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Old 18-03-2016, 14:29   #31
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Re: Alternator cooling

Ah....the problem with Alternators and LiFePO4 batteries.
The marketing and sales hype for a long time in the alternator world was to show a Cold and Hot output curves and then tout how your dual fan cooling and design got you big time amps when "hot". Sales were made...people were happy.

Then when the client called up and said, "hey, I only see the top end output on my alternator for about 10-20 minutes before it starts tailing off...what gives".

The stock easy answer was to start rattling off the charge profile of Lead Acid Batteries and explain that it's not the alternator limiting the charge current, but it is "your battery Mr Client so what we sold you is working fine and as designed".

Folks with 400AH Lead Acid battery banks and 180A alternators with serpentine belt conversion kits were cruising around with spinning dollars that didn't really give them any Charging benefit...BUT it DID give them less chance of a alternator burn out since the alternator was never really working that hard. Which in and of itself I would argue would still be a Good Thing on a Cruising Boat.

Then come the advent of LiFePO4 batteries and that same phone call goes something like this:

"Hello, my alternator burnt out after 1.25hrs of running at 90% of it's rated output...I want a warranty Replacement" And how the game changes. Alternators are failing left and right and people are forced to come to terms with the fact that a 180A alternator is not REALLY a 180A alternator! Oh sure, it can put that out for a brief time period and that time period used to be masked by the nature of a Lead Acid battery...but now with Lithium just how long it can handle that before burning out has been revealed...and the alternator manufacturers are scrambling to deal with it.

Right now they are dealing with it by saying that the use of a temperature protection regulator that ramps down the output current is Mandatory for LiFePO4 applications...it's the only real way to protect the alternator. That in combination with a belt manager function. AND to flat out oversize the alternator from the start. The LiFePO4 battery systems I have helped with have a 160A alternator with serpentine kit and the alternators have BOTH the belt manager and temp protection using the Balmar 614 Reg. Right off the bat the 160A alt is derated down to a 100A and after an hour of use (0r 45mins) it will STILL be regulated down due to the temp issue. All the external cooling fans and engine room blowers haven't solved this issue I've found.

So YES I would go larger with a LiFePO4 bank, but then just plan on derating it...that way you are operating at the mid-range of the alternator rather than at the top end for longer periods of time.

The Solution....
Install 1300W of solar
Charge with your Generator
I say that partially joking because WAY TOO MANY people look at an alternator as a generator that can run for hours and hours at full or near top output...it just ain't so with the standard GM frame alternators, which Balmar and most everyone else uses. If you really want a Continuous duty/rated alternator...pull out the Big Bucks!
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Old 18-03-2016, 15:01   #32
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Re: Alternator cooling

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Originally Posted by a64pilot View Post
I had thought, well I'll get me one of those BIG alternators and take my 140 and put in it spares, I wouldn't mine being able to throw 200 amps at my AGM bank as it will take it.

But I came to a conclusion, the BIG 200 amp alternator is the same frame as my 140 amp, near as I can tell the same amount of metal, same cooling fan etc., then logically if it did hit 200 amps, all that would mean is that it will hit it's temp limit just that much sooner than my 140, with the total amount of current if anything being less than what my 140 will do, before it too hits it's temp limit? Net gain being zip?

Whats the logic of spending BIG $$$ buying a 200 amp alternator, then using belt manager, small engine mode or whatever you call it to limit it's output so it doesn't overheat, as opposed to spending lots less $$$ on say a 100 amp alternator and letting it operate at full output?
Does a 200 amp alternator run cooler at 100 amps than the same frame 100 amp alternator making 100 amps?
That is a most excellent question. I'll be interested to hear an informed response. I must admit that I had been thinking along the same lines as yourself. But you make a good argument that perhaps I'd be better off with a smaller 120 A alternator than the mambo 180A. With that said, I think the hairpin wound 165A AT alternator from Balmar is more efficient and so would likely net higher overall power to the batteries.
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Old 18-03-2016, 16:11   #33
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Alternator cooling

Well I called the manufacturer of my alternator, he was very open and honest, he said yep, my 180 amp alternator will in fact overheat faster and temp limit faster than my 140 amp alternator, so in fact there is no advantage to the bigger more powerful alternator.
He was surprising honest. We talked for awhile and apparently about 50% of the heat comes from the rectifier, so if you remove that from the alternator, remote mount it, you can drive the alt harder, for longer.

