Bow Thruster Electrical Upgrade

[Wilfred123]

Hello
I am currently planning to upgrade the battery and charging setup relating to my bow thruster on my boat and I would really appreciate any tips or feedback that anyone would have on my proposals.

Current set up:
I have a 27 foot motorboat with a Vetus 25 kgf (BOW2512D) Thruster. This is powered from from my domestic bank of 2 x 110 ah battery's which are located at the rear of the boat via 40mm2 cables with a round trip length of aprox 15 meters.

Reason to want to change:
Although the thruster works, it seems weedy and slow when in use. I am thinking that the long cable length, relatively small cables is causing a voltage drop that it limiting the thruster output power.

Suggested Upgrade:
1) Put a battery in the bow: This seems to be best practice having read through many posts on here. The Vetus battery spec for this thruster is a battery of min 500CCA/55AH and a max of 650CCA/70AH. I really like the Optima range of AGM battery's but they all seem to be outside of these parameters - do you think it would be a huge issue if I went for one with a slightly higher spec than this?


Battery Charging:
To charge the new battery I was intending to use the old 40mm2 cables that are already in place. I would move them away from the domestic battery's and link them with the engine start battery instead. I would propose to link them with a Sterling Current Limiting VSR (CVSR). Thinking for this is that the battery would be isolated when there is nothing charging the starter battery (either alternator or battery charger) and then they would be linked when a charging source is available and the voltage rises to 13.0v+. The reason to go with a current limiting version is that in the event that the thruster battery is low, the CVRS will limit the current that pulled down the 40mm2 charging lines. Below is a link to the Sterling CVSR that I was thinking of using.
http://sterling-power.com/products/...tive-relay-12-24-auto-select-plus-fine-adjust

So what do you think? any good?
Many thanks

 

[pvb]

I'm thinking you'll go to a lot of trouble and expense, and then find that the thruster performance is just the same! The 40mm2 cables are more than adequate; the problem is most likely that your thruster is under-specified. 25kgf isn't a lot, especially if you have the windage associated with a mobo.

 

[PaulRainbow]

I am thinking that the long cable length, relatively small cables is causing a voltage drop that it limiting the thruster output power.

Could be right.

Suggested Upgrade:
1) Put a battery in the bow: This seems to be best practice having read through many posts on here. The Vetus battery spec for this thruster is a battery of min 500CCA/55AH and a max of 650CCA/70AH. I really like the Optima range of AGM battery's but they all seem to be outside of these parameters - do you think it would be a huge issue if I went for one with a slightly higher spec than this?

I'd just fit a flooded cell battery. No advantage in AGM for this. Although, if you connect it to the engine battery it would be good practice to keep it the same type as the engine battery.

Battery Charging:
To charge the new battery I was intending to use the old 40mm2 cables that are already in place. I would move them away from the domestic battery's and link them with the engine start battery instead.

I'd do that too.

But i would just connect it in parallel with the engine battery (hence why i mentioned matching battery types). You know the cables can carry enough current to run the thruster on it's own, so no worries of cooking the cabling if it draws some power from the engine battery. You would have even more power available for the thruster and the engine would be running too, which would help further and you wouldn't have to worry about flattening the engine battery.

For charging, you probably won't have to change your current split charging system. Although it might be best to mention what that system is. For instance, a dual output mains charger will still work with this layout. As would a split charge alternator system using a VSR or split charge diode.

 

[pvb]

You know the cables can carry enough current to run the thruster on it's own, so no worries of cooking the cabling if it draws some power from the engine battery. You would have even more power available for the thruster and the engine would be running too, which would help further and you wouldn't have to worry about flattening the engine battery.

But the engine will be running anyway, so he already has "even more power" available. Like me, you've acknowledged that the cables are adequate. The problem is the thruster isn't big enough.

 

[PaulRainbow]

But the engine will be running anyway, so he already has "even more power" available. Like me, you've acknowledged that the cables are adequate. The problem is the thruster isn't big enough.

I agree, it certainly isn't very powerful for the size of boat, Vetus give it as suitable for 5.5 to 7.5, so borderline at best. Simply adding an extra battery at the bow, using existing wiring apart from a couple of short cable from the battery to the thruster won't break the bank though. It may or may not help with the thruster, but it will take a load off of the domestic bank.

