Help! How to calculate this amphere hour thingy?

[Vroomtattat]

  On 9/17/2010 at 9:09 AM, Happily1986 said:

1.) Calculate impedance of each fan using input voltage = 12V and input current = 0.12A

Impedance is taken to be approximately the resistance of the fan

Thus R =V/I = 12V/0.12A = 100 ohm

 

2.) Total impedance/resistance of the 10 fans

Since fans are in series, we have to utilise the parallel addition rule.

1/(total resistance) = 1/(resistance of fan 1) + 1/(resistance of fan 2) + ... + 1/(resistance of fan 10)

Taking reciprocal, total resistance = 10 ohm

 

3.) Current flowing in parallel circuit (with all the fans connected)

Current I = V/R

I=1.2 Ampere

 

4.) Stamina of electrical setup

Time = Amperage hour / (current drawn)

= 7.2Ah/ 1.2A

= 6 hours

 

5.) We cannot assume that heat generation i.e. wastage is minimal thus you should expect the stamina time to be below 6 hours.

 

Bro, 6 fans thia . . . . can recalculate for me please? Thanks!

[Happily1986]

1.) Calculate impedance of each fan using input voltage = 12V and input current = 0.12A

Impedance is taken to be approximately the resistance of the fan

Thus R =V/I = 12V/0.12A = 100 ohm

 

2.) Total impedance/resistance of the 10 fans

Since fans are in series, we have to utilise the parallel addition rule.

1/(total resistance) = 1/(resistance of fan 1) + 1/(resistance of fan 2) + ... + 1/(resistance of fan 10)

Taking reciprocal, total resistance = 16.67 ohm

 

3.) Current flowing in parallel circuit (with all the fans connected)

Current I = V/R

I=12V/16.67ohm =0.72 A

 

4.) Stamina of electrical setup

Time = Amperage hour / (current drawn)

= 7.2Ah/ 0.72A

= 10 hours

 

5.) We cannot assume that heat generation i.e. wastage is minimal thus you should expect the stamina time to be below 10 hours.

 

pai seh, earlier on bak chiu tah stamp thought is 10 fans LOL

[Vroomtattat]

Hey! Thanks bro.

 

Went down to SL Tower on Friday and got my self the following :-

 

6 slim computer fans (25mm by 25mm each, rated 12V 0.12A)

 

A sealed lead acid rechargeable battery, 12V 7.2Ah

 

A *Super* brand battery charger for 6 & 12V batts

 

Velcro tape, 3M double sided tape, a metre of wire and 2 clip connectors.

 

Total costs : <$80

 

Taped 5 fans together in a row, wired them in parallel connection and doing a test run now to see how long they can continue running and oh boy! the fans are zipping along fine . . . . quite strong leh. WooHooo!

 

Plan to leave a gap in the car window and hook it up with velcro to blow out the hot air.

 

My CO say I seow

 

Don't laugh at me, please.

Edited September 18, 2010 by Vroomtattat

[5936]

Boleh!!! LIVE YOUR DREAM, ON YOUR FAN 2010

 

Did you get a switch for it. Or yo intend to operate out from the terminals.

[Vroomtattat]

  On 9/18/2010 at 3:27 PM, 5936 said:

Boleh!!! LIVE YOUR DREAM, ON YOUR FAN 2010

 

Did you get a switch for it. Or yo intend to operate out from the terminals.

 

Oh goober!! Forgot to buy the SWITCH!

 

Back to SL Tower on Monday . . . Thanks for the reminder bro.

 

 

[Rainman]

  On 9/18/2010 at 1:57 PM, Vroomtattat said:

Hey! Thanks bro.

 

Went down to SL Tower on Friday and got my self the following :-

 

6 slim computer fans (25mm by 25mm each, rated 12V 0.12A)

 

A sealed lead acid rechargeable battery, 12V 7.2Ah

 

A *Super* brand battery charger for 6 & 12V batts

 

Velcro tape, 3M double sided tape, a metre of wire and 2 clip connectors.

 

Total costs : <$80

 

Taped 5 fans together in a row, wired them in parallel connection and doing a test run now to see how long they can continue running and oh boy! the fans are zipping along fine . . . . quite strong leh. WooHooo!

 

Plan to leave a gap in the car window and hook it up with velcro to blow out the hot air.

 

My CO say I seow

 

Don't laugh at me, please.

 

 

End of the day, u will find it very inconvenient as u need to recharge the battery, rem to leave a gap etc. Not to say ur 6 fans is unlikely to cool the car at all....

 

 

I say save ur 80 bucks and time.....

[Caravan]

Why don't you connect to a solar panel, like what they are selling on ebay?

[Karoon]

  On 9/18/2010 at 1:57 PM, Vroomtattat said:

Hey! Thanks bro.

 

Went down to SL Tower on Friday and got my self the following :-

 

6 slim computer fans (25mm by 25mm each, rated 12V 0.12A)

 

A sealed lead acid rechargeable battery, 12V 7.2Ah

 

A *Super* brand battery charger for 6 & 12V batts

 

Velcro tape, 3M double sided tape, a metre of wire and 2 clip connectors.

 

Total costs : <$80

 

Taped 5 fans together in a row, wired them in parallel connection and doing a test run now to see how long they can continue running and oh boy! the fans are zipping along fine . . . . quite strong leh. WooHooo!

 

Plan to leave a gap in the car window and hook it up with velcro to blow out the hot air.

 

My CO say I seow

 

Don't laugh at me, please.

 

good idea. does it work?

there are similar fans running on solar to cool the car before one goes in but they don't work. i mean the fans run but the effect on interior temperature is about 0.2DegC compared to without fan (some dude this an experiment in oz summer)

 

http://www.shopwiki.co.uk/solar+car+fan

 

 

[Saycheese78]

To prevent accidents fro happening. I suggest tieing a fuse (1A, 2A, 3A also can) to the battery before connecting to the fans in parallel. if not, a short circuit fan will cause battery to catch fire!