'BOAT' needs your help and advice

[kadet]

I was looking at a 2 battery relay that stops the second battery draining the starter battery, but it says one wire goes to ground, not negative, ground.

How do we ground out a fiberglass boat???

Have a negative terminal bus that all negative battery terminals and devices use in common. If it truly needs an earth like in a SSB radio you would have to put a brass grounding plate on the base of the hull and drill a hole for the grounding wire.

I suspect they are using ground in this case to mean the common negative used in motor vehicles by connecting the battery negative to the vehicle chassis.

[BOAT]

I was looking at a 2 battery relay that stops the second battery draining the starter battery, but it says one wire goes to ground, not negative, ground.

How do we ground out a fiberglass boat???

Have a negative terminal bus that all negative battery terminals and devices use in common. If it truly needs an earth like in a SSB radio you would have to put a brass grounding plate on the base of the hull and drill a hole for the grounding wire.

I suspect they are using ground in this case to mean the common negative used in motor vehicles by connecting the battery negative to the vehicle chassis.

You guys are getting behind my posts! I just explained how we do it in motor homes and then you ask about it.

So those relays are standard equipment on motorhomes - NOT perko switches - because the relay is controlled by the voltage of the engine battery - when the engine battery reaches a voltage the relay just closes a circuit that connects a small wire to the OTHER battery - it's only a TRICKLE charge - NOT A HARD SWAP! The engine battery is ALWAYS CONNECTED TO THE ALTERNATOR WITH BIG WIRES! It is always getting a full charge from the engine alternator, but if the engine battery is at full voltage the relay will connect the other battery via a SMALL WIRE (like 10 gauge) as a trickle to the other battery. So when the relay is closed BOTH batteries are connected - there is NEVER a SWAP from one battery to the other - so the relay does not cause spikes or drops or surges.

WHY I NEVER see one on a boat is BEYOND me, but who am I to question the Marine Electric gods. I do as I'm told.

[kadet]

BOAT my solution is to use an MPPT solar controller with a DC to DC charger.

Basically it detects when the start battery is charged then redirects the charge from the start battery to the house battery. Or you can use a cheap realy like Mike was talking about.

Relay




IDC25 what I am going to use after the re-wire

[BOAT]

No no no on no - . - guys, Your off planet earth now - that's not what I'm talking about at all - I am talking ANCIENT TECHNOLOGY here - PRE-SOLAR (Heck I think this technology is PRE-COLOMBIAN)

The battery relays they have been using in motorhomes since THE 1950's !!!! is a simple ten dollar solenoid isolator - all it does is remove the coach battery from the system until the engine battery is fully charged!



These things have been around since like 1945!! The ones we use TODAY are the SAME! No change! Hey, it's me, remember! All my "tech" is from the 70's! (Why do you think I use so much wood in my projects?)

These are very cheap and VERY RELIABLE things that all motor homes have.


Here, I'm not 'plaining things well (yet again) so here is what they call it - this is from an old TRAILER LIFE magazine:

The simplest battery isolator is nothing more than an electromechanical relay. Somewhat comparable to a vehicle starter relay, the solenoid is a big electrically operated switch. When your vehicle is running, current throws the switch closed to allow current to flow from your vehicle charge system back to your RV. Turn the ignition system off, the relay switch opens, preventing current to flow from either the chassis to the RV, or vice versa.

The solenoid isolator is relatively inexpensive—it’ll set you back less than $20. You simply need to find a source of power from a circuit that’s only hot when the ignition system is “on,” and run it to the relay. Another wire connects the relay to the positive post of the SLI battery, and another runs back to the RV.

The solenoid doesn’t use any power in itself, other than a tiny amount when the ignition system is switched on. These isolators are relatively trouble free, but like any mechanical device are subject to occasional failure.

[kadet]

You guys are getting behind my posts! I just explained how we do it in motor homes and then you ask about it.

Not really BOAT

Here in OZ we always use dual battery relays in dual battery setups well mostly. Boats have those big manual switches to isolate the batteries or connect both or one or the other because boats are left idle for so long and it is to prevent parasitic charges flattening the battery or in an emergency to start. They should never be used while the motor is running as you have said as all sorts of bad juju can happen when you make the electrickery pixies angry

[kadet]

They look like this now in the 21st century

[BOAT]

Ugh, I can't get thru. Okay - well let's just get back to the project at hand - and if you guys DO come up with a way to run a third battery just for the motor let me know. (By that I mean that it will still charge the "cabin" batteries when you under power).

Now I'm getting behind - does this picture help? Make sense?

[kadet]

Ugh, I can't get thru. Okay - well let's just get back to the project at hand - and if you guys DO come up with a way to run a third battery just for the motor let me know. (By that I mean that it will still charge the "cabin" batteries when you under power).

Now I'm getting behind - does this picture help? Make sense?

Simplest way is with that relay it senses when the start battery is fully charged and then redirects the surplus charge to the house just like your old motor home relay.

