Joy,
The UniVolt is what is called a constant voltage charger, it operates
at a bit over 14 volts in most cases. It is what Livingston describes as
a single output floater, no seperate charging and power circuits.
Now, here's why the UniVolt, et. al. are crap:
To charge a 'low' battery in a decently short time, you have to have the
charging source set at about 14.4 volts or maybe a bit more. That will
cause a good charge rate and it will taper off as the battery approaches
full charge. However, that's too high to float the battery at, you'll
cook out the water. ('cook out' isn't technically correct, but you get
the idea). In an attempt to prevent cooking the battery during long idle
periods where the unit is connected to shore power, they might design
the converter so the voltage is right at 14 or maybe a bit less. The
problems however, are still there, the battery will now charge very
slowly, taking maybe 24 hours or more to be fully charged if it's down
from a couple of 'no power' days, yet that's still a bit too high for
long-term floating.
A proper 3-stage charger such as the StatPower or Inteli-Power sets
itself to 14.4 volts during the "bulk charge" part of the charging
cycle. Once the battery is 80%+ charged (just a few hours), it switches
to 13.8 volts to finish the job. When the battery is fully charged and
there's no current draw, it goes to 13.2 volts for "storage mode". The
Inteli-Power automatically switches to 14.4 volts for 15 minutes, every
21 hours, to keep the battery cells equalized; the StatPower has a
manual control for equalization.
You can easily check to see what your UniVolt is doing by connecting
your DVM ammeter in series with the battery. Set it to "10 Amps" and be
very careful how much load you turn on. You'll find that the charge rate
will be very low to non-existant when you have a couple of lights on,
yet will be 1 or 2 amps when the system is idle and the battery fully
charged. Pushing even an amp into the battery when it's already charged
will cause the water to cook out.
See:
http://www.progressivedyn.com/_frames/frames_rv_power_converters.html
and:
http://www.amplepower.com/primer/full/index.html
for more information.
Obviously, you can get by with a UniVolt (or equivilant) converter. If
you are nearly always connected to shore power, only boondock
occassionally and have plenty of time to recharge after, watch the water
level in your batteries, and don't mind a bit shorter life from them,
then the UniVolt will usually work OK. If you want to treat your
batteries with kindness, need to be able to recharge quickly from shore
power (using a small genset during extended boondocking, for instance)
and want to get away from that God-awful hum, then a new unit should be
on your shopping list.
<<Jim>>
"Mr. Joy H. Hansen" wrote:
>
>
> Livingston's RV repair and maintenance booklet has a great section of
> converters as there are two types that need to be considered. The "dual
> output" converter is the least expensive and the most common. It has two
> output circuits - one for battery charging and the other for the appliances.
> The output is often dirty and not suitable for delicate electronic
> accessories.
>
> Livingston also describes the single output that is called a battery
> floater.
> This is more expensive as the voltage is filtered and the battery is always
> on-line. Since the voltage is not split - one line to the battery and the
> other to the appliances - all the output of the converter is sent to the
> battery and allows very high charge/recovery rates. As appliances are
> turned on, the charge rate drops. The advantage of the higher-line
> converters is the provision for temperature monitoring and/or owner setting
> of operating conditions.
>
> Guess this is as close as I can plagiarize without writing the complete
> text.
>
> I'm pretty sure that the original Univolt was a single output and for
> vintage units was a pretty expensive ferromagnetic mechanism. Contemporary
> units are solid state electronic switching for what ever that means. The
> A/S owner's manual claims that the Univolt has regulated output that changes
> the charge rate as the battery charges and shuts off when the battery is
> fully charged. My old univolt still works as described in the owner's
> manual. I can hear a loud hum until the battery is fully charged and then I
> hardly notice the hum (while bedded down on the gaucho nearly over the
> Univolt). The only time the Univolt refused to operate properly was when I
> was off the 110 shore line and removing and attaching the battery cable
> while lights were on in the Safari. The 40 amp fuse opened and it took much
> longer to find a 40 amp fuse than most would have to replace the Univolt.
>
> I'm not sure why many A/S restorers claim that the Univolt is crap.
> However, Herbach and Rademan (H & R) www.herbach.com sells salvage and
> distressed electronics. The list a 20 amp charger at $99 and a 48 amp
> charger at $299 and all claim to be linear and produce 13.8 volts. They
> feature regulated output, current limiting, crowbar, OVP on 32 amps and
> larger, fusing, low noise and ripple output, illuminated on/off switch, and
> line cord. Suitable for bench testing of auto transmitters and audio
> equipment. From the descriptions, it might be that H&R has units with 40 or
> 30 amps output. $299 seems like a major purchase; however, the 48 amps
> output seems entirely satisfactory for a quick recovery charge, though not
> as quick as the 120 amp tow alternator. Dr. G is likely to explain or has
> already explained in the archives how these systems function.
>
> I don't know that the Intellipower and the Charge Wizard constitute what
> Livingston describes as a dual output system, but it seems likely. The
> Camping World "True Charge 40+ Charger/Converter is pricy at $459, but it
> seems to have features that might be useful in an RV application. I recall
> some discussion about these converters and display panels that I'll have to
> search the archives for. My Univolt might conk out at any time and I'll be
> in the dark? :)
>
> I hope this adds some substance to your deliberations; however, knowing my
> postings might lead you to take all this with a grain of salt!
>
> '69 Safari, Joy
>
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>
--
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<<lower SE Michigan, USA>>
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