Author Topic: 48V alternator (ICE driven)  (Read 14199 times)

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madlabs

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48V alternator (ICE driven)
« on: December 23, 2014, 10:27:55 PM »
Hi All,

I want to build another small engine/alternator charger. Problem is that I am now on 48V I can't find any alternators for less than a kilobuck. It's gotten to the point where having a 12V alt rewound or having my buddy in Shanghai see what he can find for me. Any leads or suggestions? I'll be building the controller for it, all I need is the basic alt.

Thanks!

Jonathan

dnix71

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Re: 48V alternator (ICE driven)
« Reply #1 on: December 24, 2014, 08:11:54 AM »
There are 48v AirX's. Maybe pick up a used one and mount it. They have a pretty good front sealed bearing.

madlabs

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Re: 48V alternator (ICE driven)
« Reply #2 on: December 24, 2014, 08:45:43 AM »
Dnix,

Too small and no field coil for control. I'm looking to pull 3kW or so from the unit, or around 60 amps. So I'd like to find something capable of around 100 amps so as to have some overhead.

Thanks!

Jonathan

wpowokal

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Re: 48V alternator (ICE driven)
« Reply #3 on: December 24, 2014, 11:47:14 AM »
You could build a Hugh Piggot design, they don't have to be wind driven, but you will need a regulator.

I have a Mecc Alte 110v alternator 55-0-55 long coupled to a small Lister, I rectify the AC output for my 48v bank, control is Allanmatic but a regulator could be used. I only use one of the 55v windings as my little Lister can do 1.75 Kw (it's a little tired).[img]http:/


They are sold under many labels.

Allan
A gentleman is man who can disagree without being disagreeable.

madlabs

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Re: 48V alternator (ICE driven)
« Reply #4 on: December 24, 2014, 02:52:32 PM »
Hmm, now that's an idea. I'd have to look into controllers. I'm guessing that they are more complicated than controlling an alternator - pwm'ing a field coil is just so easy.

I'll go take a look into that right now, thanks for the suggestion.

JOnathan

Mary B

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Re: 48V alternator (ICE driven)
« Reply #5 on: December 24, 2014, 03:21:47 PM »
24 volt 100 amp automotive style alternators are readily available on Amazon etc. run a pair in series?

dnix71

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Re: 48V alternator (ICE driven)
« Reply #6 on: December 24, 2014, 04:27:38 PM »
Some John Deere alternators are 48v, but even used they aren't cheap. $2k new.
http://www.ebay.com/itm/John-Deere-TCA21706-TCA17247-48v-Alternator-8000-E-Cut-Reel-Mower-Generator-/291277057596
$900 on eBay used.

48v alternators are normally telecom equipment in the US.

http://www.ebay.com/itm/ALPHAGEN-DCX3000-36-48V-DC-GENERATOR-NEW-WITH-ACCESSORIES-041-028-10-/321611424684
New, complete 36-48v genset including the engine for $1100 shipped.

madlabs

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Re: 48V alternator (ICE driven)
« Reply #7 on: December 26, 2014, 10:53:28 AM »
That Deer alt looks great. Spendy though. I like the look of that genny too, it is exactly what I am intending to build, right down to the choice of motor. Very tempting, I know it will cost me more than that to build one. Of course, building it is fun, but then goodness knows I have enough to keep mt busy anyway....

Many thanks!

JOnathan


PaulJ

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Re: 48V alternator (ICE driven)
« Reply #8 on: December 27, 2014, 05:27:01 PM »
A 12V externally regulated alternator works fine at 48V if you spin it fast enough, make sure the internal diodes are rated at 100V though.

I use an old Ford 12V 55A alternator geared up about 3.5:1 on a 16 hp motor, energise the field off a separate 12V battery.
The dump load on the rest of the system takes care of regulation in my case, wasteful I know but I only use the generator infrequently in winter for bulk charging.

