Making a 60v alternator

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
Hello, I am a new member.

I have a project that I am working on, not to make money , but just because I like work around projects. I could just go buy something but what is the fun in that.

I have a 60v motor that I drive a 26' sailboat with. 5 12v batteries in series. I have 5 solar panels each with a controller each connected to a battery. So I have charge to the batteries to keep them full. But on a day when I use the motor more than I should I need a way to put a bulk charge into them. So I found a truck alternator with an external regulator, well it actually has a box that you just put 12v to and go full field. I have had it up to 90v. Now comes the problem, I was going to just run it to 72 volts with the rpm's and regulate it like that. Then I thought maybe I could find a regulator. I found a regulator that would work, then they said the alternator may not work, so I called around and found I need a much more expensive 60v alternator. I am using a 10 hp diesel engine. I could go to a 15 hp. I would like to get 50 amps at 60/72 volts. Can I just rewind my alternator with smaller wire? Can I just use it the way it is? I planned on using an external rectifier with 10 amp 200 PIV diodes. Where am I going wrong??

Thanks for any help, Dan
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
A LM311 regulator could be set up the limit the alternator to 60/70v+ volts etc.
I controlled a 240v DC generator field this way.
Max.
 

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
A LM311 regulator could be set up the limit the alternator to 60/70v+ volts etc.
I controlled a 240v DC generator field this way.
Max.
Thank you for the response, I have a regulator that will also do the job, but then an alternator shop told me the alternator would not handle it. I am not an engineer so I need some guidance on whether a regular although heavy duty alternator can handle 72 volts @ 50 amps. I believe the alternator is 140 amps @ 12 volts. I am thinking @ 60 volts the amps would be 35 but that is just a guess on my part.

I will look into the LN311.

Dan
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
140amps at 12v is 1680 watts, so the equivalent at 72v would be 24amps.
It's LM311.
Max.
 

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
140amps at 12v is 1680 watts, so the equivalent at 72v would be 24amps.
It's LM311.
Max.
That's only half of what I need. I really need at least 50 amps. I am hoping I can rewind the alternator or go with a PMA I know they make them in 48 volts. I have to try and understand the technology of an alternator 12v vs 60v to get this to work. I need 3000 watts if my math is correct. 50 amps @ 60 volts. That gets me to around 4 hp ICE 3000 watts = 4 hp. So I think it can be done. If I start with a 10 hp diesel ICE and an alternator that can produce 50 amps at 60 volts. Unless my math is wrong it is possible.
 

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
The other thing I thought about was using a genset head off of a 4000 watt generator, but I am not sure how that would charge a DC battery.
 

cork_ie

Joined Oct 8, 2011
428
On any alternator the output voltage will be determined by the speed of the alternator, the number of turns on the stator and the strength of the rotor field.
In almost all automotive the output voltage is controlled by varying the strength of the rotor field via a voltage regulator.

Important considerations are: 1) Cut-in speed - while it is theoretically possible to get your alternator to charge at 90V you don't want your engine screaming like a jet engine to get there . For any kind of reasonable cut-in speed you will need to rewind the stator with lighter wires and more turns.
2) Thermal - all alternators generate heat when charging and need to dissipate that heat. Most are equipped with fans either internal or external attached to the rotor shaft. Very few machines in extreme conditions like mining and handling dusty animal feed , use sealed finned alternators that are derated and a much larger size.
3) Voltage control - To charge 5 12 Volt Lead acid batteries you will need to output ~ 72V, 60V is just the nominal voltage. You will have the added complication that the rotor was originally wound for a 12V system and you will need to limit the rotor current by either rewinding it or reducing the duty cycle.
) The Voltage regulator. - Rotor fields by their nature are highly inductive with high kickback voltages , even on 12V systems. Normally voltage control is achieved by varying the PWM duty cycle of the rotor current. Most voltage regulators are sealed and difficult to modify.
However there was one - The LUCAS CAV 440 that had an accessible PCB with discreet components and was easily repaired. They were available in 12V& 24 V versions and fitted to eveything from Rolls Royce cars to military vehicles and everyday trucks & buses. I know they were easy to modify to 48V by replacing the zener diode and uprating other components to 60V or greater. I see no reason why the same could not be done to achieve your 72V. They are still widely available in several aftermarket versions and at very reasonable cost. The schematic is widely available online. They also have the added advantage of having external battery sensing with three external connections for High med or Low in the charging voltage range.
All in all I have no doubt that you know what you are at , but I thought I would point out what you need to do a lot of research before deciding what to do. I hoe the info I have given you is useful.
 
  • Like
Reactions: xox

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
Thank you for that response. I understand the 72 volts. I am only charging these batteries to 80% between 50% and 80%. This is when the batteries can take the most current. I will have temp sensors on the batteries and the alternator. I am regulating the voltage one of two ways. First I was going to just do it manually. and run the engine at a set speed watching the voltage. Then I found a company that has a stand alone regulator that I can program that will work with 60 volts. I also am going to use an external rectifier diode set. Set up for 72 volts and 150 amps. I am going to look at the Lucas CAV 440. I did find out just by looking at alternators on the web that I have a Leece Neville alternator most likely came off of a construction equipment. I am going back to the alternator shop tomorrow and find out what it actually is. I've already had the alternator on thier test bed and it turns 60v with ease as far as speed goes. I also had it on a 5.5 ICE with a belt and I also got it to turn 74 volts. I am more concerned with the amp output. Hopefully I can get a rewound or just rewind mine to get more amps at 60 volts. This is not just a little car alternator it is a big alternator with an external regulator. So from your information I will need a rewound rotor and stator.
 

