What is this thing? (Electrical)

[cal40john]

Originally Posted by Chotu

I worked up a drawing. A schematic. This is the wiring.

In your earlier diagram you had another pair of small wires going to the isolator. with an inductor symbol. Is this still the case? This would argue that it is a solenoid switch, which seems at odds with the diagram on the isolator.

Earlier you said the engine will start with the switch set to 2. Are you sure it started with the switch only on 2?

Which of the two posts on the isolator is connected to the battery? It matters if it is a diode isolator.

If it is a diode isolator electricity only flows one way through it. Depending on which post on the isolator goes to the battery. It either
1. - allows the start battery to charge, but undercharge, if the switch is on 2 or both. And the start battery cannot power anything as it's on the wrong side of the diode.
or
2. - allows the start battery to start the engine in switch positions both and 2. And in switch position both allows the start battery to discharge into the house battery if it is more than around 0.7 volts higher voltage than the house. The start battery has no way to charge in this scenario.

If it is a solenoid isolator with small wires to turn it on and off, then it is another electrically actuated switch that probably the power comes from the ignition switch. Leave the master switch on both. When you turn on the ignition switch the isolator closes and the batteries are connected and the engine will be running which charges both. Ignition off, the start battery is isolated. If there is something seriously wrong with the start battery drawing down the voltage with the ignition switch on, switch the master to 1 to start the engine on the house bank.

[s/v Jedi]

Originally Posted by Chotu

I worked up a drawing. A schematic. This is the wiring.

Where is the alternator?

[cal40john]

Originally Posted by s/v Jedi

Where is the alternator?

It's the picture of the back of an alternator on the left under the starter.

[AKA-None]

Sure this isn’t an acr?

[s/v Jedi]

Originally Posted by cal40john

It's the picture of the back of an alternator on the left under the starter.

That is a busbar.

[Chotu]

Still working on the alternator. But this is a diagram straight from Perko. I added the less than professional looking part of the diagram.

This is exactly how it’s wired, minus figuring out where the alternator goes.

And yes, that’s a bus bar to the left. A positive bus bar.

I THINK the alternator is connected to that, but I need to verify. The alternator wires are lost beneath the motor and there is no access. Not easy.

[s/v Jedi]

It’s obviously wrong. Alternator to isolator input and the isolator outputs to the batteries. You should be able to tell if the thing is diode based? If so, you can use the diode test on the multimeter to see if it’s okay, but I think it is not.

For replacement I would recommend a Victron ArgoFET (I think that’s what they call it). It’s the same but with hardly any losses.

If it’s connected like in the diagram, I would rip it out as well as the switch and all wiring connected to that…. then put it back the right way.

[Chotu]

Originally Posted by cal40john

In your earlier diagram you had another pair of small wires going to the isolator. with an inductor symbol. Is this still the case? This would argue that it is a solenoid switch, which seems at odds with the diagram on the isolator.

Earlier you said the engine will start with the switch set to 2. Are you sure it started with the switch only on 2?

Which of the two posts on the isolator is connected to the battery? It matters if it is a diode isolator.

If it is a diode isolator electricity only flows one way through it. Depending on which post on the isolator goes to the battery. It either
1. - allows the start battery to charge, but undercharge, if the switch is on 2 or both. And the start battery cannot power anything as it's on the wrong side of the diode.
or
2. - allows the start battery to start the engine in switch positions both and 2. And in switch position both allows the start battery to discharge into the house battery if it is more than around 0.7 volts higher voltage than the house. The start battery has no way to charge in this scenario.

If it is a solenoid isolator with small wires to turn it on and off, then it is another electrically actuated switch that probably the power comes from the ignition switch. Leave the master switch on both. When you turn on the ignition switch the isolator closes and the batteries are connected and the engine will be running which charges both. Ignition off, the start battery is isolated. If there is something seriously wrong with the start battery drawing down the voltage with the ignition switch on, switch the master to 1 to start the engine on the house bank.

Sorry. The earlier diagram was bad. The most recent diagram is accurate. The earlier one was not correct.

[Wotname]

As others has stated - it is a battery isolator.