Paul.

madlabs

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Re: 48V alternator (ICE driven)
« Reply #9 on: December 27, 2014, 10:28:38 PM »
Paul,

Hmm. So you are charging a 48V bank that way?Any way to calculate how many RPM's an alt needs to reach 57.6 volts? I seem to recall the LN-555 alt I have says max 7k rpm.

Jonathan

dbcollen

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Re: 48V alternator (ICE driven)
« Reply #10 on: December 28, 2014, 08:59:42 AM »
you don't even need to spin it really fast for 48v, you can get a few hundred volts out of most alternators if you need to. It is mostly controlled by the regulator in the alternator. You can build a regulator for any voltage.

madlabs

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Re: 48V alternator (ICE driven)
« Reply #11 on: December 28, 2014, 09:55:00 AM »
At what kind of current? The controller is no prob. Can you drive the field coil with more than 12V?

I'm guessing the efficiency of the alt goes down, I'm sure there is a reason the do make 48V alts. Still, might be a good compromise for me.

Jonathan

dbcollen

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Re: 48V alternator (ICE driven)
« Reply #12 on: December 28, 2014, 10:50:27 AM »
You could theoretically get rated amps out of the alt, in real life they only provide rated current for a few minutes before they heat up. micro hydro has been using delco 10si and 12si and large frame motorcraft alts for years in 12,24 and 48v for many years, They commonly use a rheostat to control the field. You could build a pwm field controller  for any volts you want, but remember those alts are lucky to be 50% efficient and take lots of power to drive. 50a @ 50v is 2500w and would take 7+ Hp to drive. The large frame motorcraft alts in the 70-100a range for a 70s full size ford or Lincoln are good choices and still fairly cheap and available and externally regulated. The claw rotor can take more than 12v, but the pwm duty cycle could easily be limited to 25% duty and the rotor would "see" 12v, and probably be more field than you need.
« Last Edit: December 28, 2014, 10:54:35 AM by dbcollen »

madlabs

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Re: 48V alternator (ICE driven)
« Reply #13 on: December 28, 2014, 01:55:11 PM »
I have a Leece-Neville 555 that I have run at max current (160 amps, 12V) for hours on end. It did have some decent extra cooling and I was running it pretty fast (forget RPM) which helps cool it too.

I also have a 250 amp /12V Leece alt that I have never used. Thing is a beast. I wish there was an easy lash up to see if I could charge my 48V bank with it. Might have to poke around about that.

Jonathan

joestue

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Re: 48V alternator (ICE driven)
« Reply #14 on: December 28, 2014, 03:06:18 PM »
all of the larger alternators i've torn apart are delta, at a minimum they can be rewired for wye which is a near doubling of voltage.

madlabs

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Re: 48V alternator (ICE driven)
« Reply #15 on: December 28, 2014, 04:13:20 PM »
Joe, I'll pull mine apart at the end of the week and see what I have. Good to know, thanks.

JOnathan

dbcollen

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Re: 48V alternator (ICE driven)
« Reply #16 on: December 28, 2014, 07:14:54 PM »
 you will not need to reconnect the stator, it will easily make 48v as is, try it and see.

PaulJ

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Re: 48V alternator (ICE driven)
« Reply #17 on: December 28, 2014, 08:23:53 PM »
"Paul,

Hmm. So you are charging a 48V bank that way?Any way to calculate how many RPM's an alt needs to reach 57.6 volts? I seem to recall the LN-555 alt I have says max 7k rpm.

Jonathan"

Yes, charging a 48V bank.

The 16 hp motor is overkill, but was the cheapest I could get with electric start to make it user-friendly for the rest of the family.
At idle with 12V on the alternator field coil it puts out ~10A into 50+ volts, 1500 - 1800 rpm (at a guess)  gives 30-40A, so 5000-6000 rpm or so at the alternator.
It's a longish and barely adequate wire run to the batteries so the alternator is running at 65-70V at these currents.
At 40A the alternator gets pretty hot and the efficiency must be dropping off so that's as far as I push it.

