Boat Talk

[Mikey B]

Dual Battery Installation.

 

My Orkney 520 has only a single 85amp battery.

 

So before the new season starts I intend to fit a dual battery set up for safety.

 

Sterling Power Products make a split charge low loss blocking diode which isolates each battery and charges the batteries according to there charge state and eliminating human error.

 

The down side is a voltage drop of between 0.78volts and 0.93volts @ 30amps which varies according to demand.

 

Inboard motor set ups produces 75amp/hr or more.

 

The alternator on my Yamaha F30 only produces 15amp/hr.

 

Will the blocking Diode work with my set up?

 

Or should I just stick to the normal Dual battery and isolating switch set up and get into the routine of switching between batteries?

 

Any advice would be appreciated.

 

Mikey B

 

[Bob F]

Hi Mikey

 

I phoned Sterling when I was planning my dual battery set up a couple of years ago, and asked the same question.

 

For the "low" power requirements we have in our "small" fishing boats, their advice was that it was an expensive overkill in our situation, and to simply use the battery selection switch.

 

I leave my switch in the dual position all the time. Both batteries get charged when the motor is running.

 

BF

Edited February 23, 2007 by Bob F

[Bob F]

And here's our document for fitting a dual battery set up.

 

BF

[Adam F]

Bob - Where is your article you wrote?

 

I need to put two batteries in OotB - I have got my switch, but not too sure how to wire it?

 

BTW - If anyone wants a battery x-over switch let me know as I have a spare one due to a mix up when ordering.

[Adam F]

Oh!! There it is!

[Adam F]

Link doesnt work matey....

[alun j.]

Mine does Adam!

 

Alun.

[Maverick Martin]

works for me to but does take a little while to upload

[plaicemat]

I'll take the spare switch, Adam. PM en route.

 

Terry.

 

BTW here's Bobs article on a different site Bob's Bits

Edited February 23, 2007 by plaicemat

[Mikey B]

Thanks for the response Bob.

 

I finally got a reply to an email enquiry from Sterling Power Products.

 

They recommend a dual selector switch as you have recommended.

 

They quoted the reason being that a diode system can reduce the charge rate by as much as 70%.

 

Due to the low output of small outboard alternators it would take hours to fully charge a pair of 85amp batteries.

 

So a dual battery isolating switch it is.

 

The best price of

[Paul D]

Terry,

 

Bob's article on the other site ( as in Coddy's site ) has a slight error in it.

I think originally Bob connected the outboard leads to the Battery 1 connector and now has them connected to the common connector.

 

The article on coddy's site has a diagram with the lead from the outboard connected to the common terminal on the switch but has a note referring to the lead from the outboard being connected to the battery 1 connector.

 

Connection of the outboard to the common connector is the way to go IMHO ( I recall having a discussion on the pro's and cons with Bob a while ago ).

 

[plaicemat]

Thanks for that, Paul. I'll look for the correct one as I'm about to do the same job myself (switch courtesy of Adam).

 

Terry.

[Coddy]

Hi Paul

 

Thanks for the info, I also noticed in the Note the diagram that there is a wording problem.

Quote [No charge current from the alternator will get to battery 2 if the switch is moved to Battery 2 only. ]

This is incorrect because if you select Batt 2 the outboard starts from this battery so will charge this battery so long as the selector switch is on Batt 2 position.

 

I will amend the words acordingly.

 

Coddy

[Sinbad]

Here we go again...

Two thingies.... On my last boat when fitting the second battery, I opted for a standard car battery to reduce the space requirements, as I figured out that my leisure battery would be better for running my instrument / light load when night fishing, and what I really needed was a second chance to start the engine when/ if the leisure battery was flat or was rendered flat. On the run out I could at least charge both batteries up.

 

Also, I thought that Bobs circuit diagram left the Engine connected to the battery even when the switch was in the off position - reason to avoid potential switch failure preventing you starting the engine. I tend to agree this is the best approach as long as you physically disconnect the terminals for engine maintenance, rather than rely on the switch.

 

I'm also speaking to my tame electrician about doing a line in (pucker) solar panels, as he's currently doing this to Bournemouth and West hants company trucks at the moment to keep infrequently used vehicles available 24hours. If I get some details, I'll post in due course.

 

Paul

 

 

 

[Paul D]

Paul,

 

That was the logic behind Bob connecting the outboard to the battery 2 directly as opposed to the common terminal of the switch. ( plus being able to use the power tilt whilst switch is in the off positions ).

 

However, this means the outboard will always be connected to a battery. Could do with an isolator switch - but the 1 - 2 - both switch is really an isolator switch anyway.....

 

Also if Battery 2 ( or whatever one the outboard is connected to ) then it will mean that battery 1 also could become unusable ( as you can only select in effect 2 or both )

 

The only downside of connecting to the common is failure of the switch could cause a problem - unlikely in my opinion, although I understand it happened to Bob.

Get a good switch

 

 

 

[Bob F]

Coddy,

 

I can't find that error in the rev 4 document. Are you referring to the older document that you have on your web site?

 

BF

[Coddy]

Sorry Bob, I corrected a small number of typo errors and the one about connecting the leads from the outboard.

 

Coddy

[toerag]

If you have the black & red rotary switch be aware that the internals can undo themselves if you always rotate it the same direction. It happened to me.