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Which Battery For Bow Thruster


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Hi - I currently have 2 leisure/multi purpose batteries with individual isolators giving a 1/2/both type arrangement.

I am going to add a starter battery and make the current 2 batteries a single bank for house and a VSR between them.  So will split domestics to house  Bank and starting/instruments etc to starter battery.

I also have a bow thruster.  Not sure whether this should be on the starter or house battery circuit.  Seems maybe it should be on the starter due to large power draw and starter battery being built more for that, but somehow that feels wrong as it’s used coming in to moor, so don’t want to knock the charge down on that when your about to switch off the engine and the starter has way less capacity.

any advice or wisdom?

cheers

Jeremy

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52 minutes ago, JeremyG said:

Hi - I currently have 2 leisure/multi purpose batteries with individual isolators giving a 1/2/both type arrangement.

I am going to add a starter battery and make the current 2 batteries a single bank for house and a VSR between them.  So will split domestics to house  Bank and starting/instruments etc to starter battery.

I also have a bow thruster.  Not sure whether this should be on the starter or house battery circuit.  Seems maybe it should be on the starter due to large power draw and starter battery being built more for that, but somehow that feels wrong as it’s used coming in to moor, so don’t want to knock the charge down on that when your about to switch off the engine and the starter has way less capacity.

any advice or wisdom?

cheers

Jeremy

Hi Jeremy, welcome from me too. 

I believe electric bow thrusters are extremely power hungry, so do NOT connect it to your starter battery. I would NEVER connect anything other than the engine starter motor to your starter battery, as a starter motor itself is power hungry, so anything else connected to it could see a flattened battery and unable to start the engine to "charge up the batteries".

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One solution, if you have space, would be to have a separate battery for the bow thruster. If not tend to agree with others about not using the starter battery for anything other than starting the engine.

There is a very compact battery capable of producing high currents for short('ish) bursts, pricey but long living i.e. I've had one for over 15 years. https://optimabatteries.co.uk/

Hope that helps.

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Thanks all, that makes a lot f sense so decision mad.  Stick it on house.

i agree it would be nice to have a separate battery for thruster, but space would mean I think that I would need 2 of the red tops, one for starting and one for thruster.  Pricey.  I might go for the red top for starter though as that will leave me space if I change my mind later.

TBH I have managed fine for the last 5 years on the 2 batteries I have.  Never go on shore power unless at my home mooring but don’t have big power draw.  Rarely use the tv, fridge is on all the time though.  No inverters and all LEDs, so pretty frugal, just always in the back of my mind that I don’t have any emergency backup.

cheers

Jeremy

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Hi Jeremy starter battery is best using welding power cable  leads which is cheaper in the long run than having a separate bow thruster battery and doesn't need any maintenance as they are designed for supplying high currant PROVIDING you charge it up to full charge this applies to domestic batteries as well no battery should be left uncharged why not get a solar panel this will then keep ALL your batteries fully charged and increase there longevity, plus if you are coming into your home mooring you are unlikely to use the bow thruster much any way,  you are more likely to use the bow thruster more when away when the engine will running any way and as you are staying you can run engine for ten minutes or so if necessary,  where as on your home mooring you will have shore power to recharge the battery, solar is best for all for round battery maintenance as its 24/7 and free. John

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The one thing I miss is the solar panel. We had one on the last boat and that gave us the backup needed to keep batteries charged without running the engine. As we now have an electric fridge I should be looking to get another solar panel, oh yes, and maybe led lighting.

 

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Yep, we had the thruster on Thunder moved onto the starter battery (as per the recommendation of the sparky).

As others have said, it pulls a lot of current but you use it for a matter of seconds a day and rarely when the engine isn't running.

The starter battery usually has priority for charging, but if the thruster goes on the domestics ('house' is a US term) then it's - theoretically at least - yet another thing to pull a load out of that bank. Domestics and starters are not always the same battery type, either.

 

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Sorry to be late on this thread, but the bow thruster must be on the starter battery, unless it has its own battery on a separate circuit with a charge splitter.

A starter battery can take a short, heavy load, called CCA (cold cranking amps) but a domestic battery is designed to take a long, deep discharge at a lower amperage, but over several hours.

Consider your car. The battery is always fully charged, as you are only using it when the engine is running. When the engine is not running, you get out of the car and walk away. No further use of electricity. Not like a boat, when you are then living and sleeping on board.

When your car engine is running and you want to use headlights or wipers, etc., the regulator immediately cuts the alternator in and compensates for the power drain. Most bow thrusters will use around 40 amps, but only for a few seconds at a time. So if you have a 90 amp alternator, no problem!

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Again, thanks all.  So my first assumptions was to put it on starter battery.  It’s already professionally installed so I just need to decide which bank.  So I know about the differences between starter and leisure batteries hence why I originally thought starter.  I had read conflicting reports on domestic/starter (yes I know house is an americanism, but seems to be become more used in the UK and we live in a global world now!  But mainly it’s less to type! 😀)

so - I think I’ve changed my mind and going back to using starter battery.  I will have a emergency switch on the VSR anyway so I’m not too worried about flat batteries.

John - re: solar panels... I just don’t don’t think I need them.  Had the boat 5 years with 2 multipurpose batteries and no starter battery and all has been fine.  I tend to spend a lot of time cruising and not much time stopped.  Also draw very little power (Fridge being the main thing.

i also intend to put a battery monitor on so I can get some decent info on what I’m using (might show that I need solar).  Anyone used one of those cheapo battery monitors on eBay/amazon?  30 quid instead of £100-£170 and get decent review on YouTube etc...

cheers

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36 minutes ago, Vaughan said:

Most bow thrusters will use around 40 amps, but only for a few seconds at a time.

Take a moment and sit on the wall, the one on the seaward side of Mutford Lock. Best time is the Sunday before August Bank Holiday when the sports cruisers are locking through ready for the fireworks. The tortured screams of over used bow thrusters tend to far exceed  a few seconds at a time! 

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13 hours ago, Matt said:

Did we?! I must of missed that!

What about the mud weight?

M

 

Yep. There were four distinct banks previously, but it was simplified down to three when the rewire (and new argofet etc) was done.

I'm not sure about the windlass, it may be on the domestics.

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