Charging System, Moderately High Voltage, need ideas

[fcooper]

The motorhome is described in signature block below. With the VMSpc monitor, I normally see voltage in the range of 13.6 to 13.8. Today on the highway, I am seeing 14.1 to 14.3, then back to 13.9. When stopped for a quick lunch with the engine on fast idle (1000 rpm), I was seeing 14.3 and sometimes 14.4 volts. We were operating in temps of 40 to 50 degrees, so I don't suspect the grid heater turning on.

On this coach, the house batteries are not linked to the cranking batteries in any manner, so the alternator is only charging the cranking batteries and supplying voltage to operate the chassis.

Need advice on what the most likely cause of this could be, or maybe some troubleshooting advice. I'm thinking one or both of the 2 year old cranking batteries may be going bad, but they still crank great. I felt of both of them as soon as we stopped for the day, and they were not warm so I don't suspect overcharging. I'm also considering that the voltage regulator in the alternator may be beginning to fail. The alternator has about 100,000 miles on it.

Is 14.3 to 14.4 too high for charging voltage? Your thoughts appreciated.

Thanks

Fred

[JimM68]

Fred, good going getting your isolator delay working.

Monaco used several systems thru the years, all were addons to the mainboard. Yours can be replaced with any of several "Bidirectional Isolator Delay" systems to get you charging in both directions. Send me an email, or pm me your email address, and I'll send you what info I have.

[rgatijnet1]

Everything sounds like it is just fine. I travel with my OBDII gauge hooked up continuously to monitor important functions that are going on. One of the things I monitor is the charging voltage. During normal operations, Winter or Summer, my charging voltage will swing from 13.5 to 14.5 volts. If I was to pick an average, I would say that would be around 14.2 volts BUT, it never stays at one voltage long enough to call it an average.
By watching the charging voltage fluctuate you get an idea of what the computer controlled charging system is doing. Basically it is compensating immediately for any needed charge to keep the house AND chassis batteries at peak voltage. If your inverter is on, then your house batteries will need charging a little more often than the chassis batteries.
My AGM batteries have endured this charging pattern for about three years with no damage at all. I am guessing that everything is normal and your charging system is operating just fine to keep your batteries at peak charge.

[hardtobe]

fcooper wrote:
OK...I stand corrected. After having this coach for 9+ years, I'm still learning about it. My coach did have a means of charging the house batteries when the engine is running,but it did not work (until I cleaned up the wires).

While installing new 6 volt batteries (I believe they made it 14 years), I cleaned up connections and got curious about a small black box above the aux start relay. After removing it from the wall, I could see the label "Intellitec Isolator Relay Delay". Some research reveals this is supposed to close the relay therefore charging the house batteries as well as the chassis batteries when the engine is running. Using the handy voltmeter, I could tell it was not working. After cleaning up the connections on on the relay, it is now working.

Unfortunately, there is nothing in place to keep the chassis batteries charged when on shore power. This will be a future project.

Fred

Do what we all do or have.Install a mini trickle charger that plugs into 120V outlet and will keep your Chassis batterys charged up
On a side note I don't see 14.2V from alternater while driving as a concern(at least not to me)

[fcooper]

OK...I stand corrected. After having this coach for 9+ years, I'm still learning about it. My coach did have a means of charging the house batteries when the engine is running,but it did not work (until I cleaned up the wires).

While installing new 6 volt batteries (I believe they made it 14 years), I cleaned up connections and got curious about a small black box above the aux start relay. After removing it from the wall, I could see the label "Intellitec Isolator Relay Delay". Some research reveals this is supposed to close the relay therefore charging the house batteries as well as the chassis batteries when the engine is running. Using the handy voltmeter, I could tell it was not working. After cleaning up the connections on on the relay, it is now working.

Unfortunately, there is nothing in place to keep the chassis batteries charged when on shore power. This will be a future project.

Fred

[topflite51]

Just asking.

If it does not charge both sets of batteries (chassis and coach) why would one need such a high output alternator?

[fcooper]

FIRE UP wrote:
Fred,
(...text deleted...) as long as I've been camping, starting with a couple of trucks and campers, then, two class Cs, a '78 Dodge "4-Star" (440 cu.in.), an '89 Ford Class C, (460 cu.in.), a '99 Fleetwood Bounder Class A with the V-10 and finally, our present coach, an '04 Itasca Horizon 36GD with the 330 C-7 CAT and, every one of those units have the engine alternator charge both sets of batteries.
(...text deleted....) but, are you sure that you don't have something broke or, disconnected that is supposed to be charging your house batteries while driving? Sure seems a bit odd to me but, again, I'm no expert. Just wondering.
Scott

Scott

Thanks for your post.

