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Old 16-09-2016, 12:06   #1
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Hi voltage alternator benefit

I have a 50 amp alternator (Arco 84150) mated to a Yanmar 2GMF engine feeding two golf cart batteries (207 AH). The alternator feeds about 25-30 amps into the batteries at 13.8V, while the shore charger manages 40-45 amps at 14.4V under the same conditions.

I am thinking of getting an 80 amp 14.7V alternator ($79 from Amazon) to improve my charging performance under engine. Should I expect this alternator to significantly improve the charging performance? Then, the way I understand it, the only problem would be if I do extensive motoring, the batteries get fully charged and start gassing. I do not motor extensively but I imagine that in such rare situations I could i) just add water as needed; ii) put some load on the boat to keep the voltage lower (i.e. run the fridge continuously, etc.); iii) get a charge controller but that is expensive for my use.

May be I am just overthinking the problem. I thought that a simple PWM solar controller would do the trick of lowering the charging voltage but I am worried the PWM control may burn the alternator (the alternators are regulated via current not PWM).

Any thoughts/suggestions?
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Old 16-09-2016, 12:49   #2
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Re: Hi voltage alternator benefit

Batteries can't accept more than a certain current rate. Depending on the batteries capacity and state of charge, the max. is around 20%. You would be better served to change the regulator to control the stage of charge.
There is a wealth of info available on the internet regarding this principle with which you would be better served reviewing.
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Old 16-09-2016, 13:15   #3
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Re: Hi voltage alternator benefit

Sounds like many benefits, if your present alternator peaks at 13.8v then it will take forever to charge the batteries. Like ain't gonna happen. Mine peaks at 14.6v at the battery terminals, trojans, which recommend 14.8v for 2 x 6v in series anyway. If you want to get your batteries to somewhere near full charge then that takes a long time even at a high voltage, checking the water now and again isn't that much of a price to pay.
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Old 16-09-2016, 13:31   #4
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Re: Hi voltage alternator benefit

If your existing alt can be converted to use an external regulator, that will solve the problem. A local alternator shop can advise you on this. A 200 Ah bank will never accept more than 50 amps so what you have will suffice if regulated correctly.
I'd be suspicious of the quality of a $79 alt anyway.
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Old 16-09-2016, 13:56   #5
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Re: Hi voltage alternator benefit

I'm not sure how it all works out. At 14.4 volts and max output an alternator may run for 15-20 minutes at near max output, then the regulator backs off and puts out less amperage. (you cant pound 80-90 amps into batteries for very long)
One wonders how this works out compared with less voltage and less amps but putting it out longer?
ie: let's say you run the engine for 45 minutes each way. Which one really puts more charge in the batteries?
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Old 16-09-2016, 14:02   #6
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Re: Hi voltage alternator benefit

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Originally Posted by capt jgw View Post
If your existing alt can be converted to use an external regulator, that will solve the problem. A local alternator shop can advise you on this. A 200 Ah bank will never accept more than 50 amps so what you have will suffice if regulated correctly.
I'd be suspicious of the quality of a $79 alt anyway.
Mostly agree except a bank will pretty much take what amps are there, getting an alternator to actually output its full rated power output is a different matter.
Does seem a bit cheap.....
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Old 16-09-2016, 16:50   #7
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Re: Hi voltage alternator benefit

Thank you for the feedback. This is the alternator if people are interested. I will order it then report back. Will keep the current one as a backup.

DB Electrical AHI0059 Alternator (For Yanmar Diesel Hi-Output 80 Amp Lr180-03 Lr180-03C) https://www.amazon.com/dp/B0081SBFZ2..._Mri3xbZ1QWCSJ


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Old 16-09-2016, 17:18   #8
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Re: Hi voltage alternator benefit

Pizzazz, I have the AHI alternator in your link on my Yanmar now. It was the backup for a factory Hitachi that was a rebuild.

After years with these two alts I'm familiar with them inside as well as out. The AHI unit looked well made. The rebuilt factory alt had the same internal parts after rebuilt.

But here's why I post. This Hitachi design has an overheat function that limits output if the alt heats up too much. And the thing is they always heat up if asked to charge a large bank for extended time periods. The 80 amps available is throttled back too soon, but not by the regulated needs of the bank, but by alt temp.

I've had 55 amp first, and two 80 amp since and never realized more than a modest improvement in charge times or engine intervals.

There is a Delco revised design for our engines, even from DB Electrical I think, that I have had in mind for some time now. Not as expensive as the popular solutions and complexity of say a Balmar. But more than the aftermarket Hitachis.

