Alternators - What's the Difference ?

[hellosailor]

"Is resting battery voltage the best measurement of charge state?"

Yes and no, since the charge state can be measured by the voltage, but unless you know the exact voltage for those cells (each brand is a slightly different alloy, slightly different voltage, and 1/10th volt is roughly a 10% charge difference) all you are measuring is a return to "the same" charge state versus a different one.

A load test, with a load tester or an improvised load, would tell you more. A specific gravity test on the electrolyte would help. And, you could also use a multimeter to compare the charging output to what the battery maker recommends for the different charge phases. (Even an inexpensive multimeter, as long as you stop to calibrate it or confirm the readings on the 12 volt (20v) scale. Again, you may need a grain of salt because the readings may be off by 1-3 digits, and there's no way to tell if 14.4 is really 14.7 or 14.3 without calibration or testing.)

[allanpeda]

I have been looking at these CUCV alternators, which have isolated grounds (though I am thinking that's sort of overkill on a fiberglass boat... with a starter that is grounded to the block).

Amazon.com: New M1008 M1009 M1028 CUCV HUMVEE Alternator 12v 1105500 OE 100amp: Automotive

Eh, they wouldn't fit anyhow.

[Unicorn Dreams]

That's what I like about wind and solar, batteries don't ever get low ebough for monster alternators.
I've spent enough pn wind/solar so don't want to spend a lot more to get a 250-300 amp alternator. Just use my little 45 AH.

[Cheechako]

"Is resting battery voltage the best measurement of charge state?"

IMHO it is as good as any. Just verify your voltmeter is accurate using a good Fluke or other meter. Let's face it, your battery state is going to be somewhat different every morning anyway, and regardless... you need to charge things up! Get setup to put back in enough so 24 hours later your batteries are not below the point where they are being damaged (50%?)and you're good to go!

[Jamel]

In regard to alternator sizing for the battery bank. I have a Catalina 42 withe the 4 cyl motor which has the 80 amp Hitachi alternator which I'm sure is internal reg'd.
It's often stated to have an alternator approx 25% of battery bank AH's. As I have a 800AH bank is the 80 amp Hitachi too small?
It was obviously not a problem for the PO because the boat was usually connected to shore power for charging, also the boat has a Honda 2000i genset for when away from home to power up the 110v microwave, coffee maker, etc.

As I'm taking the boat on a South Pacific cruise to Australia from CA. my question is will the 80 amp Hitachi be adequate to keep the the 800AH bank up with daily 1 hr or 1 1/2hr charging? I think not, particularly underway with autopilot running 24/7 on long passages.

Could we discuss the most practical solution or is it staring me in the face in the form of the Honda 2000i even at sea?

[Albro359]

To really keep your batteries up you need at least 25% of Ah from your alternator...so you really need a 200A alternator.
Yr Hitachi is almost certainly internally regulated...that will NEVER fully charge your batteries in 1-2 hours if at all.
You need a much bigger alternator and a good external 3 stage remote sensed regulator to keep a bank that size going.
You probably need some other form of generating power also to keep up with daily needs ..eg solar and / or wind.

Thats an awfully big battery bank for a 42 ft boat.... I guess you have electric refridgeration ?...That won't work well in the South Pacific..you'll be running it all day just to keep the beer cool. You probably need a good engine driven system with a very good condenser to pull the system down and then maintain it with an electric system.
The Honda genersator ?..if you want to keep your neighbours wake at anchor, well yes you could do that.
BUT better option is to properly size yr alternator and use environmentally sound systems for maintenance.

This is all juts my opinion of course, 'cos that's how I do it !

Feel free to disagree people !

[donradcliffe]

Originally Posted by Jamel

In regard to alternator sizing for the battery bank. I have a Catalina 42 withe the 4 cyl motor which has the 80 amp Hitachi alternator which I'm sure is internal reg'd.
It's often stated to have an alternator approx 25% of battery bank AH's. As I have a 800AH bank is the 80 amp Hitachi too small?
It was obviously not a problem for the PO because the boat was usually connected to shore power for charging, also the boat has a Honda 2000i genset for when away from home to power up the 110v microwave, coffee maker, etc.

As I'm taking the boat on a South Pacific cruise to Australia from CA. my question is will the 80 amp Hitachi be adequate to keep the the 800AH bank up with daily 1 hr or 1 1/2hr charging? I think not, particularly underway with autopilot running 24/7 on long passages.

Could we discuss the most practical solution or is it staring me in the face in the form of the Honda 2000i even at sea?

