THREE WAY SWITCH

[puggsy]

I have just fitted the following...Oh! so simple...three way switch...No probs you say...Well...



The main earth wire back to the motor has a simple twist type connect/ disconnect isolating switch. Could not see much point in changing that...its on the earth lead.

And I wanted the accessories to operate solely off battery 2. The original wiring diagram shows accessories connected to 'common'. I have redrawn the line to No. 2.

Here's the problem...With line B connected to the positive of either battery and with the switch on the earth lead ON, and the BIG switch to OFF, I still get a current on the accessory fuse board. Where is the power coming from ? When I open / cut off any possible current flow at E, then no more power to the access. board.

Please guys...what am I doing wrong ? Puggsy

I forgot to show it, but the accessory board earth lead joins back to the main earth line.

[blueskiesup]

Sorry, I had to edit my last post... I looked at the schematic too quickly... so now I offer another non-expert opinion.

I believe you need to have the panel (bottom by side with switch A) hooked to ground and not to power. Power goes into the panel and the panel also needs a ground, not the common pin which is power as well. (Note: be sure the correct post gets power/ground, when I bought a panel the bus bar for power was well marked.)

Greg

[c130king]

Pugs,

I assume you have read the thread on "Battery Switch Location" (posted by me...you can do a search for it under my name if you like). Lots of info on this topic...and near and dear to my heart because I plan to install this same 3-way switch in December when I get back to my boat.

Disclaimer up front...I am a neophyte at electrical stuff. So I have some questions about your setup.

Why do you use line "B'? The power to the circuit breaker/fuse panel is coming off the "Common" post. When you set up the switch per the original diagram when the switch is position 1 then battery number 1 is powering everything hooked up to the "Common" post and position 2 on the switch hooks up battery 2 to the "Common" post.

I think the only thing you need to do in this case is hook up the common negative from the circuit breaker/fuse panel and the negative from the starter/alternator to the negative of one of the batteries and then hook the two negative posts on the batteries together.

If you want your accessories (circuit breaker/fuse panel) to always run off batttery number 2 then I think you hook it up to Post 2 on the switch and not the "Common" post.

Did that make any sense at all?

I am sure one of the resident EEE's will jump in here and straighten me out shortly.

I plan to hook mine up so that everything is hooked to "Common". On odd-days I will select postion 1 on the switch and everything on the boat will be powered by battery 1. On even-days I will select battery 2. But I am also joining the two batteries together with a Yandina Combiner so that I will always be charging both batteries. Both batteries will be brand new Group 24 wet cells...but pretty sure it would work fine with any batteries.

Got this plan from FrankC and a few others that recommend that strategy.

Good Luck,
Jim

[puggsy]

Thanks for responding...it seems like I have to get a 'combiner'. We do have a "12 volt shop" here but they are mighty expensive...but seem to be more ' shopkeepers' than 12V experts...noy much help at all...AND they sell 'Blue Seas' equipment...Will be patient on other replies...Puggsy

[Oskar 26M]

Puggsy
I suggest you consider what is happening inside the 2-way switch and redraw your diagram accordingly.

If I understand your switch correctly, positions 1 and 2 should simply connect either Battery 1+ OR Battery 2+ to the "Common+" terminal. Everything else connects to the Common+ (including starter, accessories and charging circuits).

If you want to select which battery is used for accessories, you would need to take the positive feed for accessories from the other side of the switch (eg Number 2), but NOT from or connected back to Common+.

Bear in mind that you would still have to select 2 if you wanted to charge Battery 2, and if you then used the starter, that would also draw its current from Battery 2.

If you want to isolate the accessories from the starting/charging circuit, you could fit a separate lower amperage toggle switch to choose which battery they draw from.

[puggsy]

Thanks, Oskar...I'll do that...much appreciated...Puggsy

One other thing...can anyone see any problems in leaving that cut off switch in the earth circuit...All it does really is break the circuit.

[Oskar 26M]

I'll stand corrected by the electrical experts, but I cant see any reason why the earth (-) cutoff switch should not be left in place as a sort of a master switch although it would be more usual to have a master switch on the + side of the circuit.
I have a 1-Both-2-Off switch on Oskar. The Off position is a master switch that ensures that you have not inadvertently left some accessory running, draining the batteries when you leave the boat.

[blueskiesup]

The combiner switches are expensive but they do the job of 3 switches so I guess they're worth it...

I would suggust you don't break the ground but rather the power side. This is traditional for a number of reasons:

1 - If you have the switch in "OFF" position there will still be power in the wires that can seek their own ground causing a short. With 12VDC you don't really need to worry about electricution however you could arch and spark if you forget that "OFF" isn't really "OFF".

2 - If you have an accessory which uses a case ground (sometimes done to protect against shocks) when you remove the ground circuit with the "OFF" switch that device could establish a ground through it's case to something metal. Best case it would keep working when you don't want it to, worst case it could arch and spark...

It would be a good idea to move it to the power side if you get back in there for anything...


Greg

[John Christian]

Blueskies said

The combiner switches are expensive but they do the job of 3 switches so I guess they're worth it...

I guess "expensive" is relative but at $78 this is a pretty good buy. ACR

and remember a combiner will allow you to charge 2 batteries with a single output charger, that will save you $50 alone on the 2 output charger. Prosport chargers

JC

[puggsy]

For Blueskiesup, thanks for the info on the possibility of arcing. I think with the rotary switch fitted, i will dispense with the cut off switch in the negative line. anyway, whoever fitted it placed it at the bottom of the steps to the left and anyone who is a bit clumsy could slip and snap off the red key with their foot. Shame about the holes they drilled in the F/G. As I bought SEAHORSE a year old, I do not know who did the wiring...its a bit rough and all the ends are not soldered. Time could cause corrosion problems. I wonder if the importer Phillip King would tell me who did the job? And WHY would they put the cut out switch in the NEGATIVE line? It sort of implies that they have done the job with reveresed polarity...Is this possible....The 27 meg radio works o.k. with a red positive. Always ready to listen to advice. Puggsy

[Kelly Hanson East]

Putting a cutoff switch in your ground will give you a way of isolating your boat from stray current in a marina - you usually cant get your ground away from the water since your motor is grounded and will be in the water of course.

the main cutoff has to be on the POSITIVE side, for safety reasons. If you have an electrical fire in any wiring, the insulation will quickly melt and wires will touch and all kinds of paths to ground will be found - you need to be able to quickly disconnect your battery from the wiring with a single switch to fight an electrical fire of course.

My 10 year old kids are trained to kill the main power switch (Perko 3 way) in the event of fire.

ss

[Hamin' X]

Putting a cutoff switch in your ground will give you a way of isolating your boat from stray current in a marina - you usually cant get your ground away from the water since your motor is grounded and will be in the water of course.

Stray currents are not a problem, unless you are grounded to shore via shore power cord. Any boat that has a shore power setup should have an isolation transformer to prevent a return path for these stray currents.

the main cutoff has to be on the POSITIVE side, for safety reasons. If you have an electrical fire in any wiring, the insulation will quickly melt and wires will touch and all kinds of paths to ground will be found - you need to be able to quickly disconnect your battery from the wiring with a single switch to fight an electrical fire of course.

My 10 year old kids are trained to kill the main power switch (Perko 3 way) in the event of fire.

Excellent advice.

~Rich