Here is one from amazon

https://www.amazon.com/dp/B00WTAFR84?psc=1

[BOAT]

EIGHTY FOUR DOLLARS???? (what is that in Australian money? Like 1000 bucks??)


NO No no guys - the motor home solenoid is like 10 or 15 bucks at PEP BOYS!!

[kadet]

EIGHTY FOUR DOLLARS???? (what is that in Australian money? Like 1000 bucks??)


NO No no guys - the motor home solenoid is like 10 or 15 bucks at PEP BOYS!!

Yes but your old tech does not just trickle charge as you said, it connects both batteries in parallel while the ignition is on and charges both at the same time, this is not good for the batteries that are possible different chemistries and at different SOCs. Those new smart ones detect when the start battery is full then redirects the alternator flow to the house battery so they both get a good top up independently .

The old tech works at the expense of the longevity of your batteries. This was probably not as a big deal in a motorhome as you drove for hours at a time to give the batteries a chance to equalise and fully charge. But with a sail boat where the engine is used rarely you risk continually under charging which for a deep cycle battery leads to sulfication which will reduce it's life. Under charging is as bad as overcharging. Which is why I also have solar and put the boat on a 4 stage smart charger when on the trailer or an ac generator when away on the hook.

[Tomfoolery]

So I go with the flow - you guys say to use PERKO switch's so that's what I do. (You guys DO know that if you use that switch when the motor is running it will pretty much fry every electronic component on your boat including the diodes on the alternator, right?) You guys already know that, right?

Not if they're 'make before break', which they should be. But I never switch mine anyway - I just alternate batteries for each outing (before staring the engine, as I have to engage one of them to lower the OB into the water), and use a 2-channel mains charger to keep them both up. If the older battery starts sounding weak, I'll know before it's too late to do anything about it, as the other will be the newer one.

I'm putting it on a mooring for a week this summer, so no shore power charging, but it should be ok. I hope.

[BOAT]

I can reply to both posts above with the concept that electronics like today were not invented when we first started building motorhomes and that the old technology has not harmed any batteries or had any problems - I had a setup that was over 20 years old that never failed and I always got more than 8 years on a battery, I had some go for TEN years so that made me apply the proper use of the perko switch the first time I encountered one. I say "the proper use" only because I fall back on my motorhome experience more when it comes to electricity than i do sailing because my days as a sailor were mostly BEFORE the age of electricity

Based on the incredible success motorhomes have had for over 60 years with dual batteries here is what I do with the perko to try to imitate the motorhome:

Motor in the water: perko set to ALL BATTERIES
Motor out of the water: perko set to ONE or TWO or OFF
Boat in the driveway: perko set to ONE
Boat on a charger: perko set to NONE

That's pretty much the same thing the motorhome solenoid does automatically , WHY you need to do it manually on a boat is beyond me (Seems a LOT easier on the motorhome) but that's the way they do it on boats I guess - they use a manual switch instead of the tried and true technology of the 40's and 50's that has been working in motorhomes since forever. I just try to imitate what a good motorhome solenoid would do.

[grady]

Ok so a simple solenoid would work. However one issue with it I did not see brought up. The parasitic load of the coil. For intermittent use it will not be an issue. However for leaving it on for a day or more not good.

[BOAT]

Ok so a simple solenoid would work. However one issue with it I did not see brought up. The parasitic load of the coil. For intermittent use it will not be an issue. However for leaving it on for a day or more not good.

I'm pretty sure the coil is held in position when the ignition is on, and is relaxed when the ignition is off. So there is no parasitic draw when the motor is not running. There is a spring in it so the unit can be mounted upside down or sideways but the instructions recommend mounting the unit in the upright position so that tells me it's just a holding coil in the on position. (Also when you shake it there is something bouncing up and down inside. Hey if you guys like the electronic kind that's fine by me - I'm just old fashioned but not so old fashioned that I think a hard perko swap is better. That's just dumb to me, but what do I know.

Anyways,

I still need more help - you guys any good as interior designers?? Any of you pink shirt guys or automotive style-shop designers can chime in with some recommendations for me cuz the wife is away at work and can't opine - I just finished the basic shape of the dash board and here is the bracing on the back:



And it sort of goes on the boat like this and I have not put the finish on yet or the rest of the trim:



I say WOOD LOOK cuz it.s made of WOOD

And I'm looking at it and I'm saying: "Hmm, still something just not right" "Still missing something . . . "

Mmm, still not enough -

How about . . .

CARBON FIBER!! ? !



So, what do YOU guys prefer? The WOOD LOOK or CARBON FIBER! What do you think?

[Highlander]

the wood adds a warmer effect , I used laminated flooring I think it,s called Caribean Mohogany matches the mac mohogany very nicely I also painted the cut edges with black plastic paint to give off a 3 D effect !

I also used rivit nuts on the bulkhead & attached the dash with brass screws 8/32nd rivit nuts & brass screws

J