Hi Kevin,

Is it ok to have to different size batteries in my boat?

I’m putting in a size 34 and a size 31 separated by a 1/Both/2/Off battery switch.

The batteries are Optimax blue tops. The Group 31 has 1125 cranking amps and the Group 34 has 870.

Kenny

Hi Kenny,

It is OK to connect different size batteries on the same battery switch.

Keep in mind that if you put the battery switch in the Both position, you will basically have 1 large battery with 1,995 CCA.

Separate your loads and use circuit protection as close as possible to the battery.

Kevin

Hi Kevin,

I’m an airplane guy who’s redoing the boat wiring on my brother-in-law’s 1972 22’ Reinell.

I have a couple of questions.

We ordered a boat horn and a Smart Battery Switch from EzAcDc yesterday. However, we only ordered the VSR thinking it was all we need but after looking closer I’m not sure.

The boat has two batteries and a manual 1/both/2 switch. Should I change our order to the complete Smart Battery Switch System?

This boat has an original one-wire Delco alternator. I want the following but I’m not sure how to achieve it:

• The ability to disconnect the alternator from the battery when the alternator fails (if this is not important than I’ll forget about it)
• The ability to turn on a warning light when the alternator fails (we removed the original ammeter but the 3 in 1 gauge we installed does have a volt meter)

Do you have any suggestions i.e relays or any other components I can use to achieve the above results? I wouldn’t mind upgrading to a more modern alternator if that solves the problem.

Any direction you can give would be greatly appreciated.

Kevin

Hi Kevin,

A VSR works best when you have a dedicated engine battery and a dedicated house battery. The VSR makes the connection between the two systems.

A conventional battery selector (Off, 1, 2, Both) controls which battery the engine is connected to but does not control which battery the house is connected to.

The key to our partner’s complete Smart Battery Switch System is the dual pole On/Off battery switch. This acts like two on/off battery switches combined into one body.

• When the switch is Off, only emergency devices are connected to the house battery.
• When the switch is On, the engine is connected to the engine battery and the house is connected to the house battery.
• When the engine is running, the alternator first charges the engine battery. When the engine battery hits 13.7 volts, the VSR connects the engine battery and house battery together and begins charging the house battery.
• When the engine is off, the VSR keeps the batteries connected until the battery voltage hits 12.6 volts. When it drops below 12.6 volts, the VSR breaks the connection and allows for enough reserve in the engine battery to start again.

I would not worry too much about a way of disconnecting the alternator if it fails.

In the event of an alternator failure, your system voltage would begin to drop. With the complete VSR system, once 12.6 volts is reached, the VSR will open the connection between the engine and house batteries. Your engine will continue to run until the battery voltage is below 10 volts. When the engine dies due to low voltage, you can turn the battery switch to the COMBINE position. This will manually parallel the batteries and allow you to start your engine and continue running until your battery voltage is to low to run the ignition system.

You will probably run out of gas before you completely drain two batteries running only a simple ignition system on a single stern drive.

Thanks

Kevin

Hi,

I was given your email address by a friend who highly reccomended you.

I’m just about to rewire my boat as it’s winter. There are a few things that I would like to know before I start.

What would you suggest as to the thickness of cable from the battery to the 6 gang switch panel? I’m only running the normal things:

• Fishfinder
• VHF radio
• CD player
• Bilge pump
• Lights
• Horn.

I am also wondering if I should put an inline fuse in the live cable between the battery and switch panel and what size fuse?

Any other advice you could give me on boat wiring would be much appreciated.

Many thanks for your help

Paul

Hi Paul,

I am posting a handy spreadsheet that will help you calculate all of your boat wiring sizes.

Once you fill in the blue boxes for total wire length, the sheet will calculate the correct wire size needed for each wire run and for your main panel feed.

You will want to put a fuse or circuit breaker as close as possible to the battery. The size of this will be dictated by the total draw of your panel (Cell C20)

Emergency devices (nav lights, horn, VHF radio, bilge pumps, and blower) are typically wired for 3% voltage drop.

All other devices are usually 10%. Some stereos cannot tolerate 10% and you will need to run them at 3%.

