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Topic: Using Chassis battery to start Onan Genset? (Read 787 times) previous topic - next topic
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Using Chassis battery to start Onan Genset?
I did away with the trojan lead acid coach batteries during my upgrade to lithium but now need to configure a way to start the Onan generator.  Could I somehow use the chassis battery to also start the generator?
Re: Using Chassis battery to start Onan Genset?
Reply #1 –
Hi Howard; The generator starter motor requires a lot less power, about 90 Amps than the engine starter, (about 150 Amps). So very possible.  The wire that Lazy Daze provided in my '99 to charge the house batteries, a #4 red wire, can be repurposed to start the generator. Obviously the 12 volt engine alternator won't charge 24 volt batteries.  This wire does go through the diode isolator. (mine was rated 120A) so it might work fine. Or the isolator could turn into a big (expensive) fuse.  You don't need that isolator now.  I did run a Renogy DC to DC converter to charge my Lithium 12vdc, (actually 13.6vdc) SOK's from that wire, (isolator removed).
   Did you get 24v. S.O.K. batteries?  I'm curious why you went to 24v batteries?   RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Using Chassis battery to start Onan Genset?
Reply #2 –
Quote from: RonB  - 
   Did you get 24v. S.O.K. batteries?  I'm curious why you went to 24v batteries?   RonB

No I got 4 x 12v and wired pairs in series and then paralleled the two 24v banks.

I did 24v for efficiency and cost savings on wire.  24v pulls half the amps so I could use a much thinner battery wire, smaller fuses and less heat produced.  At 12v the recommended wire was 4/0 but at 24v I could have used 1AWG;  I decided to go with 2/0 to future proof.


Re: Using Chassis battery to start Onan Genset?
Reply #3 –

Hi Howard;  Those losses are only a problem when transferring a lot of power (amperage) over long distances.  Battery to battery, say less than a few feet, not so much of a problem.  I would have stayed with all 12 volt nominal. (14.6 VDC at most)   I used flexible (fine stranded) welding cable, #2 for my system. The highest load I run is about 8 feet there and back to the 2 KW True Sine Wave Inverter. About 94  to 96 Amps. (about 1200 watts, easier on the 2kw + surge inverter, less heat developed, internal fans not as stressed)
   I used real copper, Made in the USA, ASTM standards wire. 2 Gauge 2 AWG 15 Feet Black + 15 Feet Red (30 Feet Total) Welding Battery...    None of that copper clad aluminum wire that China has been trying to pass off as real wire.   RonB

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Using Chassis battery to start Onan Genset?
Reply #4 –
When the chassis battery starts the engine, the alternator replaces that energy quickly. That will not happen when that battery is used to start the generator, which can take longer to start too. Risky, say, in cold weather if camped awhile with several generator runs without starting the engine...

Steve
2004 FL
2013 Honda Fit
Re: Using Chassis battery to start Onan Genset?
Reply #5 –
Why not install a battery tap and use one of the 12-volt lithiums to start the generator using the Factory wiring? The power usage is small and the battery's BMS should allow balancing, once solar is available. I would figure out a way to jumpstart the starting battery too.
Along with 24-volts advantages, it also comes with some downsides.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Using Chassis battery to start Onan Genset?
Reply #6 –

Hi Larry and Steve.  The SOK's are limited by the internal BMS to 100A discharge rates per EACH battery.  That's pretty close to the 90 Amps needed by the two cylinder Onan Emerald plus if you were using a single battery.  The newer MicroQuiet , just a one cylinder engine, may take less to get started.
   One of those Renogy 20 A Dc to DC set for lead acid charging could be used in reverse to take 24 volts and properly charge the chassis battery.
   I start my Onan Emerald with my two SOK batteries in parallel.  I have an Amp-L-Start specifically designed for LiF voltages to back feed the chassis battery with up to15 Amps.  I also carry a portable (small) Li jump start battery for the 'towed', or someone else's car (or motorhome) if needed. It will start the V10. During my 4 month solar conversion, the Trik-L-Start was inoperative, and the 8 year old chassis battery couldn't start the engine. (I got a new chassis battery the night before we left for the AIBF).
   Howard; with that much solar, and that much battery capacity could have a jump starter plugged in and charging 24/7.  Amazon.com: NEXPOW Battery Jump Starter 2500A 22000mAh Car Jump Starter (up...      RonB

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Using Chassis battery to start Onan Genset?
Reply #7 –
Quote from: RonB  - 
The SOK's are limited by the internal BMS to 100A discharge rates per each battery.  The newer MicroQuiet , just a one cylinder engine may take less to get started.

The low, 100 amp discharge limit was one reason why I didn't use a SOK for my lithium conversion. Instead, two 100-amp lithiums (both with 100-amp outputs) were used.
The other reason is that SOKs were too large to fit in the available space.
The change to lithium was fairly simple with the reprogramming of the solar charge control and battery monitor, being set to the battery manufacturer's specs was all that was needed, besides redoing some of the 2-gauge cables..

The battery isolator only passes 25-amps maximum, so it was left, for the time being, not being concerned it would overcharge the batteries while driving. This really isn't much of a concern, the lithiums have a robust BMS that prevents overcharging or letting the battery be drained too deeply. The HD design of the modern BMS is what makes lithium batteries practical today.

