Does Alternator Need Protection from AGMs?

[batkins61]

I have about 400ah of AGM house and a Optima red-top start battery on an Xantrex Echo-Charger. Normally, the house is charged by a 20A Sentry AC charger during the week (with the Echo keeping the start up). We usually day sail with an occasional night on the hook. However, this summer I can foresee long weekends (3-4 days) and perhaps a week away from shore power.

My only charging source off shore power is the Hitachi 55A on my Yanmar 3GM30F, stock, internally regulated, connected to the house (not to the starter, as is normal). I'm usually using chart plotter, auto-pilot (on standby mostly), refrigeration, wind instruments or, at night, anchor light and cabin lighting (LED, mostly). A stereo playing an external CD changer at moderate volume levels is likely to be involved as well.

Is my alternator at risk without temp. sensing regulation? Assuming I draw down the AGMs enough to require bulk charging, how long can the 55A alt. keep that up before cooking?

Eventually, I would like to upgrade the alternator, but before that I want to make sure I don't burn up my Hitachi (which will serve as a backup post upgrade). If it's at risk trying to feed the AGMs after a full day of sailing, then I need to either externally regulate it with temp. sensing (difficult, I've read, for that Hitachi), or upgrade the alternator/regulator sooner.

If I externally regulate the Hitachi, I would want that unit to serve as the regulator for a bigger alternator in the future (probably something in the 100A-120A range, which (according to a couple of alternator companies I've talked to) is what the 3gm30 can handle on a single belt). Also, any specific recommendations for regulators would be most welcome. I noticed that some of the popular brands don't even have alt. temp sensing (e.g. Ample Power), at least from what I read.

As always, thanks!

[djmarchand]

It sounds like you have a well set up DC electrical system with the house bank getting the alternator output and the start battery charged by the Echo charger. Simple, hands off system.

I have never seen more than about 30 amps on my Hitachi 55 amp alternator on a 3gm30f even with 75% discharged batteries. It quickly drops to 20 or less in about 30 minutes. So I don't think you will burn one out.

I have used a Balmar 100 amp alternator which as you note is as big as can be driven by one belt, with good success. I had the Balmar regulator and the alternator temperature sensor. The regulator would cut the alternator power output in half when the alternator got hot, which is a good thing. I added a little muffin fan blower and ducted it to the back of the alternator to keep it cooler so the regulator now rarely reduces output.

With that kind of DC useage you will use 80-150 amphours a day depending on how efficient your refrigeration is. So after 48 hours on the hook you will have depleted your batteries in half which is as low as you want to go. Don't even consider running your propulsion engine to recharge with the Hitachi alternator. If you need to anchor out more than 48 hours, upgrade to a Balmar or similar.

Another solution to extended on the hook time is to upgrade your shorepower charger to about 50 amps then power it with a Honda EU 1000 when the batteries get low. That little generator will be well loaded powering a 50 amp charger. IOTA is a good brand. You will have to run the generator for 2-3 hours each day after 48 hours.

David

[donradcliffe]

Great advice for your situation. You will probably not burn out the Hitachi if you keep it internally regulated, but you will have to run it about 4 hours a day.

Originally Posted by djmarchand

It sounds like you have a well set up DC electrical system with the house bank getting the alternator output and the start battery charged by the Echo charger. Simple, hands off system.

I have never seen more than about 30 amps on my Hitachi 55 amp alternator on a 3gm30f even with 75% discharged batteries. It quickly drops to 20 or less in about 30 minutes. So I don't think you will burn one out.

I have used a Balmar 100 amp alternator which as you note is as big as can be driven by one belt, with good success. I had the Balmar regulator and the alternator temperature sensor. The regulator would cut the alternator power output in half when the alternator got hot, which is a good thing. I added a little muffin fan blower and ducted it to the back of the alternator to keep it cooler so the regulator now rarely reduces output.

