pvb
Well-Known Member
It won't do anything to the alternator.
Bow thruster battery & wiring
- Thread starter LittleSister
- Start date
It won't do anything to the alternator.
pvb
Well-Known Member
You can't draw "300-odd amps" from an average alternator, it will only supply what it can, based on its design and the engine speed. Your post simply shows that you don't know anything about it, which most people are already aware of.
lw395
Well-Known Member
You can certainly damage the typical simple boat alternator by overloading it.
A bow thruster connected too directly can overload it.
It will indeed supply what it can, based on its design and the engine speed. But also based on the load it sees.
If it's designed to give 90A at 14V, something like a thruster might drag it down to say 10V, where it might put out a fair bit more current and there endeth the warranty.
A bow thruster connected too directly can overload it.
It will indeed supply what it can, based on its design and the engine speed. But also based on the load it sees.
If it's designed to give 90A at 14V, something like a thruster might drag it down to say 10V, where it might put out a fair bit more current and there endeth the warranty.
pvb
Well-Known Member
No, this is simply reinforcing the fact that your "advice" is unsound. Why bother?
EugeneR
Well-Known Member
The biggest risk, IMHO, is ending in a situation - planned or through a simple failure - where you exceed the current capacity in the cables going forward and things catching fire.
OP has cables already, a good battery to battery charger is about £120 and will avoid or reduce pretty much all the risks mentioned so far. It also provides an independent backup in emergencies.
OP has cables already, a good battery to battery charger is about £120 and will avoid or reduce pretty much all the risks mentioned so far. It also provides an independent backup in emergencies.
PaulRainbow
Well-Known Member
What a load or total drivel.
PaulRainbow
Well-Known Member
How can you exceed the current capacity of the cables and cause a fire, if you fit a fuse or circuit breaker rated for the cables current carrying capacity ?
PaulRainbow
Well-Known Member
I will provide here, in writing, a warranty to the OP that connecting his bow thruster as i described, will not harm his alternator and will not overload the 10mm cable connecting it to the engine battery.
My contact details are in my signature and my boat is berthed in the same marina as the OP, so he'll have no trouble tracking me down in the event of a warranty claim.
Furthermore, i am prepared to make, in addition to my warranty, a donation of any sum you would care to name, to the charity of your choice, if my advice results in either, the destruction of the OPs alternator, or a fire caused by the cable being overloaded. Provided that you will match that amount, to a charity of my choice, should my advice do exactly what is says on the tin.
Money where your mouth is time ?
Monique
Well-Known Member
My thoughts. I've had 2 boats with bow thrusters. Absolutely essential on the present boat due t layout etc. BUT, WE'VE NEVER USED THE THRUSTER FOR MORE THAN 15 SECONDS on either boats. Otherwise, you risk some serious overheating.
Oter self imposed rule; always wait 2 seconds between port and starboard activation... you may shear the pin if the prop is not fully stopped. BTDT
All has been said about the electrics.
GL
Oter self imposed rule; always wait 2 seconds between port and starboard activation... you may shear the pin if the prop is not fully stopped. BTDT
All has been said about the electrics.
GL
LittleSister
Well-Known Member
The manual for mine says it is good for around 3 minutes continuous operation (not that I envisage using it for longer periods than you). After about 3 minutes continuous running an overheat device will stop it, and then limit it to running around 10% of the time until it's switched off and allowed to fully cool.
lw395
Well-Known Member
I really can't be bothered any more. (and I have serious aversion to gambling).
If anyone is really interested in the possible bad effects of overloading an alternator, they can find people who've destroyed alternators with such things as winches in LandRovers, or maybe talk to people who've fitted big inverters to certain vehicles with lots of aerials on them. All alternators are not the same when it comes to pushing the limits.
Bosch will even tell you that a regular car alternator isn't even actually intended to charge a flat battery.
For the sake of balance, most of Paul's advice is sound and little of it actually contradicts anything I've said.
Paulg25
Well-Known Member
This seems to be, by far, the easiest solution. No need for big cables running along the boat or diodes or relays. Keep it simple.
C08
Well-Known Member
I took an alternative approach to charging my bowthruster battery in the bows. I could not face paying the £250 for heavy duty cables from batteries at the port rear to the lead acid BT battery in the sb bow so I installed light charging only wires with a plug key to disconnect the charging wires. I hang the plug key that disconnects the charging wire on the BT joystick so if the plug is not there I should not use the BT. The charging wire is fused for that light wire connected to one of the battery banks. Although my boat is only 8.5m, being a cat and needing to go across the boat as well well as forward I was concerned about voltage drop unless I had ridiculous size of cable. So my system is not ideal but works for me.
lw395
Well-Known Member
You could disconnect the charging wire automatically when the thruster runs. A relay or two, lot of change out of £250.
