What amperage alternator

[Restitution]

I have twin Perkins engines. Each engine has a 65 amp alternator. One for house batts, the other for start batt. I’m considering getting a much larger amperage alternator for the house batteries. Is there a down side to this? Pros vs cons.

Thanks,

Sam

 

[O C Diver]

I have a 220 amp alternator with 3 stage external regulator for the house bank. Depending on the amp capacity and type of battery, there is a limit to the rate you can charge them at. Also, larger amperage alternators require either thicker, multiple or serpentine belts to handle the additional load. Power cable sizes will likely need to be increased to handle increased amps. Finally, there is the mounting bracket and the space it must fit in. It's very worth while, but often not as simple as buying a new alternator.

Ted

 

[sunchaser]

I have twin Perkins engines. Each engine has a 65 amp alternator. One for house batts, the other for start batt. I’m considering getting a much larger amperage alternator for the house batteries. Is there a down side to this? Pros vs cons.

Thanks,

Sam

Options galore.

Flywright did a modification (much bigger alternator and new belt drive setup) similar to what you desire. He has a Californian and Perkins engines.

Another consideration is increasing the size of your alternator(s) to somewhere around 110 amps such that the same motor sheave and a single belt can be used. Then add a combiner or switch such that both alternators can power the house bank.

Do you have a genset?

 

[High Wire]

How big is your house bank? What type of battery?
A normal single belt pulley setup is only good up to about 100 amps. Above that you need either a second belt or serpentine belt kit.

 

[DavidM]

To summarize the foregoing good advice and add some of my own:

1. Keep the alternator at or below 100A if driven by a single belt.
2. Don't use an alternator any bigger than 25% of your house bank AH capacity if flooded cells, maybe more with AGMs.
3. You need a three stage external regulator to get the most out of an alternator. These require the appropriate connections on the alternator to hook up.
4. Some standard HO alternators have these connections on some models like Leece Neville. Specialty HO alternators like Balmar, Hehr, etc have them.
5. You need to wire the regulator's voltage sense wire directly to the batteries.
6. A 100A HO alternator with external regulator feeding a 400AH battery bank will probably charge 3-5 times faster than what you have now.

One approach is to replace one of your engine's alternators with a HO and external regulator. Wire it directly to the house bank with big wire- #6 minimum. Use the other engine's alternator to charge both starting batteries. Lot's of other ways to do it though.

David

 

[Restitution]

All very fantastic advice. Thank you so very much.

The house batts consist of two 8D deep cycle batts. Start battery a larger standard ? start battery about the same size as the 8D's.

 

[Maerin]

I faced a similar dilemma although with a Cummins 6BT. David's recommendations are spot on. A couple thoughts, I used a Zena marine alternator in 250A. It's a Leece-Neville that has been beefed up, it has an external rectifier bridge to relocate some heat, mine has a 2" hose that divides ambient air from a 250cfm blower between the back of the alternator and the battery box. My bank is 1150AH in AGM, so it will take whatever the alternator can throw at it. It's regulated with a Balmar 612 with temp sensor for alternator and battery, and it pretty much takes care of itself. I'll see in the 180A range when charging the bank at 60% SOC. The alternator loads at 90% for an hour then is down in the 65% range. The Balmar does a terrific job and can be tweaked to the precise needs of your individual configuation. It also has a belt setting, so if you have an alternator >100A, you can limit it to keep the belt wear under control, and not worry with overheating a marginally-sized alternator.

Don't overlook your running load; you'll have a standing 12V load under way that must be met before anything is going to go to the bank. Most importantly, don't be short-sighted and focus on a part of the system. It is, after all, a system, and as such you need to consider every part as it relates to the other in order to accomplish the objective.

 

[DavidM]

Two 8D have roughly 440 amp hours. FWIW most 8Ds are not really deep cycle and replacing them with four GC batteries wired in series/parallel will give you much better battery life and two GC batteries will fit in an 8D's battery box.

Did you say that you have one starting battery that serves both engines? That makes it easy to wire up a HO alternator as described in my previous post.

But in any case, that means that you can use a 100A HO alternator to charge your 440 AH house bank.