Please let me know if you have any questions,

Kevin

Kevin,

Ok, I have a good one for you.

I am working on a 1984 Trojan 10 Meter with twin 454.

The problem that I am having is when starting the starboard engine the port engine cranks over as well. Of course, that engine will not start because the ignition is in the off position.

One more thing. When starting the port engine the starboard engine does not crank!

What do you think?

Hi,

The boat wiring on a 1984 454 is very simple.

The yellow/red wire goes from the key switch S position, to a neutral safety switch, and to the starter.

I would try eliminating components in the system one at a time to find the problem.

The crossed wire is probably at the neutral safety or ignition switches. Sometimes starter wires get mangled in the shifter controls or there is some form of ignition combining circuit (used to power fuel gauge, depth finder, etc) that has a crossed or shorted wire.

Hope this helps,

Kevin

Kevin,

With no generator or selector switch, my boat’s galvanic isolator is currently located between the shore power ground connection and the 110V ground bus. The 110V ground bus ties into the 12V negative bus and the boat ground (a steel pontoon).

I have recently restored my onboard generator and have installed a source selector switch (shore power or generator). I’ve read everything I can and I still can not identify to my satisfaction how to connect a galvanic isolator into an electrical system with shore power, an onboard generator, and a source selector switch.

The confusion (on my part) is that the battery selector switch being used has a separate connection for the ground wire from each source on what appears to be a solid bus bar connecting them. This suggests that both the shore power ground and the generator ground are connected and wired to the isolator inlet and the isolator outlet is wired to the 110V ground bus, the 12V negative bus, and the boat ground (steel pontoon).

Is this correct? Maybe the separate ground connections to the battery switch exist only to support the reverse polarity LED light, but it is still confusing.

Your guidance is requested.

Dave Freeman
Richland, WA

Dave,

The main reason for a galvanic isolator is to prevent stray current corrosion through your boat’s shore power connection. It basically induces enough of a voltage drop to prevent a galvanic cell from being created between your metal underwater gear that is electrically connected through your shore power ground wire to other metal gear in the same body of water – usually the dock.

To be effective, the galvanic isolator must break the shore power ground wire – the green wire between your inlet and your AC panel. All of the AC grounds on your boat wiring system should be connected together – Generator and existing AC systems.

You should have a single wire that connects the DC ground to your AC ground.

Hope this helps,

Kevin

Hello,

I would like to add a smart battery switch system with VSR, but am not sure how to do it.

On my 2008 Yamaha F150TXR, there is a second battery plug under the engine cover. This is illustrated in the owner’s manual along with a wiring diagram for adding a second battery with optional part available from Yamaha.

I contacted Yamaha customer service and was told that the part’s suggested retail is around $70. I asked what it consisted of and the agent pulled the part and informed me that it is a piece of 10 AWG wire with a bare end and terminal to connect to the mating plug under the engine cover and a battery connector on the other end.

They further informed me the Yamaha’s regulator/rectifier actually splits the ac from the stator to achieve isolation. In effect, I have two charging systems with a common stator/rotor assy. Both batteries will charge when running and will be isolated from each other when the engine is turned off! It sounds like a wonderful innovation and a real no hassle rig to me.

Can you tell me if I even need a VSR? If so, how would I go about adding the smart battery switch kit from EzAcDc?

Kind regards,

Bryan

Bryan,

If I had a F150TXR, I would take full advantage of the dual output alternator. Most engines do not have this and then a VSR is the best alternative.

I would make sure you have circuit protection at the battery end of your 10 AWG wire.

Great question,

Kevin

Hi Kevin,

I am rebuilding a 26 Zeta – installing a single 8.1 liter Volvo gas engine.

I want to put in two house batteries that I can switch for usage and one starting battery solely for starting – three batteries in total.

I want to install a charger for the house batteries, but would also like to have the option of charging the house batteries when travelling.

I have some ideas but saw your site and thought I would get your opinion.

Thanks

Andy

Andy,

The simplest solution for you would be to install the EzAcDc Automatic Smart Battery Switches. The only modification you would need to make would be to add an additional pair of battery cables to connect your second house battery.

This system will charge your house batteries when travelling but not allow you to drain your engine battery with overuse of your house systems.

