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alernator/battery/charging
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Author:  vnflores13 [ Thu Apr 13, 2017 6:30 pm ]
Post subject:  alernator/battery/charging
hello, i have 5.8 omc with a 65amp alternator only upgraded the stereo pushing 2k watts also a 27 and 31 batteries with a switch...Problem: when i park to hangout i switch to the house battery then when its time to go i switch to the starting battery once on the go i switch back house battery to charge but half way back to our launch site the boat starts to hesitate so i decide to switch the battery back to the starting battery and the hesitation stops, could it be that im drawing more then producing amps remember the alternator is 65 amps could it be not charging enough that im just drawing??? should i get a bigger alternator?? need help thank you in advance :D
Author:  alex8q4 [ Thu Apr 13, 2017 7:15 pm ]
Post subject:  Re: alernator/battery/charging
2,000 watts on a 12 volt system draws 167 amps.

1 hell of a stereo you have there!

Not sure what exactly you need, but yes you will have to upgrade your DC system.
Author:  Wylie_Tunes [ Thu Apr 13, 2017 7:17 pm ]
Post subject:  Re: alernator/battery/charging
Are you shore charging once back at base?
I would start by testing the state of the battery
Testing the output of the alternator off idle with some load. Both at the alternator and at the batteries.
This is based on the assumption that the switch is wired in its more ideal manor and not some one-off scheme. Meaning the house bank gets alternator input with engine running.
Author:  vnflores13 [ Mon Apr 17, 2017 5:48 pm ]
Post subject:  Re: alernator/battery/charging
yes, im considering upgrading the alternator to put out more amps instead of drawing more then it puts out, just need to find a place that sells high output alternators...thnx alex8q4
Author:  Wylie_Tunes [ Mon Apr 17, 2017 5:53 pm ]
Post subject:  Re: alernator/battery/charging
Just a quick note. 2000W on the audio output side is in AC, and does not equate to DC draw at 12V. another thing to consider, is that 2K watts in true RMS or using the amp manufacturers advertising "peak" numbers?
Author:  vnflores13 [ Mon Apr 17, 2017 5:54 pm ]
Post subject:  Re: alernator/battery/charging
No im not charging once back at shore only charge the batteries before we got out for the day or weekend. already tested the alternator its fine but havent tested it at the battery while running im going to do that next time out or msybe in the driveway with running water....the main charging cables have been upgraded to thicker gauge they are both set up to charge as long as the perko switch is set to the specific battery....thnx for the input captains
Author:  vnflores13 [ Mon Apr 17, 2017 5:57 pm ]
Post subject:  Re: alernator/battery/charging
im lame when it comes to tech talk captain can you explain it a lil more clearly..LOL..
Author:  vnflores13 [ Mon Apr 17, 2017 5:59 pm ]
Post subject:  Re: alernator/battery/charging
Wylie_Tunes wrote:
Just a quick note. 2000W on the audio output side is in AC, and does not equate to DC draw at 12V. another thing to consider, is that 2K watts in true RMS or using the amp manufacturers advertising "peak" numbers?

im lame when it comes to tech talk..LOL..what the translation?? :D
Author:  vnflores13 [ Mon Apr 17, 2017 6:01 pm ]
Post subject:  Re: alernator/battery/charging
alex8q4 wrote:
2,000 watts on a 12 volt system draws 167 amps.

1 hell of a stereo you have there!

Not sure what exactly you need, but yes you will have to upgrade your DC system.

i already upgraded the main charging cables to a bigger gauge, just looking for a place that sells high output alternators..thanks captain.
Author:  Wylie_Tunes [ Mon Apr 17, 2017 7:40 pm ]
Post subject:  Re: alernator/battery/charging
vnflores13 wrote:
Wylie_Tunes wrote:
Just a quick note. 2000W on the audio output side is in AC, and does not equate to DC draw at 12V. another thing to consider, is that 2K watts in true RMS or using the amp manufacturers advertising "peak" numbers?

im lame when it comes to tech talk..LOL..what the translation?? :D

In your opening post, you stated you have a 2000 watt stereo. it was then calculated that it is putting a 167 amp draw on the boat.

The 2000 watt is in AC but the stereo draws DC. You cant apply ohm law using audio AC and come up with a DC current draw. Realistically, your 2000W system is not drawing anywhere near 167A DC.

next piece of the puzzle. That 2000W could be an unrealistic never achieved peak amplifier output number used for advertising. A more real world figure would be no more than half that in terms of watts RMS. In this case, the amp draw calculations would be much much less than 167A DC.

You need to charge batteries as soon as possible. Leaving them down until the next trip out will hinder their return rate.
Author:  vnflores13 [ Mon Apr 17, 2017 10:56 pm ]
Post subject:  Re: alernator/battery/charging
Wylie_Tunes wrote:
vnflores13 wrote:
Wylie_Tunes wrote:
Just a quick note. 2000W on the audio output side is in AC, and does not equate to DC draw at 12V. another thing to consider, is that 2K watts in true RMS or using the amp manufacturers advertising "peak" numbers?

im lame when it comes to tech talk..LOL..what the translation?? :D

In your opening post, you stated you have a 2000 watt stereo. it was then calculated that it is putting a 167 amp draw on the boat.

