Go Back   iRV2 Forums > MOTORHOME FORUMS > MH-General Discussions & Problems
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
Thread Tools Search this Thread Display Modes
Old 11-03-2010, 12:23 PM   #1
Join Date: Oct 2010
Posts: 36
Electrical Questions...

I have a few electrical questions...

Does the engine alternator charge the house batteries along with the engine battery? The reason for the question would be if I hook up a inverter to the house batteries, I would want them to be charged as I am driving.

How large of an inverter can typically be plugged into the 12volt cigarette lighter?


2011 Forest River Georgetown 350, 36 ft, 3 slides and bunk beds for our 2 boys.
RVing since 2002.
Craig M is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 11-03-2010, 12:28 PM   #2
Moderator Emeritus
RickO's Avatar

Join Date: Jan 2007
Location: Litchfield Park, Arizona
Posts: 10,530
I would think that on a new coach like yours they would be charged while driving. I believe this is usually done through a bi directional solenoid which connects the two battery banks. It's the same one that's energized if you press your "emergency/aux start" button. I think a common way for you to answer your question is to measure voltage of you house batteries at the battery and then start the engine...give it a few minutes and then measure again. If it's higher then I think you're charging.

Good Luck...


Rick, Nancy, Peanut & Lola our Westie Dogs & Bailey the Sheltie.

2007 Itasca Ellipse 40FD
RickO is offline   Reply With Quote
Old 11-03-2010, 12:47 PM   #3
Senior Member
Old Bounder's Avatar
Fleetwood Owners Club
Ford Super Duty Owner
Join Date: Mar 2009
Posts: 1,636
Yes, your house batteries are charged from your alternator while driving. Typically, an inverter up to about 400 watts can be used from the cigar lighter plug for powering laptop, GPS, maybe a small TV, etc... NO larger loads should be attempted. It would be better to attach the inverter to the batteries with a much larger set of wires (cables) and extend the ac to the required area via a regular 120v extension cord.
Old Bounder is offline   Reply With Quote
Old 11-03-2010, 01:45 PM   #4
Join Date: Oct 2010
Posts: 36
Thanks, another related question.

The generator would also charge the house batteries, correct?

So, if I wire my TV outlets to run on a inverter all the time, the house batteries will never die as long as the engine is running, I'm plugged into shore, or the generator is running, correct?

Thanks again, I love this forum....
2011 Forest River Georgetown 350, 36 ft, 3 slides and bunk beds for our 2 boys.
RVing since 2002.
Craig M is offline   Reply With Quote
Old 11-03-2010, 02:41 PM   #5
Senior Member
GaryKD's Avatar
Newmar Owners Club
Join Date: Jul 2006
Location: Wellington, Florida
Posts: 12,533
Hi Craig M,
Your post is correct at a high level. However, I would never say never. Ya gotta put in more than you are taking out.
2005 Newmar KSDP 3910 + GMC ENVOY XUV 37K lbs Moving Down The Road
The Avatar Is Many Times Around The USA
Nobody Knows Your Coach Like Somebody Who Owns One Just Like Yours
GaryKD is offline   Reply With Quote
Old 11-03-2010, 04:47 PM   #6
Senior Member
Alan_Hepburn's Avatar
Fleetwood Owners Club
Workhorse Chassis Owner
Join Date: Feb 2000
Location: San Jose, Ca, USA
Posts: 1,091
Here's a rule of thumb for inverters: the current required on the input is 10 times the current desired at the output. So, if you're trying to pull a 10A load on the 120V output of the inverter it is going to pull 100A out of your 12V system. The numbers aren't exact, but they're close enough for you to make sure your 12V wiring is adequate for the load.

For example: let's look at a typical 400W inverter. If you use its full 400W capacity, that's 400W/120V = 3.3A available at the output of the inverter. In order to supply 3.3A at the output you need to put 33A in at 12V (actually a bit more due to inefficiencies in the inverter).

Many 12V accessory plugs are provided with a 20A or 30A fuse, so running a 400W inverter at its max output may or may not work without popping the fuse.

Scale that up to a typical 1000W inverter and you'll be surprised: that's 1000W/120V = 8.3A available at the output, and 83A required at the 12V input! I've never seen a 12V accessory plug wired to supply 83A - that's why decent inverters are installed real close to the battery bank, using LARGE 12V wiring. The currents involved are considerable.
Alan Hepburn - San Jose, Ca
2007 Bounder 35E being pushed by a 2008 smart fortwo Passion
Good Sam Member #566004 * FMCA Member #F431612
Alan_Hepburn is offline   Reply With Quote
Old 11-04-2010, 12:36 PM   #7
Senior Member
wa8yxm's Avatar
Damon Owners Club
Workhorse Chassis Owner
Join Date: Mar 2009
Posts: 23,951
Question 1: Yes
Question 2: 75 to 100 watts tops.

Home is where I park it!
wa8yxm is offline   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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
30 amp to 50 amp Electrical Upgrade mikwallace Winnebago Industries Owner's Forum 17 11-30-2009 10:17 AM
Installation of a New Open Grill Partition in the Electrical Compartment SteveG Winnebago Industries Owner's Forum 0 10-14-2009 06:46 PM
First Time Owner, Electrical Outlet Issue ATLFleetWood RV Systems & Appliances 18 09-02-2009 09:28 AM
Newbie Questions round 2 prpickett Newmar Owner's Forum 3 08-10-2009 12:22 PM
05 Journey Electrical Questions Wolf S Winnebago Industries Owner's Forum 11 08-10-2005 02:46 AM

» Featured Campgrounds

Reviews provided by

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 09:33 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.