I should finish documenting my installation now that it has been well tested over the last few months, I'm happy with the result and have suggestions for those considering changing to lithiums.

Larry



Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Using Chassis battery to start Onan Genset?
Reply #8 –
Hi Larry;  The SOK's I have in parallel will each supply 100 A, and the microwave (2kw inverter) takes about 100 A continuous. The big draw is the hair dryer at 1650 Watts and it takes about 150A out of the batteries. The 206 still has the better form factor for me at least. And I have no trouble starting the generator, and I'm sure I could start the V10 also if needed.
   I'm not quite finished with the total package. Pictures have been taken. The documentation (hand drawings and photos with notes to myself) will have to wait for those 'too cold to work outside) winter days.   RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Using Chassis battery to start Onan Genset?
Reply #9 –
Quote from: RonB  - 
Hi Howard;  Those losses are only a problem when transferring a lot of power (amperage) over long distances.  Battery to battery, say less than a few feet, not so much of a problem.  I would have stayed with all 12 volt nominal. (14.6 VDC at most)   I used flexible (fine stranded) welding cable, #2 for my system. The highest load I run is about 8 feet there and back to the 2 KW True Sine Wave Inverter. About 94  to 96 Amps.
   I used real copper, Made in the USA, ASTM standards wire. 2 Gauge 2 AWG 15 Feet Black + 15 Feet Red (30 Feet Total) Welding Battery...    None of tht copper clad aluminum wire that China has been trying to pass off as real wire.   RonB
Probably should have talked to you first haha.  I'm storing my batteries against the opposite wall and the circuit run is about 15-17ft so I wasn't 100% sure.  I started a couple of months ago as a blank slate and the 24v system was recommended by my "trusted sources" on YouTube based on power consumption so maybe not the best metric by which to make that decision; live and learn.  I do think I found a good place for battery cable (batterycablesusa.com) which sells by the foot (or even by the inch), fine stranded and several types from basic to marine grade tinned copper.  I'm always nervous to order on Amazon for that very reason you mentioned.
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Using Chassis battery to start Onan Genset?
Reply #10 –
Quote from: Larry W  - 
Why not install a battery tap and use one of the 12-volt lithiums to start the generator using the Factory wiring? The power usage is small and the battery's BMS should allow balancing, once solar is available. I would figure out a way to jumpstart the starting battery too.
Along with 24-volts advantages, it also comes with some downsides.

Larry

That's a good idea.  I wasn't sure if the LiFePo4s could be safely used to start the generator as I read in the Onan manual that the battery needs to meet 450CCA, also the batteries are in a 24v configuration so would I need to convert to 12v going to the generator?  I have 24/12 dcdc converter but it's only 70A rated.  Am I looking at things incorrectly?
Re: Using Chassis battery to start Onan Genset?
Reply #11 –
Quote from: RonB  - 
   Howard; with that much solar, and that much battery capacity could have a jump starter plugged in and charging 24/7.  Amazon.com: NEXPOW Battery Jump Starter 2500A 22000mAh Car Jump Starter (up...      RonB

Don't think that will work for me as me ultimate goal is to hook the Onan starter cables up to the programmable relay on my Victron and have it auto start if the the voltage the battery voltage drops too low.  I'm anticipating this would be needed only in case of power emergencies as I sometimes need to leave my pooch in the RV during the day with the A/C on.  My recent A/C test of a fully charged battery bank ran for about 7 hours at almost 80 degree ambient temp keeping the coach plenty cool, so maybe this plan is a bit overkill.
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Using Chassis battery to start Onan Genset?
Reply #12 –
Hi Howard;  You positively can't use 24v connected batteries on a 12v. starter motor. For what you want to do, use the chassis battery to start the generator. It will start it just fine. That CCA rating is to size the battery for cold weather (Cold Cranking Amps). The chassis battery is more than that. Your 2005 Onan is the MicroQuiet and won't take that much to start.  But it is not like starting a car engine that is controlled by a computer. The generator, isn't as easy and I wouldn't rely on that to be started correctly.
   Steve is right that there needs to be a way to recharge the chassis battery, especially if the V10 alternator isn't charging it. The AMPLStart will take it's time, but will top off the chassis battery fine as long as you don't start the generator too often.
   The 70 Amp DC to DC charger is meant to charge battery banks from a source like a generator, and isn't meant to operate intermittent things like a starter motor.
   Running the A/C during the day, if it is hot and sunny, the panels will be able to extend the time that the batteries will last.  RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
 
Re: Using Chassis battery to start Onan Genset?
Reply #13 –
Quote from: RonB  - 
Hi Howard;  You positively can't use 24v connected batteries on a 12v. starter motor. For what you want to do, use the chassis battery to start the generator. It will start it just fine. That CCA rating is to size the battery for cold weather (Cold Cranking Amps). The chassis battery is more than that. Your 2005 Onan is the MicroQuiet and won't take that much to start.  But it is not like starting a car engine that is controlled by a computer. The generator, isn't as easy and I wouldn't rely on that to be started correctly.
   Steve is right that there needs to be a way to recharge the chassis battery, especially if the v10 alternator isn't charging it.

Thanks Ron…I’ll pursue this route.  My Victron multiplus has a separate aux charger for starter batteries and this might be the way to keep the chassis battery charged.  I just have to figure out if I can charge at 12v.  Thanks for the help.