Look for the Delco with the modified dual foot housing. 100 amp and no temp throttling and consider it maybe.

The AHI runs fine though. I have worn out brushes, and had the regulator go bad in the factory rebuild. On the hook 24/7/365 engine only charging for several years.
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Old 16-09-2016, 19:20   #9
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Re: Hi voltage alternator benefit

Quote:
Originally Posted by Pizzazz View Post
I have a 50 amp alternator (Arco 84150) mated to a Yanmar 2GMF engine feeding two golf cart batteries (207 AH). The alternator feeds about 25-30 amps into the batteries at 13.8V, while the shore charger manages 40-45 amps at 14.4V under the same conditions.

I am thinking of getting an 80 amp 14.7V alternator ($79 from Amazon) to improve my charging performance under engine. Should I expect this alternator to significantly improve the charging performance? Then, the way I understand it, the only problem would be if I do extensive motoring, the batteries get fully charged and start gassing. I do not motor extensively but I imagine that in such rare situations I could i) just add water as needed; ii) put some load on the boat to keep the voltage lower (i.e. run the fridge continuously, etc.); iii) get a charge controller but that is expensive for my use.

May be I am just overthinking the problem. I thought that a simple PWM solar controller would do the trick of lowering the charging voltage but I am worried the PWM control may burn the alternator (the alternators are regulated via current not PWM).

Any thoughts/suggestions?
If you have a 50amp alternator for a 207ahr bank you should be doing just fine. I assume these are Flooded Lead Acid (FLA) batteries and not Gel or AGM. A larger alternator will not push to electricity into your FLAs any faster, the rate of charging during bulk charging should max out around 35-40amps. Less really if you want to have them last as long as possible.

25-30amps does seem low for bulk charging and the 13.8v is low so my guess is that your regulator is set wrong. I think 13.8v is bulk charging for Gel batteries, not FLAs but I haven't checked.

You talk about a PMW regulator, PMW is for regulating solar panel output, not alternators.

Understand also that you need to be comparing the charger to the alternator at the same state of charge. At 50% full you should be able to max out charging current at about 40amps or so. By the time you get to 75% full your battery will become voltage limited and current will be dropping. Increasing the voltage will increase the rate of charge but it will also damage the battery rapidly.

If you have AGMs a larger alternator might be useful, but understand it will only shave an hour off of the 7 hour charging process. The higher acceptance of AGMs taper off to match FLAs and Gels by the time you get to about 75% full.

Look at how you alternator is regulated and fix that.
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Old 16-09-2016, 20:20   #10
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Re: Hi voltage alternator benefit

All alternators (I know of) for battery charging/DC power supply really produce AC voltage that is converted to DC by a diode bank. Unregulated, actual voltage is almost unlimited. By modifying your requlator or building another one, you can change the voltage it produces. The higher the voltage, the more amps. You can also include a rheostat for adjustable charging. But... it's easy to hurt or destroy your batteries or alternator. Heat, too many amps, melted wiring, boiling away electrolyte, etc.
If money is an issue, probably any current alternator can be converted to external regulation. Lots of "how to" stuff on the web. Probably people here, too, that can make a regulator.
Common practice when I commercial fished and older electronics drew high amps. My old radar drew 20 amps on 32 volts.
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Old 16-09-2016, 22:07   #11
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Re: Hi voltage alternator benefit

Raising the voltage by 0.55V is as easy as adding a diode to the external sense line. That will raise the voltage from 13.8V to 14.35V. I might do this over the winter with a switch to select between diode and non-diode sense. Gee with GC2 batteries (6V), you could add two diodes in series, that would allow for 14.9V, which allowing for wire voltage loss, would give 14.8V at the batteries. It's on my list. Of course I have solar so it's not high on my list.

The other negative is the larger alternator puts more loading on the belt which puts more side loading on the water pump bearing.
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Old 16-09-2016, 23:01   #12
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Re: Hi voltage alternator benefit

Let me try to focus this thread a bit. My particular issue is that at one particular state of charge I get the shore charger to put in 45 amps vs. the alternator at 25 amps at the lower voltage. The question was what it would take to get the same charging performance from the engine. I think four winds summarized it nicely. One way is to go with a Balmer alternator and regulator which costs $1000. Hard to justify. On the other part of the spectrum is to get this cheap alternator rated at 80 amps/14.7V, hoping that when hot it will provide better parameters (higher voltage) than the stock one. It is 1/12 of the price.

The in-between solutions do not work, at least not on the Hitachi style alternators. For example, what is the point of breaking out the brush wire for an external regulator when the alternator would not be able to handle the current due to its temperature control circuit? May be that is why it is so cheap, they use thin wiring and put in the t control. Not ideal for marine use.

