Bow thruster battery

[markleuty]

When we bought our new to us boat I was a bit confused by the batteries.

She started life having 1 x 110ah starter battery, for a volvo d2-55 and 2x140ah batteries in parallel as the house batteries.

The windlass is connected to the house batteries.

Then the previous owner had a bow thruster fitted.

The people who installed it, put a new 110ah battery in the forward locker for the bow thruster. This they connected with very thick cables in parallel with the starter battery. So now i effectively have a 220ah starter battery that the engine and bow thruster share.

All these batteries are on the starboard side..

We list a bit too starboard but that is probably a different matter..

My question is, do I need 220ah for engine and bow thruster or could I lose the battery up front and just use the big thick cables to connect direct from the bow thruster to the starter battery or possibly the house bank?

Thanks

Mark

Ps. This was typed on my phone and for volvo, the auto correct suggested, volcano, bolton and b*ll*cks!

 

[LionsDen]

The windlass is normally connected to the starter battery bank and only normally operates when the engine is running.

Please advise firstly why you want to remove the bow thruster battery so we can answer this part.

 

[Phoenix of Hamble]

You could use the big thick cables (that's what i'm planning to do on my installation underway).

Only, to be absolutely clear.... by big thick cables, You MUST mean big thick cables.... serious heavy cables... min 50mm2 or bigger if a long run.... and they are expensive!

Mine, BTW will be off the starter battery, not the domestics.... for two reasons... one I never run the windlass or bowthruster without the engine started, and two, if I run them off the domestics, then I get in a mess with the battery monitor and shunt.

 

[alant]

When we bought our new to us boat I was a bit confused by the batteries.

She started life having 1 x 110ah starter battery, for a volvo d2-55 and 2x140ah batteries in parallel as the house batteries.

The windlass is connected to the house batteries.

Then the previous owner had a bow thruster fitted.

The people who installed it, put a new 110ah battery in the forward locker for the bow thruster. This they connected with very thick cables in parallel with the starter battery. So now i effectively have a 220ah starter battery that the engine and bow thruster share.

All these batteries are on the starboard side..

We list a bit too starboard but that is probably a different matter..

My question is, do I need 220ah for engine and bow thruster or could I lose the battery up front and just use the big thick cables to connect direct from the bow thruster to the starter battery or possibly the house bank?

Thanks

Mark

Ps. This was typed on my phone and for volvo, the auto correct suggested, volcano, bolton and b*ll*cks!

Its normal, for the bow thruster battery to be close to the thruster, more efficient leckywise.

 

[EugeneR]

As above, you could remove the front battery however it is critical that the cable and all connections are capable of carrying the current required by the thruster. If not, not only poor performance but fire risk.

I would use the engine battery, first because I normally use the thruster when engine is running and secondly because the house battery might get run down more, leaving you with a poorly performing thruster.

 

[Marsupial]

In case you don't realise this is what is going on with your installation.

The thruster battery does really need to be close to the thruster, any voltage drop is bad news for thruster power.

The thick cables are there to allow the thruster battery to charge - so why are they so thick? if they were just charging cables they could be thin? sorry no! they are correct.

IF the thruster battery fails the thruster will try to get its power from the next available battery - in your case its the starter battery. So 400 or so amps is supplied from the starter battery to the thruster - hence the big cables.

In any case Kirchhoff's law has to be obeyed and unless you have a completely isolated charging regime for the thruster battery there will always be a load on the starter battery via the charging wires when the thruster is used as some current will be drawn from the starter battery.

The good news is that should the starter battery fail the starter can get its power from the thruster battery - all very well in theory but as I have found it depends on how the errant battery fails, mine failed in such a way as the only solution was to remove the failed battery from the bank before the other battery would take over the load. I think is was because the the good battery was trying to dump its charge into the failed battery so nothing worked but the duff battery became very hot. Its a theory I didn't cut the battery up to see what went wrong.

In your case I would add another 110AH battery to the port side in the bow to balance up the boat and make the thrusters life even easier.

 

[LionsDen]

We have 2 number 125amp starter batteries located in our lazarette which also handles the windlass and bow-thruster - no battery is located in the bow area and this works ok.
Plus we also have 4 number 125 amp auxillary batteries.

