Community Forums

DEG503 · 12-13-2009, 02:20 AM

I know this subject has been discussed a lot but my issue seems to be slightly different

. I have a 97 Monaco Exec. Most of the charging issues I have read are with the chasis batteries not being charged while on shore power. My RV accomplishes this as far as I can tell. My chasis and coach batteries are charged by the solar panels, generator, and shore power. But I do believe that my coach batteries are not charged by the engine alternator. Therefore, while driving, the coach batteries (which run the house sound system and that is the only way I can hear the radio) get drained and the only way to recharge them is to start the generator!

To the point, I believe the echo charger will do the trick because it will charge both sets of batteries (chasis and house). Correct??

I saw some great discussions and pictures for a BIRD. Does my older rv have this board that can be retrofitted? ( I know, I will pull wiring diagrams as soon as I can get to the coach but I dont have them right now) I'm hoping that someone with a similar year/model will have some additional insight.

Happycarz · 12-13-2009, 12:36 PM

Dave,
Does your coach have two run (electrical) panels in the engine bay? I believe it does. The one on the right should contain an aluminum finned device with three battery cables attached to it. It might be green, blue or just unpainted aluminum. This is a solid state battery isolator and is what Monaco used at the time to charge both batteries from the engine alternator.
Let us know if your coach has one of these devices.

Dutch Star Don · 12-13-2009, 10:19 PM

DEG503......HAPPYCARZ has you looking for the right part and you can probably plan on replacing it once you find it. It would have to be a REALLY old coach not to have a battery isolator that charges both batteries.

The isolator allows the alternator to jump back and forth between the lowest batteries (house and coach) and keep them charged.

You shouldn't have to buy a replacement from Monaco. Most RV/Auto parts stores should sell the one you need. Just check the numbers on the old one for size.

DEG503 · 12-15-2009, 08:26 AM

OK, I will be home on Thurs AM Dec 16. I can't wait to explore for the battery isolator. It sure will be nice if its that easy a fix.

One question though. Is the battery isolator in the engine bay ONLY for the engine alternator or does it function with the genset,shore power and solar panel? Cause like I said, all other sources of power seem to charge both sets of batteries.

David

Happycarz · 12-15-2009, 07:27 PM

The isolator consist of diodes mounted in a big finned heat sink. There are three studs (sometimes 4) to attach the alternator, the house battery and the starting battery. When the engine is running the alternator current flows through the diodes to both battery banks with the lowest bank getting most of the charge until they are at the same voltage and then they continue to come up together. When parked, the current cannot get past the diodes, as they are one way gates for electricity. Now the batteries are isolated from each other.

To answer your question, the isolator is only for charging the batteries with the engine running. This device is not in use with the genset or shore power.

Link to battery isolator: http://www.rvupgradestore.com/index....OD&ProdID=2069

DEG503 · 12-16-2009, 03:40 PM

Alright, here we go. If I understand y'all correctly the blue finned device is the battery isolator.

My game plan is to study my wiring diagrams. Figure out which post goes to the house/coach batteries and put a tester on it to check for output. Any reason why that wouldn't help me troubleshoot it? Could it also be one of the relays in there? I'm assuming again, but that's what those rounds metal devices that are in the upper right hand portion of the box?

David

Happycarz · 12-16-2009, 05:45 PM

Dave,
You're correct, the blue finned device at the bottom is the battery isolator. The relay directly above it is the battery boost relay. When holding down the dash boost switch, both battery banks are tied together when this relay is energized. That is why you have the red cables between the boost relay and the isolator.

To test the isolator, take three voltage readings at the three studs on the isolator with the engine off. The center stud is from the alternator and will (should) have no voltage. Then take readings at the upper and lower studs - the ones with two red cables attached. One goes to the starting battery and the other goes to the house batteries. The voltage on these two will be the same as, or very close to, the voltage of the respective battery bank.
Now start the engine and run it at fast idle and take the voltage readings again. The center stud should now have voltage and both the upper and lower should be higher than the original readings. If both have gone up you should be in good shape. If only one goes up, the the isolator is bad.

An alternative test would be to shut off the battery disconnect switches, then take the 5 cables off the 3 studs. Set you meter to diode test, or if not equipped, to the ohm scale, and take reading between the center stud and the upper stud. Then using those same studs, take another reading, reversing your meter probes. One reading will show open (O L on most meters) while the other reading will show close to zero ohms.

Let us know the results.

Happycarz · 12-16-2009, 08:29 PM

Dave,
You also have a dual battery maintainer. It is the green finned device to the left of the battery isolator.

DEG503 · 12-19-2009, 01:48 AM

I immediately ran into a problem while testing the isolator. With everything turned off I was getting a votage reading of 11.83 volts at the center (alternator) stud. The other 2 studs read essentially the same voltage of their respective battery banks. Through this process I could deduct that the top stud is the one for the coach batteries. Any idea where the voltage through the center stud could be coming from? or is this indicative of a bad isolator. With the main engine on and generator off I saw no change in the charge going to the coach batteries. With the gen on and the main engine off I did see charging current going to the coach batteries. (13.75 with gen on vs 12.5 volts with gen off)

Happycarz · 12-19-2009, 10:56 PM

The diodes in the isolator are one way streets for the electricity and they aren't doing their job. Replace the isolator.

But first take the cable off the center stud and put you volt meter on the stud. If you now have voltage there you just verified the isolator is bad. The factory wiring was that the alternator cable went directly to the center stud with no other voltage source attached anywhere along the way. When you test the cable that came off the center stud, there should be no voltage. This will verify such. Keep testing, you are getting close.

MonacoMama · 12-20-2009, 02:30 AM

Harry- I am trying to decide what type of label that we should put on you!!

hardy1000 · 12-20-2009, 06:07 AM

Mama, Harry has also helped me by phone and is truly a very knowledgeable person willing to share his expertise. Not only is he knowledgeable he goes beyond as demostrated in this post. I have learned alot from this forum about my MH, but the real value is the great people that support it. I look forward to meeting alot of you in Quartzite.

Thanks everyone,

Happycarz · 12-20-2009, 08:53 PM

MM,
I already have a label - Happycarz. For years I have been making cars happy, hence the label. I'm glad I can help make someone's day better. Many have done the same for me.

DEG503 · 12-25-2009, 09:04 AM

Yep, there was still voltage at the center stud, bad isolator. Called LazyDays, they had one in stock, 180 dollars. Called Southeast power systems in Orlando, they had one in stock for 81 dollars. Case closed, installed, now I have charging as I go down the road, no more drained battery from stereo, I bet I'll even be able to run the fridge on AC while driving!

Thanks to eveyone!!!