Dedicate Onan Gen Battery

[abyrd]

Has anyone installed a dedicated battery to start you Onan 7500 Quite Diesel?

I have found that when boon docking in cold weather if I allow my coach batteries do drop below 50% charge that my generator struggles to start.  I have checked the glow plugs and all tested OK.  The generator starts up just fine if house batteries are fully charged under cold conditions (<32 degrees).

My generator is mounted on a slide and there is plenty of space to mount a battery on the back of the generation enclosure, this would eliminate the long run of cable to the coach batteries and is also give you the assurance that you would a fully charged battery for stating your generator.

An thoughts would be appreciated.

Jim

 

[richard5933]

Your comments are somewhat confusing and require more information before being able to really offer accurate advice.

First, are you using your coach batteries to run your house systems or do you have a separate set coach batteries? You say that if your coach batteries drop below 50% it's hard to start the generator but with your house batteries fully charged there is no problem. That why this is confusing...are you starting the generator from the same batteries that start your coach engine or from your house batteries? Or are they all one and the same? Or are you bridging the two sets somehow?

If you are using your coach's engine batteries to start the generator and have separate house batteries, then your first problem is figuring out why the coach batteries are getting that low. The coach batteries should not be deep cycle, and they should never be allowed to drop anywhere near 50%. If you have a single set of batteries that serves to both start the coach and to run the house systems, then you should check carefully the lowest recommended discharge level. Even a high-quality deep cycle battery should never be dropped below 50%. If you have a separate battery bank for house systems, then you'll want to figure out what's draining your coach batteries. Once parked, they should be able to go quite some time before needing to be charged.

The short answer to your question is it possible to have a separate battery dedicated to starting the generator. That is what we have. However, you'll need to have a way to charge this battery. Does your generator have an alternator attached for charging batteries? If so, then you can simply hook it up and charge whenever your generator is running. If it doesn't have an alternator, does it have a 12v battery charging output? If so, then you can connect this to your battery and use it to charge. Be cautioned though, as many of the built-in battery chargers will not be a modern 3-stage charger. The older style will simply keep charging whether or not the battery needs to be charged, and this can easily boil a battery and destroy it. In this case you'll have to manually monitor the battery and turn off the charger as needed.

Another way to charge the dedicated start battery for the alternator is to simply connect a small automated 120v to 12v battery charger to the generator battery and plug it into an outlet which is powered by the generator. It should be able to keep the generator battery charged and ready. There are other, more complicated ways to charge this as well.

To size the dedicated generator battery you'll need to consult the generator's manual to see how big a CCA capacity is recommended.

I personally am glad to have the dedicated generator battery. In a worst-case scenario where both my house batteries and my coach batteries get discharged too low, at least I can use the generator to run the battery chargers and get back up and running.

 

[abyrd]

8 minutes ago, richard5933 said:

Your comments are somewhat confusing and require more information before being able to really offer accurate advice.

First, are you using your coach batteries to run your house systems or do you have a separate set coach batteries? You say that if your coach batteries drop below 50% it's hard to start the generator but with your house batteries fully charged there is no problem. That why this is confusing...are you starting the generator from the same batteries that start your coach engine or from your house batteries? Or are they all one and the same? Or are you bridging the two sets somehow?

If you are using your coach's engine batteries to start the generator and have separate house batteries, then your first problem is figuring out why the coach batteries are getting that low. The coach batteries should not be deep cycle, and they should never be allowed to drop anywhere near 50%. If you have a single set of batteries that serves to both start the coach and to run the house systems, then you should check carefully the lowest recommended discharge level. Even a high-quality deep cycle battery should never be dropped below 50%. If you have a separate battery bank for house systems, then you'll want to figure out what's draining your coach batteries. Once parked, they should be able to go quite some time before needing to be charged.

The short answer to your question is it possible to have a separate battery dedicated to starting the generator. That is what we have. However, you'll need to have a way to charge this battery. Does your generator have an alternator attached for charging batteries? If so, then you can simply hook it up and charge whenever your generator is running. If it doesn't have an alternator, does it have a 12v battery charging output? If so, then you can connect this to your battery and use it to charge. Be cautioned though, as many of the built-in battery chargers will not be a modern 3-stage charger. The older style will simply keep charging whether or not the battery needs to be charged, and this can easily boil a battery and destroy it. In this case you'll have to manually monitor the battery and turn off the charger as needed.

Another way to charge the dedicated start battery for the alternator is to simply connect a small automated 120v to 12v battery charger to the generator battery and plug it into an outlet which is powered by the generator. It should be able to keep the generator battery charged and ready. There are other, more complicated ways to charge this as well.

