Twin alternators, anyone done it?

[roland stockham]

Hi all. Done some upgrades to the electrics and going to be fitting new high power inverters. I want to run some heavy power tools and a welder (3Kw). Batteries can absorb around 100a on bulk charge. So the aim is a system that will give 100a at about 1,000rpm (engine revs) and 170a at about 1500rpm. There are single alternators that claim to do this but seems to be a major hassle getting them to actually do it without overheating. Looking at fitting 2 standard 110a units instead. Means making custom brackets but space is not a problem. Wondering if anyone on here has tried this and how it worked out. Only issue I can see is that I may need to upgrade the alternator controller, current one has a max 8a output.

[tkeithlu]

Whoa, Nelly. You need to hear from one of the forum's electrical gods, which I am not, but running two alternators at over 50% capacity is going to do the same thing - you'll fry them, within my experience. If you are feeding them into the same bank of batteries, there's another problem. The voltage regulators are not synchronized, such that one may drop charging and unbalance the load onto the other. Smell of burning insulation. Smoke. Spoiled day.

Running a welder off inverters raises some of the same issues. At capacity? Two, yoked together?

How about starting over and running your tools and welder of an appropriately sized genset? That would be easy.

[SteelEagle]

We have run twin alternators off one engine into the same bank for a while now and it works well for us. The Balmar MC-612-DUAL external regulator is designed for this purpose.

We have a pair of large-frame Leece Neville 8LHA2070V 12V/130A alternators, with the internal regulators removed. We are able to run them at 130A (each) for maybe 2 hours before we reach the temperature limit (100C per manufacturer but we set it at 94C). We rarely run them that hard, turning them down to 100-110A (each) keeps our alternator temps within reason for longer charges.

All of that output is available for us at 1800 engine RPM (3600 alternator RPM) and maybe 75% at 1000 engine RPM (2000 alternator RPM). You can put on different sized pulleys if you need a higher alternator RPM.

I don’t see how you could get that output out of a single alternator, long-term, and not cook it to death. Maybe with some monster cooling system?

Cheers

[roland stockham]

Ok Thanks steel Eagle. I would be running both of a single Sterling power regulator so they should give a balanced output but will check with them as to whether there is a 'right way' to set it up. Going for the Balmar setup would be way more expensive and getting spares for specialist alternators is often a problem as I don't sail in places with chandlers on hand.

[mvweebles]

Good blog article on someone who ran two balmar off one engine. You can cut corners with other brands such as Sterling. Do so at your own peril. Balmar has decent tech support and purpose built gear.

http://www.mvtanglewood.com/2016/11/...roved.html?m=1

[Sternwake]

I was hoping this would be one of those threads that turns into multiple pages of information and shared experience. though the link in the 1st post is quite useful.

I plan on adding a second externally regulated alternator at some point, and never considered using one VR controlling both. Not sure my transpo540HD manually adjustable regulator can pass that much field current. I have measured it but did not have a depleted enough battery to max out the field current and have not tried again. I was more or less wondering if it sent a constant voltage to rotor and varied the amperage, or both voltage and amperage rose and fell together. It is the latter. A clamp meter on the
field output wire read much differently than the clampmeter on the wire + or - feeding the VR.

I was considering having an individual transpo 540hd controlling each and being able to use a rocker switch to choose either or or both, but am unsure whether the switch should be on the field wire, or the ignition wire that turns on the Transpo. I was thinking the latter and am still leaning that way.

Also was considering a hall effect Ammeter on each alternator output individually, so I can dial each alternator to share the load more equally as I have modified the Transpos with remote potentiometers, more heatsinking and 60mm fans blowing across them. It would be easier to simply see field voltage of each , but the alternators i plan to use, are different and have different output curves, but whether one is providing 40 and the other 60% is not really a concern, compared to 90/10.

I'm not really into automatic anything regarding battery charging. I'd rather choose when to lower voltage to float, or lower it for a hot battery or hot alternator and if I can't be bothered, then recharge times are not important either, and I just set it to 13.6v.

[roland stockham]

Couple of notes, people are talking voltages as alternator output control. I may be missunderstanding what that say but as far as I am aware alternators work effectively as current amplifiers. Output A is proportional to field coil A in. V in is only relevant in that you have to increase V to increase A in field coil (to overcome resistance). Basic principle involved is that when a wire passes through a magnetic field a current is produced. The energy available is proportional to the magnetic field strength and speed of movement. The amperage and voltage are both dependent on the total circuit resistance. The field current is what produces the magnetic field.

[Sternwake]

I only have put measuring tools on the voltage regulator's field output wire once, and the tool I did does not turn on until it reaches ~5v and low loads and a full battery were not able to turn the digital Volt meter on.

