Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 21-08-2014, 19:13   #76
Registered User

Join Date: Apr 2006
Posts: 4,413
Re: Inverter Dying?

Quote:
Originally Posted by transmitterdan View Post
Sandero,

I see this all the time. It takes a tiny difference for heat to build up and run away. Please don't be too surprised by what happened to you. It happens very often the way you described.

Good luck with your new installation. But don't be too surprised if the same thing happens again.
Different connectors... perhaps that will make a difference. It did last for 10 yrs before frying.
__________________

__________________
Sandero is offline   Reply With Quote
Old 21-08-2014, 20:24   #77
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,725
Re: Inverter Dying?

Quote:
Originally Posted by Sandero View Post

It's difficult to accept that the neg connection and pos connection were done differently and that one failed and the other remained perfect.
Both wire probably warmed up. The negative just got a bit hotter - slightly less torque on the nut holding the lug on, a bit of dirt between the mating surfaces, a crimp not quite as good as those on the positive cable, or moisture present on the connections. As posted the results you found are common.

All the more reason to use heavier wire than recommended. There is no downside to heavier cabling except for the few extra dollars it costs. Inverters probably last longer with heavier cables.
__________________

__________________
mitiempo is offline   Reply With Quote
Old 22-08-2014, 02:31   #78
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,019
Re: Inverter Dying?

I had time to run some numbers for those whose eyes have not yet glazed over. If the average (i.e. DC) battery current is 100A for a given inverter then assuming an ideal battery with no voltage sag the peak current is pi/2 times which is approximately 160A. The RMS (i.e. effective heating) current is pi/sqrt(8) times which is approximately 111A RMS. The heat generated is RMS current squared thus about 23% more than what one would expect from pure 100A DC.

The voltage drop will be at least 60% more than the simple DC math indicates. This is another good reason for using the recommended wire size or bigger.
__________________
transmitterdan is online now   Reply With Quote
Old 22-08-2014, 08:32   #79
cruiser

Join Date: Feb 2008
Location: North Charleston, SC
Boat: Camano Troll
Posts: 4,669
Re: Inverter Dying?

Quote:
Originally Posted by transmitterdan View Post
Before everyone starts foaming at the mouth about this please understand I am not looking for a fight nor to teach AC/DC circuits.
That's probably a good thing. You may know something but you're not doing a very good job of trying to explain it.

Again, you can't get alternating current out of a battery. And the DC current drawn by the inverter won't be more than what the manufacturer specifies so the manufacturer's installation instructions can be followed. There's certainly no harm in using larger capacity cables than required except for the cost and the difficulty installing them.

If you're trying to say that the inverter draws a high current followed by no current followed by a high current, etc. That's true in a sense but it's the average current over time that would cause the ampacity requirement..
__________________
rwidman is offline   Reply With Quote
Old 22-08-2014, 15:28   #80
Registered User
 
sparrowhawk1's Avatar

Join Date: Jan 2014
Location: Miami Beach Fl
Boat: Colombia Cc 11.8
Posts: 1,252
Anyone care to explain why both of the slots on the outlet to my west marine inverter are the same size. Meaning a two prong" safety"plug can go in with the neutral (larger) on the left or on the right. Answer because both are hot
__________________
sparrowhawk1 is offline   Reply With Quote
Old 22-08-2014, 16:31   #81
Registered User

Join Date: Jul 2013
Location: San Diego, CA
Posts: 3,157
Re: Inverter Dying?

Quote:
Originally Posted by transmitterdan View Post
No, it's not pulsating DC I am referring too (although cheap inverters do that too). It is the real 60 (or 50) Hz current waveform that flows from the battery. If you could see it, it would look like a sine wave except every other half cycle would be inverted. I'm not at a place where I can draw a picture easily but I will try to when I can.
I see.


So batteries sold in the US are 60 hertz and the ones in Europe are 50 hertz? Is there a way to tell if you're getting a 50 or 60 hertz battery in the store without an AC ammeter?
__________________
socaldmax is offline   Reply With Quote
Old 22-08-2014, 16:35   #82
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,019
Re: Inverter Dying?

Quote:
Originally Posted by rwidman View Post
That's probably a good thing. You may know something but you're not doing a very good job of trying to explain it.



Again, you can't get alternating current out of a battery. And the DC current drawn by the inverter won't be more than what the manufacturer specifies so the manufacturer's installation instructions can be followed. There's certainly no harm in using larger capacity cables than required except for the cost and the difficulty installing them.



If you're trying to say that the inverter draws a high current followed by no current followed by a high current, etc. That's true in a sense but it's the average current over time that would cause the ampacity requirement..
The current demand from the battery has both DC and AC components as you correctly stated above. The peak battery current demand can and does greatly exceed the published DC value. I would just ask you to measure it sometime and then we discuss why it must be so.

Ampacity is an RMS number because heating is due to RMS current which is not the same as mean or DC current. Inverters draw higher RMS current than DC current. That is because of the AC current component. The AC component does not contribute to the DC but it does cause heating. In an ideal world it causes 23% more heating and even more in the real world.