To size the dedicated generator battery you'll need to consult the generator's manual to see how big a CCA capacity is recommended.

I personally am glad to have the dedicated generator battery. In a worst-case scenario where both my house batteries and my coach batteries get discharged too low, at least I can use the generator to run the battery chargers and get back up and running.

 

Sorry to confuse you, I considered the coach and house the same (4 six volt series/parallel) they now provide starting for generator. 

No, I do not have a charging circuit in generator. I would place an automatic battery combiner in the positive circuit of the new dedicated generator starting battery and  coach/house bank to charge the dedicated generator starting battery.

Jim

[richard5933]

Jim,

Well, that explains how your coach batteries are getting discharged - they are also your house batteries.

Assuming that the new generator battery is the same voltage as the existing battery bank, I don't see why it wouldn't work. That is, as long as you are able to charge the batteries when the generator is running or when you're plugged into the pole. 

The combiner you're talking about will have to connected properly so that your are certain that when you are not running the generator or plugged in your batteries are not connected. If they are, you'll be back in the same place again except with an extra discharged battery when you are boon docked. You'll want to have no way to accidentally discharge the generator start battery.

Curious if you're able to start the coach with the batteries that low? If you can't turn over the generator how are you able to start the coach? This would scare me every time I was boon docking for fear of getting stuck with no way to start the coach engine.

[kaypsmith]

I would believe that a 2004 HR Endeavor has two sets of batteries, one, the chassis battery bank, probably 2 12 volt in parallel for starting the coach, and the other set is house batteries, 4 6 volt in series/parallel for house usage. A dedicated generator battery for me is a great idea, could still be hooked to the existing wires to the house batteries, with an isolation circuit to keep the house batteries from pulling away from the generator battery. A good three stage charger can also be added to make sure the gen battery is always up, but probably not needed if an isolation circuit is used. I pulled up a 2003 manual, could not find a 2004 for your unit, which describes both battery banks.

[abyrd]

9 minutes ago, richard5933 said:

Jim,

Well, that explains how your coach batteries are getting discharged - they are also your house batteries.

Assuming that the new generator battery is the same voltage as the existing battery bank, I don't see why it wouldn't work. That is, as long as you are able to charge the batteries when the generator is running or when you're plugged into the pole. 

The combiner you're talking about will have to connected properly so that your are certain that when you are not running the generator or plugged in your batteries are not connected. If they are, you'll be back in the same place again except with an extra discharged battery when you are boon docked. You'll want to have no way to accidentally discharge the generator start battery.

Curious if you're able to start the coach with the batteries that low? If you can't turn over the generator how are you able to start the coach? This would scare me every time I was boon docking for fear of getting stuck with no way to start the coach engine.

Sorry that I am difficulty explaining my situation.

I have the typical DP battery systems.

1. Chassis Batteries (2, 12 v batteries parallel)  Starts Main engine, charged by main engine alternator when engine is running

2. House Batteries 4, 6 volt batteries series/parallel). Provides 12 volt for house and starting voltage to Onan. House batteries are charged by inverter/charger when connected to shore power or when generator is running and by main engine alternator when traveling down road.

Hope this clears up any confusion.

I'm not a novice at RVing, this in my 6th MH over 42 year period and my  career was in operations and maintenance of hydroelectric for over fifty years.    I continue to work as a consultant performing evaluations and assessments of hydro power plants to determine current conditions, performance and operating costs for prospective buyers.

 

Thanks,

Jim

[richard5933]

Jim,

With that added information, I think you're spot on adding the dedicated battery for the generator. It will give you a sense of security knowing that you'll be able to start the generator even if the house batteries are low.

[desertdeals69]

If the house batteries are too low to start the generator try pushing the emergency start button that parallels the eng and house batteries.

[manholt]

Jim.

Since you want to boon dock, do you have any solar panel/panels?  If you really want to get expert advise, send a PM to Bill Edwards!

[abyrd]

14 minutes ago, desertdeals69 said:

If the house batteries are too low to start the generator try pushing the emergency start button that parallels the eng and house batteries.

Acording to my electrical schematics the source of power to energize the relay when you press the emergency start is the house batteries,   is the  house voltage is already low it might not be much help.   I will try it the next I run across the situation.

Thanks for the suggestion.

Jim

[manholt]

Jim.  When I have to press the start assist, it starts the engine, charges batteries, then I start my Generator...I can't use the assist for generator.  The generator only charge the house battery packs, not the 2 start batteries!

