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Old 27-09-2012, 13:39   #16
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Re: Hitachi 55 amp alternator

Originally Posted by EveningTide View Post
My system is basic- 55 amp alternator/internal regulator charging 2 100 ahr AGM batteries (no separate starting battery). When cruising I let both batteries discharge to the 50%-70% level before charging. When new I would see 50 amps and 14.6 volts when charging began and naturally the amperage would taper off as the batteries charge. The Lifeline battery manual says full charge is when the current drops to 0.5 amps per battery.

Now the alternator is 10 years old and the batteries are new (same type). The voltage at start-of-charge is 13.8V to 14.1V and the current is rarely above 35 amps. I carefully checked all my wiring for voltage drops and found no problems- the output voltage measured at the alternator seems to be low. The Hitachi manual says the regulator is set at 14.4 +- 0.3 volts so it is still close to being within spec. Lifeline says the absorption voltage should be 14.65V so obviously we are charging much slowing than we could be.

I am not looking to upgrade as the original system reasonably met my needs. I would like to restore my system with minimum $. Here are some options: (1) Replace regulator/brushes, (2) Replace alternator, (3) Convert alternator to external regulation (and find an inexpensive adjustable regulator), (4) Live with it as it is.

A new 55 amp alternator is $170, Balmer regulators are more than that. But if I get a new alternator the output voltage might only be 14.4V and there is no adjustment.

Anyone have any suggestions?
I've got a similar issue with my new lifeline agm's. With my old ones the alternators (also Hitachi 55a, but I have 2) regularly gave me 14.5-14.6, now I can't get them above 14.2 thus I can't get my AGM's to 100% charge on the engines. I suspect that the internal design has changed a bit since now they are rated at much higher charge rates than the previous set. My batteries have not been below 70% yet, at least according to my battery monitor, which I suspect is lying to me. It decides what the percentage is by subtracting AH out from when it senses the float voltage switch over. When I first got them the voltage at 70-75% was in the rage of 12.5-12.6 with a 5 amp load. Now it's about 12.1-12.2. I've had some long motoring days and they are still not 100% charged because I can't get them above 14.2 volts. The highest amperage I have seen is in the order of 70 amps which is about the same per alternator as you are seeing.

My AC charger gets confused by my solar output so it won't get them to 100% during the day and I have to run the genset for just about ever at night. I haven't been plugged in to shore power since right after I bought the batteries 3 months ago. They are already showing signs of reduced capacity. I'm going to have to go into a marina so I can give them an equalizing (Concorde calls this a conditioning charge) charge and hope they come up to capacity.

I was thinking of the diode solution, but am afraid that raising the voltage to 14.8V might be a bit much to do all the time. I had not thought of a scheme where I can switch them in and out. Thanks Gord.


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Old 03-10-2012, 10:00   #17
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Re: Hitachi 55 amp alternator

btrayfors is correct so listen to him.

AGMs need as much charge as you can give then and they they will charge much faster which is what we all want.

Regulators that are not externally regulated have no place on a cruising boat. You must let the batteries go down to a float voltage when they are fully charged. Odyssey batteries have now said that if the charger does not go down to 13.8 volts or less in a float mode then the warranty will be invalidated.

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Old 03-10-2012, 11:49   #18
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Re: Hitachi 55 amp alternator

I use cheap 60 amp alternators, I use a cheapo smart charger on my Honda 2000i or when hooked up to the dock, but my 380 watt solar array and outback charge controller are what maintain the batteries. If my battery bank is down by more than about 100 amp hours in the morning I will charge them up enough so that the solar can do the rest by the end of the day. This way I can continue with the cheap alternators without worrying about how "smart" they are.
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Old 03-10-2012, 12:23   #19
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Re: Hitachi 55 amp alternator

Hi, I had an alternator start falling in its output. I found the problem to be a burnt phase wire just where it connects to the diode. No problem, I'll just solder the lug on again, except, the phase wire then broke off in the winding.
So I rewound the alternator. This brings me to your original question. I think you could just give the old alternator a good service and add an external, adjustable regulator. Strip it down, and make sure that all the diodes are forward conducting only, and that the voltage drop forward across the alternator is the same on all diodes. IF this fails, replace the diodes. Next, Check that the windings are not shorted to the frame, and that all windings ring out to each other. It also would be a good idea to "megger" any winding to frame. Check that there is no carbon build up on the cooling plates and anywhere around the diodes, it must be clean. Check that the insulating washers are not cracked and located well on the studs. Replace the bearings, which probably entails desoldering and re soldering the commutator or Slip Rings. Use top quality bearings. Next, check the rotor windings for resistance to ground, should be zero on a megger.
On re-assembly you probably will find it back to its own self again. Alternators are not "Black Magic" they are very simple.

