[C320-list] Xantrex shore charger

[Jeff Hare]

Hi Folks,

CRA's boat is similar to mine, so if I mentioned 2/0 gauge before, I
probably meant 1/0 gauge like he said.  :)

Short answer to the question is:  "No, don't upgrade the wire diameter from
the Charger to the batteries, they're probably just fine as long as the
terminals are in good condition."


This is how I come to that conclusion... (if interested)


Regarding the Chargers:
=======================
The wires from the charger are likely "4 AWG".  A 3-bank 30 Amp charger
produces 10 Amps of charging current PER BANK for a for a total max output
of 30 Amps.  So, the maximum charging current you'd ever see if you ran all
3 legs to the same battery would be 30A.  Note that the manuals usually say
to short the unused bank to one of the banks being used, which would result
in one bank seeing 20A MAX charge current, while the other would see 10A
under max charge output conditions.  (for a 12v/30a/3-bank charger)

So, 4awg is perfectly acceptable LOAD-Wise for the wires between the Charger
and battery.  Note that the KEY wire in this circuit is actually the size of
the BLACK Ground wire to the charger!  Since the return path for all 3
charging legs is through that single ground wire, it's the only wire that
needs to be sized for 30A.   (another example of many voltage sources,
sharing single ground return)

Also remember that the voltage drop on the Charging wire is only a factor
for a short period of time during the initial Bulk charge cycle.  Ie:
whenever the charger is going full tilt.  Once the current drops down as the
battery comes back up to charge, the wire resistance stops being a factor
anymore and the battery charger regains it's precision.

So... The net effect of slightly undersized charging wires *might* actually
just SLOW the bulk charging phase, but not really affect the charger's
ability to deliver a full charge if allowed to progress through all 3
stages.

Wire Gauges?
============
Prior to wiring higher current Marine DC stuff, I really hadn't needed to
know about the relationships of wire sizing much below 8AWG wire.  So, I
made a table that helped me with the big picture.

Diameters below don't include the thickness of insulation, just the copper
inside, and the currents are VERY approximate max ideal continuous currents
just to give you a feel for sizes and currents.  Also, they're assuming
basic plastic/PVC insulation.

Don't use this chart as a sizing gauge, just to give you general ballpark
feel.

Sizes run like this:
<<SMALL>>
22awg = ~0.02" diameter  (  2A continuous)
18awg = ~0.04" diameter  (  5A continuous)
14awg = ~0.06" diameter  ( 15A continuous)
12awg = ~0.08" diameter  ( 20A continuous)
10awg = ~0.10" diameter  ( 30A continuous)
8awg  = ~0.13" diameter  ( 40A continuous)
4awg  = ~0.20" diameter  ( 70A continuous)
2awg  = ~0.26" diameter  ( 95A continuous)
1awg  = ~0.29" diameter  (110A continuous)
1/0   = ~0.33" diameter  (125A continuous)
2/0   = ~0.37" diameter  (145A continuous)
3/0   = ~0.41" diameter  (165A continuous)
4/0   = ~0.46" diameter  (195A continuous)
<<LARGE>>

FUSING BETWEEN THE BATTERY AND STARTER?
=======================================
All of these wires can take many times their maximum current for very brief
periods of time if you can keep them cool, we COUNT on the starter not
running for extended periods of time which is why we can get away with 1/0
or 2/0 gauge wire.  They won't see this starter current long enough for them
to heat up enough to melt and burn (we hope).

Look for a Nigel Calder or the mfgr's spec for actual application.

Cheers!
-Jeff



-----Original Message-----
From: c320-list-bounces at lists.catalina320.com
[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of
crashley at gte.net
Sent: Saturday, February 16, 2008 10:37 AM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] Xantrex shore charger

Myron,

FYI, the positive wire from the battery switch to the engine (starter 
solenoid) is 1/0 on my boat (#882). The negative from the battery to the 
engine block is also 1/0. (The means "single 0 gauge" I believe). That's 
also what it says in the "official" wiring diagram.

CRA
Rosebud #882


----- Original Message ----- 
From: "Myron Welch" <myron-welch at uiowa.edu>
To: <C320-List at Catalina320.com>
Sent: Friday, February 15, 2008 8:16 PM
Subject: Re: [C320-list] Xantrex shore charger


> Jeff,
>
> My smaller wires are from the charger to the battery, not the battery to 
> the starter.  I wish I could give you the size, but the boat and owner's 
> manual are in cold storage in northern Michigan.  Should those be changed 
> to the larger size wire on the newer boats?
>
> Thanks for all your help.  I think we should all take a week long 
> electrical systems seminar with you.  I would enjoy that.
>
> Myron Welch
> Wind Instrument #238
> Iowa City, Iowa
>
>
>
>
>
>>Yes.  That's my opinion.  No danger, just adds more voltage drop along the
>>run, so that the starter will maybe see less voltage than the battery has 
>>to
>>offer when cranking.
>>
>>It would affect trying to start the engine with a run down battery just a
>>bit sooner than if you had a larger gauge wire.
>>
>>-Jeff
>>
>>-----Original Message-----
>>From: c320-list-bounces at lists.catalina320.com
>>[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Jon Vez
>>Sent: Friday, February 15, 2008 8:30 AM
>>To: C320-List at Catalina320.com
>>Subject: Re: [C320-list] Xantrex shore charger
>>
>>Myron,
>>
>>When consulting with Jeff on my project, I know he feels the original 
>>gauge
>>was too small for the length of run/amps--but I don't this issue is that 
>>of
>>danger, just resistance and efficiency--Jeff, do I have that right??
>>
>>Regards,
>>
>>Jon
>>
>>-----Original Message-----
>>From: c320-list-bounces at lists.catalina320.com
>>[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Myron Welch
>>Sent: Thursday, February 14, 2008 9:24 PM
>>To: C320-List at Catalina320.com
>>Subject: Re: [C320-list] Xantrex shore charger
>>
>>Kirk,
>>
>>I'm interested in your project of installing the breakers in the line
>>from the charger to the batteries.  I know this should be done,
>>bought some in-line fuses a few years ago, but have never followed
>>through.  I was not certain the fuses were the correct size.  I would
>>be interested in knowing the part name and number of your breakers
>>and how you installed them.
>>
>>Also, I believe that our more mature boats have much smaller wire
>>from the charger to the batteries than the newer boats.  I believe my
>>wire is perhaps 6, 8, or 10 gauge.  Is that true for your boat?  The
>>wire is small enough that I had no difficulty attaching it to the
>>Xantrex 20 charger posts.  Jeff and Jon, do you see any problem with
>>the smaller wire and should it be changed?
>>
>>I have the link 20 for monitoring my two house batteries.  Jon,
>>although you gave me the diagrams for adding a starting battery in
>>2003, that will have to be a post-retirement project next year.
>>
>>Thanks for any suggestions.
>>
>>
>>Myron Welch
>>Wind Instrument #238
>>Iowa City, Iowa
>>--
>
>
> -- 
> Dr. Myron Welch
> Director of Bands
> Professor of Music
> Collegiate Professor, College of Liberal Arts and Sciences
> The University of Iowa
>