Its not the size of the bank, its what you take out of it each day. If you are using the batteries to power the fridge, you will need some more power, be it solar panels, a trolling generator, or the Honda. LED lighting, especially for the main cabin lights and the tricolor, and a netbook instead of a laptop will significantly reduce power requirements. Be sure the the Honda will power the battery charger before you leave--it may work fine when the batteries are near full, but overload when the bank is depleted. I met a boat in Hawaii which had planned to use his 2000i on the passage from the mainland, and ended up running his main engine 8 to 10 hours per day!

Converting your 80 amp alternator to external 3-stage regulation will do more than going to 100 amps, but be sure to carry a spare alternator of some sort. If it were my boat, I would take at least 250 watts of solar panels--they are quiet, reliable, and the more variety in charging sources the better

[Jamel]

Thaks guys, confirms my thinking on this issue. Problem is ....time! Solar is a possible ontop of bimini, spare alternator, YES, will do. External to the Hitachi...not confident to mess there! 200 amp alternator with external reg is huge, requiring double pulleys setup... will look into it seriouslythough!!

Many thanks,

Alan

[atoll]

solar panels and a towed generator would be your best and easiest "quick fix"

both can be lashed on for the passage,just requires cash injection and a small amount of work to get them up and running.

also would reccomend replacing all bulbs with led's.

[DeepFrz]

You mentioned that the boat had been mostly sitting at the dock. Have you had it out for an extended shakedown cruise? Minimum 3 day cruise while using the autopilot (5 days is better) will start to give you some information on your systems. Key word here, system. Match your electrical system with your usage and test it the way you will be using it.

[hellosailor]

Jamel, in terms of FAST fixes:
1-Add water generator, bolts on to stern rail, plugs into regulator/battery to charge. Quick job.
2-Add solar panels, similar.
3-Replace alternator. Buy one with the same footprint, same mounting shoe, but with an EXTERNAL REGULATOR which will provide much higher charging efficiency. Put your old one away as a spare. And of course, change the belt while you're at it.

All fast fixes.

You can also whittle away at your power consumption by ordering LED replacements for any bulbs that are going to get a lot of use, including cabin and nav lights. It may not sound like much but saving 90% of the power on your lighting can add up after a couple of nights, and that's something you can replace one at a time when and as you have time.

You might want to take a look at your fridge box, if there's any simple way to add more insulation around the outside of it, or if you can place some foam boards inside of it to cut down the space and add insulation there, that may also be a significant improvement. Maybe a day job, maybe less, depends on what you can/want to do.

[donradcliffe]

Another simple suggestion--unless the wiring from the alternator to the batteries is 2 gauge or less, make it heavier. The Hitachi regulator will hold the alternator output at 14.2v, but voltage loss at 80 amps may be as much a 0.5v with the original wiring.

[ADMPRTR]

What are the hidden costs of replacing an alternator with higher output version in terms of engine wear, fuel, HP, etc?

[Jamel]

Originally Posted by ADMPRTR

What are the hidden costs of replacing an alternator with higher output version in terms of engine wear, fuel, HP, etc?

I would suspect very marginal, infact may even reduce time of engine running to charge batteries.

I've taken onboard the need to have a larger alternator to match 800AH batteries (not by choice, they were aboard when I bought the boat!)

Electromaax combo of 200amp alt + external reg + pulleys & belt = $1800 approx. If this addressed my concern re charging on long passages I think I would make the investment.

The long Pacific cruise is just the start, as I will be living aboard permanently back in Australia, away from marinas usually!

Has anyone heard reports of Automaax alternators, they seem intent on taking it right up to Balmar! The equipment looks good, anybody tested it out?

[Pete7]

Originally Posted by donradcliffe

Its not the size of the bank, its what you take out of it each day. If you are using the batteries to power the fridge, you will need some more power, be it solar panels, a trolling generator, or the Honda. LED lighting, especially for the main cabin lights and the tricolor, and a netbook instead of a laptop will significantly reduce power requirements. Be sure the the Honda will power the battery charger before you leave--it may work fine when the batteries are near full, but overload when the bank is depleted. I met a boat in Hawaii which had planned to use his 2000i on the passage from the mainland, and ended up running his main engine 8 to 10 hours per day!

Converting your 80 amp alternator to external 3-stage regulation will do more than going to 100 amps, but be sure to carry a spare alternator of some sort. If it were my boat, I would take at least 250 watts of solar panels--they are quiet, reliable, and the more variety in charging sources the better

I think your answers are in Dons post. Calculate how many amps you use each day at sea before you start spending hard earned money. At sea will probably be more than at anchor to account for nav lights, radio/GPS and autopilots etc.

We have a Honda 20i, it doesn't even increase speed when the 40 AH is switched on, just sits there at tickover. I need to switch the water heater on to make it work hard.

Pete