electric study overload, need a lil'guidance

bantamcattle · Apr 20, 2012

hi all, i've studied my brain into mush over the electric issue. i've read many many posts and webpages and understand the basic ideas but need a little real world double check. i am brand new and will be shoving off this spring/summer. i hav electric desires and in general i will be charging a cell phone every few days, using electric clippers every few days for about 20 minutes, running a 15w or less light an hour every few days. i also charge AA batteries occasionally (at home its 9hrs in a wall socket(might have to find a better system!)). i mostly follow the sun and try to adapt but i do have some computer projects that i want available to me, so that means i may charge a laptop once every 3 days or may use a desktop for about 2 hours every 3 or 4 days. i plan to go to a town once every 2 weeks and drive an hour or more to get there. that will be the extent of my driving. i am poor and simple and thus don't feel the need to dump 400$ into having some electricity before i've even gotten my feet wet but at the same time i feel i should protect my starting battery. so the best i can think of is to get a home battery that is around 200Ah. a AGM deep cycle type seems the easiest/safest way to go and i think to start i should just wire it to the starting battery so it charges off the alternator when i drive. i will also install a switch to protect my starter battery should i drain the home battery. this will still be pricey but i feel ok spending around 200$ to do this. i believe with this setup, i risk running out of electricity after one week but i am ok with that while i'm learning. i can adapt and use very little electricity the 2nd week or i can run my van or go to town or suffer and use that as motivation to get a solar situation going. in the end i really don't know how things are going to go but i want to make a small investment to start so i hav electricity as an option. does my above plan sound reasonable to you more experienced NOMADS?

SoulRaven · Apr 20, 2012

i was at this point a while back... i realized the system i had, much like yours just could not keep up... what i did was to find a local watering hole and plunged into free elec. saying i was a writer for a boondocking magazine writing about them and the surrounding area... This worked for internet and charging the net-book battery but is only good for so long... You have to either drop your electrical needs or increase your available power... What i did was bite the bullet and got a 2kw genny and this worked for a long time, allowing me to save up and finally install a solar system that solved my power needs... There is no easy answer, for each is different for everyone and their consumption... Probably right now you need to set-up a duel battery set-up, isolating your starter battery and the second battery a good deep cell with over 200 amp hours... run off the second battery your electronics, dump all needless power consumers like desk top, trimmer etc and run just the essentials... charging the deep cell when you choose to drive.... and go from there... proper duel battery set-ups can be found on line for info and cost... good luck and happy trails

bantamcattle · Apr 20, 2012

thankyou SoulRaven, this gives me good perspective and makes me more comfortable to get my feet wet with a 2nd battery charging solely off the alternator.

SoulRaven · Apr 20, 2012

No worries mate, I and many have been there... It is a long road, but we have time to get things figured out... I am always open to PM's if you need help... Do not hesitate... honest real world answers are free from me and many others... live, love and enjoy life...

Corinne · Apr 21, 2012

Ã¢Â€ÂœDivide the Volts Ã¢Â€Â˜in toÃ¢Â€Â™ the Watts, of any particular item, to get the Amps it uses per hour.  If I have a 7 watt DVD player I divide 7 watts by 120 volts and I get .58 amps. Then, divide the Battery Amps, whatever battery you happen to be using, by the Amps of the particular item to get the hours it will run off of that battery. For instance, if you have a 100 amp battery, you would divide 100 amps by .58 amps, the amps of the DVD player, to get 172 hours.  That's how long you can run your DVD player off of one battery, and watch MASH episodes till the cows come home.  <img src="/images/boards/smilies/smile.gif" align="absmiddle" border="0">  I know it's confusing and you really need to put your thinking cap on and focus.  <img src="/images/boards/smilies/smile.gif" align="absmiddle" border="0">  Personally, it gave me a headache.   lol...  But I'm over it and learned a great deal in the process - also took two aspirins for my headache.  <img src="/images/boards/smilies/smile.gif" align="absmiddle" border="0"> I'm sure you already know this so please don't think I doubt your intelligence.  I don't.  Just sharing my own two cents is all.  (I don't have my glasses at the time, pardon the font size.)  <img src="/images/boards/smilies/smile.gif" border="0" align="absmiddle"> "Happy Trailers." Be True to Yourself~

bantamcattle · Apr 21, 2012

Corinne said:
  Ã¢Â€ÂœDivide the Volts Ã¢Â€Â˜in toÃ¢Â€Â™ the Watts, of any particular item, to get the Amps it uses per hour.  If I have a 7 watt DVD player I divide 7 watts by 120 volts and I get .58 amps. Then, divide the Battery Amps, whatever battery you happen to be using, by the Amps of the particular item to get the hours it will run off of that battery. For instance, if you have a 100 amp battery, you would divide 100 amps by .58 amps, the amps of the DVD player, to get 172 hours.  That's how long you can run your DVD player off of one battery, and watch MASH episodes till the cows come home.  <img src="/images/boards/smilies/smile.gif" align="absmiddle" border="0">

