Bob Bob says:

      Karen, I’m really glad it was helpful! That is a very good way to look at the initial cost of solar power. Most RV parks charge at least $25 a day to stay there, and the main reason people use them is for the electricity. If having solar power will keep you out of RV parks, you can easily save $175 a week. That will quickly pay for the solar. As a bonus, boondocking in nature is just a tremendously better way to live!!
      Bob

  8. Great post although I didn’t see a link for purchasing these systems. I would be interested in getting a portable system like that and put it on the dash of my van during the day.
    Martin
    Martin Hamilton recently posted…How Do I Regain Control Of My Blood Pressure?My Profile

    • Bob Bob says:

      Martin, they are much too large to put on the dash of your car. About the only panel that will fit on the dash is a trickle charger or one to charge a phone or tablet. These are more of a whole house panel. You can find them in my Store, there is a link at the top of the page. I also did a post on them last week.
      Bob

  9. Diane Kirkendall says:

    LOVE your explanation 🙂

  10. Dixie says:

    Thankyou Bob, What an easy way to explain Solar (for me anyway!) Much appreciate this post! Very interested in adding something like your suitcase system. Dixie

    • Bob Bob says:

      You are welcome Dixie! You can find more about the Portable Suitcase system in my Store. There is a link to it at the top of the page.
      Bob

  11. Al Christensen says:

    Though the analogy helped, the most useful part was the list of how much power various items tend to use and how much stuff one would probably be able to run with a 90W system. It looks like my system wouldn’t need to be as large as I thought. The system sizing guides I’ve seen start with the assumption you’re running HVAC, a bunch of lighting, a kitchen full of appliances, water pumps, multiple big screen TVs, tracking satellites…

    • Bob Bob says:

      Right, Al, once you grasp the idea that solar is like a bank, then all you have to do is learn to live inside your budget. I have 190 watts on my trailer and never lack for power. The key is in adapting the simple living lifestyle. When you minimize your stuff, you also minimize your electrical needs. LED lights draw very little power, and charging your laptop, phone, camera, tablet etc, it also very low draw. Add in a DVD player and fan, and that just about covers a vandwellers typical needs. For most of us 135 watts is about right. If you want a cushion or have a 12 volt compressor fridge (Engle, Dometic) than 200 watts is better.
      Bob

  12. John Lamb says:

    Great explanation Bob!! I started out with a similar 90 watt package hooked in to 2 Lifeline AGM 220 AH each and soon found I “had more tail than dog to wag it”…lol….I now have 280 watts of panels wagging that tail, and I can really spend those dollars!!

    • Bob Bob says:

      I agree John, 90 watts is barebones, 140 is good, 200 is very comfortable and 300 is an abundance! I have 420 in total, there is someone in camp now with 800 watts, and I have a good friend with 1000 watts (a Kilowatt). This is one of those rare cases where MORE IS DEFINITELY BETTER!!
      Bob

      • Al Christensen says:

        I read somewhere that the ratio should be about 1 watt of solar panel per 1 amp hour of battery. When it comes to the batteries staying properly charged, I suppose it’s better to have a bit too much panel than too much battery.

  13. CAE says:

    Could you mention the value of a deep cycle piggy bank?
    I’m guessing that it would allow you to make larger withdrawls at any given time. But the replenishment would always take the same amount of time with any given solar panel arrangement..depending on sunlight hours.

    At least one could get at all their money, if needed, with a deep cycle piggy bank, and not cause undue harm. Sounds like your example piggy bank may live in Cyprus?

    • Bob Bob says:

      You are right CAE, buying a deep cycle is critical in putting together your system. In this post I wanted to avoid in of the normal jargon associated with typically learning about solar.

      I don’t think a deep cycle versus a starting battery will allow you to make larger withdraws, but it will keep your piggy alive a lot longer!!The typical starting battery would be destroyed by 5-10 discharge cycles, while a true deep cycle would barely be impacted at all.
      Bob

  14. Trisha says:

    FINALLY! That was an excellent, I mean excellent! way to explain solar power and how it works and how the batteries work in relationship to it all! This will go viral for sure. I certainly am going to pass it on!
    I don’t need to know or understand the watts and amps and all that stuff, I just need an easy way to understand in put and output and you have done just that!
    I kept thinking that a 2nd battery would give me the extra piggy bank, but I couldn’t be sure until now.
    I don’t know if I told you but someone in El Centro needed my solar system more than I did, (ya, after all the hard work installing it on top of my new van-home it got stolen!)
    Funny because I usually stay away from neighborhoods like I was in in El Centro, but I took my chances and lost (again!) This seems to be my year for things getting lost or stolen!

