...my alternator output goes to the + post on the starter. My starter cable from the 1-2-B switch is fed based on switch position, so aren't which batteries receiving the charges based on my switch position?
Yes, Steve, you are correct. That's the rambling, ongoing points that I've been having here in my discussions about the 1-2-B switch. Because the output of the alternator wired that way, once the engine starts, goes through the switch, the switch position does exactly that.HERE'S HOW THE OEM WIRING ORIGINALLY WORKED AND WHY YOU SHOULD CHANGE ITIn the diagrams below, please change B to C. B is a position on the switch, it is NOT a point of wiring connection. There are three "posts" on the back of the switch: 1, 2 AND C. There are four positions on the switch: OFF, 1, 2 and BOTH. Thanks.
Figs. 1 & 2 show factory wiring (B1 is the house bank, B2 is the reserve bank). Sometimes they wired the switch with two wires (which is how my boat was wired in 1986, or the PO could well have had someone add the second wire - doesn't matter to this discussion). Either later on or around the same time, they reduced it to one wire with a little connector between the alternator output and the starter (Fig. 2) Why? It was cheaper to build. That one big wire served two purposes: when starting it took power from the (selected) battery-or (ies) and fed it TO the starter, and through the small wire between the AO and the starter (small wire, short distance, high current, short time period of current flow); once the engine was running, the small wire did nothing, but the AO started flowing current BACK from the alternator to the switch in the opposite direction. Same wire, current flowed in a different direction.
It was a very functional and cost efficient design, because it used one wire to do two two things. "Gee, how nifty!," you say.
'Cept for a few things:
The switch determined which bank got charged when the alternator was charging (engine running). For years people incorrectly thought they had to start on B because they "needed" the power of two banks. Wrong. And still wrong. In "the olden days" two equal banks were the design norm. People would switch daily between one and two for house use. In fact, new boats still come that way, don't they? Who says the "good old days" are gone?!
When people mistakenly either moved the switch with poor contacts or the brother-in-law turned the switch off with the engine running, the diodes on the alternator fried. Why? Because the output of the alternator was interrupted. (We discussed this years ago and sometimes with full batteries that won't happen, but it did and still does and is an expensive "maybe" to mess with, when you don't ever have to).
With new higher output alternators, the OEM #4 wiring became too small based on voltage drop, so you were losing charging power, just when you needed it the most: to charge a depleted house bank after a night or two on the hook.
Fig. 3 shows the "preferred" design. This way, AO always goes to the house bank, which needs it more than the reserve bank ever does, and you can even turn the switch to OFF with the engine and alternator running because the AO is always directly connected to a load (battery). PDP is the post to collect all wiring going to the house bank (positive distribution post --- to avoid loading up a lot of wires on the battery post - some use a bus bar, I used a Power Post Plus).
The switch then simply does one thing and one thing only: determines which bank provides power for DC loads on the boat, which are starting the engine and running the DP (distribution panel - your electrical panel with the DC loads).
And it does it very well. That's why I continue to "defend" the simple 1-2-B switch.
Since the reserve bank hardly ever needs a "big" charge, because it only uses a few amps to both energize the glow plugs and start the engine, and the house bank is perfectly capable of starting the engine, we leave our switch on #1 (house) all the time. The reserve bank is just that: emergency, backup, reserve. Not "start." Many like to use the reserve bank to always start their engines. That's fine, but is merely an operational issue, rather than a switching issue, because with one 1-2-B switch, with the Fig. 3 "preferred" wiring, you can use the 1-2-B on #2 to start the engine and leave it there until you shut your engine off, because the alternator output is still going to the house bank, always.
A search on the phrase "In Defense" or an advanced search on "1-2-B" with my name will pop up many earlier discussions on this topic.
Also, Steve, between now and when you change your batteries, you can functionally do this by simply moving the AO from the C post on your 1-2-B switch to the house bank post, and install your echo charger now. This gets the AO off the C post and always goes to the house bank. If you've already installed a high output alternator, I wouldn't do this now because the OEM #4 wiring between the banks and the switch would be too small, but with the OEM alternator it'd be fine. This works only with the Fig. 1 wiring, 'cuz if you did it with the Fig. 2 wiring the starter wouldn't work on switch position 2, the reserve bank.
See the Alternator Output and Battery Switch topic: http://c34.org/bbs/index.php/topic,4934.0.html
I edited this topic accordingly.
Another discussion of this issue is on the co.com 'site, here, bottom of page one starts that discussion and moves onto page 2: http://forums.catalina.sailboatowners.com/showthread.php?t=104505In the diagrams below, please change B to C. B is a position on the switch, it is NOT a point of wiring connection. There are three "posts" on the back of the switch: 1, 2 AND C. There are four positions on the switch: OFF, 1, 2 and BOTH. Thanks.