Arse About Face Electrics

[Skyraker]

My boat sat for 4 years so I managed to knock a 6 grand paint job off. Ill do a new thread on this soon because wonders can be done with elbow grease.

 

This craft has not being modified as I have the original documents.

 

Stern shes great 4 new 150ah batteries, with no issues. 240v throughout. Victron multi 3kv whatsit with a controller that displays nothing. Also a 3.5kv electrolux travel unit, which is awesome, twin alternators that run faultlessly.

 

Now then, she was designed with a bow thruster, never fitted, however the battery and electrics exist. This is where it becomes bonkers to me.

 

The bow battery is charged vua 240v socket. The front cabin lights, water pump, tv boost etc ALL run frkm this one battery. Only 12v mind. It doesnt last too long.

 

surely, surely all systems should run from tbe rear 600ah system.

 

it seems like a corner has been cut when she was launched.

 

Any advice welcome.

 

pics to follow.

 

Des

[Paul C]

Yeah doesn't make sense. Bow thruster battery for bow thruster only, really. Maybe there's an argument for the horn and headlights to be on it too.

[The Bagdad Boatman (waits)]

Voltage drop on long runs of 12v systems?

[Mike Tee]

Voltage drop on long runs of 12v systems?

Big expensive cable works wonders. An expert will be along to say how big.

[NMEA]

Big expensive cable works wonders. An expert will be along to say how big.

Impossible to know without the following two perameters: Thruster current draw and round trip length of cable. It is perfectly valid practise to install a battery close to the truster but not to have other stuff running from it, it is also usual to have it use the same charging method(s) as the other systems but this again requires quite heavy cable, not nearly as heavy as dedicted thruster supply but pretty heavy, precise circular mil governed by length and current again.

[Phil Ambrose]

So exactly what are the other batteries doing? Are you sure you have not missed something because as Paul said BT bat is only for the BT. Just a thought, if boat has brand new set if domestics maybe the original owner fitted new ones for the sale. They may well have dine a numpty thing when they knackered the old domestics and to save money just hooked onto the BT bat some way.

Can't get my head round this.

Phil

[Tony Brooks]

So to following on from MNEA says. If you want to avoid rather thick cable runs the length of the boat you can use a mains charger local to the BT battery as long as it is only charging when a non-battery powered 240 volt supply is running (that is from shore line, travel power or inverter ONLY when the alternator(s) charge is sufficient).

 

It all sounds fairly standard so also think that you may have missed something re all those things running from the BT battery.

[chevron]

Boats I have seen all had a battery near the bow thruster charged by a seperate battery charger.dont know much about bow thrusters but dont they get used in short bursts.would love to see your thread on paint work just bought a boat with need of paint and need some inpiration

[Paul C]

I can't see anything wrong with charging a BT battery by a separate mains powered charger. And there's nothing wrong with that charger being powered by the inverter as well as eg genny or shoreline - that way it could charge the BT battery when the engine was running, for example. You might want to not charge it while the engine is off, though, or have a way of indicating clearly it is charging so you can decide yourself.

 

There IS something wrong with running other domestic items from the BT battery simply because its the closer battery than the domestics. If nothing else, then it is inefficient from Peukert's Law principle, in that a bunch of loads is best served by one large bank of batteries, rather than 2 or more banks.

[nicknorman]

There IS something wrong with running other domestic items from the BT battery simply because its the closer battery than the domestics. If nothing else, then it is inefficient from Peukert's Law principle, in that a bunch of loads is best served by one large bank of batteries, rather than 2 or more banks.

No, peukerts law doesn't come into it for intermittent and small loads. As said, there is nothing wrong with charging the BT via mains, in fact it seems the best way to me considering the difficulties with charging via long and fat DC cables.

 

What I would be concerned about is having slightly delicate electronics on the same battery, eg a TV. When the bowthruster is turned on, and especially off, large voltage spikes are likely to be generate which may, over time, damage the electronics. Plus of course the voltage will drop substantially when the 300A or so making lights dim etc, although I suppose it's unlikely that one would want to use the BT in the dark.

[Bee]

Or the telly when on the move unless you've got a much better aerial than me. It does sound a bit odd but as long as it works and the batts. stay charged then it's probably ok.

[ditchcrawler]

OP said NO Bowthruster fitted only batteries, charger and he doesnt mention it but I guess tube.

[Arthur Brown]

A Bow thruster battery will never properly charger if fed from a simple automotive alternator at the stern. The mains charger is a good way to charge the BT battery as you have lots of 240v when the engine is on. What is madness is running the front end of the boat from the BT battery, Firstly a BT battery duty is more like a starter battery duty -short bursts of big currents. Secondly a simple BT battery does not have the capacity to drive a boat's cabin accessories for long as you have found.

 

First check that all the batteries are being charged, then start to move domestic loads to the domestic battery.

[MtB]

It obviously isn't a bow thruster battery, given there is no bow thruster...

[larkshall]

Emergency power? Just a thought

[NMEA]

A Bow thruster battery will never properly charger if fed from a simple automotive alternator at the stern.

Mine has done so from new, that's eight years to a pair of 6v batteries which are again still there from new, the cables are 25mm2 mind. It does get used a bit too, reversing into finger moorings with cross tide and or high winds.

[DHutch]

Seems off to me too.

 

We have a pair of bow batteries for our thruster, but everything domestically runs off the main battery.

 

As said, I can seen an argument for running the horn of it, with a relay up front, if you where using a large airhorn or the like and wanted a crisp sound, but really beyond that I thin they have just used it because it was close by and they where pushing to get it working.

Is there a second distribution board for the battery, or just random cables to it?

 

 

Daniel

[ditchcrawler]

But if you have a pair pf batteries at the bows that are being charged and no bow thuster it would be a complete waste not to use them for something. If the boat has 240 via an inverter and a charger on 24/7 then effectually the load is being taken by the main domestic batteries, grant you not the most efficient way. But I assume the OP doesn't have the charger running 24/7 or he wouldn't know the batteries are not performing very well.

[Paul's Nulife4-2]

Hi ya,

Have you got a '1-Both-2' Battery Selection Switch fitted ?. If so,,what setting livens up the draw from the Bow Battery ?

Could the Bow Battery be The second Battery Bank ?.

Was there ever an Electric start Generator Fitted ?.

Is it all the wiring required for future installment of a BT ?.

Have you got, or did it have an electric Windless ?

Edited June 20, 2015 by Paul's Nulife4-2

[MtB]

This could, possibly, be one of the reasons the boat remained for sale for four years and the seller accepted a £6k hit on his asking price...

[by'eck]

Nothing wrong, indeed its sensible to run occasional use equipment such as horn and/or tunnel light from BT battery(s), since they are typically located adjacent. Relays can be used to control them from the stern.

 

In the OP's case it seems that policy has been taken to extremes, although I suspect unintentionally by the builder. Suggest re-wiring all the regular use equipment from main domestic batteries, that's what they are there for. Use appropriate gauge cabling, since the battery feed will be further away. Maybe 10mm² for fridge if you have a 12 volt one. Remember to fuse each circuit.