Simple voltage limiter

[landyacht318]

I recently added a 180MM computer muffin fan to my intake window.

The fan, a silverstone FM181 which employs a variable speed 10k ohm potentiometer, has an operating voltage from 5v to 13.2v.

http://silverstonetek.com/product.php?pid=344&area=en

Well yesterday afternoon, I finally got it mounted, and I ran it all night very happy with its performance and effectiveness and no issues, but now that the sun is up and it is receiving voltages well over 13.2, the hub motor is getting extremely hot.

I have other fans which have sub 15v ranges that do not get hot, nor seem to have reduced lifespans, which is why I decided to employ this fan for this task outside its design parameters.

So what are my options to restrict charging voltages fed to this fan, yet not also handicap is maximum output when the sun is down, if possible. When I most need this fan, in summer, I have a solar surplus, so I am not too concerned about wasting electricity, I'd just prefer to allow it to goto full speed at night when no charging voltages are present.

I've gone to considerable effort to make a tight fitting 3 fan shroud for this fan( and 2 120mm fans) for maximum positive air displacement, so just going back to 3 noisier 120mm fans is not an option I wish to pursue. Unfortunately the few other 180mm fans available do not have a very high cfm rating, and that was a major consideration when acquiring this particular fan. It also is the biggest fan which can fit in my window without being restricted.

It also moves a good amount of air silently for only 0.05 amps on the lowest speed, which is one reason I wanted it.

If I lower the max speed then the hub cools down but is still pretty warm.

The 2 other fans share the same power source and fuse. I can add something inline like a diode or 2 to drop the voltage, but prefer something non bulky or just plain wasteful, if such an option exists.

[NinerBikes]

tvman44 wrote:
If you are saying your battery voltage while charging gets up to 15.3
volts, that is too high for the battery. 😞

It is the correct voltage for his battery, according to the manufacturer.

[RoyB]

My duty portable fans are a couple of the 10-inch O2COOL that works on 120VAC, 12VDC, and D-CELL batteries. (WALMART-LOWES)

They do great for us...



Roy Ken

[landyacht318]

Yeah I saw those smaller cheaper versions. I have Amazon prime, ordered it Saturday, arrived monday afternoon, that was worth a couple extra dollars to me.

Kind of like the display.

Been running it for 24 hours now, rarely at top speed though.

I got a mostly unhelpful, yet prompt, response from silverstone about the heat generated at the hub. Chingrish.

Says it will last 20 month and that computer power supply is 12 volt.

[DSchmidt_2000]

landyacht318 wrote:
The Drok LM2596 Voltage Regulator Experimental Power Buck Converter+LED Voltmeter arrived today.

I hooked it up and when fed 12.2 volts, the max it can put out is 11.3 volts.

Sounds like its a winner. Keep using it. It stays cool due to it being a switching regulator - much more efficient than the linear ones as it's a 'power' converter and not just dumping off the excess voltage as heat.

BTW, 12V at 1A is 12W of power. That motor may have always run hot.

Also BTW, they make smaller versions of what you want for cheaper in that they also come without a display.

[landyacht318]

OP here. I appreciate all the responses and info, and encourage thread drift within this topic.

I wish there were more than just a few 180mm fans available. This one is the highest CFM Fan, and is also variable speed. I purchased it some time ago, before I acquired 10 amp PWM motor speed controllers. This is the biggest fan I can use in my intended window. I have made an acrylic shroud with a 180mm cutout. I wish I had tested it longer when I first acquired it, as I might not have kept it nor employed it, nor made a shroud designed around it. But I didn't and I did. Done and done. Moving on....

The Drok LM2596 Voltage Regulator Experimental Power Buck Converter+LED Voltmeter arrived today.

I hooked it up and when fed 12.2 volts, the max it can put out is 11.3 volts. That is with the fan at full speed. At lesser speeds on the Silverstone Potentiometer, the difference (headroom?) is less.

My Sears 82369 clamp on meter ( clamped after the Drok), says it draws 1 amp at full speed.
I fear the fan itself is a dud, as the hub motor is still getting quite warm even when fed sub 13.2 volts, warmer than I remember from a few days ago when I first put it into service and voltages were in the mid to low 12's at the battery and 0.05 less at the fan.


When I switch all my loads from the ~12.2v battery to the 13.0 volt battery, the max output voltage of the Drok unit also rises, so I will need to dial it in when I have 15.3v available.

