Help - Use a battery for 12v power source?

Hi, I am looking to get a small electric park flier (like a slow stick - 6-8 cell, 400-1200mah ish batteries), and am wondering what to do
about powering the battery charger. I could use my cars battery, but it is inconvenient, and it won't be around all the time. (I guess it wouldn't be safe to charge off the cigarette lighter, and put the charger and battery in the car unattended.)
I could get a 12v power supply for my workbench, and charge at home. But around here, they are around $80-200 CAN. And then I couldn't take it to the field.
I could get a 12v battery to bring to the field - but I've heard that they give off a dangerous gas when charging them. And I was planning to charge indoors. One benefit is that I could charge off the battery while at home or at the field.
I don't know what to do. So, any suggestions? Is there a suitable type of battery that can safely be charged indoors? I may be using 6-8 amp hours of power out of it on a typical flying day. (How much power would be required for 2 hours at the field?)
Thanks, Colin
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Colin, I charge my flight packs using a GWS charger plugged in my car's cigarette lighter all the time with no ill effects. If you want to charge you batteries at home, there are 12V power supplies out there that can be had fairly cheaply (look for Pyramid power supplies on the 'net). I don't have the URL handy, but do a search for converting a used PC power supply for charging batteries. These can be had for cheap, even free, out of old computers and can put out 12V at 5A clean DC. Most RC battery chargers out there today are delta peak types, meaning they shut off or go to trickle charge when the battery is fully charged.
Morris
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I use a Die Hard lawn tractor battery installed in the bottom of a plastic wheeled tool box thingie. I regularly used to charge all my flight packs at the field with it along with powering my wireless video system ground equipment. I keep it out in the garage and on a battery tender when not in use. More than enough juice to charge about anything you would ever need at the field for a good long day of flying.
--
Dan
AMA605992
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On 20 Jan 2005 11:38:39 -0800, snipped-for-privacy@hotmail.com (Colin) wrote:

Colin-
Good thinking - a 12 V lead acid battery will do the job nicely. Good thinking re safety too. The gas that lead acid batteries give off is hydrogen - completly non-toxic, but very flammable. You wouldn't want to use a typical car battery indoors at all, because they vent gas off to the atmosphere and you wouldn't want to have it accumulate where ignition sources might be present. A sealed battery would be a better choice, and then should be charged 'indoors' in a space that is well ventilated, like your garage. Garages are designed to provide ventilation for gasoline fumes and such from your car, living spaces are not. 15-20 Amp-hr sealed batteries are widely available for things like electric mowers and powered bicycles and match your needs well based on your projected use. I use them for the same purpose you have described. I use a 15 A bench power supply too, and it's handy for charging needs while at home but of no use at the flying field.
Sources for a handy unit include your local auto parts store, Target, Wally World, etc. Most sell a portable package with battery and built-in charger for emergency car starting for about $50 US. Some include a flashlight, air compressor, and/or inverter to provide 120 VAC for tools and such,
Abel
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I went down to the car accessory shop and bought the cheapest car battery they sold. I put it in a box with handles and it follows me to wherever I need it. Every so often it gets a charge using the SuperNova. It's so draughty in my house, I don't worry about the gasses given off...
-- Philip Rawson
www.flymodels.co.uk www.aeromodeller.org

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Thank you for your replies. I don't have a good spot to charge outdoors, so I suppose my real question is: What sort of 12v battery is safe to charge indoors? I AM concerned about the gasses given off - a sealed up basement and a baby in the house!
I've looked at the power pack things, but have not been able to find out what type of battery is powering them. Thanks, Colin
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snipped-for-privacy@hotmail.com wrote:

You should look into sealed lead acid batteries (SLA) otherwise known as gell cells. The most common size is around 7amp hours and is commonly used as backup power for alarm panels. They're compact, reasonably small, the acid is in a gel form, and they're sealed so there's no fear of leakage.
Russ.
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Any type of gel cell, or a sealed auto battery (lead-acid or otherwise), should be safe. Slower charging rates on vented cells tend to give off less gasses, too.
Dr.1 Driver "There's a Hun in the sun!"
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| I went down to the car accessory shop and bought the cheapest car battery | they sold. I put it in a box with handles and it follows me to wherever I | need it. Every so often it gets a charge using the SuperNova. It's so | draughty in my house, I don't worry about the gasses given off...
`cheapest car battery'? Probably a mistake.
For this application, you want a deep cycle battery. A standard car battery will not tolerate even partial discharging for long, and probably won't last even six months.
And I wouldn't worry too much about the hydrogen gas either. A battery only emits noticable amounts of it if it's overcharged, and with a good charger that shouldn't happen. Right?
--
Doug McLaren, snipped-for-privacy@frenzy.com So many idiots. So few bullets.

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battery
I
It's already done about 6 months and seems to be going strong... besides it was only 20 so if it lasts the year out I'll be happy.
-- Philip Rawson
www.flymodels.co.uk www.aeromodeller.org
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Ummmm....
    I have been using a motercycle battery (14 AH, lead acid, wet) for this purpose for 7 years...
    I sure have the "6 months" beat....
    My understanding is that the "car" batteries are happy being partially discharged, that's the application in an automobile...
    It is the deep discharges that they don't like...
    I have an ongoing example that they work well in deep discharge situations as well, but that is a long story and OT here....
    YMMV.. :)
    Dave
On Fri, 21 Jan 2005 23:26:21 GMT, snipped-for-privacy@frenzy.com (Doug McLaren) wrote:

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On Fri, 21 Jan 2005 21:27:59 -0400, Dave

seems to be the case from my experience...been charging e-planes directly from my car battery for years with no premature deaths.
My current one (no pun intended) has seen three summers of every weekend and many weekdays of flying...lots of these 12 hour days. Never killed the battery, but it was taxed pretty good.
That battery started my car just fine at -29 on Monday and an average of -20 all this week....
cheers Papa Sharptooth
Bouncing about the living room, my then three year old grandson declared himself "a kangaroo". "If you're a Kangaroo, what is Grampie", I ask. His reply: "you a dinosaur"
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| On Fri, 21 Jan 2005 21:27:59 -0400, Dave | >    My understanding is that the "car" batteries are happy being | >partially discharged, that's the application in an automobile... | > | >    It is the deep discharges that they don't like... | | seems to be the case from my experience...been charging e-planes | directly from my car battery for years with no premature deaths.
Right. Slight discharges are fine. And I don't know where the cutoff between deep and light discharges lies, but once you get into the deep discharges, you start doing serious damage to the battery, and it won't last long.
For your car battery you're probably fine, as it will probably be charged up as you drive home. But for a battery that's loose and only charged when you think about it, it can seriously shorten the life of the battery.
--
Doug McLaren, snipped-for-privacy@frenzy.com
Shift to the left! Shift to the right! Pop up, push down! Byte! Byte! Byte!
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