computer fan, batteries, and charging

turner · Sun Mar 25, 2012 9:26 pm

So i have an lipo battery that is 9.6v and 1600mah. The problem is i only have some Nicd battery chargers that put out 12v and 200mah. Could i charge the lipo if i make sure it doesn't overcharge and explode? I also have some lower volt chargers. Also does anyone know how long it will power a computer fan that the consumtion rate says .96 watts? or does anyone have the math? i dont want to be spoon fed haha

pneumaticcannons · Mon Mar 26, 2012 4:09 am

uhhhhh, theres no such thing as a 9.6v lipo.

probably NiMH or just another NiCd. If it's a NiMH you should get a real charger. As for how long the fan will last, we need to know the voltage it operates on or the current it draws. And yes it does involve math

jackssmirkingrevenge · Mon Mar 26, 2012 4:55 am

0.96 watts = 9.6V x I

I = 0.96 / 9.6 = 0.1 amps

1600mAh means your battery can put out 1600 milliamps (1.6 amps) for one hour.

This gives you roughly (there are more variables in the real word) 16 hours of run time. Since you only need to run it for a few seconds per shot, that's a lot of spuds before you have to recharge.

inonickname · Mon Mar 26, 2012 5:14 am

1. That's not a lipo
2. No you can't recharge batteries with the incorrect charger, ESPECIALLY lipo's (even though yours isn't)
3. You don't understand lipo's, watching them isn't going to prevent them from exploding
4. Find a real charger, probably from the same remote control car the battery came from

pneumaticcannons · Mon Mar 26, 2012 5:24 am

I = 0.96 / 9.6 = 0.1 amps

he never said the fan was a 9.6v fan!

lol ok,that was one of my worst

's in a while

inonickname · Mon Mar 26, 2012 8:03 am

pneumaticcannons wrote:
I = 0.96 / 9.6 = 0.1 amps
he never said the fan was a 9.6v fan!
lol ok,that was one of my worst 's in a while

It's a 9.6 volt battery though

turner · Mon Mar 26, 2012 4:40 pm

alright i found out its a NiHM battery sorry about that.

Fnord · Mon Mar 26, 2012 5:24 pm

2. No you can't recharge batteries with the incorrect charger, ESPECIALLY lipo's (even though yours isn't)

That being said, why the hell did I get a 24vt charger with my 18vt harbor freight jigsaw ?
No, really, I have no idea either. But I verified the output and ran it through a few charge cycles. Worked fine, till the gear train broke.
I think the advice I would give is, you can use the wrong charger as long as you
A) don't care about the battery too much and
B) have verified your smoke detectors are working

But if you're like me you probably have a ~9vt charger in a drawer somewhere that you forgot about. Use that one

turner · Mon Mar 26, 2012 9:12 pm

alright well i remember hearing that your supposed to charge with 2volts over the rated capacity. i defiantly will be doing this outside, not in my house.

Gun Freak · Mon Mar 26, 2012 9:28 pm

Couldn't resist

jackssmirkingrevenge · Mon Mar 26, 2012 11:39 pm

Fnord wrote:But if you're like me you probably have a ~9vt charger in a drawer somewhere that you forgot about. Use that one

With the proliferation of mobile phones, this is inevitable

Technician1002 · Tue Mar 27, 2012 11:28 am

Time for the basic math. This assumes a perfect battery.

Rule #1 Batteries are not perfect.

Batteries have a nominal voltage. A "Perfect" battery would have the same voltage when full or nearly empty.

Volts is a measure of electrical pressure.
Amps is a measure of electrical current.
Watts is a unit of electrical power. In DC it is represented by Volts X Amps. In AC it is Volts X Amps X Power Factor.

A battery is rated in Amp Hours. This is Amps times the time it can deliver power. A 1600 mAH battery (it is metric) is 1.6 Amp Hours. It can deliver 1.6 Amps for one hour or deliver 1 Amp for 1.6 hours or 0.16 Amps for 10 hours. To charge the battery reverse the current an put current back into the battery.

Your 200 mA charger puts out 1/5th of an amp. It would put out one Amp Hour in 5 hours or fully charge your battery in about 8 hours. A quick charger would charge your battery in 1 hour if it put out 1.6 Amps.

The above example is for a Perfect battery. In reality you have to charge longer and get less back.

Using the Amp Hour rate of the battery and the rate the fan draws power, you can estimate the run time of the fan.

A DC fan on lower voltage will draw less amps as well as volts so it runs at lower power. If the fan was run on 12 volts and Watts is given instead of Amps, you can divide to find Amps at 12 volts.

Disclaimer. I am an electronics tech and I have been up all night so this post may contain errors.

computer fan, batteries, and charging

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