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Old 17-02-2020, 21:52   #1
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Charge driven cooling fan control needed.

Okay, all you lurking E.E. types...

I want to start a blower to feed fresh air to my alternator, but ONLY when my engine is running (and presumably charging). As I have other charge sources on the boat, I need the circuit to be powered by my ignition.

I’m thinking a relay that closes on ignition switch voltage feeding power to some sort of voltage driven relay to start the blower when voltage climbs above nominal.

In this way, the blower is automatic so I don’t forget it, won’t run if I have a high voltage from solar or battery charger, and also won’t run after shutting down with a high voltage on the bank. As such a blower will only draw a few amps, an acr isn’t really called for.

Does this sound reasonable, and anyone have a source for a ‘voltage switch’ or whatever you would call it?

Matt
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Old 17-02-2020, 22:42   #2
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Re: Charge driven cooling fan control needed.

Sounds complicated, many points of failure.

Why not wire it in tandem with the engine blower?
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Old 17-02-2020, 23:02   #3
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Re: Charge driven cooling fan control needed.

GIlow,
First, I don’t have an engine blower (diesel), second, it’s that whole not forgetting thing - harder every year to pull off. Third, not really complicated, a couple of relays. It would be more work to run switch lines to the helm. I just need the appropriate relays.

I was thinking of running two blowers one in one out, but ducting the our would be a bear on my boat, as the engine is below the cabin sole. So I figured I’d start off with the one and see how it goes.

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Old 17-02-2020, 23:10   #4
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Re: Charge driven cooling fan control needed.

How about this passive method.


Tie into the line between the Alternator and the Batteries. Install a diode in line so that it only powers the blower when the alternator is producing power.
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Old 18-02-2020, 08:14   #5
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Re: Charge driven cooling fan control needed.

The Combiner 100 will do the job, it is designed to only charge another battery when the starting battery gets over 13 volts so if connected to a blower instead of a house battery it will provide a 75 amp source for a blower.
Since it is automatic you don't have the problem you would with a manual switch that was left on and ran your battery(ies) down.

Combiner 100s have often been used this way to restrict a frig/freezer to only running when the engine is on.
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Old 18-02-2020, 09:25   #6
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Re: Charge driven cooling fan control needed.

Every boat I have ever had, had some circuit that was only powered when the “ignition” was on, even Diesels that of course have no electric ignition. Many or most even Diesel boats have blowers for removing hot air from the engine room, and this blower comes on with the key switch.

Anyway it shouldn’t be hard to find that terminal on the back of the ignition switch that is powered when you turn on the key.
Now as an abundance of caution I believe it’s smart to use an automotive 30 amp relay to actually power that blower, that ensures your not pulling too much through the key switch.
Very easy mod to do. I would however power two blowers, one to remove hot air and one that draws cooler air from the bilge and blows on the backside of the alternator, the backside is the hottest as the diodes are there and there are two alternator fans, one in front and one in the rear, the air blows out of the middle of the alternator.
If you look there are even ducts available that will with some modification attach to the back of the alternator, some cars have cooling ducts for their alternators, Porsche does I think.

Let us know how well it works, there is often talk about t doing it, but so far as I know no one has posted any actual alternator temp drops or power increase, it’s all been theory so far

On edit, it would seem that if it were effective that one of the high power alternator manufacturers like say Balmar would either market a fan cooled alternator, or a kit, but so far as I know, none do.
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Old 18-02-2020, 09:31   #7
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Re: Charge driven cooling fan control needed.

Single relay off the ignition. You don’t want to be drawing extra power from the ign circuit. And I don’t know why you want 2 relays as you posted. I would also fuse that ign feed with a small fuse. ~2a. so if something screws up. It does not blow the main ign fuse and kill the engine.
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Old 18-02-2020, 09:41   #8
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Re: Charge driven cooling fan control needed.

You can buy 12VDC 4" muffin fans for about 12 bucks. they draw very little (less than a quarter of an amp).

Depending on your engine, you have things that have voltage applied to them when the ign switch is on. Some engines have voltage applied to the fuel shut off when running, others only when shutting down.

A few minutes with a multimeter should find a lead that is energized when the ign switch is on and no voltage when it is off. The small draw of the fan should not be a problem on one of these circuits.

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Old 18-02-2020, 09:45   #9
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Re: Charge driven cooling fan control needed.