David

 

[Lou_tribal]

If I can add my 2 cents look also how you use your boat. I mean do you often go from the dock for 2h at the anchor and back to the dock? Do you often 1 day at the anchor, than run 1h and stay again at the anchor? In summary do you need to charge your battery the fastest as possible or not really?

L

 

[john61ct]

Without converting to or adding an LFP bank, increasing alt output will have a very limited impact on total time required to get to 100% full.

Even with high-CAR AGM, the high amps acceptance stage is under 20% of the total time required from 50% to Full.

But those high amps can be useful driving other loads while motoring, like aircon, HO watermaking or eutectic refrigeration.

 

[FF]

"If I can add my 2 cents look also how you use your boat. I mean do you often go from the dock for 2h at the anchor and back to the dock? Do you often 1 day at the anchor, than run 1h and stay again at the anchor? In summary do you need to charge your battery the fastest as possible or not really?"

This IS Question #1.

Although regardless of the answer a better faster charge can usually be done with a smarter Voltage Regulator .

 

[Tom.B]

Considering what you have as a battery system, even if you change to 4 GC batteries, I wouldn’t waste your money yet. Think and research upgrading your rig (should you have the need for it) and then decide what your charging options are that you need to explore. Look, we aren’t sailboats that spend all day under sail with minimal charge going into the banks. We are motorboats that, when we travel, provide a pretty hefty charge 100% of the time. Sure, arguments for needing quick charging when at anchor for many days at a time, but again, your current rig is not capable for this style of boating yet. For weekends at anchor, day to day hopping around, or even a long trip of coastal cruising, you will be fine.

Take a long look at what kind of boating you will be doing and go from there. Simply jacking up your alternators won’t gain you much. Like putting mud tires on a pickup truck and then just driving it back and forth to work. Certainly, that the money and time could be better spent on another project. Sometimes bigger isn’t always better.

 

[Restitution]

Thank you gentlemen for the advice. It has been well received. I now understand that while possible to charge quicker, changing the charging system now would not be pragmatic. Sailboat and the mud tire analogies were perfect.

Have a great weekend and thanks again.

Sam Nigro
Restitution

 

[Westiculo]

One alternative that wasn't brought up: let your current alternators work together by putting in an external regulator that allows both of them to charge the house batteries.
A solenoid is used to parallel the house and starter bank during the charging cycle. Twice the charging capability without messing with the engines, and both engines/alternators are seeing the same loads on the alternators and the belts.
I did this with the dual alternator controller from ample power. Could also be done with the centerfielder from balmar.

 

[DavidM]

OEM alternators rarely have the connections to the field coil to use with an external regulator like the Ample Power or Balmar.

Some say to get a local alternator shop to install the connections to your existing alternator(s). I think that is a bad idea because you are asking these alternators to put out 3-5 times more current over a long period. They don't have the diodes, windings or cooling capacity to do this for long.

David

 

[john61ct]

But with a sophisticated VR like Balmar's MC-614, there is temperature protection built-in, including a dedicated sensor,

Plus you can de-rate current output to whatever you like in pretty fine increments.

Yes they're not cheap, but will be put to use on future larger alts, and will even be suitable for LFP down the road.

Not sure about the lesser Balmars or the center fielder, not as adjustable.

Switching over from the stock internal VR is NBD.

 

[Westiculo]

I was able to make the conversion on mine without a problem - and they're doing great.
I don't understand the "3-5 times more current" - are you saying that his 65-amp alternators are actually only putting out 20 amps, or are you saying that his 65-amp alternators currently put out 65 but if they were externally regulated they would put out 200? Neither of these cases are realistic. By running the alternators in parallel, they would not be run for a longer period of time, but a shorter period of time (2x the current available means half the battery charging time).

 

[john61ct]

a shorter period of time (2x the current available means half the battery charging time).

Very common misconception, but completely false.

Say a bank takes 6 hours of charging at 50A available to get from 50% to true Full (via endAmps).

Only the first 60-90 minutes of that will even a high-CAR bank charge any faster, after the 85% point acceptance for any lead chemistry drops radically.

Going to 100A might only save 30-60 minutes, maximum.

The big advantage of a better VR is keeping voltage at Absorb longer, derating Current only when the alt gets hot.

Stock VRs are usually shockingly poor at getting a quality bank what it needs.

 

[sunchaser]

after the 85% point acceptance for any lead chemistry drops radically. .

