From: John De Armond
Subject: Re: AC/DC Power in an RV
Date: Wed, 09 Nov 2005 14:26:56 -0500
On Tue, 08 Nov 2005 20:56:33 -0800, altar wrote:
>On Tue, 08 Nov 2005 19:22:19 -0600, William Boyd
>>I have been studying the power requirements in my RV and know I do
>>not have adequate DC battery bank for boon docking. I have only one
>>group 24 deep cycle and the standard converter that came with the
>>rig. Would rather have at least two group 27s and add a couple of
>>soler panels top side or on stands. With a three stage charger to
>>help keep them charged. Am considering putting in the battery
>>compartment an APS1000 Power Inverter by Powerbright. with a 30 amp
>>adapter to plug in the RV power cord.
>>AC Power requirements are
>>Electric blanket = 150watts
>>10" ac fan = 66watts
>>20" LCD-TV = 180watts
>>VCR = 25watts
>>Printer = 120watts
>>19" LCD monitor = 84watts
>>DT Computer = 70watts
>>Of course all of these will not be running at the same time.
>>Any more power requirements would have the gen set 2000watt or
>>paralleled at 2000watts (actually rated @ 1600watts each)
>>Any body have any ideas about my proposal?
>I had a similar setup in my last fiver. Several here suggested an
>eu2000 and a Vector 1093. That's exactly what I did. And loved it.
>In the mornings I would measure the voltage, and hook the charger to
>the battery if necessary. Only took about 40 minutes, and voila! Back
I'd go with the Vector 1500 watt inverter that Sam's Club has for $79.
I have a couple and can say that they're the best I've ever had. One
major feature to look for is auto-reset on fault. A manual reset unit
requires that one at least turn the switch off and sometimes
disconnect power. If you have a refrigerator or other important load
running on the thing, disaster is in the wind. I had my older Vector
trip more than once from overvoltage during charge and a couple of
fridges' worth of rotten food was the result.
I have several inverters in my rig. A 1500 watt one with a transfer
relay to feed the house 120vac power, a 500 watt one (modified to
auto-reset) just for the electric 'fridge and an old 250 watt one for
the electric blanket.
This provides redundancy and fault isolation against losing power to
the 'fridge. The 1500 watt one will run the microwave or the coffee
pot or the electric chainsaw, impact wrench or tire pump. I use
multiple 12 volt Group 29 batteries in parallel - lower resistance and
therefore lower voltage drop under load than golf cart batteries.
As much as I like my Vector charger, I got really tired of having to
manually turn it on - and having to have it accessible. I installed a
60 amp Intellipower/Charge Wizard on my rig and never looked back.
The next addition is going to be a 12 volt voltage regulator for the
house power. This device will hold the house power to precisely 13.8
volts regardless of the battery voltage. This will eliminate
flickering lights when the pump runs and the waking up to the furnace
fan just barely running from a dead battery. Jacobs Electronics makes
a commercially available regulator but I've designed my own. I think
the Jacobs unit is rated at 30 amps. These high power regulators have
become popular for the boom-boom stereo types to keep the lights from
dimming on big bass notes.
>The only question mark would be the electric blanket. One battery
>wouldn't cut it for the night. I've run everything else you mentioned
>plus the furnace from one battery with the recharge regimen mentioned
>above. Power to spare.
The electric blanket load as far less than indicated. I use mine with
another blanket on top. Even with the rig down in the 40s inside, the
duty cycle rarely goes over 40%. Overnight with an occasional furnace
run, I typically use from 40 to 60 amp-hours from the pack.
Which reminds me, don't forget the E-meter/Link 10.
While on the subject, I should mention that I've changed the charging
architecture of my system while underway. Instead of simply
paralleling the house battery with the rig battery while underway, I
run the inverter from the rig electrical system and let that feed the
This has several advantages. One, the house system always gets the
proper multi-stage charge. Two, closely related, the battery is
charged as rapidly as possible while underway. Three, the wiring
between the rig and house is 120 volts at low amperage and so can be
lightweight. An advantage on a MH. A huge advantage for a towable.
The connection is simple. Separate the house and vehicle systems.
Install a DPDT contactor similar to the one used in the generator
auto-switches. These are rated 30 amps per contact continuous duty.
