Batteries / Bow thruster question.

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Hi all,

I have a 2600 SE that currently has 2 x 85 AH deep cycle batteries connected to a 1/2/Both switch. They are just over a year old.

I start the engine on 1, switch to 2 on the anchor then 1 to start again at the end of the day. Both charged on shore power when back at the marina.

When using the bow thruster (needed for a difficult home berth) , the voltage drops quite significantly,
even on the both switch and the other day cut out the nav device.

I'm thinking of adding a third battery and this is my plan...... parallel the 2 x 85 AH deep cycle batteries and use as the house bank (Switch position 2), buy and fit a proper starting battery with some serious CCA to use for starting and also to help deliver some decent power to the bow thruster as I don't think the deep cycle batteries can deliver the power in quick short bursts.

I figure this is the easiest and cheapest way to do it, thoughts??


(The current 85 ah batteries have been tested, all good, alternator is delivering decent charge as is the shore power battery charger)

I don't really want to add dedicated batteries up front for the bow thruster due to expense/ complexity and it really is only used for 2 - 3 short bursts.

[mmwjr]

What is the power draw of the thruster? What size and how long is the wires supplying it.

[shrew]

You might need a dedicated battery for the thruster with a DC -> DC charger from the starting battery. If you get a dedicated battery, it should be located close to the thruster.

Otherwise, I'm with Mike

What is the make and model of the thruster?
What is the amp draw of the thruster?
What is the distance from the battery to the thruster?
What size (guage) wires are feeding the thruster?

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Cheers for the replies, away from the boat at the moment but will check the wire size and distance (I guess 5 metres or so). It's a vetus bow thruster but again I'll have to check which model so I can get the current draw.

Boat was new to me in June this year and I'm trying to sort out the previous owners bodges. She's a great boat though.

[shrew]

Also check to see if the thruster is wired to the starting or the house batteries. It should be to the starting battery so that the alternator can push the thruster.

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Sorry for the delay in replying, only just been down to the boat.

Bow thruster is a side power se 40/125. The cables connecting it look thick enough, see pictures attached.

I didn't get a chance to check the battery connections. As the thick cables are in place already I think its probably the fact the boat has 2 deep cycle batteries and no decent starting battery, think i'll probably add a starting battery and use for starting and bow thruster (switch position 1) and parallel the two deep cycle batteries for the house bank (switch position 2).