SpudFiles

I have been looking at making a fan controler for my propane injected spud cannon that i'm building and I was wondering if any of you guys have ever used two 9 volt batteries in a series (18 volts) to power a 12 volt fan? Also wondering if over time will 18 volts really damage the fan that much? How long will the fan usually last if it is over powered like this?? I really don't want to purchase a voltage regulated fan controler.

I've used 3x9v batteries to power a 12v fan once, it was perfectly fine and rotated quicker then normal. It was probably a waste of batteries, but I doubt that 18v would damage it.

A single 9v will work just fine. Or even one 9v and two AAs.

The fan will succumb to the repetitive shock of combustion much sooner than "burning out" on 18 vdc. Build your chamber in such a way so that it can be replaced.

Also, consider using RC rechargeable battery packs... 9.6v, 12v, 14.4v can all be used equally effectively.

Edit: Also a basic 12v regulator is $1 or so and easy to incorporate onto a small circuit board.

See here.. http://www.partsexpress.com/pe/showdetl ... umber=7812

Thank you guys for your info. I agree that the combustion will damage the fan before the higher voltage will. I never thought of that. I will use two 9 volt batteries. When I am finished with this cannon i wll post pics of the cannon and its destruction.

Modularity is the key to good maintenance. That, and good general construction skills. I try my best to make as many parts as possible to be easily replaceable.

i use 2 9v batteries in series for my spud cannon the fan never came close to wearing out the motor anyway i did end up melting the blades of the fan when i accenetally left the propane cracked on a little and it turned the chamber into a jet engine. if left on the fan will drain the batteries before it really does any damage to the fan. the fan that i melted still works just fine the trailing edges are a little melted and rub on the housing making an irritating sound. so yes you will be fine using 2 9v's in series. if you really wanted to you could hook up 4 batteries each pair in parallel and then in series so you get the double amps and double voltage that might do some damage to the motor though

starman wrote:The fan will succumb to the repetitive shock of combustion much sooner than "burning out" on 18 vdc. Build your chamber in such a way so that it can be replaced.

Also, consider using RC rechargeable battery packs... 9.6v, 12v, 14.4v can all be used equally effectively.

Edit: Also a basic 12v regulator is $1 or so and easy to incorporate onto a small circuit board.

See here.. http://www.partsexpress.com/pe/showdetl ... umber=7812

As long as there not hobby cars your speaking of. Those cars have batteries that have quite a punch. The one I have is a Sanyo 6-cell 7.2 v 3000mA NiMh rechargable battery. I've super heated a paperclip by shorting it out once. It may do untold damages to a fan.

Just wire the two batteries in parallel. It has the ability to supply more current, but since you're still using only 9 volts (voltage is the same in parallel) and the fan's resistance hasn't changed, it will actually draw less current that normal conditions using 12 volts, and your battery pack won't run out as fast (I hate changing fan batteries).

Also, it's been discussed MANY times, the fan will not be damaged over any measurable period by being in a combustion chamber. The high temperatures exist for only a fraction of a second, and the pressure rise is nearly equal on all sides of the fan's construction, so it experiences no stresses, unless it's clogging the barrel or something ridiculous.

Heck, I've seen one computer fan rigged into what I recall was eight 9 volt batteries (for 72V total) and it was still working fine* - although a lot faster than normal.
18V won't do anything to damage one of them.

*It was finally killed when it was connected up to an improvised power source at well over 10 times it's recommended voltage (unfortunately, the multimeter used was not auto ranging, and went off scale) , but surprisingly, it did work at those voltages for about 20 seconds before catching fire - and even then, I think it was the fire that finished it.

That is awesome! I'm happy to hear this! If eight 9V batteries didn't smoke the motor, 2 definately won't put a scratch on it. Thank you for all of your feedback!

Ragnarok wrote:... eight 9 volt batteries (for 72V total) ...
it did work at those voltages for about 20 seconds before catching fire - and even then, I think it was the fire that finished it.

Hey, a new way to ignite a combustion spudgun! Just install a 12V CPU fan and plug it into 120VAV main, the fan'll work for a few seconds and mix the fuel, then burst into flames and fire the gun.

Well, that's an interesting concept...

rcman50166 wrote:

starman wrote:The fan will succumb to the repetitive shock of combustion much sooner than "burning out" on 18 vdc. Build your chamber in such a way so that it can be replaced.

Also, consider using RC rechargeable battery packs... 9.6v, 12v, 14.4v can all be used equally effectively.

Edit: Also a basic 12v regulator is $1 or so and easy to incorporate onto a small circuit board.

See here.. http://www.partsexpress.com/pe/showdetl ... umber=7812

As long as there not hobby cars your speaking of. Those cars have batteries that have quite a punch. The one I have is a Sanyo 6-cell 7.2 v 3000mA NiMh rechargable battery. I've super heated a paperclip by shorting it out once. It may do untold damages to a fan.

This makes me suspect your understanding of Ohms law basics. Just because a battery can delivery 3000mA through a paperclip short doesn't mean that it will overload or damage your fan. The load determines how much actual current will be drawn from any voltage source.

12v computer fans typically draw 100-150 milliamps @12 vdc. You will get the same performance from it with 8-1.5v AA batteries in series as you will with one 500Ah 12v deep cycle marine battery while spinning the same fan. The difference is the deep cycle battery could drive hundreds of computer fans at one time...the AAs would start struggling at somewhere between 5-10 fans in parallel.

RC batteries are the bomb for spud gun use if you can afford them. They are rechargable and last a long time per charge while just running computer fans.

BigGrib wrote: if you really wanted to you could hook up 4 batteries each pair in parallel and then in series so you get the double amps and double voltage that might do some damage to the motor though

Hey BigGrib, See above....