# Battery Question



## City Bound (Jan 24, 2009)

As some of you may know I have been trying to set up a tiny solar system. I trickle charged the battery and I have an inverter on it and I am running a table lamp with a CFL bulb in it. 

My question is how many hours should that 12 volt car battery run the light before the battery is run down? Just a rough idea of the time, I know you can not tell me exactly.

Thanks.


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## nadja (May 22, 2011)

Depends on size of the bulb. Also, if you run the battery down to far, it will soon get to the point of not taking or holding a new charge. Minimum you should use would be a marine deep cycle battery


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## Energy Rebel (Jan 22, 2011)

Definitely need more info........but you asked for a rough estimate, so here goes.

First some assumptions ( BIG ones on my part, lol)

I googled some info on amp hours of car batteries.
They vary (duh) but let's go with 45 amp hrs, mainly because I don't know what you've got, you can't use it all up - halfway is about right, and you're only asking for a rough estimate.

Next is the bulb. 
Again see what i DON'T know, lol.
But let's assume a CFL uses 36 watts.
Why? Cuz I like math that's easy !

36 watts / 12 volt = 3 amps

so 3 amps is what (or watt) you're using @ 45 amp hours..............so................about 15 hours before you need to recharge.


Your mileage may vary.

Try it and see what you get.


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## artificer (Feb 26, 2007)

If you don't have the battery already, DON'T get a "car battery." A starting battery will not last long in this application. Get a marine battery as a minimum, or better yet, get a regular deep discharge battery. A smaller deep cycle battery might have a capacity of 80amp hours. Don't go under 50% depth of discharage (DOD). This gives you 40amp hours to use. A 60 watt equivelent CFL will draw 13 watts, which is around 1 amp at 12 volts. The inverter will draw power, even when nothing is connected to it. A Xantrex Xpower digital 400 inverter will draw 1/4 amp with no load. This gives you:

40amp hour usable capacity
1.25amp draw
32 hours of run time

This is based on using a 3 stage charger. A cheap single stage charger will only get the battery charged to the 80% level. That means you would only have 30% of the rated amp hours to use, or 24 amp hours/19 hours of draw in the above example.

Everything depends on what equipment you use.

Michael


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## City Bound (Jan 24, 2009)

Thank you. I know the info I gave was vague. I was throwing out a shot in the dark. Folks in this area of the thread board are pretty experienced with solar, so I thought I would wing it and ask my question and maybe someone would clue me in in some way, which you all have.

I ran the light for five hours last night. I just checked the battery and it is still fully charged.

I have an UltraEnergy Heavy Duty 12 volt battery from Struass auto and a 120v 14w .200A CFL bulb. My inverter is 200 watt modified sinewave inverter by SunForce.

I got a car battery just because it was the least expensive battery I could find for an educational set up. Once I get the hang of the solar set up I will invest in better equipment.


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## mightybooboo (Feb 10, 2004)

As an educational system I think you did fine,Ive seen many experienced users say get a cheap battery first time so you only ruin a cheap battery while learning.

Congrats on jumping in,you will soon be be a geek with this stuff....it just wont stop....it takes over....soon all you think about is solar....SOLAR....MUST GET MORE SOLAR!!!!!!!!


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## nadja (May 22, 2011)

Yes, more solar, much more solar. Solar takes time to learn. But, if you keep at it, you will soon get the basics down pretty good. You can get even smaller cfl bulbs witch of course will use even less power.


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## Energy Rebel (Jan 22, 2011)

City Bound said:


> Thank you. I know the info I gave was vague. I was throwing out a shot in the dark. Folks in this area of the thread board are pretty experienced with solar, so I thought I would wing it and ask my question and maybe someone would clue me in in some way, which you all have.
> 
> I ran the light for five hours last night. I just checked the battery and it is still fully charged.
> 
> ...



Better info.
The volts x amps = watts isn't adding up quite right but CFL has a large start up draw and then drops the usage after it's running so........no biggie.
The last thing you need is the amount of amp hours your battery has.
Then divide by the amps you use to get how many hours you can run.

By using 14 watts @ 12 volts. I got 1.17 amps rather than the .200 listed.
i'd go with the higher number to be conservative.
again, without knowing the amp hour rating of the battery, but using the first calculation of 45 amp hours, you could conceivably run it 38 hours before recharge.
But your mileage may vary.


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## City Bound (Jan 24, 2009)

38 hours is impressive. honestly, I am totally thilled and impressed with the five hours I used last nice. 

What an amazing feeling it is to be making you own power...god, it feels so liberating.


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## City Bound (Jan 24, 2009)

mightybooboo said:


> As an educational system I think you did fine,Ive seen many experienced users say get a cheap battery first time so you only ruin a cheap battery while learning.
> 
> Congrats on jumping in,you will soon be be a geek with this stuff....it just wont stop....it takes over....soon all you think about is solar....SOLAR....MUST GET MORE SOLAR!!!!!!!!