[abyrd]

16 minutes ago, manholt said:

Jim.

Since you want to boon dock, do you have any solar panel/panels?  If you really want to get expert advise, send a PM to Bill Edwards!

Carl,

No, I don't have any solar panels.     I have considered them , but being in the Pacific NW, nut sure if it I would get much bang for my bucks.  I am considering the dedicated generator starting battery  and auto generator start option.

Thanks for your suggestion.

Jim

[manholt]

Jim.  Understood.  I thought you went other places than just PNW.  With all the moisture there, do you feel kinship to a mushroom?

Auto gen for me, is a must have.  Dedicated battery for generator is not a bad thought.  When it gets cold enough, my generator takes time to start, even with a full battery, it warms up first then kicks in...mine is a 10Kw.

Luck to you.

[desertdeals69]

2 hours ago, abyrd said:

Acording to my electrical schematics the source of power to energize the relay when you press the emergency start is the house batteries,   is the  house voltage is already low it might not be much help.   I will try it the next I run across the situation.

Thanks for the suggestion.

Jim

Thats easy to fix.  At the emergency start button just wire in a second button with the power source from the engine battery.

[desertdeals69]

1 hour ago, abyrd said:

Carl,

No, I don't have any solar panels.     I have considered them , but being in the Pacific NW, nut sure if it I would get much bang for my bucks.  I am considering the dedicated generator starting battery  and auto generator start option.

Thanks for your suggestion.

Jim

I'm not sure if the diesel gen has charging capacity for its own battery.  I know years ago when we tried a separate battery on a gas gen the charge rate was so low that a regulator was not required because it would never overcharge.

[abyrd]

5 minutes ago, desertdeals69 said:

I'm not sure if the diesel gen has charging capacity for its own battery.  I know years ago when we tried a separate battery on a gas gen the charge rate was so low that a regulator was not required because it would never overcharge.

Onan offers a charging system option for their Quiet Diesel, I don't know if it is incorporated with a separate alternator or if it is incorporated in the main generator system. I will be checking with them. The simplest probably would just to have a dedicated smart charger.

Jim

[five]

I do not see the advantage of adding a third battery system to any coach.  Four each six volt coach batteries should work fine for starting the generator.  The issue is getting and keeping those four batteries properly charged so they can start the generator as designed.  I'd try to get the factory system fixed rather than adding another battery for the generator.

[richard5933]

The advantage is when you regularly boon dock and have the possibility of running down the house batteries to where they won't start the generator.

If someone didn't want to add the third battery, it would also be possible to install a manual way to bridge the chassis battery to the generator for emergency starting. Would just take some battery cable and a manual battery disconnect switch to make this work.

[abyrd]

52 minutes ago, richard5933 said:

The advantage is when you regularly boon dock and have the possibility of running down the house batteries to where they won't start the generator.

If someone didn't want to add the third battery, it would also be possible to install a manual way to bridge the chassis battery to the generator for emergency starting. Would just take some battery cable and a manual battery disconnect switch to make this work.

I carry a short set of jumper cables just for that purpose. I also carry a Honda i2000 portable generator that can be used for last resort. 

Jim

[kaypsmith]

As I stated it my first reply, a battery isolation circuit would be my primary desire to charge the gen battery, I used to use a diode based isolater, but now use an electronic one such as this one, https://www.amazon.com/Smart-Battery-Isolator-Voltage-Sensitive/dp/B00400IYTK

The diode based ones drops voltage traveling to the isolated battery by about .6 volts, which still works well but with newer technology, the electronic ones does not incur any loss. Very simple to install, just disconnect the battery wires from the existing solenoid use these wires to feed the new to your situation battery, connect new wires from new battery to the genny solenoid. Your new battery will be charged through this device, and there will be no drain back to the house battery bank, assuring that your generator will always have a fresh charge. Many people will not see a need but the assurance that the generator is always ready when called on with no monkey business can be a wonderful peace of mind. Good luck which way you choose to use.

[abyrd]

7 minutes ago, kaypsmith said:

As I stated it my first reply, a battery isolation circuit would be my primary desire to charge the gen battery, I used to use a diode based isolater, but now use an electronic one such as this one, https://www.amazon.com/Smart-Battery-Isolator-Voltage-Sensitive/dp/B00400IYTK

The diode based ones drops voltage traveling to the isolated battery by about .6 volts, which still works well but with newer technology, the electronic ones does not incur any loss. Very simple to install, just disconnect the battery wires from the existing solenoid use these wires to feed the new to your situation battery, connect new wires from new battery to the genny solenoid. Your new battery will be charged through this device, and there will be no drain back to the house battery bank, assuring that your generator will always have a fresh charge. Many people will not see a need but the assurance that the generator is always ready when called on with no monkey business can be a wonderful peace of mind. Good luck which way you choose to use.