    I have replaced the panels with a suitcase style that I can keep inside my van-house. Shheeesshhh, sure hope my van doesn’t get stolen next! I am afraid to leave it! Well, on a positive note,l have insurance.

    And the negative karma in my opinion won’t last beyond 6 months so if I am careful and do good things for 2 more months I will probably have good karma the rest of the year–I hope! (Sorry folks I don’t really believe in karma). Stuff happens, that is life.
    Anyway, Thanks again Bob for coming to us solar needy folks!

    • Bob Bob says:

      Trisha, you mounted your Harbor Freight solar panels on the roof of your high-top van and someone stole them? Wow, that really surprises me. You have had ome bad luck with that system. Did they exchange and give you new ones after the wind broke the first one?

      What size suitcase did you buy? Remember, that in my example a 90 watt panel only produced $35 a day, but you could spend $45 day out of the piggy bank. So the solar panel didn’t make enough money to fully charge the bank every day. So adding a second bank would not help. Adding a second panel, or buying a larger panel the first time, would be a better idea. Adding a second panel would let you buy the electricity to charge your laptop and fill the piggy bank at the same time during the day. So you could buy all you wanted during the day, and still be filling the piggy bank and then be able to spend the full $45 at night.
      Bob

  15. Jan Johnson says:

    Thanks, Bob…I now understand it more. My next question is: The battery? Is this a regular car battery or deep-cell battery that I am hearing people talk about. Can the deep-cell hold more money as you say? I assume the battery does not come with you suitcase system. Thanks again for all the explanation so it can penetrate this thick skull. lol Jan

    • Al Christensen says:

      Here’s a good explanation of battery types and purposes.

      http://www.amsolar.com/home/amr/page_21

    • Bob Bob says:

      Hi Jan, yes, you want to buy a deep cycle battery, not a stating battery. it wouldn’t be fair to say it holds more money, but it would be fair to say that a deep-cycle piggy loves solar panel elves and will live a long, healthy, happy life and die old and fat, while a starting piggy would live a short, horrible life being fed by your solar panel elves.

      Let’s use a different analogy for batteries. Lets assume they are runners:

      Starting Batteries: Sprinters; they run very short distances as hard and fast as they can.
      Marine Batteries: Marathoners; they run 26.2 miles pretty fast.
      Deep-Cycle Batteries: Ultra-Endurance Runners: 100 miles or more; they run LSD Long Slow Distance.

      If you use a starting battery for your solar system, it will die very quickly, maybe in a few days or weeks. A marine battery should last fairly well 2-5 years. A true deep-cycle battery should just keep going like the Energizer Bunny and last 5-10 years if treated well.

      No, the cost of shipping would be very prohibitive, so the panels I sell do not come with a battery.
      Bob

      • Jan Johnson says:

        Okay, I’ll ask my mechanic to check the battery on the Scamp and let him know I will be purchasing your solar system and will need a deep cell battery for it. Will I need anything else besides a good extension cord long enough to put out into the sun while the Scamp is parked in the shade. I am having second thoughts on the roll up solar panels. Do you sell them and will I need to buy the inverter, etc.? You are the best Bob..I so appreciate you! Jan

        • Bob Bob says:

          Jan, if you are going to have the battery mounted on the scamp, then things get more complicated. The suitcase comes with power cords that are 15 feet long, so you can only move it that far away from the trailer. You can make them longer by making an extension cable using longer, heavier wire. They did a good thing and used a common quick-connect on the cable, so it would be easy to make an extension cord if you know how to strip and crimp cable. The best way to move it further away from the Scamp would be to carry the battery and panel away and set them up in the sun. But remember the battery is 60 lbs and the Suitcase is 34 pounds. Are you sure you can handle that much weight? To make it easier you can get a 2-wheel dolly, put the battery (in a plastic box) and panel on it and roll it as far away as you need to to get into the sun. BUT!! You still have to be able to lift the 60 lb battery, 34 pound suitcase and the 15 lb dolly (just a guess how much it weighs) in and out of the van or trailer. Can you do that? If you can then you will need an invert to hook up to the battery, Then you could get a 100 foot extension cable and run it for the inverter to the Scamp to run your 110 items. The inverter could not be left out in the weather. Even a dew in the morning would ruin it but you could keep it in a plastic battery box as well. But you would not be able to run 12 volt items from that far away, just 110. So anything that used a cigarette lighter plug would not work.

          Thinking this all through makes me realize what I need to do is make available an extension cable that will work with the suitcase. It wouldn’t be hard to make or cost much so I will have to look into doing that.
          Bob

        • Bob Bob says:

          Of course, you can buy one from amazon.com!! here is a link to exactly what you need and being made by slave labor in China it is quite cheap. If I tried to make and ship this myself it would cost at least double this price. So buy one of these and you can move your panel 40 feet from the Scamp. Buy two and you can move it 65 feet.