The External regulator of my choice was a Hueco 13 0319, but its 24 volt bought online. Here is the 12 volt version.
HUECO Online Catalogue Automotive

Attached photo after rewinding the 1st phase.
If you want or need to rewind, PM me I can give you a step for step guide on how to....
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Old 14-10-2012, 10:13   #20
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Re: Hitachi 55 amp alternator

I'm a little surprised about you getting 8 years out of batteries if you allow them to discharge more than 50%. Sounds like good batteries, as so many sources say to only use the top 40-50% to get a reasonable life.

Another comment I have is that I've been told that there are rebuild kits for the Hitachi alternators, and that you should never just walk away from a failing one.
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Old 14-10-2012, 11:02   #21
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Re: Hitachi 55 amp alternator

IMHO 55A @ 2x100Ah is absolutely sufficient. Just clean the connectors, replace the brushes if necessary, etc.. The size is not issue, the condition might be, but alternators can be brought back to good shape quite easily.

BTW Reverse your thinking and see if you can reduce your consumption somewhat. A different story but well worth investigating before comitting to producing more.

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Old 14-10-2012, 18:42   #22

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Re: Hitachi 55 amp alternator

When it comes to replacing an alternator, I don't like the japanese products. Hitachi and Denso may make fine goods, but they don't like to share the specs the way US makers do.

This is important because every alternator has a different output curve. Take three "55 amp" alternators. One may be rated 55A @ 4000 shaft rpm, another 3000rpm, the last 5000 rpm. Replace one with another at random--and you may lose or gain 20% power without ever knowing why.

in order to spec an alternator you need to see the output CURVES for amp output versus shaft rpm. Some alternators will put out 1/2 output at 2000rpm and full output by 4000rpm, others won't put out fully until 6500 rpm. That means one will give you good power at cruising speed while the other won't put out until you're at battle speed. Which would you want?

No specs? PASS ON IT.

And if you pick one that offers good output at low speed, and then you can either match the pulley to get you that speed at YOUR common engine speeds (which will vary by the engine type), or in the worst case have one machined to your spec, you can literally double the alternator output at your cruising (or idle) speed and forever cut your charging times in half.

And then there's one other important number: Maximum rpm for the alternator. If you set it up to run fast at cruising speeds, and then one day you run your engine at WOT for four hours clawing off a lee shore...make sure that alternator won't be hurt by running at top rpm. Some die at 10k rpm, others can run all week at 15k rpm. And sometimes put out the same rated power at "cruising" speed.

Don't be afraid ofthe numbers, just the folks who tell you to ignore them.
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Old 16-10-2012, 09:49   #23
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Re: Hitachi 55 amp alternator

Thank you Captain Bill, sy gilana and others. There have been many good responses and I learned from each of them. Captain Bill’s system is closest to mine and his performance change is similar. His batteries are new and alternators are old and now voltage is less.
Here are some facts from Lifeline Batteries- Bulk charge current should be at least C/5 which is 20 amps for a 100 aHr battery. Battery is fully charged when absorption current falls to 0.5 amps. Absorption charging voltage is dependent on battery temperature (14.65 at 60 deg F). After reaching full charge the voltage should be lowered to float charge, about 13.6 V, also dependent on temperature.
Here are some Hitachi facts from my Yanmar shop manual- There is a nice curve of output current vs rpm but this at 13.5 volts. The regulator is fixed at 14.4 volts but there is temperature compensation that reduces voltage as temperature rises. So why do they rate the output current at 13.5 volts unless this is the sort of voltage one expects to see when the alternator is working hard (hot).
“Automotive” charging systems (only a starting battery and motor usually running) are quite different from a cruising sailboat so perhaps the Hitachi is a reasonable compromise for its automotive application. My boat use is 70% “automotive” and 30% cruiser so my results have been generally good.
As sy gilana (and barnakiel) recommended I should just rebuild the alternator. If the heat dissipaters for the regulator are dirty this alone could lead to the effects I am seeing. It is also possible that the regulator has aged due to long use at high temperature. Thanks for the link to the Hueco regulators.
If my alternator would output 40 amps that would bulk charge my two batteries at the rate suggested by Lifeline. If it would produce an absorption charging voltage of 14.6 volts that would be nice.

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