When i refer to choosing a voltage i am controlling the remote potentiometer on my adjustable voltage regulator, and watching the voltmeter whose sense leads on my battery terminals respond to the request for more or less voltage via this potentiometer. there as a lag and some rubber band effect due to voltage drop on the charge path.
I also watch my ammeter measuring amps into my battery respond in kind to me spinning the remote voltage pot on my Voltage regulator.

I think my VR's main transistor is only good for 8 amps, not sure if it can handle fully fielding two alternators. I could find out by seeing what one when fully fielded is requiring and assuming the other of the same rating is similar, but I intend to use two VR's on two alternators regulated separately, even though if one VR could handle both, it would be simpler.

[roland stockham]

for doing work on alternators you really need a clamp meter. clips round the cable so you don't have any interruption or break in the cable ans will usually measure up to about 400A. You should get a decent one for under $100 from most good tool shops. Does not need to be 'professional' grade like a Fluke.

[Sternwake]

I've got a DC clampmeter, that agrees quite closely with my shunted meter, and other hall effect ammeters and inline 'wattmeters' that I use on loads/sources on which I employ 45 amp anderson powerpoles.

Similar to this:
https://www.amazon.com/Proshopping-P...s%2C199&sr=8-8

My voltage regulator input qualifies for a wattmeter, at least on its input, not the field output though. But it could. Loads under 0.35 amps read low however and loads under 0.05 amps do not register.

If/ when I employ two different alternators of the same rating, controlled by two on the fly manually adjusted VR's, one for each, I'll check to see of equal field voltage yields similar alternator output, so that the alternators share the load somewhat equally.

If they don't I'll install a hall effect ammeter on each alternator output + and spin my dials accordingly.

I've been using this one for about 4 years now:

https://www.amazon.com/bayite-Digita...sensor+ammeter

Its sensor once resided on alternator(+) output cable, but once my curiosity was satisfied I decided the display was more useful to show amperage into/out of the battery and moved the sensor. No issues extending the 3 wire ribbon cable to reach.

The ring sensor itself is not really weather or heatproof though and stray magnetic currents can have the display jump around + - 0.7 amps of actual. Imperfect but good enough for me.

[Q Xopa]

Originally Posted by roland stockham

Hi all. Done some upgrades to the electrics and going to be fitting new high power inverters. I want to run some heavy power tools and a welder (3Kw). Batteries can absorb around 100a on bulk charge. So the aim is a system that will give 100a at about 1,000rpm (engine revs) and 170a at about 1500rpm. There are single alternators that claim to do this but seems to be a major hassle getting them to actually do it without overheating. Looking at fitting 2 standard 110a units instead. Means making custom brackets but space is not a problem. Wondering if anyone on here has tried this and how it worked out. Only issue I can see is that I may need to upgrade the alternator controller, current one has a max 8a output.

Im not sure which motor you are looking to do this install on?

I have recently done a twin alternator install on my Yanmar 4JH4-TE.

It definately takes some working out and messing around.

Short version is-
Standard Yanmar mounts, additional mount an optional Yanmar kit/ part.
I changed to 8 rib Gates belts and pullies. I measured and ordered on ebay.
Bought standard Alt pullies, machined up water pump and crank pullies. Smallest Alt pulley, largest crank and water pump pulley I could fit.
Measured up alignment spacers and got them machined.
Adjusters took a bit of playing around with too.
Both Alternators nee 28si 28v 110A.

I have got a bunch of specific details and pics etc if it will help your install.

I assume your install will be different so my specifics wont be applicable to you.

But more importantly I can tell you how to work out all these details on your motor. Its not too complicated. Basically with a straight edge, digital verniers, and a tape measure you can work everything physical mounting out.

Let me know.

[Q Xopa]

Originally Posted by Q Xopa

Im not sure which motor you are looking to do this install on?

I have recently done a twin alternator install on my Yanmar 4JH4-TE.

It definately takes some working out and messing around.

Short version is-
Standard Yanmar mounts, additional mount an optional Yanmar kit/ part.
I changed to 8 rib Gates belts and pullies. I measured and ordered on ebay.
Bought standard Alt pullies, machined up water pump and crank pullies. Smallest Alt pulley, largest crank and water pump pulley I could fit.
Measured up alignment spacers and got them machined.
Adjusters took a bit of playing around with too.
Both Alternators nee 28si 28v 110A.

I have got a bunch of specific details and pics etc if it will help your install.

I assume your install will be different so my specifics wont be applicable to you.

But more importantly I can tell you how to work out all these details on your motor. Its not too complicated. Basically with a straight edge, digital verniers, and a tape measure you can work everything physical mounting out.

Let me know.

Some pics for you of my install