Running roof Air conditioner with generator while driving

[Wendell]

Sent: 6/1/2003

My Indian does not have an air conditioner on the engine.  Can I run my generator to power the roof air unit while I'm driving?

[mightybooboo]

Sent: 6/1/2003

Yep, you can run genny and roof air while driving.
BooBoo

[denisondc]

Sent: 6/1/2003

And I would be interested to know if you find the roof air cond. makes much of a difference to the driver. Almost none of the early 70s winnies had a.c. on the engine it seems. I tried using the roof a.c. a couple of times, but it was more comfy with all the windows open, than closed up with the a.c. on. This was in south texas, with the air temp being 90 and up. denison

[Tarsand traveler]

Sent: 6/1/2003

My owners manual for '76 Brave states "Do not turn on the 115 volt generator with both batteries connected when driving. This can cause damage to the alternator". We ran our gen set all the time last summer for AC while driving and had no problems but then again I only got the owners manual last week.

[Boat Nut]

Sent: 6/1/2003

Yes, by all means you can run the generator to power the air while driving. However, you may find, as I have that, while the roof air works fine parked, it might not provide enough cool while driving. The additional engine heat load can create more than the roof air can handle. I have found that by directing all the air forward, it will cool the driver and passenger. People in the rear will suffer.

[melyash]

Sent: 6/2/2003

My 72 brave has both air. The front one is not properly charged I am afraid, and needs service. It looks like the aftermarket variety but not sure. I use the Generator to run the roof air when needed, but it is only marginally effective.

As to the Generator & both battery thing, You have a battery switch that connects or isolates the coach batteries from your chassis ( starting) battery. This is labeled something like single/both/momentary. Single allows the alternator to charge just the staret battery, Both as the name implys allows you to charge your coach and your start batteries simultaniously and momentary allows you to use the coach batteries to help start the engine if your starting battery is dead. This switch is powered by the ignition switch, and should only work when the ignition switch is on.

Do not leave it on both with the ignition on but vehicle not running as damage to your alternator can surely occur.

When running the Roof AC on the generator, the gen is supplying charging to the Coach battery. If you were in the both position, it would feed back into the alternator and again, result in possible damage to the Alt.

Hope this helps and Stay Cool!

Matt

[bhart70]

Sent: 6/2/2003

I'm not sure of your budget or your needs, but Vintage Air offers a "generic" a/c system that can be fairly easily modified to fit almost any engine application.  Kits can run in the $1800+ range (slightly less than my budget for the entire classic Winnie), but if being cool and comfy is a big enough concern it may be worth it.

Depending on the condition of your roof a/c, it may be worth it too as they aren't inexpensive to replace.  If you would be running a/c most of the time while driving, you might be able to extend its' life.

[Wendell]

Sent: 6/4/2003

Thanks for all the replies and advice.   I think I have it sorted out now.  Some of the previous owners had made some pretty extensive alterations to the electrical system in the past including removing whatever batter isolation equipment usually comes on these things and installing a simple battery switch that connects or disconnects the generator from the batteries which are wired in parallel at present. 

I think I will simply rewire a bit and connect the auxiliary battery directly to the genset and remove it from the main engine electrical system isolating it completely. That way I won't have to worry about frying my alternator if I forget to throw a switch the proper way before firing things up.

I don't anticipate using the genset much, mostly to run the A/C while driving or to provide some A/C power while I'm working on this puppy.  I am disappointed to hear that you haven't had much luck cooling things down this way. 

Thanks again and I'm sure I'll be posting again.  I have  lot to learn.

[melyash]

Sent: 6/5/2003

Wendell,

There are reasons to keep the coach batteries on the alternator, that you should look into before making the decision to isolate or not isolate them.
1. The Engine Alternator can put upwards of 30 amps an hour into your 105 amp deep cycle batteries, (up to about 80% charge then the Voltage regulator starts cutting the voltage back rather quickly).
2. Your Genset although it puts out a great deal of AC power, your converter/charger (if it is the stock one) only puts out Four (4) amps an hour. You would have to run your Genset at least 8 or 9 hours to put in the same amount of amps that a single hour on your engine. This of course doubles if you have two deep cycle batteries.
3. As to the possibility of blowing your Alternator by throwing or forgetting to throw the switch, You could probably install a DIODE on the output of the Alternator, to keep feedback into the alternator from occuring.
If you want to charge from your Genset, look into an inteligent multi stage battery charger from Hart Industries, or Xantrex, or other manufacturers, they will output 10, 20, 40 or even more amps per hour, and will computer monitor the state of the batteries to insure that the complex process of correctly and safely charging your batteries is completed.

Pick up a book called Managing 12V systems by Harrold Barre, you can get one at campingworld, or amazon.com and you will get a great idea of what is availble in the world of batteries and charging systems. Also, keep in mind, everything has an ineffiency to it in your battery system. Diameter of the wire from your Alternator 3-8% loss, Battery ineffiency <10% loss thru heat and other chemical process inefficency, Additionally the length of your cables, corrosion on your conections and a bunch of other stuff conspire to make your system battery system less than efficent. Talk to an auto electric service guy, see if he can come up with a diode to prevent the feedback just in case. Make sure it can handle the load as required by your system.  Good Luck,  Matt

[moparmotivator]

I have wondered about the charging situation while driving.

