generators, inverters, and bears

generators, inverters, and bears - oh my!

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Steph - 25 Jan 2007 16:21 GMT

I have a nice Honda EU2000i, and use it every other day or so with a 3-
staghe 110/120V charger to keep my trailer battery charged during long
trips.

No problem.

My friend has a travel trailer and is looking for ways to OCCASIONALLY
power his A/C. He *thinks* my EU2000i can run his A/C unit -- though I am
worried about the startup drain overloaded the surge protection; I hear
you only get so many overload protections before the electronics are
fried.

So, he is shopping for a 3KW or bigger.

I was wondering about inverters in the truck.
They are available in small 80 Watt all the way up to 5000 Watt (~10KW
surge) models for not that much money. But is it making diamonds from
coal?

For example, my vehicle has a 180-AMP alternator.
I don't know if the engine idle speed would automatically rev up if
needed, but as I calculate it, 180AMP * 12v = 1,680 Watts
So attaching a 1250 Watt inverter would be okay, but a 2500 WATT or 5000
WATT could conceivably drain the battery and short out the alernator,
yes?

Also I know the charging system puts out something closer to 14-15v,
which would yield a higher Wattage output (~2500) but better safe than
sorry.

So if he planned to return to the TT and run the AC for 10-15 minutes,
could he do this off the vehicle engine with a inverter? Or he should
just go with a generator.

I found several sites with good information on converting between Amps,
Watts, Voltage, etc. I liked this one:
http://www.powerstream.com/Amps-Watts.htm

And I found many sites talking about inverters and thir "unlimited"
electricity from a battery bank. But not much in the way of a single
battery and the alternator and engine from a vehicle.

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tobe - 25 Jan 2007 17:53 GMT

You are right that a large power inverter would overpower the
battery/alternator capacity of the vehicle, and eventually cause damage
to one or the other (or both). Stick with a larger generator.

Someone out there makes generator heads which hook up to your vehicle
engine with another pulley. Might look at that, too.

> I have a nice Honda EU2000i, and use it every other day or so with a 3-
> staghe 110/120V charger to keep my trailer battery charged during long
[quoted text clipped - 37 lines]
> electricity from a battery bank. But not much in the way of a single
> battery and the alternator and engine from a vehicle.

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Jim Redelfs - 25 Jan 2007 21:43 GMT

> I have a nice Honda EU2000i, and use it every other day or so with a 3-
> staghe 110/120V charger to keep my trailer battery charged during long
> trips.

I have the same genset and think it's great!

<http://www.hondapowerequipment.com/ModelDetail.asp?ModelName=eu2000i>

> My friend has a travel trailer and is looking for ways to OCCASIONALLY
> power his A/C. He *thinks* my EU2000i can run his A/C unit

Be sure he has $1k to spend before you try it - with YOUR generator.

> I am worried

As well you should be. With the POSSIBLE exception of a HIGH EFFICIENCY
13,500btu RV air conditioner, 13.5 units may not startup. Ignoring the
potential damage to the air conditioner, consider the implications of running
a generator at FULL CAPACITY (or beyond) continually if one was successful in
getting the a/c to fire-up.

> he is shopping for a 3KW or bigger.

A *VERY* good idea.

[snipped: Inverter discussion]

Just forget running the a/c without a PROPERLY-SIZED generator and all the
inverter nonsense. Some things just NEED shore power or a big genset to
properly operate. The common RV air conditioner is one such thing.

Signature

:)
JR

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RichA - 26 Jan 2007 04:37 GMT

>I have a nice Honda EU2000i, and use it every other day or so with a 3-
>staghe 110/120V charger to keep my trailer battery charged during long
[quoted text clipped - 37 lines]
>electricity from a battery bank. But not much in the way of a single
>battery and the alternator and engine from a vehicle.

Hi,
A 2000 watt inverter is to small for most air conditioners. The 2000
watts is peak power for a short time, so at 120V AC that's around 16
amps. Most AC's use more then that to start under ideal conditions.
3000K is the minimum he should be looking at and for some air
conditioners under poor conditions that may be to small.

Forget about trying to run an air conditioner off of a single battery
and an alternator. But here is some stuff for you to ponder...

180 amps DC is equal to 2160 watts (not 1680) or about 18 amps AC.
There is no such thing as "unlimited" electricity from a battery bank.
You can only get out what the battery can store. If you take it out
faster then it can be replaced then the battery is going to go dead.
That's why cars have alternators, to run the electric stuff and keep the
battery charged.

Forget about inverters and running air conditioners off of a car
battery. The air conditioner draws so much power you would need a very
big bank of batteries to run the air conditioner long enough for it to
do any cooling. A single battery capable of doing this would be very
large and very heavy.

An item drawing one amp AC from an inverter requires roughly 10 or more
amps DC on the input side AND the correct size wiring to handle it. A
1250 watt inverter would put an 104 amp DC draw on whatever is supplying
it under full load. It could put out about 10 amps AC under full load
not enough to start an air conditioner.

Most common car starting batteries are rated at 80 to 120 amps for the
purposes we are talking about here and are not designed to be drawn down
a lot and then recharged. They will fail quickly if they are subjected
to that kind of abuse. The following web site will tell you everything
you ever wanted to know about batteries but were afraid to ask...:)
http://www.uuhome.de/william.darden/

Take care and Happy Campin...

Signature

RichA
"We Get Too Soon Olde and Too Late Smart"

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