A FET maybe.
Or put some sort of current limiter in the charge wire. Slippery slope towards a home brewed B>B charger perhaps.
In the old days, people used to add a notion of current limiting to model railway controllers by putting a car headlight bulb in series. Low resistance when cold, drops 12V (or so) at 5A. No doubt people would use a microprocessor to emulate this nowadays...
Kinsale373
Well-Known Member
I have a 3Kw thruster. Its driven from a battery fitted in the Bow very close to the thruster itself.
It is fed directly from the House Batterys (ie ,)in parallel with the house batterys from the Alternator. There is a Breaker switch which cuts supply to the Thruster battery. I use this to disconnect the Thruster from the Battery Bank when in port or not requiring the thruster , so that the thruster Battery remains at high charge. I flip off the Thruster Breaker at the same time as I turn the isolation switch for the Engine Battery once I dock , no big deal , the system works fine. VSR would automate the need to manage this.
You will get a decent assist to the thruster from you Alternator when your engine is running through your 50mm sq charging cables. so I'd advise to charge from the alternator rather than from solar as mentioned earlier.
Originally I had a Spiral wound battery which was incorrectly blamed for very poor operation of the Thruster. After replacing the Spiral with a 110 Ah Leasure battery , I discovered the source of the problem was a badly pitted Forward/Reverse relay cotacts. I replaced the relay and this fixed the issue. Ive been operatin the thrusters for 2 seasons on the Leasure Battery with no issues. I think that the Spiral Wound battery was technically more suited to this job though and bean yo revert back to it.
Kinsale 373
It is fed directly from the House Batterys (ie ,)in parallel with the house batterys from the Alternator. There is a Breaker switch which cuts supply to the Thruster battery. I use this to disconnect the Thruster from the Battery Bank when in port or not requiring the thruster , so that the thruster Battery remains at high charge. I flip off the Thruster Breaker at the same time as I turn the isolation switch for the Engine Battery once I dock , no big deal , the system works fine. VSR would automate the need to manage this.
You will get a decent assist to the thruster from you Alternator when your engine is running through your 50mm sq charging cables. so I'd advise to charge from the alternator rather than from solar as mentioned earlier.
Originally I had a Spiral wound battery which was incorrectly blamed for very poor operation of the Thruster. After replacing the Spiral with a 110 Ah Leasure battery , I discovered the source of the problem was a badly pitted Forward/Reverse relay cotacts. I replaced the relay and this fixed the issue. Ive been operatin the thrusters for 2 seasons on the Leasure Battery with no issues. I think that the Spiral Wound battery was technically more suited to this job though and bean yo revert back to it.
Kinsale 373
Jeanneau Chris
Member
Following on from this useful thread I have a question. My (new to me ) boat has a side power bow thruster fed from a bow battery. There appears to be a pair of 4mm wires running to the engine start battery for charging? I can't find any fuse on these lines, surely there should be? What size would be ok? I guess its all ok as long as the bow battery stays in good condition and charged, otherwise , would the current now try and flow from the start battery via the small cables? I would like to fit something to put my mind at rest, perhaps just a fuse or a b to b charger?
Any thoughts very welcome
Thanks
Any thoughts very welcome
Thanks
C08
Well-Known Member
This is essentially what I have. I wondered what the current draw may be through these small wires with the thruster operating but failed totally to calculate that so I just have a plug isolating switch and a fuse to avoid me finding out by setting these wires alight, perhaps. I think you need a fuse anyway.
Jeanneau Chris
Member
Thanks Co8
Do you happen to know the fuse size you have installed?
Do you happen to know the fuse size you have installed?
PaulRainbow
Well-Known Member
If it's 4mm sq cable, fit a 40a blade fuse at each end. It's very important to fuse both ends, as each end is connected to a power source (battery).
rogerthebodger
Well-Known Member
That was my approach when I built my 50 ft 24 ton steel boat.
My bow thruster has a max current draw of 600 Amps being a Vetus 95Kgf thruster.
I fitted my aluminium buss bars 38mm x 25mm from battery to thruster to drive thruster and windlass .
The only issue I have is my battery isolation switches are not high enough current rating so do get some voltage loss.
12 off 110 Ah batteries in my domestic bank drive the thruster but I could also drive then from my engine start battery.
Colour of positive buss bars have been changed now to red.