Using a car battery to power an inverter?
 

Now, I know it's possible to power an inverter off a car battery, but I'm curious about buying a spare battery and using it for 8 hours a day in tandem with a 800w inverter to power a laptop (non gaming). I got another job way closer to home (6 miles instead of 40 each way) and I need to keep myself busy as this post is boring. I would normally just use my car battery but I really don't want to strain it like that. So, real question is...

Is it possible to just use a big battery, say a RV battery that I trickle charge every night while I sleep to power an inverter for 8 hours? Or will this not work for some reason?

How much power are you using, and how much power is available in a fully charged battery.

I have no idea, that's why I'm asking. I'm thinking about powering a small laptop just to watch movies and TV shows on, not over wifi just off a USB stick. It will probably be a 13" or 14" laptop. I would think maybe 1-400w at most? If I can find a small DVD player that plays movies and TV shows off USB sticks I'll use that instead because I know that draws a lot less power.

Laptops don't take 800W to power; more like 100W when charging, and perhaps 20W in regular use.

Just get a laptop that can run for 8hrs without a charge. Mine goes 10hrs on a single battery. Multiple laptop batteries is also a better option than running a lead-acid with an inverter.

I'm assuming you are asking about "I got another job way closer to home (6 miles instead of 40 each way) and I need to keep myself busy as this post is boring.".

I'm assuming Balto is talking about a guard post and not this forum post. My guess is they are in security or some other monitoring situation where action is usually not required.

Most cheap inverters are not designed to run for 8+ hours at a time and will burn out, you would be better off getting a car charger for your lap top, a lot of lap tops are ~17 volts or so, so you might be able to just power it off a 18v cordless tool battery for about the same cost as a cheap inverter and it would fit in your pocket.

Sorry for not being more specific, yes I'm a security guard lol. I work graveyard at this job (11PM to 7am). Again, I didn't think about getting multiple batteries, but I don't know how I would charge them at work, or at home while I'm sleeping I would only be able to charge one at a time... As for a car charger, again not a bad idea, but I don't want to put the extra strain on my actual car battery and risk trapping myself at work.

don't use an inverter if possible. you would be converting DC to AC back to DC with every step along the way losing efficiency.

Do you already have a laptop for the job, or would you be buying one? You can get external battery chargers to take care of charging several batteries, but I would check on their availability before buying a laptop (business class laptops like Thinkpads would be more likely to have them).
What about an Android tablet or ipad? They already have great battery life and would work great with an external battery similar to what Xist posted.

Your problems are always funny, Balto

I would say if you have eight hours of time on your hands on the graveyard shift, you should take some night classes on that laptop ilo watching DVDs.
What are you guarding btw, that doesn't have a power outlet anywhere on the premises?

BTW, Did your brother ever get Aldo to turn left?

Just use your cell phone. You can find many battery extended cases online as well as car, solar and extra batteries.

I will suggest to you to use a 175w or 250 watt inverter.
They cost about $20 (or less) and will have less loss then a 800w inverter.

The small size is a plus.

Most laptop power supplies use about 65w. But with a already charged laptop and low power use (screen brightness turned down mid way and low % CPU use) the charger will only drain about 18w to 24w.
Or so I have noticed with my laptop when monitoring it with a kill a watt meter. They seem to trickle charge while you are using it lightly.
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I use one

I have a 250w inverter mounted under the drivers seat , its wired into the car with a on/off switch plus its own self contained on/off switch on the inverter body.
It is always there ready but never seen by anyone.

thank you guys for the help I appreciate it.

Cowmeat no he did not go to look at it because it was going to cost too much to register it in California.

also I am guarding a construction site but I am about 20 feet from the entrance and there are no plugs. I live in the desert lol.

Cobb that is what I am doing right now but I would like a bigger screen.

Ecomodded that is very good idea I think that is what I'm going to do. the only laptop I have right now has a 19 inch screen and it is a gaming laptop but it makes the 400 watt inverter I have trip and go crazy. I was unaware that non gaming laptops draw such little power.

as for all the interesting questions I ask about you guys have been very helpful and I do appreciate it. I think I'm going to be setting up a TeamSpeak for us on ecomodder soon.

I have my inverter wired directly to the battery where it is fused with one of those car stereo fuses. I think doing it this way gives the inverter plenty of juice to invert.

I am thinking if you run a fused power line from the battery to your inverter it will start charging your big laptop with no problem.
Even being a big gaming laptop its charger should still not use more then 135 - 150w at full tilt boogie.

What you can do is look at the charger and read its output or amperage , times that by the volts & that will give you its max draw in watts.

Baltothewolf, Id check your job first and see what your co workers do. Since you said post, is this on a base? In VA its an instant Federal summons for operating a cell phone without hands free.

Plan b would be to get a jump starter thing. Those have lights, air compressor, inverter, usb plugs and cigar lighter outlets depending on model.