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
OK talked to the Alternator shop, it is a Leece Neville 12 volt 180 amp alternator. He still told me it will work @ 60 volts Amps to be determined. I am going to hook it up to an ICE and put a load on it and find out before I get a regulator. I also found at the shop a Delco 24 volt 140 amp that should get me my 50 amps at 60 volts so I have options. That alternator is easier to hook an external Rectifier to as it has pass through points. I think I am on the correct track. I guess I just have to try it out rather than listen to the online alternator shops that want to sell me a $1,600.00 alternator.

Thanks for all the help, Dan
 

bwilliams60

Joined Nov 18, 2012
1,178
Hey Skipperdan,
Sorry I have been away but I think cork_ie has brought up most of the information. You would have to call a rewinder to pull the math together on the rotor and stator. The stator is going to determine your amperage output so with it being low RPM and low amperage, you may want to look into getting a wye-delta wound statot which should give you the charge curve you will need. the rotor should be straightforward.
One thing you will want to keep in mind and this is liability for everyone here, is that this is for marine use and as such, should have spark arrestors and baffles in it so that there is no incidence of explosion on-board. I believe this is a requirement for all marine units or at least it was when I was a rebuilder., gas or diesel.
As far as the regulator goes, you could look into:
https://www.genpowerusa.com/
http://www.ti.com/lit/ds/symlink/tl783.pdf
There are all kinds of options for regulator and rectifier. Large diodes and heat sinks will be necessary.
Cheers.
 

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
I believe it is for gas or propane anything other than diesel. I should be able to build in spark arrestors and baffles once I figure it all out. I am going to start with the 12v 160 amp that I have and put it under a load in the yard. If it works I can go to a 24v 140 amp and get a little more amps. If that works I could always go to 48v 100 amps. These are all alternators of of drill rigs here in ND. The shop told me I should look for a Locomotive alternator as they are almost exactly what I need. We have plenty of trains here also.
 

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
OK I am going to try a different route just to see the difference.

I want to convert an AC generator head to DC using a rectifier. I will use a 4500 or 5000 watt head at 11 hp.

I will use a big heat sink for the bridge, maybe even one from a DC welder or just build my own.

Is it going to be that hard to apply the rectifier to the head?

I will still regulate the Voltage with RPM's presumably 72 volts for a 60 volt bank.

Can I hook the rectifier to the 120 volt output or do I need to go into the head and find the 3 phase leads?

Thanks for any help, Dan
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
If the 120v is direct from the stator winding's then this is where to apply the bridge.
You could make it up from four stud mount types on aluminum plate.
You can get alternate polarity stud types for ease of mounting.
Max.
 

mvas

Joined Jun 19, 2017
538
Have you considered using a stock 12 Volt 160 Amp Alternator and connecting 5 @ 30 Amp Isolated Battery Chargers ?
160 Amp / 5 = 32 Amps each or whatever size charger the Alternator can handle without over heating
I think, a stock Alternator + 5 Chargers is a much easier solution.
Also, charging 5 @ 12 Volt batteries in series may be a challenge.
Charging each battery independently to the exact same voltage ( 14.8 Volts ? ) is a good idea.
If you put 72 volts across a string of 5 @ 12 volt batteries then what is min / max voltage across any of the 30 cells?
 
Last edited:

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
I have never heard of a Alternator battery charger. Maybe you mean 12 volt regulators. It would not make any difference as if you convert it to watts it all works out the same. A 12v 165 amp alternator will put out the same watts as the same alternator turning faster @ 60 volts.

I am not really charging the batteries per se, I am just bulk charging them so the balance is a non factor. The solar panels will charge the batteries to the correct voltage 5 panels with 5 controllers hooked to each battery.

I am having a hard time finding a 3 phase AC generating head though, I found out the cheaper heads you find are just single phase which does me no good.

Thanks Dan
 

twister007

Joined Feb 29, 2012
20
The voltage of an alternater is controlled by the voltage and current of the armature winding. You could limit the voltage of the field current so that the alternator will only put out X amount of current. This is what happens when you jump start a car. The voltage regulator limits the amount of current that is put out. It only assists the battery of the doner vehicle. Understand that a starter motor will draw 150 or more amps. All you need to do is to design a voltage regulator that will supply the correct voltage but not go over
 

twister007

Joined Feb 29, 2012
20
The voltage of an alternater is controlled by the voltage and current of the armature winding. You could limit the voltage of the field current so that the alternator will only put out X amount of current. This is what happens when you jump start a car. The voltage regulator limits the amount of current that is put out. It only assists the battery of the doner vehicle. Understand that a starter motor will draw 150 or more amps. All you need to do is to design a voltage regulator that will supply the correct voltage but not go over
24 amps. That 140 amp alternator will work perfectly. Who was the engineer that designed a motor for a boat with that voltage?
 

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
In a 12 volt alternator, if you put 12 volts to the field the voltage of the alternator is regulated by the rpm of the alternator. Depending on the windings the alternator will only put out so much current at any given voltage. On a 12 volt 160 amp alternator this would be 160 @ 12 volts 80 @ 24, 40 @ 48, and so on.
 

Thread Starter

Skipperdan

Joined Apr 5, 2019
19
24 amps. That 140 amp alternator will work perfectly. Who was the engineer that designed a motor for a boat with that voltage?
I am the one who put the motor in. The higher the volts the less amps. Less amps less heat. 24 amps will work but I not as much as I need. full throttle is just over 80 amps and the motor can do 80 amps all day. I want to have the motor at about 25 amps and be able to charge the batteries with the other 25 amps while moving. also the more amps I have the less time I have to run the engine when just charging the batteries. So charging at say 100 amps is better than charging at 25 amps. The engine runs 1/4 of the time. I only charge the batteries between 50% and 80% which is the rate that the batteries can take all the amps you can give them. The solar takes over from there.
 

Attachments

Top