Where to center tap for generator start power

[luvrbus]

These guys may know the best way but with a control board costing 200+ I would go with the battery all the Vanners I been around do spike from time to time blowing head lights JMO

[rv_safetyman]

First of all, if the generator has an alternator, why not just "isolate" the system with its own 12V battery.  That way you can start the generator if the house battery bank gets discharged.

Next, I don't know much about Vanners, but if it is rated at 50A, how would it be able to furnish the current for the generator starter?

The suggestion of having the Vanner "charge" a 12V battery that is used for the generator would get you close to isolating the generator and would give you the ability to start it in the event of a a house battery problem.  That said, you don't need to go that route if the generator has an alternator.

Jim

[Tenor]

 Jim,
The alternator does not have it's own alternator.  It uses the generator head to supply a low current to charge the battery back up.  It is a converted marine unit, so an electric cooling fan became necessary since it no longer has a lake to keep it cool.

Luvrbus,
If I understood BW right, and my Vanner diagram, you still center tap the 24V batteries for the generator start and control and fuel pump.  The Vanner just balances the load between the batteries, it does not directly supply the cranking amps.  The only load on the Vanner are interior lights, fans refrigerator control and a few other small items.  Never are all used at the same time.

Glenn

[Sean]

...
If I understood BW right, and my Vanner diagram, you still center tap the 24V batteries for the generator start and control and fuel pump.  The Vanner just balances the load between the batteries, it does not directly supply the cranking amps.
...

This is not entirely correct.  If you put a large load on the 12v center tap, such as attempting to start an engine, the Vanner will do its level best to supply as much current as it can.  If the batteries themselves are not up to the task, this can overstress the Vanner.

Moreover, the amount of lower-bank depletion caused by starting will mean the Vanner has that much more work to do over the long haul to equalize the system.  Lastly, the Vanner can never make up for the stress difference between starting and non-starting loads, so eventually the lower half will become permanently out of balance with the upper half, which will ultimately result in the Vanner working full-time and constantly draining the entire bank.

Perhaps I was not forceful enough in my original post:  I strongly recommend that you install a completely separate 12v battery to start your generator.  Get a small, inexpensive 12v battery charger to recharge this battery from the 120vac generator output.  Together these items should set you back less than a C-note.  I would also suggest you use this system to run your 12v cooling fan, although, frankly, you would be better off all around by changing to a 120vac cooling fan.

-Sean
http://OurOdyssey.BlogSpot.com

[Tenor]

Thanks for th clarification Sean!  I do have a 120v fan on the system, but I had to add the 12v fan in addition to keep the generator at 160.  It occurs tome that I might be able to delete the fan with some improved shrouding. I'll see if there is a way to get a alternator onto this generator.

[gus]

Tenor,

It does have an alternator although a very small one made just to charge the genset batt.

If you connect the genset start circuit into the bus engine elect system it will confuse the bus engine voltage regulator'

I had this problem in a 12v system and just added a small separate batt for the genset only. My bus alt went nuts until I did this.

[Tenor]

Been working on making all of the changes! 

I had a 100A 12V alternator and Regulator from my 73 Winnebago (the parts are actually much newer) laying around, so I took the day and adapted it to run off of the generator.  JUST got it finished.  Charges like mad.  No more center tap.  It has it's own start battery.  Later I'll run a light to the dash to let me know the genset is running.

Thanks for all the help!

Glenn

[TomC]

When I was running my truck cross country with the Onan 6.5 commercial, it too had only a 5amp battery charger built into it.  I had a single 8D deep cycle for the refer mainly, and just used a 20amp smart battery charger to keep the 8D charged.  Also had an ignition operated solenoid that charged the deep cycle going down the road.  Good Luck, TomC

[gus]

A 100A 12V alternator is way overkill for a normal genset batt. I used a lawn mower batt for my 5.5 Onan and the built in genset alt kept it well charged since this batt gets very little use. The alt was built into the genset flywheel.

In case of any start problems I had it connected by a switch to the bus 12v engine batts which was open otherwise. In your case you could connect it to the center tap.

[Tenor]

An update to this post.  Earlier, I mentioned that my Vanner was wired to the 24VPos, the 24VNeg and the 12.8V output went directly to the loads.  That is how the unit is diagrammed on it's own case.  I had contacted Vanner with the model numbers for an updated schematic.  The one they sent was not exactly for my unit.  Turns out, this unit is ONLY a CONVERTER!  I found that once I sent a second wire from the 12.8V Output to the lower battery, it would drain the upper battery!

So, when acquiring a Vanner, READ the label!  The converters do not work as Equalizers.  I happened to have a second unit that is an actual Equalizer and I have it installed as discussed earlier.  Works like a charm.

Glenn

[buswarrior]

Excellent report.

Terminology is king!

happy coaching!
buswarrior