Battery amperage reduction

[jdavidrich]

I bought an evaporative cooler to cool the interior of my Cessna. It uses a 4 amp fuse. I tried various batteries to power the cooler (the plane does not have a 12V cigarette lighter outlet) but keep blowing the fuse. My current battery is likely far to big but it will last long enough for a several hour flight: Lawn and Garden battery with 275 cranking amps and 230 cold cranking amps. I am an electronic novice but need to find out whether there is a simple way (required for me!) to reduce the battery's output amperage and stop blowing out this fuse. I attach the cooler via alligator clips directly to the battery terminals. Any help anyone can provide will be greatly appreciated. Thanks.

 

[Reloadron]

Your problem isn't the battery. If the unit is fused at 4 amps and it blows a 4 amp fuse the problem is the unit. When we place a load on a battery the battery will only provide the current demanded by the load, assuming it can. Your aircraft battery can deliver enough power to start the aircraft so it can deliver plenty of power. Power well exceeding what your avionics and lamps draw. If this unit is blowing 4 amp fuses it is drawing current in excess of 4 amps.

Ron

 

[jdavidrich]

The battery I'm using isn't the aircraft battery (the Cessna does not have a cigarette lighter/12V outlet) but a lawn and garden battery purchased separately (275 cranking amps) and alligator clipped to the cooler. Based on your answer the question then becomes what can I do to prevent the cooler from drawing current in excess of 4 amps. Thanks for your patience.

 

[squishy36]

I'm curious: outside the airplane, you've got more moving air at a higher velocity than your cooler. Why not use that instead of fooling around with the extra weight of a battery? Besides, don't you take advantage of the normal adiabatic lapse rate when you're flying? I know I did when I took some flying lessons 40+ years ago and it was over 100 deg F on the tarmac.

 

[jdavidrich]

I'm in Arizona and the temperature outside around PHX is approximately 110F+ in the summer; the Cessna (older, 1979) has only two top air vents and two side vents. Until I get up to 7500 feet (which I don't do around town) it's hottern'ell. I only need the cooler in the summer.

 

[Reloadron]

The battery I'm using isn't the aircraft battery (the Cessna does not have a cigarette lighter/12V outlet) but a lawn and garden battery purchased separately (275 cranking amps) and alligator clipped to the cooler. Based on your answer the question then becomes what can I do to prevent the cooler from drawing current in excess of 4 amps. Thanks for your patience.

I understand you are not using the aircraft battery. Here is the point I was making. If I take a device, any device, that is designed to work off of 12 volts that device will have a rated current it draws to work. This could be as simple as a 12 volt 24 watt lamp. A 12 volt 24 watt lamp would draw about 2 amps. Matters not how much current the battery can supply, the lamp will draw 2 amps. So let's say I have a cooler rated at 12 volts that draws 3 amps. So I fuse it at 4 amps. Now when I connect that cooler to my battery the fuse blows. The reason the fuse blew is not because of the battery but my cooler that should only draw 3 amps obviously exceeded the three amps as it blew a 4 amp fuse. The device has a problem. If I try to limit the current it won't matter. If I limit the current to my 24 watt lamp that needs 2 amps to 1 amp the lamp will not deliver its intended light.

If the cooler is designed and rated to use a 4 amp fuse and it continuously blows that fuse there is a problem with the cooler. I assume the fuse is the one suggested for use with the cooler?

Like squishy, I have many fond memories of a Cessna. We have a few active pilots in the forum.

Ron

 

[carbonzit]

Don't know where you got the cooler, but it's possible someone put the wrong size fuse in it. Is there a nameplate on it that gives the current rating (how much current it's supposed to draw in amps)?

 

[crutschow]

I'm in Arizona and the temperature outside around PHX is approximately 110F+ in the summer; the Cessna (older, 1979) has only two top air vents and two side vents. Until I get up to 7500 feet (which I don't do around town) it's hottern'ell. I only need the cooler in the summer.

Would the air from the vents have enough pressure and volume to force the air through the cooler with out a fan? If so, then you wouldn't need the fan, or the weigh and hazard of an additional battery.

 

[jdavidrich]

I'll check the documentation on the cooler and see what the cooler is rated; it came with a 4 amp fuse so I've assume that's correct. I will try a 7.5 amp fuse. Actually most of the current is used to power a bilge pump that circulates water through the cooler (evaporative) and the fan is a minor component. Thank you all for your suggestions; now I must do my homework.

 

[carbonzit]

Don't use a 7-1/2 amp fuse until you know how much current it's supposed to draw! What if it really is rated at 4 amps?

 

[ronsimpson]

In about 1930 Grand dad attached a box to his car window. The movement of the car forced air through the box and into the car. In the box was cloth and water. The cloth was wet from the water. Later he added a windshield washer pump to help keep the cloth wet. (evaporative cooler)

 

[jdavidrich]

Thanks on the 7.5 fuse; I'll proceed cautiously

 

[ronv]

Just to make sure...... This is a 12 volt cooler?

 

[kinarfi]

Just to make sure...... This is a 12 volt cooler?

ls this a 12 volt airplane or is it a 12 volt cooler in a 24 volt plane?
or did I read that the cooler is powered by separate battery?

 

[jdavidrich]

Yes, it's a 12V cooler and the battery is also 12V DC (275 cranking amps). The plane is 24V but no outlet so have the auxiliary battery. I'll check the documentation Saturday when I next fly. Thanks for all the help.