Electronic design for my tinny

[Silent]

Gidday,

Most of you have seen my new boat I posted in the boating section few days ago...
I have my homework on electronic design and got some advice and suggestions from mates.
On this thread I'm present the diagram below and the feedbacks are always welcome!



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Waterprrof case mounted 5 way switch panel with 12V socket;
- Sounder & GPS
- Nav LED Lights
- Anchor LED Light (pull out)
- Bilge Pump (500gpm)
- Floor LED Light (5m strip under rail)

Outboard 30hp CV Yamaha manual start
Alternator Output 12V - 6A with rectifier

What size & type battery should I get?

any else I miss?

Thanks for read or help...

[marty666]

You should not have the anchor light on the switch pane powered up by the same circuit that can be turned off by the isolator switch, i say this because you could simply run another power feed wire to s2 straight to the switch and then that way you can keep the light on and use the isolator switch to kill every thing else at night to save your battery too.

[finga]

Motor +ve to the battery not the load side of the isolator.

You should not have the anchor light on the switch pane powered up by the same circuit that can be turned off by the isolator switch, i say this because you could simply run another power feed wire to s2 straight to the switch and then that way you can keep the light on and use the isolator switch to kill every thing else at night to save your battery too.

Personally I would not worry about that extra feed to the all round.
If you want to isolate the rest of the installation to save the battery just turn the corresponding switches off.
I normally use a double throw switch to combine the navigational lights and the at anchor lights. ie a on/off/on switch where one on is for the navigational lights needed for motoring along (red, green and all-round white) . The middle position is all lights off the the other on is for the all-round white light. But I only do that because I'm a forgetful bugger and either leave something on/off that I should have off/on.

[Fed]

You should put a main fuse just after your main switch in the cable that goes to your switch panel.

Switches switching switches, fuses protecting fuses protecting fuses, it's a madness in small boats.

I have 1 main fuse at the battery(25Amp), plus 3 small inline fuses that came with the equipment (radio, sounder & GPS) and 2 switches on the dash for lights & pump.

If you don't break gauge you don't need extra fuses and you don't need to switch something that already has a switch.

A different story for bigger boats with a ton of electrical stuff on them.

[Silent]

Thanks guys,

I consider to remove main isolator and replace a main fuse like FED said...

My previous boat doesn't have the main isolator and had no problem, guess its for a large boat to meet requirement. maybe I'm wrong?

One more question before I start shopping for electronic,
What size & type battery should I get?

[marty666]

the biggest that will fit you can never have too much when it comes to batteries so measure up the size that it will sit in and get the biggest that will fit and also that will fit with your wallet too.

[Fed]

Your main isolator is optional Silent but the fuse I mentioned should protect the + cable that runs to your switchbox.

Don't put the fuse in the cable going to your motor.

[oldboot]

Putting in the biggest battery that will fit is incorrect.

The charging systems is boats are designed arround a particular size battery, there is tolerance a bit eather way, but too small and you will over charge too large and it will fail to charge at all.

a member here a while ago proved this by trying to use his 120AH lecky battery from his big boat with the small charging system in his small boat......the charging system would not produce enough voltage to charge the battery due to the load presented by the battery.

In the service manual or mybe the owners manual there will be a recomended battery size, 1 battery size up or down should be no grief.

your main fuse should be a close to the battery terminals as possible.....as far as changing guage.

in this day and age of LED lights a change in wire guage is unavoidable.....you will want to fuse LED navlights at 5 amps, but you will need a 15 amp fuse for you cig lighter ( that is waht the fitting will be rated at......the electronics will have their own fuses which should be used.

so a 25 amp main fuse would be reasonabl if a 6mm automotive/marine cable is used for the main feed.

you could use 1 fuse for all your lights 5 or 10 amp if they are all LED....and a 15 amp for you cig lighter.

as for the main isolator...you only need to use that when the boat is stored..so undoing the wing nuts wil do the job...... but fit an isolator if you like.

cheers

[oldboot]

OH... some of the fues holders that come with those switch pannels are horrible......I tossed all that came with mine...the plastic was sooo hard getting the lids off without pliers was impossible.

Buy fresh ones from jaycar or automotive suppliers if this is the case.

cheers

[thylacene]

It is good practice to put a fusible link between the positive terminal on the battery and everything else. This provides protection against dead short (if insulation is rubbed through or similar) allowing the link to melt before the wire heats up enough to catch fire.