The Little toggle button toggles between input and output voltages. There is a green light for the output voltage screen and a red light for the input voltage. Both voltages can be calibrated in +/- 0.5 volts, and I did so to match my Sears clamp on Ammeter.

The voltage adjustment screw is a very small slot and changes voltage slowly, about 1.2 volts in a full 360 degree turn.

I am noticing the Drok unit gets barely warm when fed 12.2v and allowing 7.1 out.

When I switch batteries from the ~12.2 to the 13.06 one, the 7.1 volt output remains.

One can turn off the voltage display by holding down the toggle button for 2 seconds, but the input red light stays on.

It came with no instructions. It was wrapped well and came with a business card advertising www.wonmeter.com

It appears this unit will work to keep excessive voltages from reaching the fan.

Whether the fan will live a long happy life is another matter.

I linked the wrong model fan in the original post. I'll go back and change it to the AP 182.

The AP182 has a rated voltage of 12v, not the 5 to 13.2v that I stated in the original post.

[ken_white]

I haven't had any issues yet when my charging system has went into equalizing mode...

[Bend]

Not my '98. Its good to ~20v. A buddy in a 2011 Artic Fox TT is really choking down his charging volts because of his 12v water heater control board.

Most newer Suburban water heaters top out at an operating voltage of 13.5. Long, skinny wires may be saving many. Many fridge 12v control boards top out in the low 15’s. Inverters are a whole ‘nother animal considering the amperage.

http://hometips.me/Mar/Suburban_Water_Heater_Service_Manual.pdf

[ken_white]

Bend wrote:
Ken-

Still trying to solve the overvoltage problem bwtn optimally charging flooded batts while running volt limited (12-14v) RV appliances without isolating the batts. Device can be per appliance (low amps) or prior to the DC distro panel (20+ amps). Mex knows of the problem but I wish he would use english instead of EE. 8>)

Mex-

Whatever the end product, I’ll buy it.

What DCV devices in our camper do we have that are that sensitive to 15-16 VDC?

I haven't verified all of the 12 VDC circuits in my camper, but my guess is the senstive electronics have regulated voltage supplies on the PCB's and the relays/switches/fans/etc... can all handle the slightly elevated supply voltages.

Can anyone give a manufactures example of the 16 VDC exceeding supply requirements?

A simple relay and overvoltage circuit can open the DC path from the battery if needed...

[Bend]

Ken-

Still trying to solve the overvoltage problem bwtn optimally charging flooded batts while running volt limited (12-14v) RV appliances without isolating the batts. Device can be per appliance (low amps) or prior to the DC distro panel (20+ amps). Mex knows of the problem but I wish he would use english instead of EE. 8>)

Mex-

Whatever the end product, I’ll buy it.

[MEXICOWANDERER]

Use SHOTTKY power rectifiers to ISOLATE IC's that don't like to work in parallel. Like regulators, power supplies etc. I got a 400 amp 60 volt shottky bar on eBay for fifteen dollars. .17 volt drop across the junction at 30 amps.

[MEXICOWANDERER]

This is what all my earlier uproars are all about with regard to MOSFETS, opto couplers, free-wheeling diodes, yadda achooo...

In the works is a massive Orient order for PC boards, heat sinks, MOSFETS, precision resistors, Opto Couplers, terminal strips, etc. Next comes the small project boxes. Someone is asleep at the switch with regard to RELAYS.

But the adjustable BUCK regulators sold on eBay are easy to use (you set the voltage out in the open BEFORE you mount the critter).

Mount the buck regulator SOMEWHERE where it will fit then adjust the length of the 12 volt wires or output wires to fit.

Remember, these critters need two volts of breathing room. 10.00 volts needs a minimum of 12 volts input. Anything closer (above 10 volts) can be adjusted ,7 volt a whack with series rectifiers. I found 10 amp 1000 volt silicon rectifiers on eBay cheap. They work fine paralleled.

[ken_white]

Bend, I am not sure how those 2 switching power supplies will play with each other when cascaded. They might work fine, or there might be some serious stability issues during various loads.

What are you trying to regulate (voltage and current) or protect from an overvoltage condition?

[Bend]

Mex-

Seems the 7809 is limited to 1-1.5 amps. Got an idea for up to 12 amps that does not have a headspace problem for a different appliance?

[MEXICOWANDERER]

A 7809 regulator is about the easiest way to go. Dirt cheap. Mount it with ADHESIVE thermal compound to a metal surface. Good for 30 volts input. At nine volts this fan should be comfortable. A two dollar investment.