Voltage sag is caused by impedance (resistance+reactance) times instantaneous current. When the current demand is at the 160% peak of DC the voltage sag is much greater than the published DC value would indicate.

Ignoring RMS heating current and peak voltage sag is why many inverter installations do not last or perform as expected. When the inverter manual recommends wire size for 1% DC voltage drop they are not kidding.
__________________
transmitterdan is online now   Reply With Quote
Old 22-08-2014, 16:55   #83
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,019
Re: Inverter Dying?

Quote:
Originally Posted by socaldmax View Post
I see.





So batteries sold in the US are 60 hertz and the ones in Europe are 50 hertz? Is there a way to tell if you're getting a 50 or 60 hertz battery in the store without an AC ammeter?

That's just silly and not what I said at all. The frequency is determined by the inverter. I didn't think I needed to say that because it is so obvious.
__________________
transmitterdan is online now   Reply With Quote
Old 22-08-2014, 17:12   #84
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,019
Re: Inverter Dying?

Quote:
Originally Posted by sparrowhawk1 View Post
Anyone care to explain why both of the slots on the outlet to my west marine inverter are the same size. Meaning a two prong" safety"plug can go in with the neutral (larger) on the left or on the right. Answer because both are hot
I am not sure which model inverter you have. The reason could be as you state that black and white are each 60 volts making the total 120V. But I don't believe that comports with ABYC requirements. It could also be that the ground terminal is not connected to the white neutral circuit. That might make it seem as if neutral is hot but in reality it isn't.

If you have the model # or a link to the inverter user manual maybe I can figure out what they have done.
__________________
transmitterdan is online now   Reply With Quote
Old 22-08-2014, 17:38   #85
Registered User
 
sparrowhawk1's Avatar

Join Date: Jan 2014
Location: Miami Beach Fl
Boat: Colombia Cc 11.8
Posts: 1,252
Transmitterdan. You will take the time to look up my inverter which is nice. but you won't take the time (a few minutes) to watch a video where they explain why cheap inverters put half of the power on the neutral side? There's probably dozens of videos of people explaining it on YouTube. I don't claim to be anything near an electrician but this is something I'm sure of and it makes total sense
__________________
sparrowhawk1 is offline   Reply With Quote
Old 22-08-2014, 17:54   #86
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,019
Re: Inverter Dying?

Then I am not sure what you want to learn from us.

I have no access to You Tube at this time.
__________________
transmitterdan is online now   Reply With Quote
Old 22-08-2014, 18:01   #87
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Singapore
Boat: Maxi 77 - Relax Lah!
Posts: 11,514
Images: 4
Re: Inverter Dying?

Quote:
Originally Posted by transmitterdan View Post
Then I am not sure what you want to learn from us.

I have no access to You Tube at this time.
This is surreal.

What I'd like to learn is how my battery is producing AC current and if it is why do I need an inverter?
__________________
Relax Lah! is For Sale <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 22-08-2014, 18:09   #88
Registered User
 
sparrowhawk1's Avatar

Join Date: Jan 2014
Location: Miami Beach Fl
Boat: Colombia Cc 11.8
Posts: 1,252
I learn a lot on this forum,that's why when I have some knowledge I like to share it. Why both slots on my cheap inverter are large was a rhetorical question. How can u not have utube if you're talking to me?
__________________
sparrowhawk1 is offline   Reply With Quote
Old 22-08-2014, 19:18   #89
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Inverter Dying?

Quote:
Originally Posted by sparrowhawk1 View Post
How can u not have utube if you're talking to me?
There are many parts of the world where utube is either blocked or takes up so much bandwidth that trying to watch it is like watching paint dry - one frame at a time. We are almost constantly in those parts of the world where this is true. Google searches and chat forums are not even in that ballpark, so there is a gulf of difference between them.

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 22-08-2014, 19:42   #90
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,707
Re: Inverter Dying?

Maybe I'm dumb, but I thought that the "alternating" in AC meant that the direction of current flow alternated, otherwise it would be called VC (variable current).

If the current is alternating, half the time you would be charging the battery instead of discharging it. Hey - perpetual motion!
__________________

__________________
StuM is online now   Reply With Quote
Reply

Tags
inverter

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
420: 420 inverter issues. Our inverter is not working and we are not able to find a manual EW-WE Lagoon Catamarans 1 25-05-2014 09:27
Inverter Draw is it relative to the appliance using it or the wattage of the inverter felixqld66 Electrical: Batteries, Generators & Solar 5 06-06-2011 06:50
True (Pure) Sine Inverter vs Modified Sine Inverter Alecadi Electrical: Batteries, Generators & Solar 19 05-05-2011 07:19
Separate Charger and Inverter or Charger-Inverter ? SvenG Electrical: Batteries, Generators & Solar 14 15-10-2010 18:14
Calculating Amps Drawn Before Inverter and After Inverter ? impi Electrical: Batteries, Generators & Solar 23 26-09-2010 23:24



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:55.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.