Leah:

Off/On?  Your Charger is the same unit as your inverter.  The only On/Off switch you have is for the Inverter side, which only comes into play when you are NOT plugged in.  When you are plugged in, your charger is operational without you doing anything.  When you are plugged in, your inverter is NOT operational, regardless of the switch setting.  You should keep your inverter switch Off, when not plugged in, unless you want to run AC loads without starting your generator.  OK for small loads, for a short time, but generally, too much inverting will deplete your house batteries.  If you are always either plugged in, or driving (where the alternator picks up the slack), you won't need to worry about it, as your batteries will keep up.

Leah,
Gil is right, if you leave the inverter/charger turned on to charge the batteries with the inverter portion turned off, all of the batteries will stay charged. There is no reason to use a battery minder on your coach.

Your corrosion problem is probably from the gas that your lead/acid batteries give off when they are being charged. There is no way to prevent corrosion with your battery banks unless you go to an AGM (absorbed glass mat) battery bank. AGM batteries are sealed, so there is no out gassing to cause corrosion, and you never have to add water. They will also hold a charge a little better than lead/acid batteries, however they cost twice as much.

Gerald

Ok guys,
I use the battery minder on the chassis batteries BECAUSE if I don't the batteries lose power and show "low battery" reading on the Aladdin screen on the dash.  The parasite drain brings them down.  I have not been in the habit of turning off the chassis switch in the engine compartment.  On the Magnum panel (mid coach) there are two (2) buttons ,one labeled for charger, "on/off" one labeled "inverter "on/off".  I always have the charger button "on"  The inverter button is always "off" UNLESS I need power if "not" plugged in to 120v.  

If there is a battery feed to the chassis batteries, either it is not working, OR I don't know how it is activated.  On my previous 99 Thunder, it was activated by tuning the coach key position to the "left".  That doesn't seem to be the case on my 08 Contessa however.  

Quoted from LEAH DRAPER

.....If there is a battery feed to the chassis batteries, either it is not working, OR I don't know how it is activated.  On my previous 99 Thunder, it was activated by tuning the coach key position to the "left".  That doesn't seem to be the case on my 08 Contessa however.  

If your 08 is like my 04, it uses two relays called the "Big Boy" and "BIRD" to make sure both sets of batteries are being charged whenever there power from any source.  The relays are automatic.  My owners manual has a pretty good description of how they are supposed to work.  Both relays are made by Intellitec http://intellitec.com/.  Manuals for the relays are at their website.  

I have not looked at it recently, but would be happy to dig out the books and re-learn it if I can help with questions.

If you don't have those relays, it is very unlike Beaver or Monaco to create something where both sets of batteries are not automatically kept charged.  On the odd chance yours does not work that way, there are some easy fixes that will make it automatic.

Good luck.

Leah,
Your coach has a "Bird' relay module that should energize the "Big Boy" solenoid to tie all batteries together when one bank is charging so that all batteries are charged equally. The "Bird" module should then de-energize the "Big Boy" when neither of the battery banks is charging to prevent one battery bank from discharging the other.

The "Bird" system is automatic and requires no operator input. So if your inverter/charger does not keep your chassis batteries charged when you are plugged into shore power, and it is charging the house batteries, the "Bird" system is malfunctioning, and should be repaired.

Gerald  

OK.........I have no idea where these BIRDS and BIG BOYS are located, or what they might even look like,  MUCH LESS how to check them.  This is a little above my skill and knowledge level.  I guess since it isn't an issue that is causing a problem right now, I'll put it on my list to have checked next trip it make to Bend Service Center.  I am not sure I trust RV dealers here.  

Appreciate all your help guys.

Quoted from LEAH DRAPER

OK.........I have no idea where these BIRDS and BIG BOYS are located, or what they might even look like,  MUCH LESS how to check them.  This is a little above my skill and knowledge level.  I guess since it isn't an issue that is causing a problem right now, I'll put it on my list to have checked next trip it make to Bend Service Center.  I am not sure I trust RV dealers here.  

Appreciate all your help guys.

On mine they are in the box above the batteries where the red cutoff switches are.  Click here http://intellitec.com/pdfs/BATTERY_web/5300366.000.pdf for a picture of what the BIRD (Bi Directional Relay) looks like and an explanation of how it works.

On my '08 Contessa these relays and their control electronics are located in the panel with the main DC switches for the chassis and house battery banks.  This is located, in my coach, in the furthest rear bay.  As I've said before, if I ever have problems with this system, I 'm changing over to the proven and far simpler systems used in boats.

Quoted from Gil_Johnson

.... if I ever have problems with this system, I 'm changing over to the proven and far simpler systems used in boats.

How do they do it in boats?

Totally self contained, high current load capability, emergency combining of banks, charging of both banks from a charging source on either bank, low voltage bank isolation.  Check it out: http://bluesea.com/category/2/productline/388

We lived aboard a 50' sailboat for almost 10 year and batteries were an essential part, perhaps the most important, system on the boat so utter reliability vital.

The system had two banks of 6 each Trojan T-105's house batteries and two 12V engine start batteries.  These were charged by a Freedom 20 (2000W inverter/charger) and a high output Powerline alternator.  The Alternator was controlled by a Balmar smart 3 stage regulator.  Note that the regulator also monitored the alternator temp and would reduce output if necessary to prevent burnout.

Charging current from the alternator fed the start battery preferentially and the house batteries were connected with a voltage sensitive relay once the start battery was refilled.  The inverter charged the house bank(s) preferentially and the start battery through another relay once the house batteries came up to a predetermined voltage.

in addition, we had a manual paralleling switch for the two house banks (used mainly for isolation in the event of failure) and a paralleling switch from the house banks to the start battery.

All functions were controlled and monitored with a Link 2000 monitor as well as the inverter remote panel.

A Westerbeke 5KW generator rounded out the electrical system but was seldom used unless anchored for a significant period.  Most charging was done with the engine duing transits.

Very simple, very robust, and totally without problems.