New boat - winter rewire project - please review for sanity

Place for all of the tips, hints, and facts around the electrical and electronic stuff found around Trailer Sailers, Trailers, and associated vehicles.
Post Reply
User avatar
ricdanger
Lakes & Bays Skipper
Posts: 419
Joined: Apr 7th, '10, 15:52

New boat - winter rewire project - please review for sanity

Post by ricdanger » May 29th, '17, 20:43

Hi guys,
Can't help myself and am going to build up the electricker in lollipop apocalypse over winter. I have most of the parts, just need to make sure I put them together in the right order.

First image is current state - typical of an original 4 switch config that's been added to by simply attaching fused connections to one of the batteries.

Problem: engine start is on same battery as all the addons (fridge etc), no recharge ability other than engine.

Image

So... add a solar panel and MPPT, shore power charger, a start battery and a relay to charge the start battery first then house. Have an emergency switch to start motor from house if all else fails, and add some extra outlets. Also, provide an inverter to charge the laptop when up bunga arm.
Image


Thoughts... ideas... missing anything?

Thanks.
Ric
Ric

Botterill Explorer 16 #10 - Captain Phasma

User avatar
zebedee
Admiral
Posts: 9907
Joined: May 9th, '07, 02:05
Location: Bayside Melbourne

Re: New boat - winter rewire project - please review for san

Post by zebedee » May 30th, '17, 00:08

How does an RCD (also known as an Earth Leakage Detector) work when neither side of your AC is grounded to anything?
No, I am not suggesting grounding your AC to anything; I'm suggesting that the RCD is superfluous and won't detect any fault condition since there is no earth.

Current design:
  1. The AC to 12V charger can only charge the starting battery unless you turn on the isolation switch between the two batteries.
  2. The solar panel -> MPPT regulator can only charge the house battery unless you turn on the isolation switch between the two batteries.
  3. Why is there a voltage sensing relay between the MPPT and the battery it is trying to charge?
You've got three charge sources and two batteries to manage; you need to decide which sources charge which battery under what circumstances. Once you've got that worked out, you can decide where and what type of isolation switches to use.

My thinking:
  1. Given you've got a 50hp motor which presumably has a serious alternator, it would make sense to allow the outboard to charge the house battery once the start battery is fully charged. A voltage sensing relay which connects the two batteries together when the starting battery is fully charged (13.7V) will allow this. When the starting battery voltage is below 12.7V, the relay disconnects the house battery.
  2. If the solar feeds the starting battery, then it will "overflow" to the house battery whenever the starting battery is fully charged, which should basically be always.
  3. You probably want to be able to apply the AC charger to either battery alone.
I suggest:
  1. Fit a simple on/off isolation switch between the house battery and the house loads.
    Image
  2. Fit a 1/2/1+2/off isolation switch between the outboard and the two batteries, so that the outboard can be connected to the start battery or the house battery or both batteries at once or off. This saves having a separate emergency start isolator, costing less and taking up less space. Clearly mark the "usual" position, which should be "1".
    Image
  3. Fit a battery isolator/voltage sensing relay so that the alternator charges the house battery too, without compromising the start battery.
    Image
  4. The solar may as well connect to the start battery too, so that it remains fresh at the end of winter. The voltage sensing relay will look after charging the house battery from the fully charged start battery.
  5. The AC charger could be connected to the start battery or to a suitable light duty SPDT centre off (1/off/2) switch allowing it to connect to either battery BUT NEVER TO BOTH. This allows independent charging of either battery without allowing either battery to drag the other down if it dies in June and you don't look at it before September. It also prevents you trying to start the motor through the light duty switch when the motor isolator switch is set to the start battery only!
    Image
A man's boat is his Castle. The Gippsland Lakes are my moat. Castle 650 #10, Roller Coaster.

INMA
Admiral
Posts: 5851
Joined: Nov 5th, '06, 13:07

Re: New boat - winter rewire project - please review for san

Post by INMA » May 30th, '17, 03:48

Be carefull switching the alternator between batteries while the engine is running, the field needs to be isolated before any open circuit occurs on the output otherwise the voltage spike will fry the regulator. Proper isolation switches have a field isolator before the load is disconnected. Those switches cost many hundreds of dollars and are beyond your needs.

https://www.thexmod.com/item_detail.asp?id=17694
RL24 Mk4 cruiser Mariner 5 2 stroke

A bad day in the Whitsundays is better than a good day at work. Unless you work in the Whitsundays.

User avatar
zebedee
Admiral
Posts: 9907
Joined: May 9th, '07, 02:05
Location: Bayside Melbourne

Re: New boat - winter rewire project - please review for san

Post by zebedee » May 30th, '17, 06:00

Battery isolation switch for two batteries with alternator field switching, matches switches shown above, $79.95 (standard version is $64.95, single battery version is $49.95)

Image
A man's boat is his Castle. The Gippsland Lakes are my moat. Castle 650 #10, Roller Coaster.

User avatar
ricdanger
Lakes & Bays Skipper
Posts: 419
Joined: Apr 7th, '10, 15:52

Re: New boat - winter rewire project - please review for san

Post by ricdanger » May 30th, '17, 09:40

Thanks guys. It's probably my crappy diagramming but I meant to show the ctek and mppt connected to the start battery all upwind of the VSR. Downwind of vsr is the house bank. The idea was to try and simplify so that no matter what charger was in use the vsr would do its job charging start then house without any switches being flicked.

Does that change anything?


I like the idea of the 1+2 switch.
Ric

Botterill Explorer 16 #10 - Captain Phasma

INMA
Admiral
Posts: 5851
Joined: Nov 5th, '06, 13:07

Re: New boat - winter rewire project - please review for san

Post by INMA » May 30th, '17, 17:25

Keep it simple.