 

[pvb]

I agree, it certainly isn't very powerful for the size of boat, Vetus give it as suitable for 5.5 to 7.5, so borderline at best. Simply adding an extra battery at the bow, using existing wiring apart from a couple of short cable from the battery to the thruster won't break the bank though. It may or may not help with the thruster, but it will take a load off of the domestic bank.

So a few hundred quid just to "take a load off of the domestic bank"? Doesn't sound like money well spent to me.

 

[PaulRainbow]

So a few hundred quid just to "take a load off of the domestic bank"? Doesn't sound like money well spent to me.

Have batteries really gone up that much ?

He only needs to buy one battery and a couple of short cables. It will make his installation better, it isn't generally regarded as good practice to run thruster cables the length of the boat. He's got a motorboat, so plenty of charging capacity, another battery can't go amiss.

Worse case scenario he spends £150 or so (assuming he does the work himself) and gets a better arrangement with more battery capacity. Best case, it gives the thruster a bit of a boost.

 

[pvb]

He's got to securely mount the battery (and possibly ventilate it), and of course he needs to fuse the cable. There's nothing wrong with running thruster cables through the boat back to the main batteries. Even with a bit of a boost, I reckon the thruster is too small.

 

[PaulRainbow]

He's got to securely mount the battery (and possibly ventilate it), and of course he needs to fuse the cable. There's nothing wrong with running thruster cables through the boat back to the main batteries. Even with a bit of a boost, I reckon the thruster is too small.

Splitting hairs a bit, maybe, but the cables should already be fused. Not sure about venting, mine are under one of the saloon sofas. Good place for them i reckon, i'll get an early warning of boiling batteries

 

[pvb]

Splitting hairs a bit, maybe, but the cables should already be fused. Not sure about venting, mine are under one of the saloon sofas. Good place for them i reckon, i'll get an early warning of boiling batteries

Oh dear, here we go again. The cables might be fused at the domestic bank end, but if you stick a battery up front, you have to fuse the cables at that end too, otherwise you have a fire if there's a short.

 

[Wilfred123]

Hello,
Thanks for your reply's. I agree that the thruster is working at the upper end of its capacity to say the lease... I was really just looking to give it a little more power if possible.

If I was to go for the full lot, it would cost a fair bit as I would also need another fuse and another isolator switch in the new thruster circuit. With all this in mind perhaps the cost/benefit ratio is a bit off.

As an experiment, I might get hold of one of those emergency starter packs from halfords and lash this up direct to the thruster to see if there is any improvement in performance. Always useful to have one on those on board. If the outcome of this is positive, then I will have a look at this again.

Many thanks

 

[PaulRainbow]

Oh dear, here we go again. The cables might be fused at the domestic bank end, but if you stick a battery up front, you have to fuse the cables at that end too, otherwise you have a fire if there's a short.

Yes of course, my bad.

 

[NorthUp]

Measure the voltage at the thruster terminals while it's running- that will tell you if there is a problem with cables or connection. Lowest permissable voltage? That's worth another couple of pages on here! 10.5
volts underload starting bid...

 

[pvb]

Measure the voltage at the thruster terminals while it's running- that will tell you if there is a problem with cables or connection. Lowest permissable voltage? That's worth another couple of pages on here! 10.5
volts underload starting bid...

That's about right! My SidePower SE60 is rated at 60kgf at 10.5 volts, but 73kgf at 12 volts. SidePower are fairly honest about quoting their thrusters' performance, and assume 10.5 volts at the thruster for a typical installation. Vetus seem to quote their thrust at 12 volts, which is maybe optimistic.

 

[Wilfred123]

Hi - Sorry to drag this thread back to life but I thought I would post just in case anyone else experiences a similar situaltion.
I eventually found some time to have a look at my bow thruster install again having not really used the thruster all summer. Having taken the top of the thruster, I found that 3 out of 4 brushes were very tight in their holders and the tiny springs on the back of the brushes were struggling push the brushes in to make a good contact inside the motor. I removed all 4 brushes and lightly filed all sides to free them up a bit and then refitted.

Result - thruster now working better then ever with loads of power (even for its small size)

 

[pvb]

Result!