My generator is charging, my power converter/smart charger is charging and the alternator is charging away also.

Would it make sense to put in a relay to disable the alternator while the genset is running??

You could use the genset pilot light to drive the relay interupting the exciter going to the alternator.

I have run the genset a lot to cool the coach(works good with the vent pointed forward).

Over the last few years I have fried the original regulator, the original power converter, and a used charge wizard power converter that came out of a 80's ambulance.  On mopar the alternator charges wide open if the regulator shorts out so I chalked up the ambulance converter failure to the voltage spike.

My current converter/charger makes 50 amps.

Too many systems overlapping to keep straight and Dodges really like to melt wiring.

Thank You

[D20T_73]

I would be careful with putting a relay to cut off your alternator...it would still be spinning and building amperage...if i'm right in my thinking it would easily burn up your alternator

[ClydesdaleKevin]

As long as you have a functional battery selector switch, either the dash board kind with a solenoid that Winnies and Itascas have or the big plastic selector switch that boats and a lot of other RVs have, then it is safe to run the genny while driving.

With the dash switch style:

If you are running the generator, then your dash switch should be set to "batt", which allows your alternator to charge your starting battery, but isolates it from the coach batteries.  That way your coach batteries will only be being charged by the genny and converter, and the trickle charge it gives won't reach your starting battery.

If you aren't running the genny, set your dash switch to "dual".  Now your alternator will charge both sets of batteries.  Also, when you are parked and hooked up to shore power with your engine off, keep the switch in the "dual" position...now your converter will charge both battery banks.

The "Mom" position, which stands for "momentary," is a spring loaded position on the switch that you have to hold in.  This is for when your starting battery gets too low for some reason...simply hold the switch in this position and it hard-jumps both battery banks together so you can get your engine (or genny) started with a low battery.

With the big plastic switches:

This type of switch doesn't use a solenoid in the battery compartment.  They are pretty big with very heavy contacts, about 5"x5" or larger.  They are usually orange or red.  They usually have 4 switch positions, and can be located in a variety of locations depending on the rig.  Depending on who makes the switch itself, the switch position names might vary.  What they all have in common is "Off," "1," and "2."  The forth position might read "1+2," "both," or "dual."

"Off" completely shuts down both battery banks, isolating them from the chassis AND the coach.  Good position for storage, especially if you have a slow draw that you can't find that drains your batteries over time.

"1" and "2" of course refers to either battery bank.  Depending on how the company that made your coach (or some previous owner's re-wire) wired it in, "1" could be for your stating battery OR the coach, just as "2" could be either.  You'll have to trace the wiring to the switch to figure out which is which.  If you are running your genny, select which number refers to your coach battery and keep in there.  Your alternator will now only charge your starting battery, while your genny charges the coach batteries.

"Both" or "1+2" or "Dual" works almost like the "Dual" position in Winnies and Itascas.  So if you are NOT running your genny, this is the position you want to select while driving to charge both battery banks.  This is again also the position to keep the switch in when you are parked and connected to shore power with the engine not running, so your converter can keep both battery banks charged.  The difference here is that while this opens your charging circuit to both battery banks, it ALSO hard jumps both banks together...you can use this position to start your rig if the starting battery is low, but remember that unlike the "dual" position on the Winnie "Mom" switch, this position doesn't just open the charging circuit, but actually links the 2 banks together.  Some rigs might be wired so that it is just the charging circuit that this opens, but the few I've seen like this were actual hard jumps.  If yours has a switch like this and it is just the charging circuit it links, then if your starting battery gets low you'll have to use jumper cables and manually jump the banks together to start your rig or genny.

Hope this helps!

Kev

[moparmotivator]

Thanks for the info.

I need to trace out the wiring and see exactly what is charging which batteries in each selector switch position.  The coach has had some rewiring done I imagine.
It used to have a separate coach battery, dedicated genset battery in the generator compartment, and a bank of house batteries.

The genset battery has been removed and a cable runs to the perko switch and I am not sure which bank it is charging when running.  It will start off either the coach or house batteries.   The convertor/charger also feeds into the overall house system when the generator is running.

I really don't think there is any way to  separate the charging systems on my rig.  I can isolate batteries but the charging systems all tie into the house side.

In theory as soon as optimum voltage is reached all the systems should quit charging.  But the dash fan sure spins fast when the regulator quits on the engine alt.

The perko switch in the Travco has positions: 1, both, or 2 but all it is doing is disconnecting the batteries, all charging circuits feed into active side of the switch not the battery side.

I can't access the wiring diagrams on the Travco.com site since it died.  A lot of good Dodge chassis info was lost when that sight quit functioning.