"Radically?" Really.

Drop it does, but not that much. But there are some old wives tales out there too regarding how slow LAs are getting to 100%. For many years I've had no problem getting my LAs to 100% quite quickly. Around 94 % they do start to slow down, but after 4 hours or so of cruising with genset off they are nicely at 100%.

Using internet charts and non LA sales jargon isn't always accurate for the real world we cruise in. Thus, the reluctance for so many of us to switch to the much more expensive stuff largely driven by hobby desires or getting the best. In other words, how good is good enough..

 

[Westiculo]

I did not mean to spark another lecture on the charging to 100% thing; I have a boat and a battery meter, so am aware of this. I wrote my post too hastily.
My question was mean to be related to the "3-5 times more current" comparing an internal to externally regulated alternator. Any thoughts on that?

 

[DavidM]

I don't understand the "3-5 times more current" - are you saying that his 65-amp alternators are actually only putting out 20 amps

Yes, that is exactly what I am saying. Here are some real world figures:

With an OEM standard Hitachi internally regulated 55A alternator feeding a 25% depleted 440 AH GC battery bank I measured 15A from the Hitachi after ten minutes of engine running time.

With a 110A Balmar HO alternator feeding the same bank 25% depleted I measured 60 amps from the Balmar alternator.

Most internally regulated alternators are not designed to put out a lot of current no matter what their amp rating. They are regulated at a fixed 13.5 V output and that isn't enough voltage to push much current into the battery. Under the same conditions the Balmar alternator/regulator was reading about 14.0 volts.

So if you take that puny OEM alternator and amp it up with an external regulator so it puts out the same 60 amps as the Balmar, it is going to get really hot after a while. Heat kills alternators.

High output alternators like the Balmar have heavier windings than the Hithachi (less voltage drop therefore less heat), heavier diodes (same) and more cooling air due to a more efficient fan.

But if you were to try to recharge a huge 1,000 AH bank fully depleted the Balmar will get too hot. That is why Balmar makes a temperature sensor that dials back the alternator output when it reaches about 200 deg F case temperature.

David

 

[High Wire]

I replaced my old Delco OEM for my Perkins main engine with an ARCO model 60122 105 amp . The output wire needed upgrading to #6 and the tachometer wires needed modification. I also needed to improvise spacer washers to get the pulley alignment right on. With a single belt, I measure 104.5 amps at 1400 engine RPM until battery volts reaches 14.4 volts, then maintains 14.4 volts until I come down to idle and start using either the windlass or thruster. I charge 6 - 6 volt wet cell Trojan golf cart batteries. No signs of any overheating damage in about 400 hours of cruising. Pretty easy upgrade if you don't want to go full Balmar $$$$.

 

[Tom.B]

If the batteries are in bulk charge (I think I have my terms correct), you can totally connect the two alternators together without using an outboard regulator. They will take what you throw at them, but for sure, a stock 65A alternator ain’t puttin’ out no 65A. Still, he needs to work all this out before he goes and buys a $1000 alternator or a fancy voltage regulator.

That’s all I’m sayin’.

My two stock 65s give me about 60A combined when underway. Not enough for my 8 golf cart batt/900AH bank, but plenty for now. We are still just weekenders.

 

[FF]

"My question was mean to be related to the "3-5 times more current" comparing an internal to externally regulated alternator. Any thoughts on that?"

The brain in a std alt is expected to replace perhaps 5% of the battery capacity , and hold the voltage up to 14+ so the lights and blower motors .

They are seldom asked to charge a well discharged batt as start batts DIE if any attempt to deep cycle them is made.

Repeated cranking covers the plates with gas , so the batt stops working for the time it takes the gas to depart, it has not been very deeply discharged .

The V reg of a car alt allows only about 50% of the required charge in any hour (to keep the load & internal heat low.

While a one wire alt can be modified to use an external V regulator , it is far simpler to install a rebuilt 75 or 80A from an early large car, and then install the 3-4 stage regulator.

The old Delco stuff from 70's Caddys was quite robust, and still cheap.