Two contacts in parallel easily handle the 1500 watt inverter.
Hook the moveable contact to the inverter, the normally closed contact
to the house battery and the normally open contact to the alternator
directly. Hook the coil to the ignition switch or even better, to an
oil pressure switch. This can also be done with battery isolator
solenoid contactors but two are required and a smaller relay to
In this configuration, the inverter takes power from the house when
parked and from the alternator when the engine is running. This is
especially nice when you need to charge the batteries after an
overnight park. I now frequently just crank the vehicle engine and
run it at a slightly fast idle rather than cranking the genny. Similar
fuel efficiencies, much less noise and with the emission system
intact, none of the fumes.
>I didn't have the luxury of the room for more batteries, or I would
>have considered it.
I've stashed three batteries around my rig in three different places.
I've spotted a place where I can stick a 4th by fabricating a mounting
bracket. All three are currently accessible. The forth will have to
be dropped by a spare tire winch from a pickup.
>After you check out the solar panel's price, the eu2000/charger combo
>begins to look pretty good. It sure made me an energy waster.
At least here in the East, solar just doesn't cut it. The sun doesn't
shine for weeks at a time and when it does shine, trees and mountains
do a good job of shading the good camping spots.
From: John De Armond
Subject: Re: Help with selecting an Inverter
Date: Sat, 30 Sep 2006 20:35:59 -0400
On Sat, 30 Sep 2006 10:34:39 -0700, Owlman <email@example.com> wrote:
>I'm the original poster, and I didn't give you the whole background on
>my situation (didn't want to provide too much info).
>What is really happening here is that I already have a 2500W Xantrex
>inverter on my unit (a 34' Sea Breeze). Ever since we got it, we have
>never had enough lasting power while dry camping (once we got beyond our
>first day with a really full charge). We have 4-6V batteries. We will
>charge the batteries for, say, one hour in the evening, which gives both
>our battery indicators a "full" charge (obviously not full, full!). If
>we watch TV at all (not usually), go to bed and have everything off
>except our 2 tiny nightlights and the projection clock, by morning our
>battery level is either already in a "red" condition or it's marginally
>"yellow"/good, such that if we have to run our microwave for a couple of
>minutes, it totally depletes the charge.
>I have had 3 different RV or electric folks look at our arrangement and
>can find nothing else that is drawing on our batteries during the night
>and cannot understand how we can run out of juice so quickly. My
>batteries (4 Trojan marine/golf batteries) are now 4 years old, so I
>thought they might be running out of steam, but they still test well.
>And this problem has gone on ever since we bought our new MH in 2002.
This is the kind of detail that we need!
There are several things going on here. First, your batteries are
probably nearing the end of life. The only "test" that matters is
that they're running down too quick. There isn't any test available
other than discharging them and measuring the energy supplied that
will accurately report the battery condition. Having them run down
too quickly is a rough version of that test.
Second, using that large inverter to run two night lights and the
clock is like using a Hemi to run a fan. It works but not very
The Xantrex will go into a low power standby mode when all load is
removed. In this mode the inverter comes to life every so often to
see if anything draws any power. If it does then it comes out of
standby and operates continuously. Those tiny little loads that you
are operating are keeping it out of standby mode. Especially if yours
is a sine wave inverter it will draw considerable power from the
batteries at this low load.
Several things you need to do. First is to get rid of those 120 volt
night lights. If you really do need night lights then get or make
some 12 volt ones. Single white LEDs would work nicely and consume
less than a watt.
If you must have a 120 vac clock then get the smallest inverter you
can find to power only it. One of those 70 watt inverters built into
an oversized cig lighter plug will do. Be aware, though, that it
probably won't keep good time. I'm fairly sure that the Xantrex
inverter's frequency is crystal controlled. None of the small
inverters will be. You'll be much better off with a battery operated
clock. If you need a light emitting clock then take a look at the
ones sold for truckers. The big Barjan one that I mention in another
post doesn't work very well but there are several other brands
available at the large chain truck stops.
Next, you must make sure that all load is off the Xantrex when you're
sleeping or away. Either remove all the load or turn it off. That
inverter is not really designed for boondocking. It's designed to let
you pretend that you have shore power while traveling.
For boondocking, the most efficient configuration is an
inverter-per-load arrangement with the power switch for each load
turning the inverter on and off. Each inverter is sized for the load.