I note that you have a single D2 55hp engine so I do not feel you need any more starter batteries than you already have imho - fyi we have 2 number D6 435hp lumps which with the above kit is handled ok by our 2 number starter batteries which is all a factory fit. Princess should know what they are doing when building these things

 

[Andrew G]

Unless you are worried about the weight of the battery in the bow I would prefer it there (closer to the drain on it) but I'd use it for both the thruster and windlass (how often do you use the windlass and thruster together??).
I would not have the windlass running off the house batteries - especially if only 2x140Ah on what I assume is a reasonbly large boat (55hp donk and thruster). The engine should be running at charging revs when using AND AFTER using either the windlass or thruster to fully charge the bow battery before shutting down. Partial charging will kill it. I have digital voltages for each bank near the engine shut down. The windlass probably had thick cables too (should have) - these may be now redundant if the other cables are much thicker.

I'd connect your bow battery via the very thick cables to your charging sources via Voltage Sensing Relay(VSRs) so that when the (now 1) starter battery is at 13.8V the house and bow batteries get charged. One starter battery should be OK but I have set mine up so I can quickly connect (jumper with wing nuts) from house to bow to starter - yep I can connect all 5 together.

The wind generator and solar go into the house bank (3 x 120Ah AGM) the alternator into the starter. I have two VSRs (one dual sensing) so that when the starter is at 13.8 the house bank gets charged and when either the starter or house are at 13.8 the bow battery gets charged. Cheers Andrew.

 

[William_H]

The simple answer as to the capacity of the cables from engine battery to thruster or windlass is to try them one at a time with the local bow battery disconnected.
IMHO they both should run from the engine battery. Interesting that if there are cables from the aft engine area to both the windlass and thruster then these cables could be connected together so doubling the cable capacity. ie connect the 2 positive cables to the engine battery (through a very large fuse and or isolator switch) The other end of the +ve and -ve should also be connected together. and so connected to the windlass and thruster controllers. This concept does rely on the high current switching being at the bow which it probably is. You could still keep the bow battery but with heavy wiring (doubled up) you should not need a bow battery. You can then use it to add to your domestic batteries.
Don't worry too much about the engine battery. It should be able to take a fair bit of high current discharge especially when being augmented by the alternator. Plus you surely can bring the domestic batteries in parallel if needed for emergency start.
Doubling up the engine battery is OK although some engine manufacturers might suggest too big a battery for the engine can overheat the starter. ie it is designed to crank on 10 volts and big battery might hold up 12v. What is important if you leave the system as is, is to occasionally try both the engine and the bow battery at engine starting on their own. A dieing battery can be disguised by a good battery in parallel until both die. Not so much of a concern with your demestic batteries as a backup.
Certainly in the long run less batteries means cheaper to run as replacement will be cheaper. good luck olewill

 

[Marsupial]

We have 2 number 125amp starter batteries located in our lazarette which also handles the windlass and bow-thruster - no battery is located in the bow area and this works ok.
Plus we also have 4 number 125 amp auxillary batteries.

I note that you have a single D2 55hp engine so I do not feel you need any more starter batteries than you already have imho - fyi we have 2 number D6 435hp lumps which with the above kit is handled ok by our 2 number starter batteries which is all a factory fit. Princess should know what they are doing when building these things

you have a planing hull power boat, the difference between that hull type and a sailing yacht is important in terms of where you put the weight so Princess have compromised on the electrical installation by putting the batteries aft so you can get on the plane easier and have a bow thruster, weight not such a problem on a yacht. In fact more weight in bow is what is needed sometimes to keep the bow down so the thruster will work.

The BEST solution, not just one "that works" is for the batteries to be as close to the bow thruster as possible, all the "issues" that we have when we do this concern how best to charge them and not create a path for high current that would fry small conductors and set the boat ablaze from stem to stern - hence the large charge wires. The BEST solution for charging them is to have a isolated independent charging system but that is very rare and costs more than big cables.

Being even more "correct" the characteristics of a thruster battery (High cranking current) are not those of a house battery so that is why they are usually banked with the starter battery which should be of the same type; my own cynical response to this that In practise of course most batteries are same except for the label.

For cheapness many manufactures run the windlass off the starter battery and just run large cables to the windlass relay, but when they fit a thruster they fit the thruster batteries in the bow because of voltage drop and use the windlass cables as charging cables if they are big enough. I did n't think mine were so we added more CSA.