 

[O C Diver]

As previously mentioned, I have a Leece Neville 220 amp alternator, Sterling 3 stage regulator, and a Victron Energy battery monitor. The alternator is designed for fire trucks and other vehicles that require high continuous amps when operating at low RPMs. As an example of how my system works, consider the following :

We left Fort Myers for Fort Pierce. On the second night we were on the hook and ran the ice maker all night to fill a large beer cooler. In the morning, the bank (1,000 amp lead acid) was down to 70%. After pulling the hook and getting underway (engine RPM 1,500), the battery monitor was showing 180 to 200 amps going into the battery bank. After the bulk stage ended, you could watch the amperage slowly drop during absorbtion stage. By the time we reached Fort Pierce (4 hours of motoring), the bank was basically full (10+/- amp charge or 1% of bank capacity).

This type of bank recharge is typical for my system and demonstrates what can be accomplished with a commercial grade continuous duty rated alternator and 3 stage regulator.

The reduction of amps from the 220 amps which the alternator is rated for, comes from power consumed by the boat and the inverter.

Ted

 

[FlyWright]

"My question was mean to be related to the "3-5 times more current" comparing an internal to externally regulated alternator. Any thoughts on that?"

The brain in a std alt is expected to replace perhaps 5% of the battery capacity , and hold the voltage up to 14+ so the lights and blower motors .

They are seldom asked to charge a well discharged batt as start batts DIE if any attempt to deep cycle them is made.

Repeated cranking covers the plates with gas , so the batt stops working for the time it takes the gas to depart, it has not been very deeply discharged .

The V reg of a car alt allows only about 50% of the required charge in any hour (to keep the load & internal heat low.

While a one wire alt can be modified to use an external V regulator , it is far simpler to install a rebuilt 75 or 80A from an early large car, and then install the 3-4 stage regulator.

The old Delco stuff from 70's Caddys was quite robust, and still cheap.

Don't try this is you have gassers. We become so accustomed to talking trawlers with diesels. Some safe diesel practices can be hazardous it tried with gassers.

 

[DavidM]

O C Diver's experience with the Leece Nevile alternator and the Sterling regulator is impressive.

As I recall, the Sterling regulator is unique in that it "fools" the alternator into thinking it is supplying a low impedence load at a reduced voltage thereby boosting its amperage and then boosting the voltage to what the battery needs. Sort of like a reverse MPPT controller.

That means the Sterling regulator can be used with a one wire alternator as no field connection is needed. But only use it on an alternator that can stand up to the long term load like the Leece Neville.

David

 

[sunchaser]

Leece Neville is owned by Prestolite. Many other alternators out there that are installed in big equipment that match the LN's well deserved reputation. They may well be made by Prestolite too.

 

[john61ct]

There are a few makers of quality HO alts, not many, and several are very specialized low volume like Eco-tech and Zena.

​Ex-military C.E. NIEHOFF & CO (CEN) units can be found reasonably on eBay, some put out 500+A at 24V.

Of course the higher the load the more of your engine's propulsion HP is diverted. I figure that latter example would take about 30HP per alt.

Need a solid belt/pulley setup!

 

[O C Diver]

O C Diver's experience with the Leece Nevile alternator and the Sterling regulator is impressive.

As I recall, the Sterling regulator is unique in that it "fools" the alternator into thinking it is supplying a low impedence load at a reduced voltage thereby boosting its amperage and then boosting the voltage to what the battery needs. Sort of like a reverse MPPT controller.

That means the Sterling regulator can be used with a one wire alternator as no field connection is needed. But only use it on an alternator that can stand up to the long term load like the Leece Neville.

David

My understanding of how the electronics work in the regulator is poor. But, you do have to be able to connect to the positive brush in the wiring process. You can leave the original regulator in place and it functions as normal if the Sterling regulator is turned off.

There are a few makers of quality HO alts, not many, and several are very specialized low volume like Eco-tech and Zena.

​Ex-military C.E. NIEHOFF & CO (CEN) units can be found reasonably on eBay, some put out 500+A at 24V.

Of course the higher the load the more of your engine's propulsion HP is diverted. I figure that latter example would take about 30HP per alt.

Need a solid belt/pulley setup!

I added a second 8 groove serpentine belt pulley to the crank shaft which only drives the second alternator. At full load, the engine fuel consumption goes up approximately .3 to .4 gallons per hour. Assuming 20 HP per gallon, this 220 amp alternator requires a maximum of 8 HP.

Ted