Outboard and split charging.

[Deefor]

I'm re-posting this thread that I started in the PBO section in the hope I'll get a few more replies in the MoBo section. Yes, I'm still confused .

I've recently purchased a split charging diode (input + 2 out) for use with my 15hp Tohatsu outboard as I wish to install a leisure battery in addition to the starter battery.

Currently (with just one battery), the alternator charge lead output goes to the +ve on the starter battery via a simple key operated on/off switch to enable both starting of the engine and charging of the battery. I understand how to wire the new/additional leisure battery but not how to wire the starter battery via the split charger.

All the wiring diagrams I've found on the net pertain to inboard engines with an alternator and starter motor and I'm somewhat confused as to how it all works. The nearest thread I've found is http://www.ybw.com/forums/showthread.php?t=84456 but I'm still unable to understand everything when relating it to an outboard.

Any help would be appreciated .

Many thanks .

 

[PaulGooch]

You disconnect the charging cable from the alternator and insulate it well, then connect a new cable from the alternator the diode input. You then connect a cable to each output terminal of the diode that goes to the positive terminal of each battery.

Your current key operated switch will still work as it does, but has no function in the charging system now.

You should really fit isolator switches between each battery and the items it supplies. I assume you will have the 2nd battery running everything except the engine and the current engine battery will be purely for engine starting ? If you currently do not have a battery isolator switch, you could fit one of theses : http://www.force4.co.uk/9643/Blue-Sea-E-Series-Dual-Circuit-Plus--Battery-Switch.html

That will isolate both batteries and give the ability to start the engine from the leisure battery. You can find a wiring diagram here : www.boat-fishing.co.cc If you ignore the ign switch it should make sense to you. Inboard or outboard, makes no difference, it's still wired the same.

 

[Deefor]

You disconnect the charging cable from the alternator and insulate it well, then connect a new cable from the alternator the diode input.

Many thanks for the info Paul, really helpful - if I'm reading this right and having looked at your wiring diagram, do you mean disconnect the cable between the alternator and starter motor?

EDIT - as the OB only kicks out a theoretical 12A, do I still need to use "big" cables as indicated on your wiring diagram?

 

[PaulGooch]

Many thanks for the info Paul, really helpful - if I'm reading this right and having looked at your wiring diagram, do you mean disconnect the cable between the alternator and starter motor?

EDIT - as the OB only kicks out a theoretical 12A, do I still need to use "big" cables as indicated on your wiring diagram?

You disconnect and remove if possible, or insulate well, the cable between the alternator output cable and the starter motor. It's wired like this originally so the charging current goes back to the battery via the starter cable, saves a cable.

Cable sizing depends on individual setups. The difference in my wiring diagram is really only to differentiate between starter and charging cables. If you want to be able to start the engine from the aux battery, as in my diagram, you need starter sized cables from both batteries to the isolator switch. As for charging cables, these simply need to be big enough to carry your max charging current.

There is some sensibly priced, tinned thinwall cable here : http://www.autoelectricsupplies.co.uk/product/884/category/159

 

[VicS]

Many thanks for the info Paul, really helpful - if I'm reading this right and having looked at your wiring diagram, do you mean disconnect the cable between the alternator and starter motor?

EDIT - as the OB only kicks out a theoretical 12A, do I still need to use "big" cables as indicated on your wiring diagram?

See the suggestion I have added to your post on Reader to Reader about using a VSR

http://www.ybw.com/forums/showthread.php?t=306375

That eliminates all your queries and uncertainties about connecting the second battery.

It will also give better charging than a diode splitter as there will not be the voltage loss that you will suffer with a diode splitter.

 

[PaulGooch]

See the suggestion I have added to your post on Reader to Reader about using a VSR

http://www.ybw.com/forums/showthread.php?t=306375

That eliminates all your queries and uncertainties about connecting the second battery.

It will also give better charging than a diode splitter as there will not be the voltage loss that you will suffer with a diode splitter.

Notwithstanding the fact that all the while the engine is running both batteries will be in parallel. Which, to some degree, negates the benefit of having separate systems for engine and domestic banks.

 

[Deefor]

I'm just about to have a look inside the OB cover to see if I can easily get to the alternator and starter connections. From memory, the upper cowling doesn't split in two like my old Johnson . If access is good, I'll be going with the split diode which I have.

If access is an issue, plan B might be to consider a VSR but we'll see .

Many thanks Paul & Vic for your help .

 

[Deefor]

Paul - here's how the standard single battery install looks at the moment, +ve side only:

Cable from battery to twin post type terminal block (#'s 1 & 2 for reference). Cable from #1 is the one back to the battery and #2 is connected to the starter motor.

Also on #1 post is a red wire and this traces back to a finned regulator. The red wire is fused at the regulator end with a 20amp fuse.

I'm 100% certain this red wire is the charging wire as it's connected to the +ve cable which goes to the battery.

The biggest clue you gave me was that the existing +ve battery cable shares both the start and charge functions. I'm going to disconnect the red wire on post #1 so it's not connected to the starter and extend this wire back to the input on the split diode.

