Bowthruster Electrics Supply

[Boathook]

I envisaged some kind of switch in the cockpit. Perhaps not a main switch, but something that would stop you from inadvertently running the thruster.
But as I said, I don't know how BT's operate.

My vetus BT has a switch by the BT control to energise the solenoid on the BT itself. BT doesn't operate if this isn't glowing green, so that it could be linked to operate another control for the charging system. I always keep this off unless about to use the BT .

 

[PaulRainbow]

I'm a little concerned that fitting some inappropriate and then working around it's limitations could develop into a bit of a bodge.

If the VSR is connected to the engine battery, a normally closed relay could be fitted to the VSR negative, triggered by either the "ignition" being turned on or perhaps the alternator. But this can be rendered inappropriate by the engine battery charging methods, so i'll await answers to the questions regarding current changing arrangements.

 

[halcyon]

I'm a little concerned that fitting some inappropriate and then working around it's limitations could develop into a bit of a bodge.

If the VSR is connected to the engine battery, a normally closed relay could be fitted to the VSR negative, triggered by either the "ignition" being turned on or perhaps the alternator. But this can be rendered inappropriate by the engine battery charging methods, so i'll await answers to the questions regarding current changing arrangements.

Don't see what your problem is, control relay with BT motor feed, drops out VSR only when BT is running.

Why do manufactures not fit a interlock option to VSR's today?

Brian

 

[Aurai]

Careful not to cross the direction guidance is headed. While also stranded a long way from my boat and or records, just moved into T4! I was guided by Powerstore Products at various boat shows, who reckoned on the bow battery. Fed from house batteries, but wired in a Xantrex (from memory) Echo Charge unit in the bow. This allowed “thin” cables battery to battery. It has been a fit and forget success, in my 11m yacht and the only addition was a 100A fuse (switchable) in the bow. Somewhere, I have the wiring diagrams etc, from when we put it in. Thanks

 

[pvb]

Careful not to cross the direction guidance is headed. While also stranded a long way from my boat and or records, just moved into T4! I was guided by Powerstore Products at various boat shows, who reckoned on the bow battery. Fed from house batteries, but wired in a Xantrex (from memory) Echo Charge unit in the bow. This allowed “thin” cables battery to battery. It has been a fit and forget success, in my 11m yacht and the only addition was a 100A fuse (switchable) in the bow. Somewhere, I have the wiring diagrams etc, from when we put it in. Thanks

As I suggested in post 4. There are cheaper echo chargers than Xantrex.

 

[101chugger]

I think we’re getting there. Some more detail for info. The motor’s a Yanmar 3JH40 (non turbo), with a 125 Amp alternator. Electrical power through the boat is controlled by a Navix control box (piccy) with switches for start and service batteries, shore power, and ancillary fuses. Solar is fed to the start and domestic battery via a Votronic 125 MPPT controller. The BT is a Vetus 25kgf which is operated by a timer/thrust direction switch beside the helm (piccy) which operates a relay in the BT to allow the main current to flow BT battery to BT and spin the propellor either way.




You’ve all been most helpful in your comments. I now think I’ll use 35mm cabling start battery to BT battery, fused at 100 Amp on the positive, with a simple two way VSR on the positive. The BT controller will ensure that the BT circuit stays inactive until it’s powered on.
Thanks again all.

 

[pvb]

You’ve all been most helpful in your comments. I now think I’ll use 35mm cabling start battery to BT battery, fused at 100 Amp on the positive, with a simple two way VSR on the positive. The BT controller will ensure that the BT circuit stays inactive until it’s powered on.

Why would you need a 2-way VSR?

Remember you need a fuse at both ends of the cable.

The way you've described it, the thruster controller won't stop the current from the start battery.

 

[PaulRainbow]

I think we’re getting there. Some more detail for info. The motor’s a Yanmar 3JH40 (non turbo), with a 125 Amp alternator. Electrical power through the boat is controlled by a Navix control box (piccy) with switches for start and service batteries, shore power, and ancillary fuses. Solar is fed to the start and domestic battery via a Votronic 125 MPPT controller. The BT is a Vetus 25kgf which is operated by a timer/thrust direction switch beside the helm (piccy) which operates a relay in the BT to allow the main current to flow BT battery to BT and spin the propellor either way.

View attachment 106044
View attachment 106045

You’ve all been most helpful in your comments. I now think I’ll use 35mm cabling start battery to BT battery, fused at 100 Amp on the positive, with a simple two way VSR on the positive. The BT controller will ensure that the BT circuit stays inactive until it’s powered on.
Thanks again all.

If you are using 35mm cable there is no need for a VSR or anything else, the cable will be able to carry as much current as the thruster could draw. You will need to provide protection to both ends of the cable, as each end is connected to a power source. The cable is rated at 240a so anything up to that is acceptable. I would fit a thermal circuit breaker at one end (the easiest to get to end), rated higher than the one for the thruster and an even higher fuse at the other. This way, neither should blow under normal use, but if you do somehow manage to overload the cable the resettable breaker will trip first. Without a VSR you have simply paralleled the thruster battery with whichever bank you connect it to. The thruster has very limited run time and would only be used whilst the engine is running, so under normal conditions the only way it could deplete the battery that's charging it, is if the thruster battery failed.