With this architecture when a load is off there is no inverter sitting
there idling, consuming battery power.
Since you have the Xantrex, you can use it for the microwave and other
heavy loads. Simply get some smaller inverters for the smaller loads
such as the TV, stereo, etc., and leave the Xantrex off except when
you're actively using an attached load.
Lastly, look at your batteries. Four year old batteries that haven't
been actively managed are probably near the end of their lives. I've
written several times before on load testing batteries so you might
want to look at Google. Or if you don't want the hassle, just replace
'em. Only a couple hundred bux.
From: John De Armond
Subject: Re: Is there a 2-way 'manual' switch to go between inverter and shore
power for the TV ?
Date: Sat, 16 Feb 2008 14:44:54 -0500
On Sat, 16 Feb 2008 09:35:56 -0800, "Jepp_23" <Jepp_23@hotmail.com> wrote:
>This sounds like a great solution. Where did you find the inverter? What
>model is it?
Trace Engineering was bought out by Xantrex quite a few years ago.
Xantrex offers pretty much the same line of RV inverters under the Freedom brand
Understand that we're talking apples and oranges. This type of inverter/charger is
very nice but very expensive. Nearly a thousand bux for 1500 watts.
http://www.oasismontana.com/Trace-DR.html (first google hit, not necessarily
If you already have a good smart charger/converter in your rig then it makes little
sense to spend that kind of money. 2000 watts of modified sine wave power can be had
for (sometimes far) under $150. For example
I use this one
In fact, I use a bunch of 'em. I have one in my RV, another in my cube van, another
in my car and finally, one in my house as part of my whole-house UPS (vital here
where day-long power outages are routine affairs.)
Sam's sold it for $49 for a long time. Then they raised the price to $79. In the
Chattanooga store they finally remaindered the last few for $59 and quit carrying it.
I cleaned off the remainder table :-)
This is a sweet inverter. Maybe the most important feature is its auto reset
feature. If it trips off because of a momentary under- or over-voltage on the 12
volt side or an overload, when the voltage returns to normal, it automatically resets
and comes back on line. Many inverters stay tripped until manually reset. If you
run a refrigerator on the inverter like I do, the result is spoiled food if you don't
catch the trip in time.
Let me chat a little more about auto vs manual transfer. Auto transfer is nice under
ordinary conditions. You pull shore power and the inverter kicks in automatically.
No muss, no fuss. However, that doesn't allow you to address some other situations.
Consider, for example, you're sitting in an RV park when you detect an abnormal power
situation approaching. Say, big dark clouds blowing up and thunder in the distance.
Or the heat of the afternoon has set in and the park's inadequate wiring is letting
the voltage sag too much. Or whatever. You're watching da big game and don't want
to miss the end. You're in the RV park so you probably shouldn't fire off the
generator. Inverter to the rescue.
With auto transfer, in most cases, you're going to have to make a trip outside to
either unplug from shore power or flip the pedestal breaker. With manual transfer,
you simply reach over and flip on the inverter.
If you unplug or flip the breaker to make the auto transfer work then you have no
idea when the power is OK again. With the manual transfer and a voltmeter to monitor
the shore power connection, you simply occasionally glance at the meter and when the
voltage is normal, manually transfer back to shore power.
Another example. In rural/mountaineous areas such as where I live and camp a lot,
the power lines are long and frequently have poorly cleared right-of-ways. The
result is that tree limbs across the lines is a frequent event. Many times the
linemen will try to blow away the fault by manually restoring power. If the limb
doesn't blow clear, this generates many very heavy surges. Even if the limb does
blow clear, at least one big surge will occur.
I've learned through the painful experience of many blown light bulbs, surge
supressors and some electronics that the first thing to do when the power goes out is
to hit the main breaker and run on standby power until the utility power comes on and
is stable. I do the same thing in my RV.
Manual transfer lets me flip over to inverter power when shore power goes out and
then stay there until the shore power is back on and stable. Auto transfer,
depending on whether there is a delay built in or not, may just connect back to shore
power in the middle of a big surge.
Both manual and automatic transfer have their happy users so if you go the auto route
you'll probably not be unhappy. But with my utility background and very conservative
nature, I like to have control over even rare events so mine is strictly manual.