Corrine, thankyou so much, i think my math has been way off! some how i had my desktop computer rated at 690w which some how i translated to 58amp hours (must of done 690w/12v) thus needing 180Ah batter to run my computer for 3hrs. looking at it more i've found that i have a 250w power supply in my computer and no idea how many watts my monitor uses but lets say it uses 250watts too, so that would be a 500 watt system and i would have to get an inverter for the 12v battery so i should divide by 110v or 115v (not sure but doesn't matter) instead of 12v, thus i'd be around 4.5amps, lets say 5amps, so a 100Ah batter would run my computer and monitor for around 20hours!? the above is very loose but i'm only looking to use my computer for 2-3hrs every few days so a 200Ah battery would probably last me just fine for a week or 2?

Corinne · Apr 21, 2012

...my current lap top is 65 watts - divided by 120 volts equals .54 amps.  I happen to have 4 - 75 amp Trojan T105 Golf Cart Batteries.  So we'll go with 75 amp batteries. If my math is right I can run my lap top for about 138 hours, times 4?.  <img src="/images/boards/smilies/smile.gif" align="absmiddle" border="0">  Give or take!  lol... The only other thing I'll have running at the same time is my flat screen tv which I believe is 100 watts.  I have two 140 watt Kyocera Solar Panels on my Trailer's roof and  a 25 amp inverter or 'converter.'  (I'm still learning too!) So far, I haven't gone totally solar because I'm still in the heat of Arizona waiting for my plates to arrive so I can leave here.  <img src="/images/boards/smilies/smile.gif" align="absmiddle" border="0">  Then, I will be heading towards Red Rock State Park in Sedona,(almost 20 degrees cooler than it is here currently) then to the Grand Canyon, then to Monument Valley Utah.  At least, that's the plan "so far."  <img src="/images/boards/smilies/smile.gif" align="absmiddle" border="0">  You know how plans go.....! The very BEST to you. Corinne.

Willy · Apr 21, 2012

One thing to be aware of is HOW the AH rating has been derived. If a 70 AH battery is considered to be so till complete discharge, then you ain't gonna get that since, AFAIK, inverters generally cut out way before that. It's best not to pull the battery below 60% anyway, and many people don't even go THAT low. Also, the AH rating of a battery is load dependent. Here's some info:  http://www.allaboutcircuits.com/vol_1/chpt_11/3.html     http://en.wikipedia.org/wiki/Automotive_battery    ..Willy.

Corinne · Apr 21, 2012

Hi Willy.  <img src="/images/boards/smilies/smile.gif" align="absmiddle" border="0">  Yes, the solar installer told me to never let it go below 50%...  I will heed his advice.

bantamcattle · Apr 22, 2012

Willy said:
 One thing to be aware of is HOW the AH rating has been derived. If a 70 AH battery is considered to be so till complete discharge, then you ain't gonna get that since, AFAIK, inverters generally cut out way before that. It's best not to pull the battery below 60% anyway, and many people don't even go THAT low. Also, the AH rating of a battery is load dependent. Here's some info:  http://www.allaboutcircuits.com/vol_1/chpt_11/3.html     http://en.wikipedia.org/wiki/Automotive_battery    ..Willy.

how do people go about knowing how much they've drained their battery? do you simply track your usage and do the math? also, if you install a solar panel into your system, is there a conversion for the rated wattage of the solar panel? so say i run a 50w light bulb for one hour off my battery, would it take a 50w solar panel one hour to recharge the 50w of usage? (of course assuming 100% efficiency with peak sun for that hour) or is there a conversion to do since the solar panel would be putting 12v into the battery and the light bulb would be using 110v via an inverter?

SoulRaven · Apr 22, 2012

in order to know the status of your battery is very simple, just buy a voltage meter... The can attach to the battery, in line with your inverter on the power in side, and every solar controller has a built in meter... never let your volts go below 12.2V's as you are getting close to that 50-60% of discharge... Batteries can charge up to 14.1 -14.4V's but anymore can cause damage or worse, this is one job of a solar controler is to also protect your batteries... If you use a genny and battery charger the battery charger will show batty voltage status also as well as protect for over charge... Hope this helps some... The battery meters can be found at any auto parts store and the best is to get a lighted digital setup for many reasons... Also shop E-bay for them...

Willy · Apr 22, 2012

Also, most inverters won't drain a battery beyond a certain point. Actually, they might do so, but there will be an audible alarm and it will be shunted to standby mode. ..Willy.

akrvbob · Apr 22, 2012

Bantamcattle, <ul><li>First let me say you have a good plan. Charging off your battery is a good way to get started. After you have lived this way for awhile, and you are sure you want to keep doing it, then invest in solar or a generator. Just be aware that you will get less power off the alternator than you think, so buy a volt-meter and watch it. When it gets down to 12.2 volts, stop and don;t use any more power, or do it knowing you are damaging the batteries.</li><li>Next, be aware that using the formulas that has been described can be misleading. Most people are dissapointed to find that the real world doesn't seem to work the way the math does. They should have enough power, but for some reason the battery keeps drawing down too much every day. That's the way it was for me until I finally got enough solar on the roof and I have never had a problem since. I bought a new pair of AGM golf carts, and use quite a bit of power during the day, but my batteries rarely ever drop below 12.5. However, while I use all the power I want during the day, I am very frugal with power at night.</li><li>I recommend you start out by buying cheap batteries to experiment on. Chances are you are going to ruin them.</li><li>You have made a mistake with figuring your power use. When you plug a 110 volt item into your inverter, and you want to figure out how many amps it will draw out of your battery, you divide by 12, not 110. So if you plug a 110 volt bulb that draws 48 watts into your inverter, you have to divide by 12, not 110. So 48 watts/12 volts=4amps. </li></ul>Hope that helps. Bob

SoulRaven · Apr 22, 2012

The ultimate goal with solar is to have more amps going into the battery bank during the sun light hours, than you use during that 24 hour period... Take 45W@12VDC harbor freight set-up... in optimum conditions you, in theory, should be putting into your battery 3.75amps/hour... If you run a 110W@12V light bulb four 4 hours you will use 9.16Amps/hour and the total usage over 4 hours is 36.6amps of power... So you can see how fast you can over whelm your system with just one 110W bulb... Fortunately there are many tips and tricks to get the same result "Light" while using very little amps... You will eventually get to "Nirvana" with the correct gear, system, and proper advise... But it also about conservation and changing your train of thought from flipping a switch at home, to moble living...

Willy · Apr 22, 2012

Also, inverters don't offer 100%  conversion of 12v to 110v.. plus there are copper losses (resistance) that get greater as the load goes up and 'parasitic' power drains from electronic devices that in a standby state. ..Willy.

vtwinkicker · Apr 22, 2012

The most accurate way to keep track of your battery is with a battery monitor. Check out the Trimetric 2020 or 2025RV by Bogart Engineering. You can input the AH capacity of your battery and it will track how much you take out and how much you put back in from charging. It's  a "gas gauge" for your batteries.

SoulRaven · Apr 22, 2012

Knowing that manufacturers inflate their claims on the amps of their batteries, but also the battery has a life span in which the amps will decrease to a dead state over time... Trimetric seems to make a serious mistake in assuming the amps by operator input... This could really bite you in the end as all it is doing is a simple equation at this point(W/V=A)... The only way to determine the amps of a battery is by special equipment that loads the battery, then reads the max amps and tests the battery... To test amps being drawn by an appliance, you need a multimeter, have the appliance turned on and then test between the battery and the load....

vtwinkicker said:
The most accurate way to keep track of your battery is with a battery monitor. Check out the Trimetric 2020 or 2025RV by Bogart Engineering. You can input the AH capacity of your battery and it will track how much you take out and how much you put back in from charging. It's  a "gas gauge" for your batteries.

bantamcattle · Apr 23, 2012

akrvbob said:
Bantamcattle, <ul><li>I recommend you start out by buying cheap batteries to experiment on. Chances are you are going to ruin them.

</li></ul>i like this advice.

akrvbob said:
<ul><li>You have made a mistake with figuring your power use. When you plug a 110 volt item into your inverter, and you want to figure out how many amps it will draw out of your battery, you divide by 12, not 110. So if you plug a 110 volt bulb that draws 48 watts into your inverter, you have to divide by 12, not 110. So 48 watts/12 volts=4amps. </li></ul>

so my original formula was actually a bit correct. if i use a 500w computer/monitor setup, it would draw around 42amps per hour (500w/12v), 125amps over 3 hours and i would thus need a 250Ah battery to run that computer for 3 hours and not drain the battery past 50%? thats probably too much usage and too big of a battery for a getting started set up that i'm shooting for.

SoulRaven · Apr 23, 2012

No matter the math, you are with your home computer are on a very slippery slope electrical wise... What I did was buy a net-book and transfer all the information you need to a portable hard drive... My Net-book has a 6 hour battery life, is 12V, and can charge from a cigarette lighter when traveling... This is part of the down sizing  for anyone planning to live/travel in a van...

bantamcattle · Apr 23, 2012

SoulRaven said:
No matter the math, you are with your home computer are on a very slippery slope electrical wise... What I did was buy a net-book and transfer all the information you need to a portable hard drive... My Net-book has a 6 hour battery life, is 12V, and can charge from a cigarette lighter when traveling... This is part of the down sizing  for anyone planning to live/travel in a van...

yer very right about the desktop. i hav a laptop and its power cord is rated at 65w so it will draw much less than the desktop, though looking into my desktop usage more, my screen uses 20w and the computer is probably using around 100-120 watts. either way the desktop will draw a lot more than a laptop but if i get a 100Ah battery, it should give me the opportunity to use the desktop a small amount if need be while i'm learning and setting things up.

electric study overload, need a lil'guidance

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