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Old 08-16-2016, 04:12 PM   #1
Al
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Inverter use/alternator wear

Thought I had posted the following yesterday. Mystery so here I go again.
Al-Ketchikan

Greetings to the forum.
Status- our craft has a 1800 watt inverter our house battery bank is two 27 opium batteries, our alternator is 90 amp Delco. Our draw at any one time is a small coffee pot, a toaster, and the 110 fridge, and a 750 watt micro. Outside of the fridge demand, there is only one of the mentioned appliances in play at a given time.

Picture- Underway, fridge on the inverter, the coffee pot is utilized. The initial pull on the inverter has the amp gage pulling over 70 amps during the boil and then it settles back to normal following the cook. Same for the toaster.

question- What is the effect on the alternator peaking out at 70 amp off and on as the demand shows? In my mind, the demand through the inverter converting 12 volt to 110 cause the alternator to react and recharge the battery. Is this high amp delivery hard on the alternator. Should I be concerned?

I read here and there on the forum of requiring 140 amp alternators or running separate alternators to supplement usage. I would like to think our demands are minute enough to not cause alarm in the applications given. We do have a 2000 Honda and use it when we are off the engine and use of these appliances are employed over drawing down the batteries while on the hook and engine off.

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Al-Ketchikan 27íMarben pocket CRUISER
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Old 08-16-2016, 05:36 PM   #2
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Great question. I am eager for the answers.
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Old 08-16-2016, 06:45 PM   #3
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I just stayed at a Holiday Inn Express so here are my thoughts. The loads you mentioned are relatively short duration loads, say 10 minutes. So 70 amps for 10 minutes is a just 11.666 amp-hrs, not much. Your 90 amp alternator probably doesn't give you 90 amps. If it give you 70 amps that is probably good. I don't think the alternator will suffer loaded at 70 amps or even 90 amps for your short duration loads.
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Old 08-16-2016, 07:09 PM   #4
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Your two Group 27 Optimum AGM batteries can source a lot of current short term. So 70 amps shouldn't phase them. Yes, while you are pulling 70 amps from the batteries, the alternator is trying its damnest to replace them, but as noted above, it probably will just keep up.


So unless you are going to pull those loads from you inverter for a half hour or more, I wouldn't worry about the effect on your alternator.


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Old 08-16-2016, 07:50 PM   #5
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The short answer is "you're probably ok".

The long answer is "it depends".

What RPM is the engine running at? Remember, proper cooling of the alternator is dependent on the fan on the front of the alternator. 1,200 RPM is going to have that 90 amp alternator putting out 70 amps, cooking. Turning 2,000 RPM is going to be significantly better. Delco doesn't make a particularly stout alternator. So using it in this way for an hour would be tough on it. I used to have a 150 amp Delco on my charter boat to run an air conditioner. Was pulling 100 to 120 amps out of it for a couple of hours at a time. It ran off a large second pulley to spin the alternator faster for proper cooling. They would last one to two seasons before the regulator, diode bridge, or the winding would fail. Always kept a spare and got quick at changing it. Finally switched to a commercial duty Leece Neville alternator. There used on fire trucks, ambulances and charter buses. Designed to run high loads at low RPMs. No failures in 6 years! That's what I put on my trawler for the second alternator.

Back to your question: You probably won't have a problem. Keep the RPM up for cooling. If you plan to do it greater than 15 minutes, turn the load off for 5 minutes to let it cool down before resuming. Buy a spare alternator and pulley so that you can swap it out away from the dock.

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Old 08-17-2016, 06:42 AM   #6
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Not only good question and responses, but excellent thread title. Kudos all round!
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Old 08-17-2016, 06:51 AM   #7
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WHO built the alt is the first question.

A car style alt will hardly put out its rated amps when warm , which is good as you have plenty of time to put a bit of juice back in the batts.

A more robust alt like from a commercial truck would be less loaded , but with alt life measured in years , so what?

The only time the alt output , and style, is a concern is when you need TOTAL Rated output for hours on end.
A small alt and a massive batt set.

A large battery bank with a smart 3 -4 stage V regulator will show up a poor alt very quickly.
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Old 08-17-2016, 07:15 AM   #8
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Quote:
Originally Posted by Al View Post
Snip...
question. Is this high amp delivery hard on the alternator. Should I be concerned?
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Al-Ketchikan 27íMarben pocket CRUISER
Not for short periods as you described .
No.
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Old 08-17-2016, 11:03 AM   #9
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If you are worried about overloading your alt, just check it's temperature. I don't know how hot they can run, but if outside of case is under 200F it should be fine. High load won't wear anything, the only issue is heat.