          In fact I want to add more value to buying from me, so I will include one of these free to anyone who buys from me. I will have it sent direct from Amazon.
          Bob
          http://www.amazon.com/Battery-Tender-081-0148-25-Disconnect-Extension/dp/B000FW2MWW/ref=pd_sim_auto_1

          • Jan Johnson says:

            Well…That 60 pound battery might be a little difficult to manage. I was thinking I could mount the battery on the scamp tongue and not have it deal with it..so..what is the next best option..the roll up ones mounted to the roof of the Scamp. Humm..I’ll have to think about this one..Thanks Bob..I’ll be contact..Jan

          • Bob Bob says:

            Jan, I figured out a solution that I think would work for you. Amazon sells an extension cable that will allow you to mount the battery on the Scamp and move the panel up to 40 feet away. I will include that cable free.
            Bob

  16. Naomi says:

    Where the heck were you when I was taking high school science and algebra??? Thanks for breaking this down into understandable English.

    ~Naomi

    • Bob Bob says:

      Naomi, I was the kid who failed and was held back! That’s why you didn’t see me. Seriously though, I am no good at math, that’s why I need analogies to help me understand.
      Bob

  17. Patrick says:

    Does it help to turn on the car when using microwave? Let the Alternator do all the work.

    • Al Christensen says:

      An idling vehicle wouldn’t spin the alternator fast enough to keep up with the power drain of the microwave. But it might mean the batteries get discharged slightly less. Maybe if you were to prop something on the accelerator to make the engine run faster. (This assumes your house battery is also wired to the alternator.)

      • Bob Bob says:

        Right you are Al! A good comparison is when you jump a dead battery off another vehicle. You always have someone get in the running vehicle and rev the engine up so the alternator is putting out enough power to start the other car. With a microwave, you would just hit the start button, jump in the front seat and rev up the engine. I am assuming you already have a big enough inverter to handle the load alone and the alternator is just assisting.
        Bob

      • joey says:

        It doesn’t matter if you rev up your engine or not,your alternator will only put out 14.6 volts maximum. The only thing it does is keep your battery full.

        • Bob Bob says:

          Joey, you are right, but I don’t think it puts out the whole 14.6 volts at idle. All I know is in Alaska I jumped hundreds of cars over the years, and universally the standard procedure for everyone was to rev the engine up as you turned the starter on the car with the dead battery.
          Bob

    • Bob Bob says:

      Patrick, Yes, that is a very good idea. However, if you are going to do that you will need a very big wire to handle the current! I use 2/0 gauge on my 2000 watt inverter and it is all short distances–less than 5 feet. If the run from the starting battery to the house battery was long, you would need 4/0. That is a very big and expensive wire. To give you a visual image, it would be the size of a mans thumb. You would want to put a 250 amp fuse in the line as well.
      Bob

  18. gretchenrose says:

    Hey Bob,
    Great post!!!! Laughed my socks off while sitting in the library in Salinas, CA, got some strange looks, I’ll be envisioning elves and piggy banks when I’m ready to buy that solar power suitcase. You’re the best, Thanks for the belly laughs:) Gretchen

  19. Stephen says:

    Nice tutorial Bob! We don’t get as much sun in the UK as you do,so we need bigger output panels to compensate .I have a 100 watt on the roof of my van.
    Stephen recently posted…Wildcamping.My Profile

  20. Rolf Fritschi says:

    How does one know how many $ are left in the Piggy.

  21. CAE says:

    Bob, This is off topic, but I was wondering if you were ever planning to have people update their stories on your first website? I think a lot of them are from 2006 to 2008. It would be interesting to hear what they’re up to at this time and how things have gone for them.
    Just a thought.

    • Bob Bob says:

      CAE, that’s a good idea, but most of those articles are people I didn’t know, I just had some slight connection over the net. So I have lost touch with nearly everyone from back then. One exception is Charlene Swankie who is a good friend. We are working on an update to her story now.
      Bob

  22. Sandy says:

    Thank you……you are a great teacher. I am learning so much about solar and boondocking. I’m trying to wean my husband away from high priced campgrounds.

    • Bob Bob says:

      Sandy, there are some really nice things about campgrounds. Lots of people prefer the social aspect of it, and of course everything is easy there. But for me being in nature is all-important. If he prefers Parks, and you prefer nature, maybe you can mix it up and be in an RV park sometimes and boondock others.