If you run the alternator side by side with the motor it will be running backwards, you'll need to reverse the fan somehow or it will fry.
I bent mine (carefully) with a couple of pairs of vise-grips so it worked backwards.

Paul.

madlabs

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Re: 48V alternator (ICE driven)
« Reply #18 on: December 29, 2014, 10:19:16 AM »
Paul,

Thanks for the information. Someone actually doing it is the best sort of comfort before trying it. I think I have a backwards fan for my smaller alt. I'd have to get one for my big alt. Both are cast aluminum so no bending. I have beaten an old GM alt to run backwards, worked fine.

Thanks!

Jonathan

Flux

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Re: 48V alternator (ICE driven)
« Reply #19 on: December 29, 2014, 12:46:49 PM »
A typical 12v alternator cuts in about 1000 rpm so it will make 48v at 4000. Drive it at about 5 to 6 000 and it will work fine on 48v.

I would use an external rectifier but in reality it is most likely the modern diode packs are good enough for 48v, some old ones may not be up to it.

I wouldn't push the field much beyond 15v it will saturate the claws anyway so you gain nothing. It will be much more efficient, for the same power out the current out will be 1/4 so the stator loss will be 1/16 of the 12v case.

Probably a nice big 24v model from a truck would be even better but a 12v one will do,

The fan will not need to do much at 48v so running the fan backwards would be possible if you have to do that.

Flux

madlabs

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Re: 48V alternator (ICE driven)
« Reply #20 on: December 29, 2014, 08:08:15 PM »
Flux,

So if I heard you, the alt won't get as hot because the amps will be lower. That sounds good. As describded above, I have a very large 12V alt I'd like to try. It has also been suggested to rewire it from wye to delta. What do you think of that.

I can replace the diodes pack with externals, no big deal. I can also limit the field coil to 15V. Are you saying the alt will be more efficient being driven at higher rpm and voltage? If so, is the sole reason they make 48V alts is to make the cut in speed lower?

Thanks for the help!!

Jonathan

phil b

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Re: 48V alternator (ICE driven)
« Reply #21 on: December 29, 2014, 08:35:14 PM »
One thing to keep on the back burner is you can buy a 120 or 240 split phase gasoline 3500 watt generator at the home renovation stores for $500 or less. Just in the case you get in a pinch...
Phil

Flux

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Re: 48V alternator (ICE driven)
« Reply #22 on: December 30, 2014, 03:04:34 AM »
On a vehicle the winding is chosen to supply normal required power at minimum engine speed. At high speeds the field voltage is reduced to a low value. If you are prepared to keep the speed up and keep a high field you can get a lot of power at 48v.

If it is delta connected you will reduce the speed needed considerably by wye connecting it. If it is wye connected now, don't try delta, the speed will be too high.

Early alternators were wye connected but with the modern output requirements the wire becomes too thick for convenience so many are now delta connected.

Going from delta to wye gives you a 170% increase in volts for the same speed so it virtually becomes a 24v alternator.

Flux

madlabs

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Re: 48V alternator (ICE driven)
« Reply #23 on: December 30, 2014, 11:16:26 AM »
Flux,

Good stuff. At work for a 72 hour shift but will dig into my alts when I get back. I'm sure I'll have more questions.

Thanks, looks like I can do this without selling a kidney for a 48v alt!

Jonathan

waitatian

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Re: 48V alternator (ICE driven)
« Reply #24 on: January 03, 2015, 02:20:55 AM »
I am using a 4WD 24v alternator directly connected to a 3.5 hp Honda motor for 48v. The field is driven from the output through a resistor. The output voltage/current is changed by varying the RPM of the motor. It can generate about 1kw.

madlabs

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Re: 48V alternator (ICE driven)
« Reply #25 on: January 04, 2015, 08:53:42 AM »
Wait, are you using a lovejoy or similar? Or is it belted? Should be able to squeeze a little more than a kW out of it.

Jonathan