Plan C, get some lifepo4 hobby batteries to make a 12 volt pack to power an inverter.

Your 400 watt inverter shouldn't be going nuts with a gaming laptop. 330 watts seems to be the largest laptop PSU I can find, my desktop complete with a phenom II 940 and a 6950 idles at 150 watts with monitor on, loads to around 330 watts (I have it undervolted, but I'm running at stock clockspeeds, if I dump the volts into it and raise the clocks, I can pull 500 watts before the air coolers get overrun with heat.)


Budget 50 watts/hour for a laptop even though newer ones can fit within a smaller footprint (my rule of thumb it to take manufacture battery life and cut it in half for a new battery, cut it to a third for an aged battery, cut it to a quarter for a worn battery.)

Cobb, I'm just sitting by the side of the road lol. I'm working for an off hand local security company. They don't mind you using your phones, laptops and any other electronic device as long as you stay alert, which I do. Thanks though for your concern (non homo hug).

Ecomodded, I think my issue is I'm going through the cigarette lighter. I'll try a direct battery hookup and see if it does it.

Read above H-man.

You could charge the battery you have when you go to sleep, then switch the battery when you wake up. A full charge, and at least a half charge.

I was going to suggest charging up battery #1 right when Balto gets home, and then putting battery #2 in to charge right before bed.

An 8hr shift leaves 16hrs of charging time; plenty to charge at least 2 batteries.

I wouldn't make this any more complicated or expensive than necessary.

I got one of the jump starters with built in 12 volt power out let, usb, already had a little inverter, don't remember watts, some even have a air compressor built in, and light, good for jump starting lawnmower, inflating tires, powering weather radio when power out. Pretty handy to have around. And a lot easier to carry than a car battery.

http://www.walmart.com/ip/Cobra-Elec...tput/146495563

Already has 110 outlet, the one I got doesn't have a compressor or 110 built in and might get another one just for backup power around the house.

I work two 8 hour shifts back to back, 2-10pm then I leave that job and go work 11-7. Takes about 45 minutes to get home from my 2-10pm job so it ends up working out well. The 2-10pm job I can't take a charger or anything like that because they are extremely anal about any type of electronics on post (that job is security as well).

Not sure how long you could use it. Definitely a deep-cycle is best

I totally missed this from your first post. So it's not 8 hours of charge you need, it's 16?

Nono, my first job (2-10pm) I can't use it, so it will just sit in the car. My second job (11pm-7AM) I can use it. The reason I asked the original question is, I don't have the time to charge multiple batteries. I just needed a big battery that holds a crapload of charge that I can charge while I sleep for 4-5 hours between jobs.

I'd just let the car charge it when you get there until lunch, then go out and unplug it and turn your engine over. 4 hour charge, then you'll have another when you go to sleep. But I would just buy an extra large capacity battery for it in the first place, and use that.

As much as I like going out of my way to do something clever and interesting, there is a time one must think about the cost and energy of trying to do it another way. Like when I wanted to repurposed an Insight battery. Yes, I COULD have done it- but it wasn't reasonable. For the energy, risk and money it would take, I could just get other batteries, save time, money, and not risk my life. Your situation is different, but the principle is the same.

I don't get a lunch break where I work :P.

dont worry, i got the solution, save electricity, save fuel, all your problems are solved.
just mount this thing on the passenger side floor, you can also do an alternator kill switch for when you have a passenger too
http://www.youtube.com/watch?v=LAz5575VqYo

i agree laptop batteries will do the trick

All laptops and DVD players work on 12 volts DC (and 5 volts, generated internally). All laptops have an external box (transformer) on the power line to the device. On it, you will find a number for either amps or watts, usually amps. If in watts, divide by 2 t(if in amps, multiply 1/2 the amps times the volts given) to get a generous typical usage figure. Note that adding a DC to AC converter then plugging in the AC to DC transformer box is adding unnecessary circuitry and power usage.
So, charge the battery on your non-gaimng computer, take it and the USB sticks and as backup, a good book and see how long the battery lasts. If it lasts all nite, then your problem is solved. If it doesn't, then take the number of hours it did not last and multiply that times the typical usage wattage figure you calculated above. That will be all that you need to cover the 8 hour shift. If your computer battery lasts over 4 hours, you can then run a line to your car and use the car battery to power the set since 4 hours of low wattage usage will leave plenty of juice for starting the car. Just use lamp cord wire to the car as it is cheap and keeps the resistance to current flow low. Don't take my word for it, test it. Run the computer on it's fully charged battery and see how long it lasts and then subtract that time from 8 hours and then run the computer on the car battery for the remaining hours on your day off and verify that it works. If this saves you a great amount of money, I accept donations.
Bob

P.S. Cowmeat is right. Taking college courses will help you a lot better than knowing the names of actors. I personally suggest courses in Political Science since it is impossible to do a worse job for your constituency than the current crop is doing. And senator pays a lot better than security guard. ($100,000+)