With that kind of DC useage you will use 80-150 amphours a day depending on how efficient your refrigeration is. So after 48 hours on the hook you will have depleted your batteries in half which is as low as you want to go. Don't even consider running your propulsion engine to recharge with the Hitachi alternator. If you need to anchor out more than 48 hours, upgrade to a Balmar or similar.

Another solution to extended on the hook time is to upgrade your shorepower charger to about 50 amps then power it with a Honda EU 1000 when the batteries get low. That little generator will be well loaded powering a 50 amp charger. IOTA is a good brand. You will have to run the generator for 2-3 hours each day after 48 hours.

David

[batkins61]

Yes, I definitely understand that I can't recharge the batteries to a significant degree with that alternator. As long as I can sustain a level to keep me comfortably above 50% until I get back to shore power, without frying the alternator, I'm happy with that for now. Alternator upgrade is definitely on the list, but hopefully after some other things.

[btrayfors]

The Honda 1000 is way too small. It can only handle a 45amp Iota charger or similar, while the AGMs can easily take up to 400amps or more when deeply discharged.

Much better would be the Honda EU2000i which can handle an Iota DLS-75/IQ4 which would give you an honest 75A or more charging capacity. The Iota's tend to hang in there with high amperage longer than many other chargers, in my experience.

RE: an external regulator, I'd recommend the Balmar MC-614 or the older MC-612. Not only do these have temp sensing for both battery and alternator, but they have two additional ways to regulate alternator output:

1. a simple toggle switch can be connected which will cut the charge current in half; and

2. you can de-rate your alternator to any desired degree. For example, you could fit a 120A alternator and de-rate it for a maximum of, say, 90A output. If the installation were good, it would never be overworked.

Bill

[batkins61]

How does the MC-614 compare to the ARS-5? I'm still not clear on what the practical differences are. And, is the Sterling ProReg-D Advanced a viable option (the price is certainly nice).

[goboatingnow]

many modern integrated alternator regulators have alternator temperature sensing in them now anyway.

dave

[sailinglegend]

Originally Posted by batkins61

How does the MC-614 compare to the ARS-5? I'm still not clear on what the practical differences are......

The MC-614 has more programmable adjustments of voltages and time - for example you can lengthen the absorption time before the unit decides to drop down to float mode. This is very useful if you have a large house bank and need a longer absorption time than the default value which is set at 18 minutes. This can be changed from 6 minutes to 6 hours. If your regulator drops down to float too early your batteries will not be fully charged.

Remember charge regulators don't know the size of your battery bank, or the current that is actually going into the battery, so default values don't suit all installations.

[Pete7]

Larger alternators, honda genny and new battery charger is all starting to sound a little expensive. How about 300w of solar panels instead?

Pete

[BriaF]

I have lived aboard for 10 years, here's my 2cents worth.

You need to make the best of what you have.
Spend your $ on chargeing systems you use everyday.

The less you discharge a battery the longer it will last.
So best not to discharge to 50%.
The last 10% of charge is not a realistic option.
Except on shore power,solar,wind.
So you must work in the 50~90% range
I aim for 70~90%.

So you should charge every day!
If you do this charge times will be shorter & batteries will last longer.

My suggestion is a Honda 10 eu plugged in to your shore power battery
Charger.
Yes I know they are expensive.
But mine is still going after 10yrs it still has the original spark plug & has never missed a beat. It will also run many power tools.

Cheaper to buy than the 20eu lighter & cheaper to run.
It will cope with a 40~50 amps depending on the charger used.
Your charger will step down the rate of chargeing as required so
Will not require high levels of chargeing for long.
If high levels of chargeing are required you can start the engine for
30~60 min as well.

My wife has been left on the boat for weeks at a time & has no trouble
Monitoring the voltage & handling the generator.

Living aboard requires solar -wind.