The 2000 watt is in AC but the stereo draws DC. You cant apply ohm law using audio AC and come up with a DC current draw. Realistically, your 2000W system is not drawing anywhere near 167A DC.

next piece of the puzzle. That 2000W could be an unrealistic never achieved peak amplifier output number used for advertising. A more real world figure would be no more than half that in terms of watts RMS. In this case, the amp draw calculations would be much much less than 167A DC.

You need to charge batteries as soon as possible. Leaving them down until the next trip out will hinder their return rate.

ok gotcha, good break down.. :D ..should i still consider upgrading the alternator to maybe 150 amps+?..pretty much learning as i go..thnx again captain
Author:  chris268 [ Tue Apr 18, 2017 3:22 am ]
Post subject:  Re: alernator/battery/charging
Wylie_Tunes wrote:
vnflores13 wrote:
Wylie_Tunes wrote:
Just a quick note. 2000W on the audio output side is in AC, and does not equate to DC draw at 12V. another thing to consider, is that 2K watts in true RMS or using the amp manufacturers advertising "peak" numbers?

im lame when it comes to tech talk..LOL..what the translation?? :D

In your opening post, you stated you have a 2000 watt stereo. it was then calculated that it is putting a 167 amp draw on the boat.

The 2000 watt is in AC but the stereo draws DC. You cant apply ohm law using audio AC and come up with a DC current draw. Realistically, your 2000W system is not drawing anywhere near 167A DC.

next piece of the puzzle. That 2000W could be an unrealistic never achieved peak amplifier output number used for advertising. A more real world figure would be no more than half that in terms of watts RMS. In this case, the amp draw calculations would be much much less than 167A DC.

You need to charge batteries as soon as possible. Leaving them down until the next trip out will hinder their return rate.


Ohms law is ohms law, the difference being in AC there is reactive power (wasted and true power(resistive) you must use an RMS value (peak x .707) or an average value (peak x .636 =DC equivalent) to compare correctly.... so if it's 2000 watts peak, it's 1272 watts average power which would still, be approx 100 amps at max volume.... I use average for D.C. And use rms for AC..... either way, it's a lot of power, I would recommend charging when you get back also, not before you leave. Manufacturers like to use peak values to make it seem huge...

Anyway, fun stuff
Author:  Wylie_Tunes [ Tue Apr 18, 2017 7:35 am ]
Post subject:  Re: alernator/battery/charging
vnflores13 wrote:
ok gotcha, good break down.. :D ..should i still consider upgrading the alternator to maybe 150 amps+?..pretty much learning as i go..thnx again captain

I think there is still some diagnosing that can be done. I would want to first rule out a failing battery. Meaning its unable to even reach full charge. This handycaps the whole house bank prior to ever heading out. Then places a larger load on the alternator once you pull anchor and head back. I would want to test all the main battery and supply cables. The alternator may be charging fine, but a bad cable along the way, is resulting in low voltage to the engine and or other system. Or, you just might have a weak alternator and its time to replace. In that case, yes, upgrade. Just keep in mind that you will also need to upgrade its output cable.

I think you need a larger, as in more AH, house bank. This will allow for shallower cycles at anchor, leaving you with higher static battery voltage levels in the house bank, when you are ready to pull anchor. battery(s) will have a longer life span.
Author:  vnflores13 [ Mon Apr 24, 2017 6:49 pm ]
Post subject:  Re: alernator/battery/charging
Wylie_Tunes wrote:
vnflores13 wrote:
ok gotcha, good break down.. :D ..should i still consider upgrading the alternator to maybe 150 amps+?..pretty much learning as i go..thnx again captain

I think there is still some diagnosing that can be done. I would want to first rule out a failing battery. Meaning its unable to even reach full charge. This handycaps the whole house bank prior to ever heading out. Then places a larger load on the alternator once you pull anchor and head back. I would want to test all the main battery and supply cables. The alternator may be charging fine, but a bad cable along the way, is resulting in low voltage to the engine and or other system. Or, you just might have a weak alternator and its time to replace. In that case, yes, upgrade. Just keep in mind that you will also need to upgrade its output cable.

I think you need a larger, as in more AH, house bank. This will allow for shallower cycles at anchor, leaving you with higher static battery voltage levels in the house bank, when you are ready to pull anchor. battery(s) will have a longer life span.

what is more AH?? :D ...im going to pull the both batteries out fully charge them and then put the load to them one at a time i will test them with a meter...
Author:  LouC [ Tue Apr 25, 2017 6:03 am ]
Post subject:  Re: alernator/battery/charging
If you're going to keep using a system that draws that kind of power, I can't imagine a normal 65 amp alternator is adequate. In fact there are vehicles made even 20 years ago that had 130 amp alternators. I think you need to contact a marine electric place, and tell them what you are trying to do, they may be able to custom build a marine alt that will put out the current you need. Try Arco Marine in Fla.
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