Can I add a battery inline to help with voltage drop for bow thruster?

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Astralis

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One of the aspects that has always confused me with our Azimut 42 is the distance from the battery bank in the lazerette to the bow thruster and the inevitable voltage drop this must cause. I’m no electrician but is there a way I can add another battery into the system near the bow thruster to help mitigate voltage drop? Is it as simple as finding a suitable location for it, connecting the existing supply wires to it and then from the terminals to the thruster terminals and if so will it also become part of the bank that is recharged from the battery charger? So for the simplistic description but I am simplistic when it comes to electrics🤣
 
Dedicated batteries for thrusters located in the bow are quite common - I have one. However not always easy to arrange, both physically and for charging from the alternators. Retrofitting needs careful thought to find a secure location. Then you need to feed the charging cables through the boat. One way of making this easier is to use a DC/DC charger from the start battery as you then need smaller size cables. On my installation I have 16mm cables which are easy to run in my simple boat but I would imagine running any cable through a boat like yours a challenge. I expect the existing cables were run before the interior was fitted. You might be able to use the existing cables with a VSR from the start battery, but much would depend on how the existing charging system is set up.
 
I thought majority were fitted with a battery at the bow. Problem is then charging.

However, OP has his fed from more distant batteries and that means existing cabling will be pretty thick. I imagine that means he doesn't need to fit a more complex system with dedicated charging at the bows. A new battery would charge in same way as existing battery that feeds the thruster. Voltage drop should be relatively low with thick cables and low charging current. He should do some calculations based on wiring thickness and length of the run.
 
Astralis said:
One of the aspects that has always confused me with our Azimut 42 is the distance from the battery bank in the lazerette to the bow thruster and the inevitable voltage drop this must cause. I’m no electrician but is there a way I can add another battery into the system near the bow thruster to help mitigate voltage drop? Is it as simple as finding a suitable location for it, connecting the existing supply wires to it and then from the terminals to the thruster terminals and if so will it also become part of the bank that is recharged from the battery charger? So for the simplistic description but I am simplistic when it comes to electrics🤣
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The bow thruster on my Azi 42 gives plenty of thrust. Are you sure the problem is due to loses in the wiring? If you need to add another battery there seems plenty of space to locate one?
 
rafiki_ said:
The bow thruster on my Azi 42 gives plenty of thrust. Are you sure the problem is due to loses in the wiring? If you need to add another battery there seems plenty of space to locate one?
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Good point. My bow thruster lost power after a year or so. I thought it was the battery as voltage was quite low, even after hours on shore power.

Traced the fault to arcing inside the post clamps on the dedicated battery. Installers hadn't cleaned anything and probably even tightened clamps on some grot.

The bow thruster wasn't delivering full power even when battery charged. Battery was also taking an age to recharge.

I cleaned everything, sanded back posts and clamps before reassembly. Perfect for next 15 years.

Well worth checking wiring for voltage drops.
 
I have a battery in the bow that serves the bow thruster, a separate charge feed from one alternator for when on engines and a from one engine and a small charger for shore power charging .
 
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Astralis said:
One of the aspects that has always confused me with our Azimut 42 is the distance from the battery bank in the lazerette to the bow thruster and the inevitable voltage drop this must cause. I’m no electrician but is there a way I can add another battery into the system near the bow thruster to help mitigate voltage drop? Is it as simple as finding a suitable location for it, connecting the existing supply wires to it and then from the terminals to the thruster terminals and if so will it also become part of the bank that is recharged from the battery charger? So for the simplistic description but I am simplistic when it comes to electrics🤣
Click to expand...
Fit a battery as close to the bow as you can, and connect it to the existing cables. Fit a fuse close to the battery. That's it, yes it will still get charged from whatever charges the battery to which it is currently connected.
 
Doesn't make a lot of sense to run the 70mm2 cables. Existing cables are going to be pretty heavy as the existing current draw will be high. OP could always run additional cables in parallel. Probably cheaper than ignoring the existing cables.

Adding a battery makes a lot of sense.

Two points.
1) OP could check the diameter of existing cable and the round trip wiring run. Check spec. on the thruster and calculate the expected drop. If it's a lot then work required. If it looks OK then measure voltage drop in use. It would point to a poor connection somewhere if the drop is much greater than expected.

2) I wonder what's the battery specification. It's possible they won't actually support the required current draw. Domestic batteries could be T105s and be limited. Even a standard engine start battery might struggle. I have a dedicated Red. Flash at the bow and that's a good one to use. Unlikely to be fitted remotely for more general use.

Just a thought.
 
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Thanks for all the suggestions, I decided to look in more detail as to what I had and removed the thruster as it was looking a little tired, off the the electric motor specialist for a general refirb and check and now installed it goes perfectly so actually what I had was a tired motor that needed some tlc. Thanks again one and all for the suggestions. Cheers
 
Previous owner had fitted a 4 hp from original 3 as was pretty pathetic and the 4 still was. Checked voltage when operating and dropping to 9v.
Fitted its own battery adjacent using original cables for charging from start batteries via a VSR isolator and fuse 300a fuse which was at start battery end replaced by 90a trip.
It was better but still not brilliant.
Bow thruster went flat couple of times and found that 90a trip for charging had tripped.
Did current check on all cables, 500a to BT taking 350 from BT battery and 150 from start battery via now charging cables.
Fitted new 500a fuse for BT and original 300a back in original place
Now works a treat
 
Astralis said:
Thanks for all the suggestions, I decided to look in more detail as to what I had and removed the thruster as it was looking a little tired, off the the electric motor specialist for a general refirb and check and now installed it goes perfectly so actually what I had was a tired motor that needed some tlc. Thanks again one and all for the suggestions. Cheers
Click to expand...
Great result.
 
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