Bow Thruster Charging Circuit

[Knodty]

Hi Guys, 

My first post on here and fairly new to owning our own boat. Our bow thruster has been working for the last year of ownership, and has just suddenly packed up. I carried out electrical tests and realised the Battery was completely flat, only 1.0 volts. Not knowing how long this has been not charging and just working off the battery voltage. We haven’t used the boat for a 3-4 months now and the thruster worked ok beforehand. 
Tracing the Charging cables back to the engine bay it has a Victron Cyrix-CT fitted inline on the charging circuit. It has voltage going to it but not through it. Is this needed on the charging circuit or can it be omitted?

Being new, to the somewhat complex nature of boat electrics, and trying to get my head around, how all the different systems work, it doesn’t seem straightforward to fit this to a charging circuit, and over complicating the system. 
I’ve had classic cars for over 30 years and have always worked on their electrics, and I’m not a beginner. I’m just wondering if I am missing something, as to why this is needed or been fitted in error?
 

Thanks Guys

Peter 

[Smoggy]

I don't know the answer and in my defence I'm currently drunk but that looks like a voltage sensing relay that should pass a charge when volts are high enough (engine running/plugged in) so may have failed.

If battery is at 1.0v it's deader than a very very dead thing, if at 10v and the decimal is a mis-type it's close to the same death buy may recover enough for a few months but I wouldn't trust it.

[OldBerkshireBoy]

Split charge relay.

https://www.victronenergy.com/battery-isolators-and-combiners/cyrix-battery-combiner-kit

 

[Knodty]

Is there any need for it in the charging feed to the Bow thruster Battery. As far as I can see it is only wired through it to the battery?

[Knodty]

[Vaughan]

I don't know how your circuits are wired, but it sounds as though your thruster has a separate battery, with its own split charge.  In other words, in addition to the starter and domestic batteries.

Firstly, the thruster itself would not have drained the battery down to one volt, so something else must be wrong with it, such as a dead cell.  In which case, there may be nothing wrong with the charging circuit itself.

I also see what looks like a fast fuse in your last photo.  Best check that as well.

Unless it is a very large thruster, it should not need its own dedicated battery and can be run happily off the starter battery, on the principle  that you only use the thruster when the battery is on charge, with the engine running.  You may find that simpler, and cheaper than buying a new battery.

Do not feed the thruster from the domestic batteries, as they are slow discharge, and may not have enough CCA (cold cranking amps).

edited to add:

Welcome to the forum!

[MargeandParge]

Hi I think some thrusters use a separate battery due to length of large cables and run smaller ones to charge it with 

Regards Marge and Parge 

[NeilB]

1 hour ago, MargeandParge said:

Hi I think some thrusters use a separate battery due to length of large cables and run smaller ones to charge it with 

Regards Marge and Parge 

My new thruster is some distance from the battery bank and due to the cable size and length required it was cheaper to add a battery near the thruster.  In addition it supplies the mud weight winch and is charged via a voltage sensitive relay shared with the engine start battery.

First job is to replace the battery and then check if it's charging.  It's probably a faulty cell but I'd also check there's nothing else attached to it and draining the power.

[Knodty]

Thanks guys, 

Vaughn to answer some of your points raised. 
The fast fuse mentioned has continuity. The Thruster does have its own battery I have 5 on the boat, 1 for each engine two for domestics and 1 for the thruster. Thruster is 110 CA if I remember correctly and I’ve taken it home to charge overnight. I checked it once disconnected from the charger this morning and it was showing 12.7 volts and will check it tonight to see how much it has dropped by or if it is holding a charge. That battery is not charging as I mentioned in the original post, as I have no voltage after the Cyrix-CT module. 
My main question was can I remove the Cyrix-CT or is it needed on this type of circuit?

Regards

 

Peter

[Vaughan]

10 hours ago, Knodty said:

I am getting a bit confused, when I start to think about this.

The Victron box as linked by Old Berkshireboy is a battery combiner, which is normally used in a vehicle towing a caravan, and avoids the need to fit the vehicle with a separate split charging circuit.  In that case, heavy duty cables are not needed as caravans don't have bow thrusters!

