Tip 'o the day - emergency start switch

[BobCT]

Stumbled across this today looking at the wiring diagram. Basically the note says that the crossover between the two batteries happens automatically when starting the engines. The manual switch is really there when you need to bridge the batteries but NOT starting..the example is using the VHF.

So, the switch at the helm is mis-labled. No harm, i have used it while starting.

Bob

[obeejr]

I believe your information is half right and half wrong. The relays do automatically kick in when you start an engine, so basically all starts are powered by the two starting batteries in parallel. When you start the port engine, the port battery closes the cross over relay, and vice versa for the starboard engine.

This works fine until you have a dead battery. If you are trying to start the port engine with a dead port battery, it doesn't have enough power to close the crossover relay and the starboard battery doesn't get paralleled to the port. Solution? The two pole switch on the dash. One way uses the port battery to close the crossover relay, and the other way uses the starboard battery. So, if the port battery is stone dead, the dash crossover switch can use the starboard battery power to close the crossover relay and join its power to the port battery, and get your engine going. Which way is which? who cares. Try it one way, and if that doesn't work try it the other way.

The downside to the automatic operation is that you may have a weak battery and not even know it until the battery is completely dead.

[prowlersfish]

On the F boats you have to use the switch to use it , no auto opp. If it was auto I would change it to manual opp .



Update per my book I am wrong see my other post . Mine had been rewired

[captainmaniac]

I had a wire to replace this winter, so last fall I cracked open the 'little black box' and photographed / sketched out how it was wired. Had intended to share the info long ago but haven't gotten to it yet. I will try to bump that up on my priority list and publish a wiring diagram and snaps of how it is wired on the F32 (at least, on my '79).

I think the dash switch trips the solenoid to parallel the batteries, but other things (like head and fridge) are wired directly into the black box too.

[prowlersfish]

I had a wire to replace this winter, so last fall I cracked open the 'little black box' and photographed / sketched out how it was wired. Had intended to share the info long ago but haven't gotten to it yet. I will try to bump that up on my priority list and publish a wiring diagram and snaps of how it is wired on the F (at least, on my '79).

I think the dash switch trips the solenoid to parallel the batteries, but other things (like head and fridge) are wired directly into the black box too.

I think Trojan used as a convenient place to pull power as you have power available from both battery banks right there . I lost some power to the trim tabs and some other stuff and found a bad circuit breaker in there .

[1967 seavoyager]

Here's how it works : The starting battery starts both engines. Starboard engine charges the starting battery. Port engine charges the house battery. In the event the starting battery is dead you push the button to transfer power from the house battery to the starting battery to start the engines & get going again. The diagram is on my photobucket page.

[RWS]

I believe your information is half right and half wrong. The relays do automatically kick in when you start an engine, so basically all starts are powered by the two starting batteries in parallel. When you start the port engine, the port battery closes the cross over relay, and vice versa for the starboard engine.

This works fine until you have a dead battery. If you are trying to start the port engine with a dead port battery, it doesn't have enough power to close the crossover relay and the starboard battery doesn't get paralleled to the port. Solution? The two pole switch on the dash. One way uses the port battery to close the crossover relay, and the other way uses the starboard battery. So, if the port battery is stone dead, the dash crossover switch can use the starboard battery power to close the crossover relay and join its power to the port battery, and get your engine going. Which way is which? who cares. Try it one way, and if that doesn't work try it the other way.

The downside to the automatic operation is that you may have a weak battery and not even know it until the battery is completely dead.

================================================================================================================================

I can confirm this is the case on my 1983 10 meter International.

it is a smart design.

I took the concept one step further. The genny battery on mine is completely isolated from everything else.

except for the generator, the battery charger and the added emergency bilge pump.

There is, however a battery switch and wiring that connects the genny battery to one of the starting batteries.

Just gives additional options in the event the two starting batteries have been run down.

Also, the addition of a 3 battery voltmeter is a tremendous value.

http://www.gridbegone.com/p/125/blue-se ... er-w-panel

I have this mounted on the helm.

Very, very valuable instrument.

RWS

[prowlersfish]

On the F boats you have to use the switch to use it , no auto opp. If it was auto I would change it to manual opp

Well , per my wiring diagram and the owners manual I am wrong . Mine has been rewired . They came with auto opp of system . But the it won't work if the battery of the engine is dead or very low so thats when the emergency switch comes in to play . I can see the advantage of this when you have a house use battery but I can see a disadvantage of only one real Cranking battery also.

I have repaired similar system on both a Post and a Viking ,both were manual opp only . But both their switches said "PARALLEL" not "EMERGENCY" . I assume mine was rewired , saved me the trouble . My house loads seem to be split up also .

Very interest post .

[Big D]

The auto crossover is a good idea but only if it is paralleling two crank batteries and NOT a crank and deep cycle house bank. I don’t like the concept of it being used on a twin screw vessel with only two banks; one crank for one engine and one deep cycle for the other engine and house which is a bad design to begin with. Paralleling a crank battery with a deep cycle one for the purposes of starting an engine on a rare occasion such as an emergency is one thing but doing it automatically every time reduces a deep cycle’s life span. It wasn’t designed to perform that task on a regular basis.

[prowlersfish]

I don't like the auto opp . You may not know you have a weak battery until the other one starts acting up .

I don't have a issue with 2 cranking batteries and using them with light house loads . But if use house loads like being on the hook , them a separate house deep cycle battery ( or battery bank of more then one) the way to go .

By light loads I mean like I use the boat 98% of the time my boat is in one these states A) onshore power and battery charger on B) engines running C) genset on and auto battery charger on . And the there are no heavy house loads like a fridge .

Deep cycle batteries and not made for high cranking loads and cranking batteries are not made to be heavily discharged over and over . You have duel purpose types but in my experience there OK but not great at ether job .

FIW: I am using 2 4D truck cranking batteries for the engines (just replace both in the past 2 weeks ) and a 24 marine cranking battery on the genset . House is split between the 4Ds .

[1967 seavoyager]

I posted the pages from the original manual describing the emergency start switch on my photobucket page.

[kenflyer]

Hello,
I found this discussion very interesting just having purchased my 77 tri cabin. When I look at my console, I do not have a switch labeled emergency crossover. Could the switch be under the console?

[Big D]

.....I do not have a switch labeled emergency crossover. Could the switch be under the console?

If it was factory installed, it will be easily accessible at the helm. Do you have a switch that's not labled or says parallel? Look for a momentary push button or toggle switch that returns to the off position when released.

[lawyerdave71]

Oh Boy I had to use my emergency switch two weeks ago - WORKED GREAT!! I had a bad battery

[kenflyer]

Hi Big D,
I do have momentary push button switch. And it is not labeled. I took the cover off nd the connectors are broken and not attached to the switch. Guess its time for replacement. thanks