Thank you. Yeah, so far I spent $500 for a complete set up. it is small, cheap and does not make too much juice, but my idea is to learn, buy a better system, and then use this little 60 watt system on an out building for free light and for small apliance use.

I can see how it can be addictive. Just sitting under that one little light changed my life. Once I can figure out how to go off grid I am never going back.

I do not understand why more people do not go solar. Some people grumble about the start up cost, but that really doesnt fly because they spend about half the cost of a decent solar sytem each year to the power company with nothing to show for it but lost money.


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## City Bound (Jan 24, 2009)

I don't know what went wrong. I checked the batery last night and it was full. i go to turn on my light tonight and the battery was less then half full and the light would not fire. I turned off the inverter last night.

Can the inverter still pull a charge out of a battery even if the inverter is off?


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## wy_white_wolf (Oct 14, 2004)

How soon after having a charge applied did you check the voltage?

Most likely too soon and you where getting a residual charge reading instead of the actual state of cherge.


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## mightybooboo (Feb 10, 2004)

City Bound said:


> What an amazing feeling it is to be making you own power...god, it feels so liberating.
> 
> I can see how it can be addictive. Just sitting under that one little light changed my life. Once I can figure out how to go off grid I am never going back.
> 
> I do not understand why more people do not go solar.


Thats what happened to me,the idea just sounded good,the first time *I,ME* actually had *MY* light going,and the fan running,all from clean silent free power from the sky,yup,it WAS a life changing moment.

Sounds hokey,but it was one of the most miraculous things I had ever seen.Literally shook me to my core.

The other that came up like that was standing in an O.R. watching an open heart surgery and seeing how that surprising *tiny *delicate looking organ could produce so much.

And wait until you get a couple LED lights up and running and see how much light they make for such little wattage like 4-6 watts,will blow your mind completely yet again! Will be PERFECT for your outbuilding small system light plans.

My theme song...."Meet George Jetson....."


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## City Bound (Jan 24, 2009)

wy_white_wolf said:


> How soon after having a charge applied did you check the voltage?
> 
> Most likely too soon and you where getting a residual charge reading instead of the actual state of cherge.


I am not sure. I think you are right it was right after. I had the battery sitting around for a year before I used it. It was half charged when i finally got around to using it. I HEard you are suposed to hook them up to a trickle charger now again whn you store them. Could that be the problem, the inactivity of the battery for so long?


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## City Bound (Jan 24, 2009)

mightybooboo said:


> Thats what happened to me,the idea just sounded good,the first time *I,ME* actually had *MY* light going,and the fan running,all from clean silent free power from the sky,yup,it WAS a life changing moment.
> 
> Sounds hokey,but it was one of the most miraculous things I had ever seen.Literally shook me to my core.
> 
> ...


 Being awake during open heart surgery sounds scary.

I don't understand why other people do not want free electric also. hmm, it will be our little secret then.


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## mightybooboo (Feb 10, 2004)

City Bound said:


> Being awake during open heart surgery sounds scary.


Patient was asleep,everyone else was awake though....:hysterical:ound:


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## TnAndy (Sep 15, 2005)

City Bound said:


> I am not sure. I think you are right it was right after. I had the battery sitting around for a year before I used it. It was half charged when i finally got around to using it. I HEard you are suposed to hook them up to a trickle charger now again whn you store them. *Could that be the problem, the inactivity of the battery for so long?*


Yes. Batteries self discharge over time. That's the purpose of a trickle charger....to keep up with the self discharge.

Once a battery sits around and discharges, odds are better you have ruined it......which is likely the condition yours is in.


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## ace admirer (Oct 5, 2005)

Basically lead acid will loose 10% charge per month...so they need to be topped off every month.


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## wy_white_wolf (Oct 14, 2004)

City Bound said:


> I am not sure. I think you are right it was right after. *I had the battery sitting around for a year before I used it. It was half charged when i finally got around to using it.* I HEard you are suposed to hook them up to a trickle charger now again whn you store them. Could that be the problem, the inactivity of the battery for so long?


Good chance the plates are sulfated (may not be correct term) and have lost capacity from it. Run it through a couple of charge/discharge cycles and see if it starts to come back. If not you can try equalizing the battery to see if that brings back capacity.


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## City Bound (Jan 24, 2009)

Will do.


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## City Bound (Jan 24, 2009)

mightybooboo said:


> Patient was asleep,everyone else was awake though....:hysterical:ound:


Ok. I just reread your post. You were standing. I was sleepy and assumed it was you getting the surgery.


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## roachhill (Jul 8, 2009)

If you need to go battery shopping I'd recommened investing in golf cart batteries. I've been testing a few Energizer golf cart batteries from Sams Club ($75 each) and so far so good. The batteries Sam's club sells as Energizers are actually being made by Johnson Controls and they have a pretty good rep.


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## City Bound (Jan 24, 2009)

We do not have sams club here, but I will look for them in costco


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## roachhill (Jul 8, 2009)

I should point out golf cart batteries are 6 volt so you'll need 2 to get a 12 volt system but at 225 amp/hrs they will hold up much better than a marine battery.


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