I will look into the Delco option. But it looks as if there are not that many good options to upgrade the Yanmar alternator.


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Old 17-09-2016, 01:22   #13
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Re: Hi voltage alternator benefit

Its all about the voltage regulator, then what the alternator is capable of producing when seeking what the voltage regulator demands, and then what the batteries can actually accept at that voltage.

Your shore charger seeks 14.X volts and can produce 45 amps and your batteries can accept that much. Yeehaw.

your alternator's Voltage Regulator only allows 13.8v and only 25 amps flow to depleted batteries at that voltage. Boooooooo!

if your VR was seeking 14.4 to 14.8 then it would ask the alternator to max out until voltage reached that high. Yeehaw!

I had a USbattery group31 which would accept 40 amps for 45 minutes when depleted before it hit 14.7v and amps would then start tapering. Saying 200Ah of somewhat healthy flooded depleted battery cannot accept more than 50 amps is NOT my experience.

I have a group27 northstar AGM battery at 90AH, which can now, when depleted to 40% at ~400 deep cycles, accept 65 amps for 25 minutes before attaining 14.7v at which point amps taper. ~4.5 more hours at 14.7 volts are then required to near 100% charged.
When new this battery depleted to 50% could accept 106 amps from my 130 amp alternator before its voltage reached 14.7v. Now at 400 deep cycles that is down to the 80 amp range for attaining instant absorption voltage.

A 200 amp alternator and a 45 alternator will produce the same amount of juice when the target/maximum voltage allowed is 13.8v on 200Ah of battery. Perhaps the 200 amp alternator would attain 13.8v a few minutes faster, but from that point it would be the same. Big difference in amp flow comparing 13.8 vs 14.4+v.

A higher rated alternator can likely better handle the heat it generates, but not necessarily charge any faster if the voltage controller does not 'let it loose' or if the batteries cannot accept anything more than the lesser alternator can make.

The key is to seek 14.X volts when depleted, not just 13.8v. The alternator will only make as much juice as needed to raise voltage to the voltage regulator setpoint.

While 13 amps might be required to hold X amount of depleted battery capacity at 13.8v, 45 amps might be required to hold that same battery at same state of charge at 14.8v.

When time to charge well depleted batteries is limited, then a voltage regulator seeking only 13.8v is one's nemesis, and the alternator will yawn while the battery cries for more and sobs when the charging source is terminated.

Seek absorption voltage ASAP, get a voltage regulator which can ask the alternator to produce enough to attain and hold 14.4+ volts. The only time to drop voltage is when batteries are hot, or already fully charged, not when they are still depleted and time to recharge is limited.

My grid powered charging source, and Alternator, both have potentiometers so I can control voltage, and I have a very happy battery that is worked very hard and retaining capacity and performance to an impressive degree because of it. But it is not automatic. My solar also allows Absorption voltage adjustments and duration.

13.8v maximum on a depleted lead acid battery is going to charge slowly and more slowly as it slowly recharges.
With 13.8v maximum, 50% to 100% can take 24 or more hours to maximize specific gravity.
With 14.4 to 14.8v maximum 50% to 100% can be done in as little as 5.5 hours with healthy batteries.
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Old 17-09-2016, 03:14   #14
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Re: Hi voltage alternator benefit

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Originally Posted by sailorchic34 View Post
Raising the voltage by 0.55V is as easy as adding a diode to the external sense line. That will raise the voltage from 13.8V to 14.35V. I might do this over the winter with a switch to select between diode and non-diode sense...
What I did about 25 years ago. Worked a treat.
FWIW: I also ran a tiny 600W generator (at anchor) through a 40A ferro-resonant charger, which never overloaded the genny, indicating that my 4 x T-105 batteries could never accept over about 40A, no matter how low my SOC.
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Old 17-09-2016, 09:12   #15
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Re: Hi voltage alternator benefit

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What I did about 25 years ago. Worked a treat.
FWIW: I also ran a tiny 600W generator (at anchor) through a 40A ferro-resonant charger, which never overloaded the genny, indicating that my 4 x T-105 batteries could never accept over about 40A, no matter how low my SOC.

There are the key factors: acceptance based on a) battery bank size and b) voltage output before throttle-back at the alternator, itself a function of resistance in the circuit and self-limiting issues such as heat sensors. Size the charge sources to the bank; the voltages are merely aspects of the stage of charging. Ever drink a pint of Guinness in an older bar? It takes two-and-a-half pulls.
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