Does this make sense so far

EDIT - I'm thinking that this means I won't have to mess around with new cables for the starter circuit but as is existing?

 

[VicS]

I'm going to disconnect the red wire on post #1 so it's not connected to the starter and extend this wire back to the input on the split diode.

Yes that is the way to do it.
Exactly what I suggested in my first reply on R to R

You asked about what size of cable is required.
It obviously must be capable of carrying the maximum alternator output current, but need not be as heavy as the cable carrying the starter current (12 A) but it should heavier than the minimum required fof 12 A to prevent volts drop along the cable.
The actual size will depend upon the length.

The table HERE will enable you to determine a suitable size of cable.

THIS TABLE will convert AWG to cross-sectional area in mm².

Dont forget though that your diode splitter will drop 0.7 volt so you will not get the batteries as well cahrged as you did when cahrgeing directly or via a VSR.

An alternative to both a VSR and a diode splitter is Driftgate's X split device.
That should overcome any concerns about charging two batteries in parallel using a VSR at the same time as eliminating the volts drop of a diode splitter

 

[Deefor]

Thanks Vic for your info and input. The split diode I bought was this one with 0.2V drop (allegedly ) http://www.asap-supplies.com/marine...ic-spilt-charge-battery-isolator-50amp-741002 or from the manufacturer's site http://www.sic-divisione-elettronica.it/sic_eng/scheda_prod.php?Cat=3&Cod=126.

The more this thread has gone on, the more I can appreciate and understand what you first told me on the PBO R to R - it all makes sense now .

Cabling - now that I can leave the existing starter circuit and wiring as it is, I can concentrate on the charge wiring side. I've rumaged through my garage and found some of this 2.5mm 50A cable which I bought a while ago and never used http://www.ebay.co.uk/itm/180825343270?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649. I'm also thinking of running a new cable from the domestic battery to my basic fuse board in the same stuff - the most we ever need is around 50w for a coolbox and a couple of lights at night.

Thanks once again for your help, really appreciated.

EDIT - the Driftgate set up looks very good but my budget is very tight at the moment or at least that's what my tells me lol.

 

[rosssavage]

What about....If you connected the alt o/p to the switched side of the starter solenoid, all the time the solenoid was engaged (engine start..) the alt would also be connected directly to the engine battery, bypassing the diodes. Once the starter is disengaged, the alt o/p would again be isolated from the starter battery via the diodes.

No extra relay, wiring change is simply moving the alternator o/p from one side of the starter solenoid to the other. You'd still need the extra charging wire, but no extra relays...

If the Tohatsu is anything like my Mariner 20 (and I think it's the same engine) then the starter solenoid is seperate from the starter motor and not an all-in-one unit like big starter motors...

Anything blatantly wrong or stupid with that?

 

[VicS]

What about....If you connected the alt o/p to the switched side of the starter solenoid, all the time the solenoid was engaged (engine start..) the alt would also be connected directly to the engine battery, bypassing the diodes. Once the starter is disengaged, the alt o/p would again be isolated from the starter battery via the diodes.

No extra relay, wiring change is simply moving the alternator o/p from one side of the starter solenoid to the other. You'd still need the extra charging wire, but no extra relays...

If the Tohatsu is anything like my Mariner 20 (and I think it's the same engine) then the starter solenoid is seperate from the starter motor and not an all-in-one unit like big starter motors...

Anything blatantly wrong or stupid with that?

I dont understand what you are suggesting or what the reason might be.

If you move the alt o/p to the switched terminal of the solenoid it would be permanently connected to the starter motor!

No relays are required if a diode splitter, or the device the OP has bought, is used.

 

[rosssavage]

No, you wouldn't - thats cos I'm trying to dispatch aeroplanes and have a seperate email conversation with Deefor and post on here all at the same time, and hence I've got a bit confused and posted rubbish!!!

This was a reply to a question about alternator excitation, and the possible requirement to provide an excitation feed to the alternator during starting on his outboard. Someone else suggested a relay controlled by the starter switch to supply the excitation feed during starting, and I was trying to work out how to do it without an extra relay.

That said, your point about directly connecting the alternator and starter remains valid, and thats why I posted a stupidness check on here for people to comment on. I was too focussed on the starting mode and hadn't got as far as thinking about running mode.

Perhaps I should just concentrate on one thing at a time in the future....

 

[VicS]

This was a reply to a question about alternator excitation, and the possible requirement to provide an excitation feed to the alternator during starting on his outboard. Someone else suggested a relay controlled by the starter switch to supply the excitation feed during starting, and I was trying to work out how to do it without an extra relay.

The "alternator" is the usual outboard style stator coil under the flywheel. Not the type of belt driven alternator that you find on inboard engines and I beleive some large outboards. ( I dont know but I suspect they are a self exciting type anyway)

No excitation is therefore required.

On the original thread on the R 2 R forum I have posted a couple of links to the parts of the ignition system and the electrical system that show the stator coil (although it is called "alternator") and the and the rectifier/regulator q.v.

 

[Deefor]

Hi Vic, have read my other thread and taken it all in, many thanks .