Adding 12v input on battery fan

[Stuee123]

hi,
I have a camping fan light that uses 4x D Batteries. I want to add a DC socket on the side so i can plug my 12v solar battery into it.
What circuit would be the best for this or can i step it down with resistors?
Thanks in advance.

 

[sagor1]

Depends on how much current the fan uses. With 3 D batteries, probably not all that much, so a simple buck/boost converter could change the 12V to 4.5V easily. For up to 2A current, ones like these would do:

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[Pommie]

How long do 4 alkaline batteries last?

Mike.

 

[danadak]

If you wanted to do this with rechargeable batteries :

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Regards, Dana.

 

[AnalogKid]

With 3 D batteries,

4 D batteries.

 

[Pommie]

With 3 D batteries, probably not all that much

Alkaline D cells can have a capacity of ~12Ah so the current could be higher than 2A. Hence my question above.

Mike.

 

[sagor1]

Alkaline D cells can have a capacity of ~12Ah so the current could be higher than 2A. Hence my question above.

Mike.

True, one would need to know the current load of the fan. There are buck/boost converters that can supply more current, like 5A to 6A and still be quite compact and efficient.
Original post had 3x D cells, I see the poster edited his question after I had answered about 3 D cells. 4 D cells makes no difference for choosing a buck converter. It is just the current rating that matters.

 

[Nigel Goodwin]

As it's a battery powered camping fan light, then it's EXTREMELY likely that it's relatively low power power consumption - and I would expect that the 2A converter in post #2 would be fine.