Alternator load..how much, how long??

[Reddog]

Thomas has a Telma retarder, 3, 8D batteries, and I am guessing about a 180-200 amp alternator, should be a fairly heavy duty charging system. If I am running down the road, with, let's say, the rooftop AC running off of the inverter (Xantrex Freedom 458 30-12 inverter/charger,Coleman Mach 15), how heavy a load can I safely put on my charging system and for how long. Seems like the first time I tried it, the ampmeter went up to somewhere around 75-100 amps, so I turned it off, seemed too high for extended use to me. Thanks for the in[ut. Doug Engel. Gunnison, CO

[H3Jim]

It doesn't sound like too much given its capacity. 

After running it for a bit, you might try stopping and checking the temp of all the components with an infrared thermometer.  That will tell you if something is running too hot, ie overcapacity.

[John Z]

Doug, that seems about right to me. 100 amps off a 12v alternator would be about 1200 watts. Is that about what your rooftop ac unit draws? If you charging system is ok, that should not be too much of a load for it.

[Reddog]

I'm not sure of the load the AC takes, but 1200 sounds familiar. I can link the 3) 8d's up with my 4) 6V house batteries to make a bigger reserve bank (it's wired that way so I can charge them all while under way), is that any better, of should I just keep it on the 8d's? Doug

[Stormcloud]

I'm installing a dedicated 200Amp 12 volt alternator on the 8V-71 to (re)charge the 12 volt house battery bank,which will in turn power the 6000w inverter, then setup through a transformer to power an 18000btu ductless split system, similar I believe to Jerry L. installation. With the ductless split pulling around 14-15Amps on 120v, that translates to approx 140-150amps on 12v; the 200 amp alternator should handle that with no problem.

Mark

[Reddog]

So am I better off charging more batteries, or less? As long as the banks is big enough to handle the draw? D

[HB of CJ]

What you can do is identify the alternator you have now.  May have been OEM/aftermarket upgraded without addressing the drive belt situation.  Then conduct a simple test.  At night with the AC running thru the inverter, engage your electric retarder, watch the volt gage and seeesss if the headlights dim.   Sounds dorky, but it would give you a good seat of the pants idea of which way the current is flowing.

There are alternators and again, there are alternators.  Usually it is the little electronic gismos inside the thing that give out and cause all the trouble.  Also there is a difference between intermintent and contineous ratings.  AC alone may be fine.  With the retarder, who knows.  And finally the darn regulator must be up to snuff or nothing will seem to work right.  Don't forget to check the battery water often. 

[JohnEd]

My limited understanding is that there are two basik alternator mechanical configs.  One is called "small frame" and the other is "large frame".  Cars have the small item and that Leese Neville (LN) item is the large frame item.  The DN 50 is enormous and a two man carry.

The thing that kills almost all tronics is heat.  The life span increases exponentially with temp drop.  Even the cheapo car stuff will last if you run a duct or cool air for them.  I would stick with the LN though and see if I couldn't do somthing to drop the engine bay temp like wrap the exhaust.

2.5 cents worth,

John

[Tenor]

I was going to post a new thread, but this seems close enough.  I'm just thinking about house battery placement, and house battery usage and alternators. 

I have 4 group 31 batteries to use as start batteries, (I only need two), that I will install in the engine compartment on the right on the old AC rack.  I do have a disconnect for them.  I am thinking of leaving the 2 8D's in place as house batteries.  I'll separate them from the bus needs, leaving them able to be charged from the alternator and disconnected from it when parked.  I plan to use the inverter (Xantrex SW4024) to run air conditioning while going down the road.  I don't know what alternator I have.  It looks like the 225A original, except it is oil cooled.  Like Reddog,  I think it will work, but I'd like to hear from others.

As for the house batteries,
Here are the things that I can think of that would run through my inverter and the 12v stuff to come from the vanner eq tied to the house batteries.

Microwave
12v lights (generally use 1 or 2 at a time, for short periods)
furnace (blower motor)
12v ignition system for fridge
12v ignition system for hot water heater (propane)
Water pump
TV? Little to no use - don't even own one yet
Maybe a blender for some mixed drinks

I also have a 7.5KW genset to help/with the load and recharge.

Anyone think that 2 8D's wouldn't be enough?  I can go later to 8D AGM's later.

[JohnEd]

The 8D's aren't deep cycle, are they?  Start bats don't last as long if you use them for deep discharge.  No doubt *D's would meet you current needs but you cost per, what....charge cycle(?) would be much higher.  These guys don't even like the "golf cart" bats for house use and they are a cross between deep cycle and start and are tough to boot.  Deep cycle bats are called for but I wouldn't throw away your 8D's.

2cents

John