Isolation switches are used for two purposes, one is to avoid flat batteries due to current drain (not turning something off), the other is to avoid galvanic corrosion (go Google it, there's heaps of info), definitely worthwhile.

Make sure that you use marine wire (it is "tinned") if you are going within 5 miles of salt water, its murder on plain copper.

Invest in a set of quality crimps (with locking ratchet) if you do not already have a set, and use the correct crimps for the size of wire you are using, and use purpose built wire strippers. This avoids dodgy connections resulting from vibration and getting slapped around. Do the job right the first time around and you can be confident that it will last the distance.

Use the right sized wire, DC voltage drop is significant over relatively short distances, so if your box is up front and the battery is in the rear, consider using 4 or 5mm cable for both the positive feed and the negative return.

If you are running wires through metal, spend the couple of dollars to acquire grommets, and if you can, judicious use of silicone to waterproof your box is also beneficial.

Take care when buying sockets etc to ensure that you get non-corrosive terminals, I had a Jaycar ciggie socket sitting in the shed that I fitted to our previous boat, it lasted four weeks after being doused by a wave over the front, even with a spray of Inox.

You get what you pay for, don't scrimp or use inferior materials, the marine environment is harsh on wiring.

Cheers

Thy

[marty666]

Putting in the biggest battery that will fit is incorrect.

The charging systems is boats are designed arround a particular size battery, there is tolerance a bit eather way, but too small and you will over charge too large and it will fail to charge at all.

While your are correct in what you are saying about how the charging system is designed if your battery is fully charged then it will stay that way the only time if will not maintain a full charge is when the battery has been drained heavily and the motor has not had sufficient time to return the battery to its float level of charge. Having said this i believe it is poor form to not charge batteries at home before leaving and making sure battery charge is full when you get home to prevent calcification of the cells that happen when the battery float voltage is below 12.4 volts, that is why a recommended larger battery is out there because any 12 volt charging system will maintain a full charge unless you leave every thing on for great lengths and not get the charge back in. but then any size battery will suffer if you do that.

[oldboot]

Sorry that is not my understanding and is not borne out by the facts I have to hand.

As I have said many times outboard charging systems are pissy.

Appart from that they are poorly regulated and high impedance sources.

Unless the machine in question is very large and has a seperately mounted alternator ( similar to a car) the charging systems are magneto bassed.

If there is no load on the magneto coil it will generate hundreds of volts. With out a battery connected the rectifier or regulator will die due to the very high voltages generated.

the very small systems that have only a rectifier and no regulator depend on the correct size battery in combination with the internal impedance of the magneto coil to achieve very approximate reasonable charging voltage......this voltage being arround 15 volts with a battery at full charge.

The impedance provided by the battery is its charging losses or its charging waste at full charge.

The battery also has to be big enough in relation to the charging systen to withstand the overcharge that would occur from being charged at 15 volts.
Even the regulated systems charge at arround 14.5 to 15 volts...which if it was a car would be considered faulty

If a battery too small is fitted, it will present too little load by way of its charging losses/waste and the terminal voltage will rise...16/17/18/19 volts...also the battery will have insufficient size and mass to disipate and withstand the overcharge.

Some time ago a member posted with exactly this problem

This is why boat batteries are very much larger than car batteries in relation to motor size and charging system capacity.

Remember many of the smaller motors have no regulator only a rectifier.

An example of the above would be trying to use a 7 to 10 AH sealed battery or motorcycle battery with an 8 amp unregulated charging system, especially if the motor did other than short runs at low RPM

toward the other end of the scale, if a very large battery is fitted to a low output charging system, the charging system may never reach a charging voltage due to the losses/ wastage presented by the battery

Remember too, being a magneto system, underload ( a battery requiring charge or accessory load) the charging system may not reach its rated output till quite high in the rev range, 3500 - 4000 RPM is common.

A 130 AH battery connected to a 4 amp charging circuit for example..at full charge even a healthy 130Ah battery can present 4-5 amps (poor way of specifying but it will do) of charging losses at full charge...... this combination may never come to a situation where the battery recieves charge from the magneto.

Again a while ago a member posted with exatly this problem.

This is why manufacturers specify a particular battery size for a charging system...it is not bassed on the cranking requirement, because outboards particularly 2 strokes crank very very easily, but because the battery is sized for best results with the charging system

You can swing a little either way, but the further you go from recomended the less efficient the already poor and inefficient charging system will be.