If you really want a VSR, there is no point in using 35mm cable, 10mm would suffice for charging purposes, but you would be well advised to disable the VSR when using the thruster. Easily done by fitting normally closed relay across the VSR negative, triggered by either the "ignition" being turned on or perhaps the alternator. (as i said in post #22)

Post #18 would work equally well, but is a little more complex.

 

[PaulRainbow]

Don't see what your problem is, control relay with BT motor feed, drops out VSR only when BT is running.

Why do manufactures not fit a interlock option to VSR's today?

Brian

I don't have a "problem", just a concern about fitting inappropriate systems and then working around them to overcome their shortfalls. My concern was no aimed at your suggestion, or anyone elses in particular, just in general given the then lack of knowledge regarding the rest of the OPs setup, which we now have.

I guess the lack of interlock is down to a combination of cost and the general need for having one. Why fit one to all VSRs when it's rarely required, i guess.

 

[CLB]

If you are using 35mm cable there is no need for a VSR or anything else, the cable will be able to carry as much current as the thruster could draw. You will need to provide protection to both ends of the cable, as each end is connected to a power source. The cable is rated at 240a so anything up to that is acceptable. I would fit a thermal circuit breaker at one end (the easiest to get to end), rated higher than the one for the thruster and an even higher fuse at the other. This way, neither should blow under normal use, but if you do somehow manage to overload the cable the resettable breaker will trip first. Without a VSR you have simply paralleled the thruster battery with whichever bank you connect it to. The thruster has very limited run time and would only be used whilst the engine is running, so under normal conditions the only way it could deplete the battery that's charging it, is if the thruster battery failed.

If you are going to run big cable from the starter battery, is the bow battery needed at all?

 

[PaulRainbow]

If you are going to run big cable from the starter battery, is the bow battery needed at all?

35mm would suffer far too much voltage drop, it would need to be 95mm.

 

[Travelling Westerly]

If you are going to run big cable from the starter battery, is the bow battery needed at all?

That's what I've been thinking all along, just bigger cables so voltage drop is not an issue. Reduces weight up forward as well.
I'm fitting a 6hp thruster upfront as we speak. It's a 7m run of cable from starter battery and I'm running 2 sets of 75mm2 positive and negative cables as per Sidepower instruction manual

 

[pvb]

That's what I've been thinking all along, just bigger cables so voltage drop is not an issue. Reduces weight up forward as well.
I'm fitting a 6hp thruster upfront as we speak. It's a 7m run of cable from starter battery and I'm running 2 sets of 75mm2 positive and negative cables as per Sidepower instruction manual

So is your thruster really only 3.5 metres from your starter battery?

 

[Jokani]

So is your thruster really only 3.5 metres from your starter battery?

That has caught me out a few times in the past as well!

 

[Travelling Westerly]

So is your thruster really only 3.5 metres from your starter battery?

No its definitely 7m unless I measured wrong, I wrote "2 sets of" which in my mind meant 2, 7m runs of positive cables and 2, 7m runs of negative cable.
A set consisting of both positive and negative cables (otherwise I guess the BT may not work so well), length from battery to BT being 7m and 2 sets meaning another set of the same. Maybe my wording confused that?

 

[pvb]

No its definitely 7m unless I measured wrong, I wrote "2 sets of" which in my mind meant 2, 7m runs of positive cables and 2, 7m runs runs of negative cable. Maybe my wording confused that?

OK, understand, but you're just about on the limit with 75mm2 cable though.

 

[Travelling Westerly]

OK, understand, but you're just about on the limit with 75mm2 cable though.

I'm on the limit of my budget to . I had no idea of the price for Oceanflex tinned cable at that size, now I see why the cables didn't come with the BT package
The SP cable size table seems to suggest a recommended (for12v set up) 7-14m run is X2 of 70mm2 or minimum of single 120mm2.
I always value your opinion so do you think I should ignore the SP chart and go bigger than 75mm2?
(SP - Side Power)

 

[PaulRainbow]

OK, understand, but you're just about on the limit with 75mm2 cable though.

He's used 2x75mm Pete = 150mm

 

[pvb]

I always value your opinion so do you think I should ignore the SP chart and go bigger than 75mm2?
(SP - Side Power)

Not if the return length is no more than 14 metres.

 

[Travelling Westerly]

Not if the return length is no more than 14 metres.

I see what you're saying. The return length has to be added to the overall length. In that case the chart would mirror your suggestion.
I'm going to call the supplier to check this as the chart does not seem to suggest taking the return length into account. It just shows you the minimum and recommended cable size for the length chosen, which in my case is the section listed under 7m - 14m run.