Hope this helps,

Kevin

Kevin,

That sounds very simple. I like the idea.

I just have to make sure that the voltage charging the batteries is OK for golf cart batteries. Just to confirm, though, with your system, am I able to switch usage of my house batteries in case one runs too low or just for even use?

Thanks again.

Your site is great! Lots of info.

Andy

Andy,

The battery switch system includes a single ON/OFF battery switch, which turns two batteries on/off at the same time. Your two house batteries would be wired in parallel with no battery switch between. The pair of batteries would run down together and always get even use.

You could add an additional battery switch for your house battery system to try to even out the usage. This usually causes confusion by the operator and the switch is always put in the BOTH position. This defeats the purpose and need for the battery selector.

Hope this helps,

Kevin

Hi Kevin,

My name is Thomas.

I just picked up a set of Lenco trim tabs and the directions say to connect the retractor wire (orange) to the engine tach signal. On my boat that’s the negative side of the ignition coil.

Is this what they mean? Or does it go somewhere else?

Thanks in advance.
Thomas

Hi Thomas,

If you want to use the retractor function of your Lenco tabs, you will need to connect the orange wire to the negative side of your coil.

I believe that the retractor function of the Lenco tabs will work by simple connecting the orange wire to your switched ignition wire, but this might explain why Lenco doesn’t seem to publish this anymore.

Great question,

Kevin

Kevin,

Thank you for all your help. I found that info.

By the by, following the suggestion on your web site, I got a boat wiring harness and a marine electrical panel from EzAcDc. It all works perfectly!

The EzAcDc boat wiring was easy to install and modify to my particular needs. I set it up independant of the ignition so the panel is live so long as at least one of the batteries is switched on.

However I am thinking that I want another automatic bilge pump, my third, unfused & wired direct – bypassing the main switch so it will pump any time and unattended while I’m ashore goofing off.

Any thoughts on that?

Thanks again for this awesome resorce!

Thomas

Thomas,

You will want to have circuit protection for your third pump. All new bilge pumps have their fuse size stamped on them.

To wire this new pump correctly, install your fuse/breaker as close as possible to the battery. You will have two wires leaving your fuse. One goes directly to your auto float switch and the other to your manual bilge pump switch. The wires leaving your float switch and your manual switch are connected together (usually near the bilge pump) to provide two different ways to turn on the pump. Attach your bilge pump ground to your battery negative or a ground buss.

Happy boating,

Kevin

Hi again,

Sadly your trim tab link didn’t work. Pitty, as I like to know all I can about any given thing.

So conecting to the tach wont disrupt the tach reading? Is one way better than the other?

Thanks,

Thomas

Sorry about that.

Do a Google search for “Lenco Bennet Lawsuit” and check out the articles on the Boating Industry site.

As for the trim tab installation, connecting the retractor wire to the coil will not disrupt the tach reading.

Have a great day,

Kevin

Kevin,

Recently I was helping a friend with a problem adding a microwave installation to his boat wiring.

He has been having problems with the controls of the microwave/convection oven failing. I am an industrial electrical contractor but not totally up on requirements for a marine electrical installation.

In checking for problems on his boat I discovered that when the shore power is disconnected, that there was not a full 120 volts from the hot side of the receptacle to the ground conductor. There was only about 60 volts to ground and also about 60 volts from the neutral side of the receptacle to ground.

We tried the same test on two other boats and found that with the shore power disconnected there was a full 120 volts to ground and no potential from the neutral to the ground–so evidently there is a bonding jumper from neutral to ground.

Is this correct?

Mike

Mike,

The only place the neutral should be connected to ground is at the source of power. In the case of a marina, this location is at the distribution panel that feeds the receptacles on the dock.

If your friend’s boat wiring includes a generator, the neutral will be tied to the ground. The generator hot and neutral are switched with a dual pole switch or breaker on the boat distribution panel. When the shore power connection is selected, the generator breaker should be off and break the boat connection between neutral and hot.

If the dock receptacle has 120 volt between the hot and neutral and 60 volts to ground from either hot or neutral, I would trace the path of the ground wire from the dock receptacle to the marina distribution panel.

Hope this helps,

Kevin