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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

How to install 2 way battery switch?

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av8rOC
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USA
121 Posts

Initially Posted - 04/12/2012 : 09:42:44

Hey guys, I just ordered this battery switch for the Hyde Aweigh:

http://www.defender.com/product.jsp?path=-1%7C328%7C51495%7C299265&id=183570

I have 2 batteries on board, one dedicated for the Tohatsu 9.8 electric start and one for ships power.

What is the best way to wire the switch? Should both the hot (red) leads for motor and DC panel come off the switch output lead? In that case I would be selecting either battery 1 or 2 to power BOTH motor and DC panel at the same time. Is that OK? I understand NOT to turn battery switch off or switch batteries with engine running.

Many thanks

Sean
Hyde Aweigh 4
1984 SRFK #4152
LINY

Edited by - av8rOC on 04/12/2012 09:44:26

av8rOC
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Response Posted - 04/12/2012 : 10:56:57

From all the reading I'm doing online it seems like that is the preferred way to wire it. My next question would be then is the tohatsu alternator capable of charging both batteries at the same time? I doubt I would do that, probably just alternate switch positions between engine runs.

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JohnP
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Response Posted - 04/12/2012 : 12:06:43

The starter battery is undoubtedly different in design from the cabin battery. You don't want to connect the two of them under any circumstances. Charge one battery with the outboard's alternator some days or portions of a sailing outing, and the other some other times.

You can test the resting voltage of each with your VOM, and you could test the voltage of the cabin battery under load with your VOM, too.

If you happen to already have a voltmeter permanently wired in-line with both batteries, you can already see that. A PO installed one of those on my boat, although I usually use my VOM or my battery charger/multimeter that runs on shore-power at the dock.

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awetmore
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Response Posted - 04/12/2012 : 12:35:21

If you are getting into electrical work I'd recommend the sailboat electrical book by Don Casey. This will also answer the question of what wire should be switched (it is the positive side).

It doesn't talk about outboard motors in particular, but except for the smaller alternator they work like an inboard motor as far as the electricity is concerned.

My boat has two group 24 batteries and I use them as both starter and house batteries. Normally my two-way switch is turned to "both". The solar charger is also connected to the switch, so this keeps them topped off when I'm not using the boat.

Outboard motors start easily (and a battery is just a bonus, not required), so I don't see too much advantage to having a "starter" battery. The normal reason to have a starter battery vs house batteries is to be able to start the motor even if you leave a load on accidentally and drain your house batteries.

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av8rOC
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Response Posted - 05/02/2012 : 07:43:30

This is how I wound up wiring it: http://continuouswave.com/whaler/reference/dualBattery.html

Unfortunately my brand new Die Hard Marine battery is now dead even after running the engine for a good hour or so. The number 2 battery was older and low on a charge but I only ran the battery switch in the 1 position. Any ideas?

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Dave5041
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Response Posted - 05/02/2012 : 07:54:32

Starting and house batteries don't need to be different. A deep cycle battery is more than capable of providing the 30'ish cranking amps of a 9.9 outboard. Disconnect your Diehard and see if it will take and hold a charge from a battery charger is the first step.

Edited by - Dave5041 on 05/02/2012 07:59:51

Sloop Smitten
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Response Posted - 05/02/2012 : 10:34:50

I have both of my deep cycle batteries wired in parallel and the Tohatsu is capable of charging both. Since you have twice the batteries it would take twice as long to fully charge them but they will eventually charge up. Better to use the engine to top them off then let them get to a low voltage situation. I go to Catalina Island once a year for about 9 days and if the batteries gets to low to start the engine I just use the easily accessible pull starter on the Tohatsu 9.8. My point is you do not need a separate battery dedicated to starting the engine. You can use both batteries to provide house current and rely on the pull starter if necessary.

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szymek
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Response Posted - 05/02/2012 : 19:41:44

I'm glad to see this thread as install of the 2 way switch is on my to do list for this summer.

When i talked to the dealer where i got the motor they recommended to use starting battery. This motor needs 480 cold cranking amps. Looking at my starting battery, it has 650. I have no idea what are CCA on deep cycle batteries. I was hoping to use 2 deep cycle batteries and connect them in parallel - seems that folks are using it successfully.

Couple of questions:
1. I was told to disconnect the motor from batteries if using manual start as it will kill alternator - why?
2. I was also told (as stated above) not to turn off the switch while the engine is running - why?
3. Sorry if this is a stupid question. I thought that the models with electric start come with alternator (6 or 7 amps), but today one fellow told me to double check it as he's sure they use magneto. Based on quick read seems that the difference is: alternator - alternating current where electrons flow in both directions (cycles); magneto - direct current where electrons flow in one direction. I'm not sure advantages/disadvantages.

Edited by - szymek on 05/02/2012 19:42:37

Sloop Smitten
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Response Posted - 05/03/2012 : 08:15:32

1. I was told to disconnect the motor from batteries if using manual start as it will kill alternator - why?
Never heard of that. I have manually started mine with the batteries connected without a problem.
2. I was also told (as stated above) not to turn off the switch while the engine is running - why?
Some of the switches actually go into a state of no connection when switching between batteries or off. When this occurs the diodes go from a load position to a no-load position and can overload and fry before they have time to accommodate the change.
3. Sorry if this is a stupid question. I thought that the models with electric start come with alternator (6 or 7 amps), but today one fellow told me to double check it as he's sure they use magneto. Based on quick read seems that the difference is: alternator - alternating current where electrons flow in both directions (cycles); magneto - direct current where electrons flow in one direction. I'm not sure advantages/disadvantages.
Just my opinion but I think all modern outboards have an alternator and not a magneto. If you have a starting motor you can be assured the engine has a ways of recharging the battery. The A/C electrons do flow in both directions (positive & negative) but the rectifier converts it to a modified DC voltage. The diodes I spoke of are in the rectifier.

Edited by - Sloop Smitten on 05/03/2012 08:19:47

szymek
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Response Posted - 05/04/2012 : 12:21:39

I decided to go straight to the source - Thohatsu - and I got my response within couple of hours! Talk about customer service!

My question:
1. Does the motor have magneto or alternator?
2. Is deep cycle battery enough to start the motor?
3. Can this motor charge 2 deep cycle batteries? if so what is the best way to connect them.

Response i got from Tohatsu:
"It has a magneto with charging coils under the flywheel and a rectifier mounted to the block.

A deep cycle should start that engine if it has 500 CCA's or more.

It will charge, but it works much better on a cranking battery. It charges up to 6 amps depending on rpm. If you charge both, you will need to connect in parallel. When this happens and one battery is low it will borrow from the other, so I do not recommend that unless a battery switch is used. Example: Battery #1 has 12.8 volts and battery #2 has 11 volts. If connected in parallel they will level at 11.9 each. (12.8 plus 11= 23.8 divided by 2 equal 11.9 each. If you use a battery switch you could wire it to allow charging of 1 battery at a time."

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av8rOC
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Response Posted - 05/05/2012 : 05:11:21

Fantastic information, thanks guys. From what you guys found out it looks like I do in fact have the switch wired properly.

Yesterday I wired a multi-tester into the switch and ran the outboard for a few hours getting both batteries up to charge. With the multi-tester installed it is very easy to tell the condition of your batteries and how the motor is charging them. When I got there resting voltage was 11.3 on one and 10.5 on another and with engine running you see close to 14 volts going back in. After running the motor for a few hours my resting voltage on both batteries is 12.5. FWIW I ran the batteries one at a time, not in the "1+2" position.

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