Re: converter diagnosed
- From: Bob Giddings <bobg@xxxxxxxxxxxx>
- Date: Mon, 11 Aug 2008 21:25:07 -0500
On Mon, 11 Aug 2008 17:32:57 -0700, altar nospam
<altar@xxxxxxxxxx> wrote:
On Mon, 11 Aug 2008 18:16:17 -0400, Neon John <no@xxxxxxxxx> wrote:
On Mon, 11 Aug 2008 12:54:45 -0700, altar@xxxxxxxxxx wrote:
So, I just ordered a new PD 2260 smart charging converter
I assume that you mean PD9260?
BTW, did you have to run a new, larger, wire to the battery from your
box because of the increased charging amps? The guy who I talked to
says he never changed the wires whenever he changed out to the new
9200's. Maybe I'm just being anal retentive.
You don't have to but you'll be wasting charging amps if you don't. The
electronics regulate the voltage at the various charging stages at the
converter's terminals. Any voltage drop through the wiring detracts from the
voltage available at the battery. Just a simple example.
Suppose the converter is regulating to 14.2 during the absorption stage. At
some current the voltage drop through the wire is 0.5 volts. At that current,
the battery only sees 13.7 volts. Only the amount of current that it takes to
cause that voltage drop at that instant will flow and not all the current the
battery will accept.
That's a very simplified example to avoid some hairy math but it gives you the
idea. As the battery accepts charge and the current drops, the voltage drop
across the wire will drop until at zero current, it is zero.
All else being equal, the battery would charge, it would simply happen much
slower. But things aren't equal. As best I can tell from experimenting
fairly extensively with the Charge Wizard, the absorption stage is a fixed
time interval. It almost has to be that way, since there is no current
feedback to the CW - something essential for terminating the absorption stage
the more usual way, at a percentage of the current at the start of absorption.
So, being as the CW terminates the absorption after a fixed interval (4 hours,
plus or minus - it doesn't use a precision timebase), the battery may or may
not have absorbed all the charge that it could at the high voltage of the
absorption stage. When the voltage drops back to the float voltage, the
battery may or may not actually accept any charge, depending on how much house
load exists and therefore how much voltage drop between the new converter and
the old where the battery lead ties in.
You can figure out easily enough how much of your new converter's output
capacity will be wasted with the OEM wire and then decide whether you do
anything about it..
First determine the wire gauge for the wire between the old converter and the
battery. Probably either 10 or 8 gauge. Find a wire table on the net
(they're everywhere) and get the ohms per foot for that wire. Estimate or
measure the length of the wire. Multiply by the ohms per foot to get the
total ohms. Add about 0.005 to 0.010 ohms to account for typically lousy
crimped connectors on each end.
Multiply that total ohms times the converter's max output - 60 amps - and you
have your maximum voltage drop. If it is more than about 200 millivolts,
significant capability will be wasted. It is possible that the battery won't
receive a full charge until the periodic equalization cycle.
When I do a changeout (only Magneteks so far), I locate the new converter as
close to the battery as possible and use welding cable* (#4 or #6, depending
on the distance) to connect the 12 volt side. If I'm lucky I can run some 120
volt wiring from the old converter to the new. If not, I simply make a new
run from the breaker panel.
* The neoprene jacket is much more abrasion resistant than PVC or polyolefin
insulation so I don't have to worry as much about chaffing and pinching.
After the installation, I run the battery down enough so that it'll draw full
current from the converter and measure the voltage drop across each cable. I
don't want to see more than 50 mv total. It can be a little more without
problems but I know that less than 50 is what correctly terminated wiring
reads so if it goes much above that, I know that something is wrong.
I remove all the old analog guts and the changeover relay and strap the two
buses together.
There is now filtered and regulated DC on everything in the rig. Most of
those cheap integrated AC/DC panels put unfiltered and unregulated DC on the
lighting circuit. OK for incandescents but murder for those nice thinline
fluorescent replacements. I can't tell you how many people have written me
asking about the same problem - very short lamp life with extreme blackening
of one or both ends of the lamps. Always, the cause is unfiltered DC.
John
Thanks, John, for that explicit explanation. I actually understood!
I will do those calculations. My guess is that when shops do it (as
was explained to me by one of them) they don't give a patooty about
the loss of capacity, because they use existing wiring, and put the
converter where the old one was. They tell the customer it's fixed,
and nobody is the wiser.
It kinda didn't make sense to me to do that, given the old converter
had a max charge rate of 15 amps, and the new one has a 60 amp
capacity through wire designed for 15 amps.
Your solution and Alan's are the same. Straight to the battery, keep
it short with the proper size wire. Jumper the reg and unreg section,
and disconnect the 110 from the old converter.
I might as well pull out the $54 PC board I just put in and sell it on
Ebay.
As always John, thanks,
Tom
And cancel what I said and do the math. I thought you were
moving from 55 amps to 60 amps. Not 15.
Bob
.
- References:
- Re: converter diagnosed
- From: Bob Giddings
- Re: converter diagnosed
- From: Neon John
- Re: converter diagnosed
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