I operate a 6 Volt DC fan with 12 Volt DC, does it damage the Motor/Fan?

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mamun2a

New Member

• Aug 9, 2010

• #1

I operate a 6 Volt 4Ah DC fan with 12 Volt 7Ah DC, does it damage the Motor/Fan?
due to battery problem i do so, how much damage it may happen to the DC Fan?

thanx in advance.

mamun2a
dhaka, BD

 

tvtech

Well-Known Member

Most Helpful Member

• Aug 9, 2010

• #2

Something is gong to break. Windings burnt would most likely be the first thing to go.

Cheers

 

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mamun2a

New Member

• Aug 9, 2010

• #3

i've to run it 1 hour at a time.

 

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picbits

Well-Known Member

• Aug 9, 2010

• #4

Use PWM at 50% duty cycle to minimise losses and help keep the windings cool.

 

crutschow

Well-Known Member

Most Helpful Member

• Aug 9, 2010

• #5

If you don't care about efficiency, you could just put a power resistor in series with the fan to drop about 6.3V.

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Aug 9, 2010

• #6

Really it depends how stressed the motor is at 6V, if it's under-run it may be perfectly fine on 12V instead.

But I would expect for most motors that it's life will be GREATLY reduced, and it may not even last the first hour.

Apparently 12V windscreen wiper motors usually work perfectly fine at 24V (even long term), obviously well under-run on 12V.

 

M

mamun2a

New Member

• Aug 10, 2010

• #7

i bought 6 Volt 7Ah Lead acid battery specially for this Fan, but i c, the battery cant serve which i think. it ran 1+ hour with 6Volt 4.5 SLA batt, but now ? happen i cant understand.

I use 12V 7AH SLA w/o hassle still now, just the fan ran very fast.

 

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mamun2a

New Member

• Aug 10, 2010

• #8

can u give me a short detail of power regisor?

 

crutschow

Well-Known Member

Most Helpful Member

• Aug 10, 2010

• #9

If the fan draw 4A, then you need a 6.3V/4A = 1.58Ω resistor. The power dissipated in the resistor is 4A x 6.3V = 25.2W.

Thus you would need a 1.6Ω, ≥30W power resistor, which is fairly large. Obviously this is not a very efficient approach.

 

kiriakos-gr

Member

• Aug 10, 2010

• #10

mamun2a said:

can u give me a short detail of power regisor?

Click to expand...

You can use five small diodes in line , this will drop the voltage at the safe 9V point,
that the 6 volts fan, can use with out issues.

 

Last edited: Aug 10, 2010

crutschow

Well-Known Member

Most Helpful Member

• Aug 10, 2010

• #11

kiriakos-gr said:

You can use five small diodes in line , this will drop the voltage at the safe 9V point,
that the 6 volts fan, can use with out issues.

Click to expand...

Small is relative. They must carry 4A and so would need to be 6A minimum power diodes on a heat sink.