It all seems common sense now with hindsight

[westwinds]

With AGM, I think you could fry your alternator without temperature sensing, but then I could not find anything on frying the Hitchai 55 amp alternator online. A partially discharged AGM can take all the current your alternator can supply because the AGM has what is called low internal resistance, unlike the normal flooded cell battery. However, if you have a battery bank of flooded cell batteries, the combined internal resistance drops because you are charging many batteries at once and you can still fry your alternator. I recently bought an alternator for an automotive application and most of the advertisements stated that using the alternator to charge for deeply discharged batteries could fry the new alternator. I went with a continuous duty 130 amp Bosch. For more information on high output marine alternators, I thought this was good: yachtwork.com/report-alternator-ideas

[Vasco]

With the stock Hitachi you won't have to worry about frying it. Without a lot of motoring your Hitachi will not keep the batteries up on your "long weekends". You only have about 140 amps out of your 400 amp bank to work with (50%-85% charged). I'd say a day and a half at anchor and you've used that up.

My 100amp externally regulated alternator died on me once on my 3GM30F on my CS36M while in the Bahamas. I had to go back to the stock internally regulated Hitachi. There was no way I could charge my modest 400 amp bank up while at anchor (without running the engine ten hours a day).

But if you're only doing the odd long weekend I would not worry too much about running the bank down once in a while. It`ll be a lot cheaper than upgrading the alternator, increasing the battery bank, and installing solar panels.

[westwinds]

Originally Posted by batkins61

...bigger alternator in the future (probably something in the 100A-120A range, which (according to a couple of alternator companies I've talked to) is what the 3gm30 can handle on a single belt). Also, any specific recommendations for regulators would be most welcome. I noticed that some of the popular brands don't even have alt. temp sensing (e.g. Ample Power), at least from what I read.

As always, thanks!

The yachtwork.com/report-alternator-ideas site (see my post #11) is created by the fellow who wrote the specification for 120 amps maximum for the Yanmar engines. Apparently this limit was determined for warranty reasons and the engines are capable of considerably higher power outputs from the front pully. See the part under Engine Mounting Configuration.

[Fuss]

Just a note on upgrading the alternator.

There are heavy duty alternators and light duty alternators.
I had a new 130a alternator on my start batteries and the most it ever put in was around 10 amps and I would say the maximum it had ever been to was 15 amps. This was extremely light use.
When I took it off after 2 years the bearings had a slight used feel. I would expect that had I run this alternator often at its full output, it would have burnt out.
This was a light duty alternator

I also have a 110a 24v alternator on my house bank. It runs at maximum output often and it runs seriously hot, sometimes for 2 hours.... no temp sensing on the alternator, I would never consider derating it for longer life (currently 6 years old).... I would run it at maximum output for 10 hours without a worry in the world. Bearings...smooth as silk.
.....Heavy duty alternator

Fire engines have heavy duty alternators for running at full output in very hot conditions. These are the sorts that should be used for house banks.

[westwinds]

Originally Posted by Fuss

Just a note on upgrading the alternator.

...I also have a 110a 24v alternator on my house bank. It runs at maximum output often and it runs seriously hot, sometimes for 2 hours.... no temp sensing on the alternator, I would never consider derating it for longer life (currently 6 years old).... I would run it at maximum output for 10 hours without a worry in the world. Bearings...smooth as silk.
.....Heavy duty alternator

Fire engines have heavy duty alternators for running at full output in very hot conditions. These are the sorts that should be used for house banks.

When I was looking at alternators the maximum temperature was about 194 degrees Fahrenheit or 90 degrees Celsius. It varied some; this was on the low side. Also of course, if you are charging, better run the RPM up to at least 2000 to get any decent amperage output. It will also help keep the engine warmed up more for less carbon buildup. Nigel Calder in his Marine Diesel Engines, states that eventually you will have to do a decarbonization by removing the cylinder heads and perhaps the pistons to remove baked-on carbon, especially if you run the engine at low speed and do not do routine maintenance. His book is an excellent one and goes into a lot of detail on open engine work. This and an engine manual for your particular diesel will allow you to do just about anything except work on fuel injection pumps, which requires clean room conditions and special equipment.