I see here that the black box has two terminals which are a physical break in the heavy duty "starter" type red cable.  The small black wire will be the 12v circuit from the key, to excite the relay.  As the photo is obvious taken in the engine compartment, why is heavy duty cable being used, if it is to separate a thruster battery up in the bows?  As Marge and Parge rightly says, that would mean that only a smaller size cable would be needed, just to provide a charging circuit, from a conventional diode splitter?

One way or another, a normal size thruster will be about 1.5KW at 12V, so about 125 amps draw (hence the thick cables) but only for a few seconds.  Some types will cut out after 10 seconds, before they overheat.

[Vaughan]

31 minutes ago, Knodty said:

That's quite a big one then.  Draws 370amps, so the website says!  Giving 4hp of thrust. The smaller Vetus thruster is much less powerful.

[Smoggy]

On a different note I've never really understood the need for a separate battery for each engine, I just have the one engine battery for both engines as you never start them at the same time (I have done once to see if they would and it was no problem at all including 30 seconds of pre-heat on a cold day) and if low you can always give a boost from the domestic bank, most domestics nowadays are dual purpose rather than purely deep cycle anyway.

Surely one of those batteries would be more use in the domestic bank.

[Islander]

Just looked at the spec pdf (sorry for quality of cut and paste) please note the delay time for the relay to cut in I.e. 10 mins at 13v and still not instant with voltage above 13.8v. Also note that start assist is available and if used cabling should be of a appropriate gauge.
 

Colin 

del
  Cyrix-ct 12/24-120
  Continuous current
   120A
  Maximum alternator rating
 150A
  Auto ranging
  12/24 Volt
  Connect voltage (delay appr. 10 minutes)
   13V / 26V
  Connect voltage (delay appr. 4 seconds)
 13,8V / 27,6V
  Disconnect voltage (delay appr. 10 minutes)
  12,8V / 25,6V
  Disconnect voltage (delay appr. 4 seconds)
   11,8V / 23,6V
  Over voltage disconnect
 16V / 32V
  Current consumption when open
  <4 mA
  Emergency start
  Yes, 30 sec
  Protection category
   IP54

[Knodty]

10 minutes ago, Islander said:

Just looked at the spec pdf (sorry for quality of cut and paste) please note the delay time for the relay to cut in I.e. 10 mins at 13v and still not instant with voltage above 13.8v. Also note that start assist is available and if used cabling should be of a appropriate gauge.
 

Colin 

del
  Cyrix-ct 12/24-120
  Continuous current
   120A
  Maximum alternator rating
 150A
  Auto ranging
  12/24 Volt
  Connect voltage (delay appr. 10 minutes)
   13V / 26V
  Connect voltage (delay appr. 4 seconds)
 13,8V / 27,6V
  Disconnect voltage (delay appr. 10 minutes)
  12,8V / 25,6V
  Disconnect voltage (delay appr. 4 seconds)
   11,8V / 23,6V
  Over voltage disconnect
 16V / 32V
  Current consumption when open
  <4 mA
  Emergency start
  Yes, 30 sec
  Protection category
   IP54

Colin you mentioned that it can be used for start assist, however it is not wired in the configuration, so can it be omitted?

 

Peter

[annv]

Hi Peter The thruster battery's often dont get maintained as they are often tucked away my advice would be to remove the battery and power it from the engine battery vie 100amp welding/battery cable this removes all the maintance and auxiliary switches, fuses, relays etc. the cost will be the same or less than a new battery John

[annv]

Hi Peter Also just to add battery's dont like being left unused, its good practice to wire your battery's up to a battery maintainer or solar panel just to keep them fully charged over the lay up period otherwise over time  they self discharge and die, and wont take a charge, which i suspect has happened in your case.  ideally you only need one engine battery and up to four domestic battery's for the average broads boat, these need to be charged via a alternator with a modified regulator to maximize the charge rate for shortest engine running time, or even better two alternators as fitted now to new boats.  this then only requires two battery isolator switches, by keeping it simple makes for greater reliability and less stress. John

[annv]

Hi Peter in your case with two engines i would charge engine battery from one engine and domestics from the other engine which will only need for one modified regulator on this engine then if you have to charge domestic bank up while moored you only need start the one engine. John

[Knodty]

I really appreciate all your input guys, however nobody has answered my main question. Can I omit the Cyrix module, Yes or no? If no, why not?