You could always ask the Nijad owner whose boat caught fire in Leftkas a couple of years ago what he thinks about about undersized cables and batteries a long way from the thruster - the first time he used the thruster in anger the boat caught fire, no-one was hurt but undersized conductors were the problem.


edit: the boat caught fire when docking in Leftkas, the thruster wasn't fitted in Leftkas. It was an upgrade, I don't know if the original was Nijad fit or not but the increase in the thruster size could not be accommodated by the existing cables.

 

[Aurai]

There is an alternative approach

Which supports a dedicated battery for the Bow Thruster/Windlass up front.

However, use an Echo Charge sensor, to take charge from house batteries as and when it is available and you only need "thick" cables from Thruster/Windlass to the now close by battery.

I can send you a wiring diagram that works for us.

Cheers

 

[EugeneR]

There is an alternative approach

Which supports a dedicated battery for the Bow Thruster/Windlass up front.

However, use an Echo Charge sensor, to take charge from house batteries as and when it is available and you only need "thick" cables from Thruster/Windlass to the now close by battery.

I can send you a wiring diagram that works for us.

Cheers

This is what I chose as well. The main reason for this, for me, was to avoid the expensive cables. However, OP already has those - assuming they are thick enough not to drop voltage to much.

 

[markleuty]

Many thanks for all your replies.

They make very interesting reading.

I think I'll probably go for hooking the windlass up to the bow thruster battery at the front, rather than the domestics and then some sort of VSR charging arrangment from the the starter battery.



Mark

 

[Marsupial]

Many thanks for all your replies.

They make very interesting reading.

I think I'll probably go for hooking the windlass up to the bow thruster battery at the front, rather than the domestics and then some sort of VSR charging arrangment from the the starter battery.



Mark

Good luck, don't forget the fuses!

 

[Boathook]

My bow thruster battery is connected to the main bank by an Adverc 12/12 battery charger. This charges the BT battery at about 4 amps once the main batteries are topped up. Has worked well for many years and now a windlass is connected to the BT as I can't see both being used at the same time unless I grow an extra pair of arms ! The whole is suitably fused too cable load, etc.

 

[john_morris_uk]

I remain unconvinced by all the people who are adamant that the battery needs to be in the bow. I know why they say it, but its not necessarily the only solution.

I completely understand the arguments involved yet we don't have a 'bow battery' and the anchor windlass works perfectly and I have no worries.

This is because it IS connected with very large welding cable type wires. The cabling is impressively large; ie at least as big or bigger than the engine starter circuit cabling. The main battery bank is more or less in the middle of the boat so the run is about 6 metres.

Interestingly our windlass is run off the domestic bank but I still tend not to use the bow thruster without the engine running. In fact it's better to be run off the domestics in our case as I wired the smart alternator charger that charges through a diode splitter to be voltage sensed off the domestics bank.

 

[Marsupial]

I remain unconvinced by all the people who are adamant that the battery needs to be in the bow. I know why they say it, but its not necessarily the only solution.

I completely understand the arguments involved yet we don't have a 'bow battery' and the anchor windlass works perfectly and I have no worries.

This is because it IS connected with very large welding cable type wires. The cabling is impressively large; ie at least as big or bigger than the engine starter circuit cabling. The main battery bank is more or less in the middle of the boat so the run is about 6 metres.

Interestingly our windlass is run off the domestic bank but I still tend not to use the bow thruster without the engine running. In fact it's better to be run off the domestics in our case as I wired the smart alternator charger that charges through a diode splitter to be voltage sensed off the domestics bank.

John,

Its all about losses, as you say you can have the batteries a distance away and to compensate you need very large conductors to mitigate the losses. The manufactures of thrusters and windlasses suggest a preferred installation and this includes mounting the batteries as close to the motor as possible. I remember very well the extensive discussion in the motor trade when the MK1 mini was launched (yes 1959) with the battery in the boot, it did work but the fact remains it cost a lot in cables, if small gell batteries were available back then perhaps the installation would have been different, I am sure it would. The boat situation is slightly different when we have two batteries, as the path for high currents has to be taken care of if the charger is in parallel to another battery bank (you dont have that problem) - I am not convinced that light (relative) charge cable and VSR's with on demand charging achieve this requirement while the bow batteries and others are being charged at the same time by the same charger and the equipment is in use (not your installation) - fit lots of fuses.