Re: [A/S] Re: EU3000is , Honda

["Jim Dunmyer" <jdunmyer@xxxxxxxxxxx>]

John,
 Standard RV converters like the UniVolt (A/S's brand name for their
converters) are meant to supply 12 volts to your trailer while plugged into
shore power. As an afterthought, they also charge the battery. But:

A converter is a low-quality constant voltage charger, putting electricity
into the battery at 5 amps or less. If your typical "RV/Marine" battery is
50% discharged, it'll require AT LEAST 10 hours to get it fully charged from
the converter. On top of that, they typically don't "taper" (reduce) the
charge like they should, so will overcharge a 'full' battery, cooking the
water out of it.

Two things lead to short battery life: excessive deep cycling (brought on by
undercharging) and overcharging. Our typical RV Converters are guilty of
both transgressions.

Because of this very low charging rate, running a genset to power your
converter to charge batteries is an exercise in futility, it just takes too
long. I checked a friend's system last Labor Day w/e and found his converter
charging at only about 3 amps, and his battery was flat dead. He'd be
looking at 30+ hours to charge that battery, but it had already been ruined
by the converter. (he leaves the trailer plugged in while at home)

Remember, the battery charging function of a standard converter is strictly
a byproduct/afterthought.

There's a number of good chargers available to replace your UniVolt:
StatPower (http://www.statpower.com) has refurbished units that they sell on
the Web; it's about $190.00 for a 20-amp job. IntelliPower makes a converter
with an optional "Smart Charge" module. They're sold through Camping World,
and run about $250.00 for a 30-amp converter with S.M. Module. Both of these
units have an additional advantage in that they're quite light weight
compared to a UniVolt.

If you buy a regular DVM (Digital VoltMeter) from someone like Radio Shack,
you can educate yourself in a hurry. Set it on the "10 Amp, DC Current"
scale and connect it in series with one of your battery leads. (MAKE CERTAIN
that everything is 'off' in your trailer first, because it's very easy to
exceed a 10-amp draw and burn up your meter.) Then, go around and energize
things, one at a time. You'll find that a regular light fixture with 2 bulbs
will draw about 3 amps. The overhead light with the Edison-base bulb (looks
like a household bulb) will draw 4 or 5 amps. Your pump will draw 5+ amps.
The furnace uses a bit less than 4 amps. But, do this yourself, and write
down all the numbers. Don't forget your TV and radio if you use them.

Plug in the shore power cord and note how much charging current you read.
Note: depending on which way you connect the meter leads, it might read "+"
when you're actually discharging the battery and "-" when you're charging
it. No big deal.

Remove your meter and reconnect the battery.

Now, a standard "RV/Marine" Group 27 size battery is rated at 105 Amp-Hours
capacity. It's actually only good for 85 AH, and you don't want to run it
down more than 50% in any event. So, we have 40-50 AH of 'usable' capacity
with a single battery, double that with a pair. (if you can fit them in,
Golf Cart batteries are far better, and no more expensive. You need a pair,
connected in series, because they're 6-volts)

Estimate how many hours each of these lights and appliances will operate in
24 hours. Multiply the hours times the current draw to figure out the AH
usage of each appliance. Example: you use the overhead light for 3
hours/night, it draws 4 amps, so that's 12 AH. You watch TV for a couple of
hours and have one of those popular 9" units that draw 3 amps; that's 6 AH.
The furnace runs for 2 hours, that's 8 AH. We're up to 26 AH so far, but
will need to add a couple of AH for the pump and a few more for the other
lights over the sink, in the bathroom, etc. If you're like us (we're quite
conservative in usage), you'll use 20-30 AH in an evening and early morning
if we don't run the furnace, and 30-40 AH if we do.

My StatPower charger will recharge the batteries in our trailer in 3 or 4
hours, so using a genset is practical. Our solar setup will give us at least
30 AH on a bright, sunny day. Yes, a solar system has a high initial cost,
one like mine would run nearly $1000.00 from most places. I have about half
that in mine, but I got the components dirt cheap and installed it all
myself.

If you MUST run an A/C and are off the grid, you MUST use a genset, no solar
setup that you could afford (or carry in an RV situation!) will do the job.
If you're in that situation, you're not running from your battery anyway, so
you can disregard most of the above. Figure on replacing your batteries
every 2 or 3 years instead of the 5-7  that you'll get if you treat them
kindly, and don't figure on actually operating from them for any length of
time. IE: they'll be good for the lights and pump during that quicky
roadside stop, but probably not much else.

For further reading, go to Phred's Poop Sheets at http://www.phrannie.org.

                                                            <<Jim>>