Heavy duty automotive alternators have been cooled by engine oil in many applications. No reason to worry about air flow through the alternator with oil cooling. If interested, look at TRANSIT bus alternator applications but be prepared to find a high price.
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Old 18-02-2020, 13:14   #10
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Re: Charge driven cooling fan control needed.

in thinking about it, I believe a voltage-tripped relay wouldn't work out, as if the bank is down, the relay wouldn't trip, yet the alt. would be working hard.

So, I think single, on when key is on, relay will have to do

I typically use a bosch-type waterproof relay like this:

https://www.amazon.com/HELLA-H847090.../dp/B000VU9D0C

https://www.amazon.com/HELLA-0077943...ED213DQ4GRMGXS


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Old 18-02-2020, 13:33   #11
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Re: Charge driven cooling fan control needed.

Put a temperature sensor on the alternator ground terminal. Balmar already has this but they use it to limit output if alternator gets too hot. You would need to find such a lug-mounted sensor and an adjustable 12V thermostat to connect it to. Thermostat will control a relay to connect blower to ignition circuit.

Search hobby sites for those parts. Sounds like a fun project.
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Old 18-02-2020, 14:09   #12
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Re: Charge driven cooling fan control needed.

Clamp a high limit thermostat to the side of the alternator and use it to turn the cooling fan on and off. This one is on at 125F and off at 105F, but there are others if that range does not suit.

https://smile.amazon.com/Vicool-Ther...2059794&sr=8-2

or for more... https://www.alliedelec.com/sensors/thermostats/

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Old 18-02-2020, 15:06   #13
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Re: Charge driven cooling fan control needed.

No engine room blower sounds like a bad idea to me.

Is it REALLY that well naturally ventilated? If so, I canít see the alternator needing extra cooling.
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Old 18-02-2020, 17:12   #14
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Re: Charge driven cooling fan control needed.

If it is externally regulated alternator, I would use the Field wire from regulator to trigger a relay to feed a high power brushless computer fan.

Some Delta fans have the focusing steering vanes on the hub support, and instead of air exiting them at wide angles in 4 hotspots of flow, there is a dense speedy narrow column of air which stays compact and dense several feet away. Its really impressive. Aimed precisely there I no need for a shroud with such fans. Most options in the 120Mm x 38mm size format.

The Delta FFB1212EHE is rated at 3 amps, but that is start up surge, it is about 1.8 amps at 12.8v and rated at 190 cfm, and a very high static pressure rating for that cfm.

It is my current favorite 120mm fan and I have tried many. At 14.7v it is equal to the 252 cfm version(Delta TFC1212DE) at 12.7v, which does not respond nicely to voltage as speed control, shutting off at 7v while still consuming close to 2 amps and being incredibly loud and powerful.

I just got some 140mm Delta fans, the 24v version 51mm thick, is a beast among beasts. @ 26v it sucks up about 50 watts, and it slows perfectly to a silent crawl and consumes about 0.15 amps at 4.4 volts through the bucker. New favorite!

These 12v Delta fans are LOUD when Fed 12 to 14.7 volts but most can be tamed nicely via voltage. I use XL4005 or XL4015 based 5 amp voltage buckers with great success as speed control, the 4005 drops 0.27v across it the 4015 drops 0.18v. You can dial in a desired airflow/noise level/amp draw via them. Some of these come with current limiting pots too. I've not had good luck with these, longevity wise, and recommend against them.

Not much use for lowering the speed of these high rpm Delta fans in alternator cooling duty I guess. I do recommend covering the wire entry into the hub with some dielectric grease or similar and spraying the circuit board with Deoxit shield s5 spray with the red hose getting inside the guts. I've not had one of the Delta fans fail from corrosion, but almost all fan failures of other brands have been caused by it.

Spinning a 11 blade external fan alternator at ~2500 rpm for truing the slip rings, I was amazed at just how little air the fan moved radially. Its a tiny fraction of these computer fans. One of these high power delta computer fans forcing all its flow through a shroud into the back of the alternator, would be 10x more effective than the external fan, in my opinion

A lot of the Deltas are PWM 4 wire fans. I have successfully controlled a few of them via the PWM 4th wire, but they use more juice than using a voltage bucker as speed control at maximum and minimum speeds, so I just use Buckers, or in the case of some 24v fans, buck/boost converters.
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Old 18-02-2020, 18:59   #15
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Re: Charge driven cooling fan control needed.

The easy way is to wire a relay to turn the fan on. Hook the plus of the relay to a fuse to plus and the ground of the relay to the oil switch. Only is grounded when the engine is running.
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