Kay

I have a automatic battery combiner between house and chassis battery banks, and yes it does the job, just concerned of overloading the  chassis alternator, it rated at 160 amps.  The owners manual specifically states the chassis alternator is not designed to charge a dead battery.

Jim   

 

 

[abyrd]

Attached is RV Generator Owner Handbook by Onan  with interesting information on how long it takes to charge different capacity battery banks with different rates of charge.

Onan RV Generator Handbook.pdf

[abyrd]

33 minutes ago, kaypsmith said:

As I stated it my first reply, a battery isolation circuit would be my primary desire to charge the gen battery, I used to use a diode based isolater, but now use an electronic one such as this one, https://www.amazon.com/Smart-Battery-Isolator-Voltage-Sensitive/dp/B00400IYTK

The diode based ones drops voltage traveling to the isolated battery by about .6 volts, which still works well but with newer technology, the electronic ones does not incur any loss. Very simple to install, just disconnect the battery wires from the existing solenoid use these wires to feed the new to your situation battery, connect new wires from new battery to the genny solenoid. Your new battery will be charged through this device, and there will be no drain back to the house battery bank, assuring that your generator will always have a fresh charge. Many people will not see a need but the assurance that the generator is always ready when called on with no monkey business can be a wonderful peace of mind. Good luck which way you choose to use.

Kay,

I'm going to first install the generator auto start and see how that works out, If that satisfy my needs, I will install the dedicated generator starting battery and will incorporate combiner/isolator as you recommended. 

Thanks for your advice.

Jim

[richard5933]

8 hours ago, kaypsmith said:

As I stated it my first reply, a battery isolation circuit would be my primary desire to charge the gen battery, I used to use a diode based isolater, but now use an electronic one such as this one, https://www.amazon.com/Smart-Battery-Isolator-Voltage-Sensitive/dp/B00400IYTK

The diode based ones drops voltage traveling to the isolated battery by about .6 volts, which still works well but with newer technology, the electronic ones does not incur any loss. Very simple to install, just disconnect the battery wires from the existing solenoid use these wires to feed the new to your situation battery, connect new wires from new battery to the genny solenoid. Your new battery will be charged through this device, and there will be no drain back to the house battery bank, assuring that your generator will always have a fresh charge. Many people will not see a need but the assurance that the generator is always ready when called on with no monkey business can be a wonderful peace of mind. Good luck which way you choose to use.

The big difference between a VSR and a diode-based isolator is that the VSR is two-way and the diode isolator is one-way only. In other words, when the VSR detects a charge on either side it will bridge the two battery banks. Once bridged, it current from the charger will flow to both battery banks together AND power will flow between the battery banks. If one battery bank is severely discharged it would be possible for it to pull current from the more charged battery bank leaving you with two somewhat discharged battery banks and taking much longer to charge things. If the house batteries are at 50% and are a larger battery bank than the smaller generator start battery, they'll also take all the charge from the charger while possibly also discharging the more charged generator battery.

The diode based isolator will allow power to flow only in one direction - from the charging source to the two battery banks. It's not possible with a diode based isolator for current to flow between the batteries.

For some situations where manual control is desired it's also possible to bridge battery banks using a manual switch or a latching relay switch which only draws current for the moment it's switching. Once switched, no current is used to hold position.

[abyrd]

5 hours ago, richard5933 said:

The big difference between a VSR and a diode-based isolator is that the VSR is two-way and the diode isolator is one-way only. In other words, when the VSR detects a charge on either side it will bridge the two battery banks. Once bridged, it current from the charger will flow to both battery banks together AND power will flow between the battery banks. If one battery bank is severely discharged it would be possible for it to pull current from the more charged battery bank leaving you with two somewhat discharged battery banks and taking much longer to charge things. If the house batteries are at 50% and are a larger battery bank than the smaller generator start battery, they'll also take all the charge from the charger while possibly also discharging the more charged generator battery.

The diode based isolator will allow power to flow only in one direction - from the charging source to the two battery banks. It's not possible with a diode based isolator for current to flow between the batteries.

For some situations where manual control is desired it's also possible to bridge battery banks using a manual switch or a latching relay switch which only draws current for the moment it's switching. Once switched, no current is used to hold position.

Good pint Richard.

Thanks,