Community Forums

maddog468 · 03-20-2018, 06:55 AM

Hello,

Looking to install a dedicated battery for my onan quiet set 7500 (7.5HDKAJ11451D) in my 1998 Monaco Windsor.

The generator is equipped with a DC alternator, but it disabled due to the fact the start battery is the chassis battery from the coach.

Does anyone know how to re-enable the dc charging circuit from the generator?

Thanks

Scott

distaff · 03-20-2018, 08:39 AM

Don't have an answer, but a question - why?

oldguy70 · 03-20-2018, 09:06 AM

Why is the alternator disabled. It would charge the chassis battery while running.

maddog468 · 03-20-2018, 09:17 AM

Quote:

Originally Posted by oldguy70

Why is the alternator disabled. It would charge the chassis battery while running.

Yes it would, but when the coach engine is running the coach engine driven alternator could charge it as well if they were both running at the same time.

The system is not designed to run the alternators in parallel.

maddog468 · 03-20-2018, 09:24 AM

Quote:

Originally Posted by distaff

Don't have an answer, but a question - why?

Long story but if you are having generator issues and the generator uses the chassis battery the manual directs you to install a dedicated battery.

From the onan manual:

2. Check whether the vehicle engine and genset share the same starting battery. If so, and this fault
occurs when cranking the vehicle engine, low battery voltage may be causing this shutdown. Increase
battery capacity or install a separate battery and battery charging system for the genset. If
the genset still shuts down and has Option Code “11296” in the Model Number, go to Step 3. If not,
go to Step 4.

YC1 · 03-20-2018, 09:24 AM

No to answer your question but here is a suggestion.

It seems you want that battery isolated so the generator never sees a dead chassis or coach battery depending on how it is installed.

Instead of trying to get the generator to charge the battery just install a simple "diode" based isolator to the new battery.

Your alternator, shoreline, and generator will all supply ample charging to that battery.

Who cares if there is a little loss in the isolator and wires from wherever they came from in the beginning. Your generator will not get used enough to discharge the new battery.

maddog468 · 03-20-2018, 09:37 AM

Quote:

Originally Posted by YC1

No to answer your question but here is a suggestion.

It seems you want that battery isolated so the generator never sees a dead chassis or coach battery depending on how it is installed.

Instead of trying to get the generator to charge the battery just install a simple "diode" based isolator to the new battery.

Your alternator, shoreline, and generator will all supply ample charging to that battery.

Who cares if there is a little loss in the isolator and wires from wherever they came from in the beginning. Your generator will not get used enough to discharge the new battery.

I tried that, current setup but for some reason the shore power/ trace 3000 watt inverter /charger is not keeping the battery at the gen-set charged properly. The generator battery had 11 volts after sitting plugged in for a month. My issues with the generator are back with the weak battery. Replace/charged battery no more issues.

Either the battery is bad but its less than 6 months old or the voltage drop up to the generator battery is not enough to keep it charged on float charge.

I just want to isolate the batteries and go from there.

Twomed · 03-20-2018, 10:58 AM

A battery tender or ultra trik l start plugged in to 110v since you have shore power would keep that battery charged with your current set up.

If you use a 110v that is not on the inverter 110v circuit, it will charge any time plugged in camping, stored with 110v, or gen running.

vito.a · 03-20-2018, 11:47 AM

Scott,
There is an older thread on here where someone installed a separate gen set battery.
What coach do you have?
Most Monaco coaches are set up so the generator starts from the chassis battery. This is because the inverter powering the house may run the house battery down. After the generaotr starts, or if the coach is plugged into shore power, then the Inverter charges the house batteries until they reach 13v and then charges the chassis batteries.
If you add a third battery group to this you will need to add an isolation/charging circuit to it from the house batteries.

Many of us have a problem with the chassis battery charging system. Mine uses a Big Boy soloenoid and it is notorius for being dirty inside and not working. I disassembled it and cleaned the copper contacts and my gen start issues went away.
Hope this helps.

maddog468 · 03-20-2018, 01:15 PM

Quote:

Originally Posted by vito.a

What coach do you have?

Thanks Vito,

I have a 1998 Monaco Windsor.

The generator battery is connected in parallel with the chassis battery.

The chassis battery has a Lambert enterprise battery maintainer on it. To keep the chassis battery charged. I do not have a big boy solenoid.

YC1 · 03-21-2018, 06:25 AM

A 6 month old battery can be bad. A brand new one can be bad.

I would address the charge line. Sure sounds like it is not doing the job.

If you measured low voltage at the generator battery and proper voltage at your other banks you absolutely have a charge line problem. Simple as a corroded connection.

I always recommend fixing the "obvious" first. "Obvious" to an electronic tech just means see why the charge iine voltage is low.

Why possibly create other issues?

vito.a · 03-21-2018, 10:14 AM

When the generator is difficult to start, what is the chassis battery voltage checked at the battery?
Trying to sort out if you have a chassis battery charging issue, or if the cables from the chassis battery to the generator are too small.

Soppy · 03-21-2018, 11:14 AM

You should be able to find a wiring diagram for your generator and go from there. The internal charging circuits very basic . It could be as simple as a wire removed from the rectifier. I have also seen a small battery charger connected to the generator battery that will charge it anytime you have AC power. If you are using a separate battery for the generator , be sure to keep the entire generator 12 volts separate from the chassis and coach 12 volt systems. I would also add a battery disconnect so the battery can be disconnected for storage.

Tony Lee · 03-21-2018, 07:00 PM

Given that the cable from the chassis battery to the generator SHOULD be able to supply the generator starter motor without significant voltage drop, then it should be able to supply a piddling amount of charge current without even puffing.

Are you sure that your chassis battery IS being charged when on shore or generator power. Not supposed to be, but IS because if that isn't happening then of course your generator battery is going to slowly discharge. Also you will need to have either a split charger feeding the generator battery or some sort of diode or contactor interlock or even a Trik-l-charge.

Cheap multimeter and a few simple measurements should be able to sort out what the problem is.