There is no concern about charging the starter battery first if the house battery is available to boost the start.

Concentrate on charging the batteries separately and properly but also remember not to waste the alternator charge when the start battery is charged.

A bit of contradiction there but I've seen complex systems on trucks do stupid things when smart expensive electronics don't work due to simply faults.

Design it so you can see faults before they cook batteries or leave you stranded.

A battery connected to a modern outboard is a very reliable system.
RL24 Mk4 cruiser Mariner 5 2 stroke

A bad day in the Whitsundays is better than a good day at work. Unless you work in the Whitsundays.

User avatar
zebedee
Admiral
Posts: 9907
Joined: May 9th, '07, 02:05
Location: Bayside Melbourne

Re: New boat - winter rewire project - please review for san

Post by zebedee » May 30th, '17, 20:27

To me, simple is a starting battery which, just as in a car, is always charged first, overflowing via the VSR into the non-essential house battery. The switched AC charger allows you to charge the house battery alone if the starter battery fails.
A man's boat is his Castle. The Gippsland Lakes are my moat. Castle 650 #10, Roller Coaster.

User avatar
ricdanger
Lakes & Bays Skipper
Posts: 419
Joined: Apr 7th, '10, 15:52

Re: New boat - winter rewire project - please review for san

Post by ricdanger » May 30th, '17, 20:54

zebedee wrote:To me, simple is a starting battery which, just as in a car, is always charged first, overflowing via the VSR into the non-essential house battery. The switched AC charger allows you to charge the house battery alone if the starter battery fails.

Cool that's pretty much what I intended... just didn't add the switch to just charge house if needed.

Thanks all.
Ric

Botterill Explorer 16 #10 - Captain Phasma

User avatar
ricdanger
Lakes & Bays Skipper
Posts: 419
Joined: Apr 7th, '10, 15:52

Re: New boat - winter rewire project - please review for san

Post by ricdanger » May 30th, '17, 21:29

What switch do you reckon would work for switching between inverter and shorepower...

I can use this for $14
https://www.ebay.com.au/p/?iid=18232728 ... s&&&chn=ps

or this for $400+
https://www.bluesea.com/products/8386/A ... OFF_4_Pole

something in between?
Ric

Botterill Explorer 16 #10 - Captain Phasma

User avatar
zebedee
Admiral
Posts: 9907
Joined: May 9th, '07, 02:05
Location: Bayside Melbourne

Re: New boat - winter rewire project - please review for san

Post by zebedee » May 30th, '17, 22:10

ricdanger wrote:What switch do you reckon would work for switching between inverter and shorepower...

I can use this for $14
https://www.ebay.com.au/p/?iid=18232728 ... s&&&chn=ps

or this for $400+
https://www.bluesea.com/products/8386/A ... OFF_4_Pole

something in between?
I did wonder about that, but it got lost in all the 12V stuff.
I am not a licensed electrician and there may be regulatory considerations I am not aware of.

Having said that; it is vital that whatever you use is rated to sufficient voltage and that it disconnects both neutral and active together. Unlike 12 V systems, miswired power points or extension leads mean that neutral may turn out actually to be active and vice versa, and everything will work normally until someone switches what they think is the active wire only, leaving the actual active connected.

To be honest, I'd be inclined to have a short stub cable with a 240V plug on it emerge from a panel adjacent to two power points; one from the inverter and the other from the AC input plug. You can see clearly which it is plugged into, you can plug it into an extension lead instead, it's cheap and it works.

The RCD on the input from shore power (or the power point in the garage at home) should be the first thing after the AC input plug, so it always protects from faults in the earthed system, while the inverter has no earth, so an RCD won't work since there is no alternative path to unbalance the RCD.
A man's boat is his Castle. The Gippsland Lakes are my moat. Castle 650 #10, Roller Coaster.

User avatar
zebedee
Admiral
Posts: 9907
Joined: May 9th, '07, 02:05
Location: Bayside Melbourne

Re: New boat - winter rewire project - please review for san

Post by zebedee » May 30th, '17, 22:22

BTW, I have a friend who is an ex-pat in Vietnam. His home there has a backup generator which came with an extension lead with a MALE PLUG ON BOTH ENDS!!!

The routine is that you turn off the mains power and then plug the lead into the generator outlet and a household outlet before starting the generator. Needless to say this is a potentially lethal system with all sorts of ugly ways to go wrong, including but not limited to:
  • Unplugging from the house while the generator is running and electrocuting someone with a live male plug.
  • Unplugging from the generator but not the house, then turning the household power back on and electrocuting someone with a live male plug.
  • Forgetting to turn off the house mains supply, thus applying mains voltage to the supply network and electrocuting someone who is trying to repair it.
  • Forgetting to turn off the house mains supply, and attempting to power all the other houses downstream of the supply network fault.
  • Forgetting to turn off the house mains supply and exposing the generator to the mains system when the power comes back on (BANG!)
  • Supplying all the power needs of the house through a single power point which is not rated or fused to carry so much current; setting fire to the wiring and the house.
What he really needs, in an unregulated country where nobody really cares, is a changeover switch wired into the right part of the house supply. If the house were much smaller, (like, say, a boat...) he could put a plug on the house and a socket on both the generator and the grid supply and plug the house into whichever he was using, just as we happily move appliances around from one power point to another.
A man's boat is his Castle. The Gippsland Lakes are my moat. Castle 650 #10, Roller Coaster.

Post Reply

Return to “ELECTRICKERY (Electrical and Electronic Stuff)”