If you smell that "electrical" smell, or if smoke is coming out, that's too much load!!
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Old 08-17-2016, 02:08 PM   #10
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A 200 deg case temperature is pretty hot. I think that the Balmar temperature probe on their external regulators cuts the alternator output in half at 160 degrees. But Ski is right, it is heat, not wear that will toast your alternator.


But 10 minutes to make your coffee or toast your bagel isn't going to hurt anything. And in most cases your propulsion engine won't even be running when you do these. When you start up your propulsion engine after two ten minute high wattage inverter events, your batteries will only be down another 20 AH or so, and the alternator won't have to work hard to replace those AHs.


But do consider other overnight loads. A refrigerator can pull 50-100 AH in a 24 hour period, lights another 10-20 AH. So if your Optima batteries are down to half, it can put a significant load on your propulsion engine alternator.


But I have done the same thing, with 440 Ah of battery capacity and stayed on the hook two nights. The OEM 80 amp Hitachi alternator on my engine had to work hard at first when the engine was started after two days on the hook and some 125 AHs consumed. It put out 60 or so amps at first but within 30 minutes it had dropped to 30 amps output.


I am sure it was in the upper 100s and maybe 200+ when it was putting out 60 amps, but the temp probably dropped after the current dropped off. No harm done, but I only did that once or twice each year.


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Old 08-18-2016, 06:41 AM   #11
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"It put out 60 or so amps at first but within 30 minutes it had dropped to 30 amps output."

Was this because the batt set was charged enough so 30A was all that was needed, or is that the Hot output of The OEM 80 amp Hitachi?

Your SOC meter will tell which .
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Old 08-18-2016, 08:55 AM   #12
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Quote:
Originally Posted by FF View Post
"It put out 60 or so amps at first but within 30 minutes it had dropped to 30 amps output."

Was this because the batt set was charged enough so 30A was all that was needed, or is that the Hot output of The OEM 80 amp Hitachi?

Your SOC meter will tell which .
I didn't have a SOC meter on that boat, but I suspect it was some of both, but probably more as a result of SOC than reduced hot alternator output. Based on the AH used (not from a SOC meter, but from extrapolating instantaneous readings) and the 30 minutes of higher charging rate, the batteries were about 80+% full which should have resulted in lower amperage demand while charging.

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Old 08-18-2016, 07:32 PM   #13
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Thanks fellows,
The responses are outstanding! We will go forth with confidence knowing our process of use is within boundaries of smart usage.


While the Delco alternator is rated at 90 amp as one poster stated, our amp gage reflects a max of 70 amp under draw.
I have an extra Delco alternator from our prior engine, it is 60 amps but will serve as a backup, thanks for mentioning I had stored this unit on shore and now it will be back on the boat along with a soon to be spare starter.


We run at 1350-1400 RPM. Our climate is such that heat other than engine compartment, is not a factor. As the engine temp shows 160 degrees, I assume the engine compartment is similar. Will have to remember to pack a thermometer out of curiosity.


Wanting to stay with a single pulley system when I purchased this alternator, I had asked for the highest amperage available. It would appear from the comments the need to go higher in amperage is not there given the loads created.


This forum rocks!! Your willingness and participation on this inquiry and so many others read serves as a priceless resource. Yes, I know, free advise often is worth little, yet, experience has a value, Thanks again for sharing.

Al-Ketchikan, 27' Marben Pocket CRUISER
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Old 08-18-2016, 07:43 PM   #14
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I really can't add anything to the discussion but I would like to know where you got those batteries..."1800 watt inverter our house battery bank is two 27 opium batteries, "?
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Old 08-18-2016, 08:20 PM   #15
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NAPA - Would the question be: We replaced two 27 size NAPA batteries with these. As well a correction is required, we have a 1500 watt inverter, not 1800. Outside of mis-spoke, this inverter covers the wattage of our 'stuff'.


Does this help? feel free to make inquiry


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Old 08-18-2016, 08:36 PM   #16
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NAPA sells opium???? No more buying it on the street corner for me!
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Old 08-18-2016, 08:43 PM   #17
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😂😂😂😂😂😂
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Old 08-18-2016, 11:06 PM   #18
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Aaaaaaaa Explicit!


Okay fellows, I be the 'Dope' here!
Al
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