ATM, it is wired incorrectly and is useless. It might have been wired correctly at some time in the past and a PO changed stuff and did a poor job or it might have been wired incorrectly from day one.

Me - I would remove it from the circuit and then check the battery voltages (with engine running) and note what happens as you switch from 1 / 2 / Both. This will tell you where the alternator is connected.

[Chotu]

Originally Posted by Wotname

As others has stated - it is a battery isolator.

ATM, it is wired incorrectly and is useless. It might have been wired correctly at some time in the past and a PO changed stuff and did a poor job or it might have been wired incorrectly from day one.

Me - I would remove it from the circuit and then check the battery voltages (with engine running) and note what happens as you switch from 1 / 2 / Both. This will tell you where the alternator is connected.

This is pretty good advice. This is the way to go. I agree.

[goboatingnow]

My alternator like many has a remote sensing battery voltage wire. That’s connected to the diode isolator. No need for Argo Fets. Mind you since the Orion is going on to charge the starter I’m removing the isolator anyway.

[capn_billl]

On several boats I've bought, I've seen things like this that made zero sense.

Maybe something else used to be connected, or a rewiring project never completed.

After mysteriously having batteries go dead with apparently everything disconnected, I do what I recommend you do.

Trace out the wiring, and disconnect anything you don't know where it goes, or what it does.

Test everything on boat including bilge pumps.

Everything work? Throw anything not connected away, you don't need it.

Something not working?

Trace out that wire, maybe run a new wire, (you will thank yourself later).

[Chotu]

Originally Posted by capn_billl

On several boats I've bought, I've seen things like this that made zero sense.

Maybe something else used to be connected, or a rewiring project never completed.

After mysteriously having batteries go dead with apparently everything disconnected, I do what I recommend you do.

Trace out the wiring, and disconnect anything you don't know where it goes, or what it does.

Test everything on boat including bilge pumps.

Everything work? Throw anything not connected away, you don't need it.

Something not working?

Trace out that wire, maybe run a new wire, (you will thank yourself later).

Thankfully this isn’t my job. Ha ha ha. I hope my family is reading this thread still. He’ll be doing the tracing. I have enough new wires to install personally.

[Redline452]

Originally Posted by Wotname

As others has stated - it is a battery isolator.

ATM, it is wired incorrectly and is useless. It might have been wired correctly at some time in the past and a PO changed stuff and did a poor job or it might have been wired incorrectly from day one.

Definitely a battery isolator, possibly intentionally wired only to prevent the starter battery from discharging into the house side. It will add a voltage drop to the start battery, but probably not that serious IMO.



I have a similar model except with a third diode/terminal which goes back to the alternator's external sense input, so the alt puts out just enough additional voltage to overcome the diode losses to the batteries.



You could replace it with a "smart" ACR, but it's doing the job of protecting your start battery from accidental discharge by your fridge etc., and is totally solid-state.

[ilCigno]

Originally Posted by s/v Jedi

... I would rip it out as well as the switch and all wiring connected to that….

Exactely that. Those 1-2- both switches are a relic of the past. They usually lead to far more trouble than they do good. And with modern ArgoFET's (or with smart switches like the Vicron Cyrix) there is absolutely no need for these 1-2-both switches anymore.

And I hear some sailors say "hey, such a switch comes handy when one of my batteries are dead, then I can switch to 'both'!". That is true, apart from the fact that you are very likely to loose the good battery also, since it will try to charge your dead battery fast and fruitless ...

How it should be done: With a defective battery (empty or broken) you do not want to destroy the good battery. In order to be able to use the service battery for starting in an emergency, or to use the starter battery as a service battery (with minimal load), an crossover emergency switch can be used. This according to the following principle:

The circuit consists of three normal key-operated battery switches. Only two keys (for the starter battery and the service battery) should be present on board. To close the emergency switch, use the key from the switch of the empty battery. As a result, the three switches can never be closed simultaneously. Connecting the batteries in parallel and thus unintentionally draining the remaining battery is impossible in this way.

Normal situation:


Example: starter battery dead, service battery is also temporarily used as a starter battery: