Starting issue with my monaco

[bigdomino]

I have a 2008 Monaco Knight. Has a Cummins ISC.

Coach has been sitting at the camp for a month and a half plugged in to 50 amp service. I went to start it this afternoon and the engine was slow to turn over. Engine did not start right away. Usually it cranks right over and starts. The coach was also still plugged into the 50 amp hookup.

When it did start the charge showed 14.2 to 14.4. It usually is around 13.9.

You think the batteries are going? Is it possible the switch that allows juice to go to the batteries is not working?

Thanks.

Steve

[Steve Ownby]

Originally Posted by bigdomino

I have a 2008 Monaco Knight. Has a Cummins ISC.

Coach has been sitting at the camp for a month and a half plugged in to 50 amp service. I went to start it this afternoon and the engine was slow to turn over. Engine did not start right away. Usually it cranks right over and starts. The coach was also still plugged into the 50 amp hookup.

When it did start the charge showed 14.2 to 14.4. It usually is around 13.9.

You think the batteries are going? Is it possible the switch that allows juice to go to the batteries is not working?

Thanks.

Steve

Your coach may not be equipped to charge the chassis batteries from shore power. It does not happen without a specific circuit known at a "BIRD". Next time your are parked & plugged into chore power, check both battery banks with a VOM. They should be at the same level. If the chassis battery is showing less than 13 VDC then they are not being charged.

[bigdomino]

Started the motorhome today without an issue. Voltage was running at 14 and then down to 13.9, about normal. Drove the rig to have some work done on it.

Batteries are 5 and half years old. I wonder if it is time to change hem out?

Steve

[Gary RVRoamer]

5 1/2 years on starting batteries is more than you can reasonably expect. I would start shopping for new ones.

[bigdomino]

These batteries do not allow you to add water. They are sealed.

Anyone know what kind they are? Have two for starting the coach. 12 or 6 volt?

Steve

[EngineerMike]

Your start batteries are 12V.
Get new start batteries before you burn up the starter &/or alternator. You got your use out of the old ones. I just load tested mine & they beat the 950cca label spec by a squeak (960-970cca). I load tested my 1 year old toad battery that says 550cca- result = 715cca tested; note the massive difference vs original label spec. I bought new start batt's for the coach; no reason to let that go to the last ounce while wearing down more expensive gear.

If your starter ordinarily draws 600A when batteries are at 12.8, it probably drops voltage to 11.5 running the starter for ~7000 watts. Drop start volts to 10.5 and amp draw goes up to 667A, an increased draw of 11%. Starter has to work harder, generate more heat, etc. when you starve it for voltage. You saw the increase on voltage from alternator; same thing- heavier load. Batteries are cheap. A buddy just bought a new alternator while we were traveling; $700 installed. Better to protect that w/$300 for new batteries while the old ones are still good.

BTW, while traveling we limped my buddy's coach along just fine running the gen & inverter/charger (which on his rig charges both banks). If he killed the gen, his chassis volts dropped steadily to low 12's before he chickened out & restarted the gen. Good trick when you need it because the alternator is fried.

[YC1]

You still have not satisfied the issue of why they were low the other day. Yes you are due to replace that battery. As steve mentioned you really need to get a voltmeter across each bank while charging. If you would take a picture of the battery compartment and especially one of back side of the compartment better advice will be available. I cannot imaging the coach sitting for three months and starting at all if that set of batteries is not getting some sort of charge. While it was sitting did you leave the battery switches on inside the compartment? The issue I am driving at is two parts. If your rv has the Bird circuit as suggested then the engine batteries should have been well charged. However the large solenoid in my battery compartment (2008 Endeavor) is a know failure item. I'm on my third one. Be careful touching the solenoid. If it is being driven by a Bird circuit it will be hot to the touch when any charging source is available. This large solenoid is also used for the Boost start function and will not work when you need it if it has failed or partially failed.

[bigdomino]

Thanks to everyone for their comments.

We are full timers and the coach is always plugged in to a 50 amp circuit other than for traveling. As I said earlier, it started good this morning and every time I tried it afterward this morning. I can't take any pictures at the moment. I drove the coach to the body shop this morning and will be there this week. I scratched the side and damaged a storage door on our way from California. I hope to get it Friday. We are in a inn along with our dog for the week. Out of the motorhome does feel good.

So it is either the switch or the batteries. I will try to figure it out after I get it back.

So 5 years is really pushing it for the life of the two batteries?

Steve

[YC1]

Electrical layout.pdf

Bi-Directional Charger Card.pdf

Five years is near their end usually. And what do you mean by "switch" ? If the site will cooperate this time I will attach several diagrams.

[YC1]

More attachments

[bigdomino]

I understand there is an electrical device that will switch back and forth from charging the house and Coach batteries. Depending on need. Is this correct?

Steve

[JimM68]

Yes.
Your coach, like my 08 knight, is factory equipped with a device that is supposed to ensure that both banks of batteries are always charged. This is often referred to as a BIRD.

The bird on mine has been kinda flaky sometimes too. Often, when not plugged in, it has stayed connected "too long" and drawn the batteries down. It doesn't "boost" anymore either, probably a bad relay (see yc1's post above. But everytime i go to start troubleshooting, everything works fine.

I did put a pair of digital voltmeters in the dash to always show me the state of both battery banks, and if the BIRD has energized. Cheap insurance. There is a thread on that install on the board somewhere.

[conmoto]

I have been told by a tech. that on my 06 Knight the chassis batts will not begin to charge until the house batts are full. If there is a bad cell in one house batt it will not fully charge and the chassis will never get to charge. Right or wrong I have put a separate maintainer on my chassis batts for this reason.

[bukzin]

Originally Posted by YC1

Attachment 27109

Attachment 27110

Attachment 27111

Five years is near their end usually. And what do you mean by "switch" ? If the site will cooperate this time I will attach several diagrams.

YC1,

Are the attachments you kindly provided specific to your coach
or more generic?