AND
all this is before we consider the charging systems best effort at charging the correct battery in the short run time many of us do.

with my 60Hp evenrude having a 12 amp charging system and 2 arround 85AH batteries, the the half hour out and half hour back to green island, it would not have an oportunity to do meaning full charging.

Even more so smaller boats
This definitely hilights the importance of charing your batteries at home.

I do ask myself if there is any point at all having a charging system on a small boat that does short runs like many creek anglers do.
A big battery and a good charger at home would work just as well.


cheers

[Silent]

Thanks guys and interesting information your input,

I just decide to going with deep cycle marine battery same as previous boat
I have research on internet and select Marine Pro 400 57M



This battery below would be too big for my boat

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Any comments?

[marty666]

old boot mate dont you remember the daisy chain at school where everyone holds hands and one end the person holds a magneto and the other end earth out the chain and every one gets zapped. In the magneto or alternator there is always a regulator, it is not dictated by battery size other wise it would not matter what size battery you had you would over surface charge the battery due to the prevention of saturation from excessive voltage. It would also mean there is no way to control voltage as it would uncontrollably go through the roof at hi rpm or the opposite and have nothing at idle you can charge very large batteries with a low voltage it just takes longer. it is in fact better to use less voltage to charge a battery slower to properly saturate the cells and to prevent a static surface charge on the cell plates. I do this all the time in recovering batteries with a 1amp solar panel and a charge regulator. i have expensive test equipment for batteries and it has not failed once charging large rated batteries. It is a time issue that has to be remembered as 1 amp at 13.8 volts is not much so to make 400 cca you need 400 hours it is that simple.

[oldboot]

marty mate you need to go and get any mercury or johnson/evenrude service manual.

The magneto stunt at school has absolutley nothing to do with this issue..BTW as an apprentice we rang a bell thru 6 blokes, I was the one doing the cranking I'm not silly.

All the smaller outboard motors DO NOT have a regulator, they have a rectifier only..... 2 big diodes ( well not all that big) in half wave bridge... nothing more.
This is understood by all who have anything serious to do with outboards and this is borne out by the descriptions and test procedures in the manuals

The regulation such that it is, in these motors is achieved by the internal resistance counterposed against the load precented by the battery....the "regulation" is very poor, the magneto voltage varying greatly with RPM even with a fully charged battery....... at low rpm the rectifers will be reverese biased and no current flows.
As RPM and magneto voltage increases, charge or waste current into the battery also increases, thus loading down the magneto due to its internal impedance.

Thus selection of battery size is important.

In larger motors where there is some form of regulator, there is still a magneto coil impedance counterposed against the load of the battery

forget all this surface charge, absorbtion charge stuff, it is irrelivent in this situation.
Even at saturation, a battery presents a load to the charging circuit and this load is energy wasted as heat and producing excessive gassing.

you will not charge a battery if the terminal voltage of the charging circuit is not greater than the battery terminal voltage by a decent margin.

put very large battery on a very small charging system..like a 120 AH battery on a 4 amp magneto rectifier charging circuit the system may never apply any charge even at high rpm, the magneto voltage may not even reach 12 volts, at the output of the rectifier

If a magneto charging system has no battery connected there IS nothing to stop the terminal voltage of the magneto coil rising and it will reach hundreds of volts.
An this is a very common cause of blown rectifiers and regulator packs in outboards.......so common my local merc dealer knows the numbers and prices by heart.

As far as charging time......we do not have for ever to charge a battery in a boat particularly a small one, because the run time is short....so low voltage charging is pointless.

sorry but your last sentence the maths and the terms do not add up.
cold cranking amps has no direct relationship to battery capacity or charge times and 400 CCA is quite a small battery probaly arround 35 to 40 AH, about the size you would find in a 2 door 4 cylinder car.

If you think you can charge a 400 AH battery ( that is a big battery) with a 1 amp charger you are dreaming....the charging losses of such a large battery would be many times that......even if you could charge a battery over 400 hours.....that is 16 days. that would be pretty impractical.

It is important to take note of manufacturer recomended battery sizes for outboards and not go too far from that if you expect your charging system to work efficiently and not to go a long way from that if you expect your charging system to work at all on the unregulated smaller systems that have only a rectifier.

generaly charging systems under 10 amps will be rectifier only and above will be regulated..there may be some smaller regulated systems, but mostly not..

For those who are interested, I'll dig out some manuals and detail what recomended battety sizes I have information for.



cheers