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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 06-13-2012, 11:15 PM   #1
soaringhigh718
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Default Understanding power supplies

I am somewhat confused as to how a "Power Supply" works. Is the power supply charged at the user's home and then brought to the field to supply power to the user's battery charger?
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Old 06-13-2012, 11:36 PM   #2
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The power supplies for hobby use convert AC to DC. The DC is consumed by the charger to charge the batteries. The power supply must be powered by a generator or an AC line.

A lead acid battery can also be used to power a charger. In that case, its more a power source than a power supply. The power supply is more a "power converter" than power storage device.
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Old 06-14-2012, 03:32 AM   #3
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Your power supply can be a battery. When we go fly our gas planes, we have a smallish 12v motor cycle battery on our flight box to power the starter for the gas motor. Sometimes we charge our batteries for electrics off of it, and most of the time I bring4-6 eflight 12v clip on and cigarette lighter chargers and charge the motors as I use them up.

At home we have an old power supply converted to only output 12v's, using the same clip on chargers I bring to the feild. When I only bring one or two smaller planes, I just use our jumpstarter box we keep in the back for dead batteries, and I charge off that, or only the car battery.

Certain chargers will need a much larger power supply. I think its kyleservicetech that brings a gas generator setup he made to charge his li-ion battery packs in his larger models. He couldn't supply enough power with two deep cycle batteries to charge them.

What you look for is the maximum amp charge rating. 22v at 6 amps is 132 watts. 6 amps at 11v's is only 66 watts. Most comouter power supplies will provide in the neighborhood of 150 watts on the 12v rail, but they also have 5 and 3.3v rails. So you can't just get any 350w power supply and convert it to any charger. Some more expensive high dollar stuff will charge over 10 amps on a 6 cell. That is over 220watts. You must size your power supply properly. Even charging a couple of 1800's for a couple hours in my car, I have had to jump it to start it back up once or twice.
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Old 06-14-2012, 05:22 AM   #4
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Originally Posted by hayofstacks View Post
Certain chargers will need a much larger power supply. I think its kyleservicetech that brings a gas generator setup he made to charge his li-ion battery packs in his larger models. He couldn't supply enough power with two deep cycle batteries to charge them.
Depending on the size of your model, the batteries that power the electric motor in the airplane can deliver significant horsepower levels. It's not hard these electric motors to exceed one horsepower output on a 60 inch wingspan acrobatic airplane.

Then, recharging the LiPo battery after a flight might take an hour or so, so the LiPo charger has to put out something on the order of 100 or 200 watts in this process. Again, 200 watts is over 1/4 horsepower.

The LiPo chargers are usually designed for a 12 Volt DC input voltage (some are rated to some 30 Volts DC). And, 200 watts at 12VDC is about 17 amperes.

To run these LiPo chargers, you need either a good quality deep cycle marine battery, or a 120 Volts AC to 12 Volts DC power supply (or power converter) rated for at least 20 Amps at 12 VDC.

(Yeah, I'm the guy that built up the gasoline engine/alternator setup. It's been working very well.)

This might put a little light on the subject for the larger electric models.

Thread on 70 size glow engine conversion to electric: (Check out "Field charging issues")
http://www.wattflyer.com/forums/showthread.php?t=45222

Typical power supply:
http://www.jameco.com/webapp/wcs/sto...0001_207204_-1

And, that DC alternator setup:
http://www.wattflyer.com/forums/showthread.php?t=66066

DennyV
Retired and the days are just too short, busier than ever!
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Old 06-14-2012, 12:19 PM   #5
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I think Gregor nailed it in the first response. What's commonly referred to as a 'Power Supply' is a device that plugs into your wall socket at home and converts high voltage AC to low voltage DC that most chargers needs to operate. The actual output voltage and power capacity need to be matched to your charger's requirements. Power supplies dont store power and so need to be plugged in at all times.

A device that you charge up at home and take to the field to use as a power source is simply known as 'a battery'. As noted earlier the type of battery you need to do this is a large capacity deep cycle lead acid type (very big and heavy). It's usually more convenient and possibly cheaper simply to buy several LiPo flight batteries so you dont actually need to recharge at the field.
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Old 06-18-2012, 06:59 PM   #6
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Which AC power supply do you need for your charger? Two handy calculator-tools:
Zie
The Script Asylum (add to favourites?)
-> RC calculations
-> electrical
-> lithium battery chargers
and also
-> charger calculator


-> LiPo pack wiring
en
-> System wiring


Vriendelijke groeten Ron
diy motor tips Drive Calculator
diy motor group Cumulus MFC
Get a life ... get a 3$ Wattmeter
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