I would love to find an existing charging circuit to keep the house batteries up while driving.

When the chassis is produced by Freightliner and delivered to the manufacturer of the motorhome, it only has cranking batteries. The house batteries are added by the motorhome manufacturer. As far as I can tell, Holiday Rambler (Monaco) did not add the charging circuit to this model. If anyone out there that has a 2000 era Holiday Rambler on a Freightliner chassis reads this, please chime in and let us know if your chassis has a device to automatically tie the two circuits together.

Any/all ideas welcome.

Fred

[fcooper]

dougrainer wrote:
ALL Monaco/HR built motorhomes charge BOTH battery banks from the Engine Alternator. Regardless of year. The fact that you have verified yours does NOT, means nothing except your system is malfunctioning. Find and fix the dual charging problem also. IF your APU (Genset) was running during the voltage spike, that may be your problem, Was your Genset running? Doug

Thanks for the reply Doug. I have learned a lot from all of your posts.

I am positive that there is nothing in the battery compartment tying both battery banks together, and I've been into/around most everything on this coach since buying it about 10 years ago. This coach is on the Freightliner chassis. Is there somewhere beside the battery compartment that could house the dual charging components?

Fred

[wa8yxm]

Sounds like a GM alternator.. Those are the same voltages I often see.

[dougrainer]

ALL Monaco/HR built motorhomes charge BOTH battery banks from the Engine Alternator. Regardless of year. The fact that you have verified yours does NOT, means nothing except your system is malfunctioning. Find and fix the dual charging problem also. IF your APU (Genset) was running during the voltage spike, that may be your problem, Was your Genset running? Doug

[FIRE_UP]

Fred,
First off, I'm certainly no expert on vehicle/motorhome engine charging systems. And, I certainly don't doubt you know what you're doing when checking your own equipment. But, as long as I've been camping, starting with a couple of trucks and campers, then, two class Cs, a '78 Dodge "4-Star" (440 cu.in.), an '89 Ford Class C, (460 cu.in.), a '99 Fleetwood Bounder Class A with the V-10 and finally, our present coach, an '04 Itasca Horizon 36GD with the 330 C-7 CAT and, every one of those units have the engine alternator charge both sets of batteries.

I would think that Monaco, as advanced as I've been lead to believe, and or the chassis they used at that time, would have designed into the coach, the ability to charge the house batteries with the engine. I mean, if one really liked Monacos and, did a lot of dry camping, then moved around a bit, the only way one could charge the house batteries is by generator.

I'm just learning things here. I don't mean to beat a dead horse but, are you sure that you don't have something broke or, disconnected that is supposed to be charging your house batteries while driving? Sure seems a bit odd to me but, again, I'm no expert. Just wondering.
Scott

[fcooper]

PawPaw_n_Gram wrote:

Where is your voltage measured? Most of the time voltage reported is at the output of the charger/ alternator. So your batteries will actually be getting significantly less than 14 volts if that is the case.

12V has a significantly higher voltage drop over a cable run than 120V.
(text deleted)

The VMSpc takes the voltage reported over the data bus to the diagnostic plug at the front of the coach. I really don't know specifically where it measures the voltage. I suspect the engine ecm sends it to the chassis VDC then into the data bus.

Fred

[fcooper]

wolfe10 wrote:
Look at your alternator. If it has a separate "sense" wire vs just having it wired off the B+ terminal, you might check that its connection to your chassis battery, isolator or where ever it is connected is clean and tight.

With an external sense wire, if there is resistance, it does not "sense" the full voltage and can lead to overcharging.

I am not suggesting that a little over 14 VDC is overcharging in cold conditions, but is something that can be easily checked.

Thanks for the tip. I didn't even know what a separate sense wire was, but just found a good description on the net. I'll check for this.

Fred

[PawPaw_n_Gram]

fcooper wrote:
Is 14.3 to 14.4 too high for charging voltage? Your thoughts appreciated.

No.

When measured across the battery posts - 14.2 to 14.5 is desired.

Where is your voltage measured? Most of the time voltage reported is at the output of the charger/ alternator. So your batteries will actually be getting significantly less than 14 volts if that is the case.

12V has a significantly higher voltage drop over a cable run than 120V.

A chart from a battery manufacturer - http://www.trojanbattery.com/batterymaintenance/charging.aspx

[conmoto]

Interesting that you do not have a Roadmaster chassis according to your sig. I was under the impression that all the Monaco products in this age group did charge the house batts. I believe that I am running approximately the same voltage readings you are experiencing with your coach. Best of luck!