 

[grendel]

considering its a split charge relay, I would imagine that if it was omitted then the battery would try and share with any other batteries on that circuit, which means that if something caused the battery to go flat, it might well take the starter battery with it, plus when you cranked the engine it would possibly try and draw power from that battery through the charging cables, which might well exceed their capacity and cause them to overheat, possibly catch fire. the split charger is there for a reason so probably best left in circuit, the split charge relay may not be faulty, as others have said above, it can take ten minutes for the thing to cut in (to ensure the starter battery has received some charge before diverting the power to charge the auxiliary battery)

might there be a better way of doing this- maybe, but some form of separation must be maintained.

 

[Knodty]

Great thanks Grendel,

I understand it a little more now. I had the engines running for at least 30 mins the other day and there was no sign of it switching over to my knowledge. I will have to check it again when I’m next on the boat. I think I will get a replacement just in case. I seem to remember a few months back noticing that the thruster was not sounding as powerful as it was, which might have been the start of the fault in question, and the battery not charging properly. Would this switch over happen once the voltage in the starter battery had recovered enough, and then it switches over to start both batteries together?

What does the black wire under the module do, is it used to energise the Cyrix to switch over? 
 

 Peter

[Vaughan]

I think we must be clear that this not a charge splitter.  As I said above, it is a battery combiner.  When it is not excited (by the small black wire), it physically separates two batteries, not just the charge to them.  You can see this by the two large terminals, which make a physical break in the main feed to a battery.

I am still trying to work out in my mind why someone would want to do this in a boat and until I do, I cannot advise you whether this box is necessary as I don't know what it is supposed to be doing!

I am beginning to wonder, even, if this is to connect the starter battery in series to the thruster, to provide 24 volts?  I am not sure whether this would actually work in practice, as I have never thought to ty it, although I know that a boat with dual voltages can still use the same common negative return.

That thruster draws 370 amps, which is getting on for twice the draw of a Nanni starter motor, and running for a lot longer.  It may be that your thruster battery doesn't have enough CCA to drive that, without bending its plates and thus causing one or more cells to short out.

Do you know the CCA rating of the battery and do you know if the thruster is 12 or 24 volt?

 

[MargeandParge]

I am a numpty as you all know by now but would it stop the batteries connecting and shoving the big amps down the small charge wires. Back to my cuppa. 

Regards Marge and Parge 

[Vaughan]

1 hour ago, Vaughan said:

Do you know the CCA rating of the battery and do you know if the thruster is 12 or 24 volt?

It appears from the website that your thruster is 12 volts, so that cuts out my 24 volt idea!

I see that they recommend a minimum battery size of 600CCA (EN rating) for this thruster.

CCA is the current available at -18º C for 30 seconds, whilst maintaining a cell voltage of 1.2 per cell.

MCA (marine cranking amps) is the same principle but based on 0ºC.

I would think 800CCA would be sensible, remembering that if a battery is not fully charged, it needs more CCA to turn the thruster motor.

This still leaves the question - why fit a battery combiner?  Unless this is not the thruster circuit and is actually to parallel the two starter batteries if necessary?  In which case, that black box is not suitable and it would need a manual "master" switch.

[Islander]

Just my thoughts. The bow thruster is a later fit and not part of the original electrics. 

The cables to run from one of the existing batteries to provide 350A over a long distance with minimal loss would be excessively expensive so a cheaper option was chosen. I.e. 110Ah 800cca placed next to bow thruster and much smaller charge cable. 
Rather than a charge splitter an intelligent combiner relay has been used.

We have the same thruster on Lady Linda. The cable thickness required from the existing starting battery would have been way in excess of another battery and associated charging components. In our case the alternator was upgraded feeding a Victron get 3way FET splitter (start, domestic and bow thruster) and a Victron 3way mains charger. 

You may also find your little black box will need a minimum voltage on its thruster side for it to engage. If a half decent battery doesn’t spring the relay into life, I would give Victron technical a ring, I’m sure they will tell you the best way to test it.  
 

Colin 

[Knodty]

 

This is the diagram from Victron and as far as I can see from tracing the wires it is not wired as the diagram. It is wired through the cable on the charging circuit  from the alternator not the battery. This is why I asked if it was installed incorrectly?