I knew there was a reason the alternators on Military trucks were big, huge things


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Old 18-03-2016, 16:19   #34
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Re: Alternator cooling

Quote:
Originally Posted by a64pilot View Post
We talked for awhile and apparently about 50% of the heat comes from the rectifier, so if you remove that from the alternator, remote mount it, you can drive the alt harder, for longer.
My pal cruising with an 800AH LiFePO4 bank in Mexico on a Cat with two 160A alternators just did the external rectifier upgrade in hopes of removing heat and cooling down the alternators as a way of not having his Balmar reg cut back the output due to overheating. As of now, he is VERY disappointed and hasn't seen the increase in Amps he was looking for an expecting....so....the verdict is still out on the cost effectiveness on this modification.
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Old 18-03-2016, 16:50   #35
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Re: Alternator cooling

But Rich, your telling me a little softball sized alternator won't make 200 amps, or 2800 watts, that it takes my 200 lb Diesel Generator to make?
I wanted to hear I could replace that 200 lb genset with a softball sized alternator

When you think about it, it's just not logical that something that light and small can generate that much power.
I also learned something else about the alternator cooling, seems there are two fans, one pulls from the front and exhausts out the side, the other pulls from the rear and exhausts out the side. If you want to try boosting air cooling, it's best to blow air at the rear of the alternator, not the front like I thought.


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Old 18-03-2016, 16:51   #36
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Re: Alternator cooling

Quote:
Originally Posted by SV THIRD DAY View Post
Then come the advent of LiFePO4 batteries and that same phone call goes something like this:

"Hello, my alternator burnt out after 1.25hrs of running at 90% of it's rated output...I want a warranty Replacement" And how the game changes. Alternators are failing left and right and people are forced to come to terms with the fact that a 180A alternator is not REALLY a 180A alternator! Oh sure, it can put that out for a brief time period and that time period used to be masked by the nature of a Lead Acid battery...but now with Lithium just how long it can handle that before burning out has been revealed...and the alternator manufacturers are scrambling to deal with it.

Right now they are dealing with it by saying that the use of a temperature protection regulator that ramps down the output current is Mandatory for LiFePO4 applications...it's the only real way to protect the alternator. That in combination with a belt manager function. AND to flat out oversize the alternator from the start. The LiFePO4 battery systems I have helped with have a 160A alternator with serpentine kit and the alternators have BOTH the belt manager and temp protection using the Balmar 614 Reg. Right off the bat the 160A alt is derated down to a 100A and after an hour of use (0r 45mins) it will STILL be regulated down due to the temp issue. All the external cooling fans and engine room blowers haven't solved this issue I've found.

So YES I would go larger with a LiFePO4 bank, but then just plan on derating it...that way you are operating at the mid-range of the alternator rather than at the top end for longer periods of time.

If you really want a Continuous duty/rated alternator...pull out the Big Bucks!
Bingo.. While cooling will certainly help it is not the savior..

The problem is that all these alternators are rated based on automotive test criteria not a constant duty rating. Yes when the alt is hot it may produce 195A at 6000 RPM and 90C but that is just a measurement at 90C and fails to tell us for how long.....

There is no small case alternator on the planet rated at constant duty. The only way to get even close to continuous duty with a small frame alt is to rip the diode rack out and do remote rectification and even then you may not get full output for as long as you'd think..

I run a custom built 160A alt at 115A - 120A and even then I am pushing 230F and it occasionally still dips into temp compensation above and beyond belt manager. I am currently ripping the diode rack out & converting it to external rectification.... I see if that works because I can't fit a 98 series, APS or an Electrodyne...

The reality is these alts can spin at up to 17,000 RPM and we spin them at a paltry 4 - 4.5k at best. The demand for low RPM high output characteristics has led to even more issues.

Expecting the face value rating from any alternator driving LFP is really not going to happen for very long.... A big J180 type large frame brushless alt, or an Electrodyne, or even small frame with external rectification will perform much better but still bake the crap out of a small engine space.

The C-36 is a horribly tight engine box, I owned one, that really needs both input & output fans for that type of current...
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Old 18-03-2016, 17:20   #37
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Re: Alternator cooling

I too believe there would be much to gain from overdriving these things, I believe most pulleys are set up like automotive applications and many automobile engines can easily hit 6000 RPM or higher, we need to spin them I believe at least twice as fast as we do, assuming of course a common engine RPM limit of 3600 or so.
Double the RPM and fan cooling goes way up, more than double I feel sure and requirement for field current goes down, meaning lots less heat, so you ability to remove heat goes up and the heat comes down.

