Alternator Charging Wire To Battery

[Barry7363]

Gentlemen, I'm in the process of re-wiring my house and start batteries with new DC switches and panels, but am having difficulty identifying the alternator output wire back to the battery switch and then to the battery. I know that the #10 or 12 gauge orange off the alternator is the output to the harness, but can't identify which goes to the battery switch (and/or batteries). My M-25 Universal has the original alternator (as far as I can tell a 51 amp or 55 amp motorola). I have an M-25 wiring diagram from universal, but that deals with the engine to cockpit panel interface, and is "uninformative" when it comes to the routing of the charging wire from alternator to batteries. I'd appreciate any suggestions, particularly from those of you who have already carried out this upgrade.

Cheers, Barry

 

[Bob S]

I'm doing the same thing as we speak. I suggest you look here http://www.c34.org/ for some answers. The Catalina 34 group has a great project page with all kinds of answers. Stu Jackson will be giving you some great advise.
#1 suggestion - run the alternator directly to your house bank and skip the switch. Use a combiner or echo charger to charge your reserve/start battery.

Good luck.

 

[Rich Stidger]

If you are deciding between the #10 or the #12, the #10 is a better choice.

If you have a stock 55A alternator, the max current that you can draw with it full-fielded (ie. maxed-out) is about 37A. If you go to the West Marine catalog and check the wiring charts you will find that for a round-trip run of 10 feet the choice would be #8 for a 3% drop.

If it were me, I would measure (don't guess) the distance from the alternator to the switch and then to the batteries and then enter double that length as the round-trip distance for a 3% drop and see what wire size is recommended. If in doubt, go up one size. I wouldn't be surprised to see a wire size of #6 once you establish the actual distances.

 

[Ron20324]

Rich, there isn't a round-trip on the alternator output. The return is the battery cable itself, considerably larger than his #10 or 12. Besides which, the wire is already in place and like all of us, it's too "bundled" to be able trace by following.

Barry, it's likely your wires each have a different number on them every couple of feet or so to identify them outside of the bundles. Mine does..

 

[Maine Sail]

If

If your boat still has the ammeter in the engine panel the alt runs through the ammeter and back to the batteries. Lose the ammeter, this was a dumb idea any way you slice it on Universal's part, and replace it with a volt meter. Then run a new wire directly from the alternator to the house battery. I prefer at least a #8 or #6 wire for the alt output..

 

[Barry7363]

Thanks so much for the quick responses. My intention is to wire directly alternator to the house bank, and I have an echo charger that I will install between the house and start battery. Maine Sail (as always) has hit the nail on the head regarding the circuit back through the alternator... I saw that on the drawing, but thought that I was missing something, believing that they wouldn't run a charging current though a gauge...that's what they did apparently. So if I run a #6 directly back to the house bank, what is the risk if I leave the rest of the "harness connections as they are? Also, following Mainsail's suggestion of replacing the ammeter with a voltmeter, how does that affect the harness wiring? Also, does anyone know the best source for a voltmeter that would fit? Thanks again for your insights and suggestions,

Cheers,

Barry

 

[Maine Sail]

Also, following Mainsail's suggestion of replacing the ammeter with a voltmeter, how does that affect the harness wiring? Also, does anyone know the best source for a voltmeter that would fit? Thanks again for your insights and suggestions,

Cheers,

Barry

Barry,

The gauges Westerbeke/Universal use are Teleflex Red International Series. These gauges can be purchased at any marine chandlery for about $22.00 to $30.00 depending upon the gauge.

As for the wiring you can disconnect the wire feeding the ammeter from the back of the alt and the back of the ammeter and tape both ends and leave it in the harness. and when you replace it with a volt meter use the wire that fed directly back to the battery for you volt sense.

 

[Barry7363]

Thank You Mainsail, that answers my question.
Cheers, Barry

 

[Stu Jackson]

The AO goes back under the head sink

then under the nav station and up to the panel. Least it does on my '86, #224. What year C34 do you have?

Forget the discussion about #10 or #12 wiring. The OEM is #4 RED. You may have two #4s one from the AO and one to the starter, some boats have two, mine did. If one only, then there's a short small jumper from th AO to the starter.

See: http://c34.org/bbs/index.php/topic,4934.0.html and also read the links provided.

This, too: http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

 

[Benny]

Ammeter/voltmeter? I grew up with cars that had generators and voltmeters and then alternators and ammeters. What has changed?

 

[Stu Jackson]

One has to understand "how it's wired"

because the boats with ammeters had the entire alternator output going through small wires back to the cockpit before the charging current ever got to the batteries. That's why.

That's why the engine harness upgrade is necessary, besides it being a fire hazard. Really. Boats have started up by themselves and there has been at least one report of a fire due to the sh*tty connectors used. That's why.

Engine wiring harness (not an upgrade, but a real flaw, but not so admitted): http://www.c34.org/wiki/index.php?title=Engine_Harness_Upgrade That's why.

 

[Barry7363]

Re: The AO goes back under the head sink

Hi Stu, Thanks for the specific routing info and the links... Our C-34 is an '86, Hull # 98, so we probably had/have a lot of common issues,

Cheers,
Barry

 

[Stu Jackson]

Yes, Barry, we do, why not join us over on the C34 website mb, too?

 

[druid]

(See my post on $(*&(*#& Electricity...)

I much prefer an ammeter over a voltmeter, but agree that running the alt output back to the engine panel is Bad. I wire the alt to the switch, so have an ammeter there. And you can't have too big a wire for your alternator or starting cct! Go #4 or even #2 - you won't regret it.

A voltmeter (supposedly) gives you battery condition (%charge), and you should see the voltage increase when the alternator is charging. BUT, an ammeter tells you how MUCH your alternator is charging, and from that you can calculate how long you need to run your engine to recharge the battery. You ran that fridge that draws an average of 2A for 24 hrs and the alternator's putting out 30A? Run the engine for ( (2x24)/30 ) 1.6 hrs. More or less.

druid

 

[Stu Jackson]

druid, I hear ya about the OEM wiring on this and the other post. The other issue about an ammeter is that the ammeters used on our boats have internal shunts because they make 'em in that range that way What that means is IF you still want an ammeter in your cockpit engine panel or anywhere else but the nav station and near your power supply, you have to run whatever current is running through your boat ALL THE WAY back there. It was stupid to do it in the 1980s and makes less sense now in 2009. There are few boats who lurk around here who aren't too big to have an ammeter at the nav station. Let the skipper go down below to take a look, instead of running yards of wire all the way aft and back again, 'cuz to make the ammeter useful it's gotta have all the current that's flowing running through it, (+) or (-).

 

[Stu Jackson]

OEM Wiring back of Alternator

Barry,

We also have wiring diagrams with all the wiring you're discussing.

Look here: http://c34.org/bbs/index.php/topic,4548.0.html