      Many times though, people don’t really like RV parks, they just don’t know they have an option. They assume boondocking has to be a sacrifice, If your husband falls into that category, then the more you can show him (especially about solar power) the better! If there is anything I can do to help, feel free to ask.
      Bob

  23. Fred says:

    Bob,
    I know we have had our differences but I have to commend you on these articles on solar for their ease of explanation. Excellent analogy and well done. By the way, I believe that your website cheapgreenrvliving MAY have been hacked since when you log on it asks for the admin pswd to the forum, NOT just your normal logon.

    • Bob Bob says:

      Fred, thanks for the kind words. Yes, the forum was hacked but not by a bad guy, but by bumbler who messed it up-ME!! It is back to normal now.
      Bob

  24. Bob Bob says:

    Sandi, one of the wonderful things about the internet is that it makes it possible for such independent people like us to meet up and become great friends. I’m looking forward to meeting you!!
    Bob

  25. kathy says:

    Wow. So how do I figure out how many dollars are spent on each thing I would want to charge/use. Is that on the cell phone, mp3???
    This article makes a little bit more sense to me. I think if I read it a few more times some thing will penetrate this thick skull of mine.
    lol Figure out what you will spend each day and work backwards to battery, then to solar panel. Whaaaawhoooo!!!!
    thanks
    kidiekat

    • Bob Bob says:

      Kathy, every electrical appliance is required to say somewhere on it how much power it uses–and most do. There is a formula you can use to determine how much “money” it will cost you but it adds a whole new level of difficulty to the topic.

      Yes, you have the right idea! To decide how much solar power you need, you first calculate how much power you need (money in my analogy). it’s like looking for a new job. First you do a budget and see how much money you spend. Then you know exactly how much you need to be paid at your new job. So I use the formula to calculate my amp hours (dollars) I will use every day then I buy a solar panel that will make that much money (amp hours).
      Bob

  26. Douglas says:

    Even for someone that understand electricity, this is way simpler to learn. If you’re not planning on working on anything more complex, this is all you will need.

    Douglas recently posted…Ammunition and electronicsMy Profile

  27. dan says:

    im a newbie at this but have some common sense. heres my thing.. i will driving my isuzu rodeo around florida this winter staying off the grid for propably 2/3rds of the time. maybe staying at each place up to 3 or 4 days. my only electricity needs are charging my phone and it would be nice to charge my laptop (and interior lights as i will be sleeping in the vehicle). i was thinking of getting an inexpensive battery “maintainer” and inverter to plug in my laptop. does anyone have thoughts on whether this would work. i did read about how starting batteries are sprinters and am wondering if this would kill my battery? and is that only if i drained it down repeatedly?? thanks in advance for comments!!

  28. dan says:

    Hey Bob – Thanks much for the advise and when i HAVE a moment i will join the forum. i do still wonder if a maintainer would be helpful… dan

  29. Mike says:

    Awesome post thanks (again!) Bob.

    I just wanted to ask about connecting 1 (or 2) big standard (car) batteries with one medium-sized deep cycle AGM battery (say 110Ah) in parallel, with a switch.
    The purpose simply to use the extra car battery for short ‘peak’ usage; such as a microwave for a minute or two, or a powerful blender for a min or two. This may save me having to buy 2 big expensive 110Ah long cycle batteries (for a 200W solar system).
    (Most of the time, and at night /for prolonged use especially, I would disconnect the car battery from the system using a simple cut-off switch in the connecting cable.) So two questions:

    – is it ok to charge a car battery using solar /have it connected up to the solar charge controller?

    – is it ok to use the two different batteries in combination (in parallel) assuming that the withdrawals from the combined system are only for a brief duration; the car battery would only be connected /used to take short high loads… ?

    Thanks for any insight!

    • Bob Bob says:

      Mike, you should never use a car starting battery as a house battery. Unless the engine is running, then it’s fine. They will die very quickly. All batteries in a bank should be the same size and very close to the same age.

      Sure, you can connect solar panels to the car starting battery.
      Bob

      • Mike says:

        Thanks Bob – I just read your other sections on batteries and realise connecting the house battery to the alternator via a continous-duty solenoid as you mentioned is ideal. This way we can turn the engine on for helping handle peak loads if neccessary, and especially for recharging batteries on cloudy days as we drive along. Its perfect in combination with a solar system. (and can allow us to get by with a slightly smaller battery bank if we’re not budgeting power for multiple days for instance). Thanks again!

  30. bigfuzzy58 says:

    Just found this! Thank you so much for making this understandable. Some folks think in pictures and narrative. Me. Again thanks!!!

  31. Suzanne says:

    I am retiring in 3 years and hope to live in an RV (5th wheel trailer). I have been trying to understand alternative forms of energy for years. Thank you so much for your easily understood explanations of solar and wind power. I’m getting it . . .
    And everytime I buy anything from Amazon (which is often) I am going through your website.
    Thanks again.

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