But I have this expensive serpentine pulley kit and am kind of stuck with it, all I believe I could do is source a smaller alt pulley if possible and I'm not doubling speed that way.


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Old 18-03-2016, 21:44   #38
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Re: Alternator cooling

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ID:	120979Working on making a bracket to mount this to a CAT 3208. I'll let you know temps and AMPs when done. It's on a Fleming 55, but we are old sailors and going cruising soon.


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Old 18-03-2016, 23:24   #39
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Re: Alternator cooling

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Originally Posted by a64pilot View Post
But I have this expensive serpentine pulley kit and am kind of stuck with it, all I believe I could do is source a smaller alt pulley if possible and I'm not doubling speed that way.
The alternator pulley is already pretty small - I am not sure what the minimum bend radius is for the belt but I can't see gaining enough by reducing the alternator pulley diameter.
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Old 18-03-2016, 23:35   #40
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Re: Alternator cooling

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Originally Posted by Maine Sail View Post
I run a custom built 160A alt at 115A - 120A and even then I am pushing 230F
<snip>
The C-36 is a horribly tight engine box, I owned one, that really needs both input & output fans for that type of current...
Hmmm ... so my idea of de-rating a 200A alternator to 160A was obviously too optimistic ..... but it works without the cover on the engine ....
I actually believe I can do it as long as I get the fresh outside air to flow over the alternator. The fans are rather pathetic and a good flow of air should do wonders.
I am still concerned about the implications of more fresh air should there ever be a fire.

Yes, the engine compartment is pretty darn tight ! I will contemplate how to best generate a hurricane in my engine compartment!
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Old 18-03-2016, 23:41   #41
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Re: Alternator cooling

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The Solution....
Install 1300W of solar
Solar is definitively on the long term list no matter if I can get 160A out of my current setup or not. Just the redundancy factor alone calls for that addition ... but only after the US/Can currency exchange rate gets back to a more reasonable ratio.
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Old 20-03-2016, 10:16   #42
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Re: Alternator cooling

Interesting thought... My 951 uses one of these...

Porsche 944 S2 951 Turbo 968 Alternator Duct Cover | eBay
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Old 20-03-2016, 10:24   #43
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Re: Alternator cooling

Happy,
All the aircraft we manufacture have such a duct on the back of the starter / generator and connect to a scoop on the engine cowling through 3" scat hose. But they are 250 amp at 28VDC too and weigh maybe 50 lbs.

I think blowing cool air into the back of mine will help, but do not think it will produce 140 amps without overheating, actually highest I've seen was 110 and even speeding up the RPM didn't give more, it is seemingly a 110 amp alternator, with maybe a 40% duty cycle?


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Old 20-03-2016, 10:37   #44
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Re: Alternator cooling

Back in about 1980 I was a contract welder in the oilfield building oil rigs. I had an old one ton truck that had a Lincoln welder in it made back in the 50's I believe. Was a 200 amp welder, weighed I honestly think close to1000 lbs and took a four cylinder Franklin or Continental flat head four cylinder engine to run it.
We used to run what was called Jet rod in welding out tanks, and this rod was huge, you turned the welder wide open and went for it, burning one rod after the other. Guy working with me had a smaller Japanese truck with some kind of little Japanese welder in the back, this little thing weighed less than half what my old Lincoln did, yet made more power, it had aluminum windings, my old Lincoln copper and I think it was an alternator and my Lincoln a generator, seemed to be pure magic, I assumed newer technology was responsible.
Anyway we had been running Jet rod for maybe 20 min or so and his welder just quit, you could hear it idling, but it wouldn't speed up or strike an arc, so we climbed out of the tank, looked and the back of his little truck had aluminum all in it where the windings had literally melted.
He took it back trying to get his money back, and that is when I found out what duty cycle meant. Seemingly you could only run this thing for a few minutes, then had to let it cool for twice as long as you had run it.
The old Lincoln's on the other hand I've seen used to thaw pipes, they could run at 100% output until they ran out of gas.


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Old 20-03-2016, 11:10   #45
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Re: Alternator cooling

If there is enough space, you might try attaching aluminum cooling fins to the alternator's housing to increase surface area. Loctite makes a compound specifically to help transfer heat.
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