Fitting a windlass... local battery charging from alt or wire to house battery

[smeaks]

I am fitting a windlass options

1) fit seperate battery locally in forecabin with isolator from the charging system then limit the run on the motor control feed cables. What diameter cable would be needed to charge it?

2) run the cables direct from the house battery but utilise a larger cable to limit the v drop...... again what size of cable ....? boat is 31 ft

thanks

smeaks

 

[VicS]

I am fitting a windlass options

1) fit seperate battery locally in forecabin with isolator from the charging system then limit the run on the motor control feed cables. What diameter cable would be needed to charge it?

2) run the cables direct from the house battery but utilise a larger cable to limit the v drop...... again what size of cable ....? boat is 31 ft

thanks

smeaks

The answers to both questions depend upon the total length of the cables ( Positive + negative) and the current involved. In the first case the expected charging current , In the second case the windlass current. The latter probably being more critical as excessive volts drop would affect the windlass performance whereas in the first case it would only extend the charging time.

I suppose we could make a guess at around 40 to 50 ft for the total cable length but need to know the current expected in both cases

 

[Rafiki]

In my previous boat of very similiar size I powered the windlass from the Engine starter motor on the grounds that;
The engine battery would be fully charged when anchoring and more than likley would be under engine when anchoring, similiarly when hauling up the engine would already be started. Worked very well for 8 years.
As regards size I think I used 25mm, but I think ideally it would have been larger, maybe 35mm.

In my current boat I have a dedicated forward battery for bow thruster and windlass, the charging cable from engine/shorepower is 50mm ( boatyard fitted it so probably over specified) however the cable from the forward battery to the windlass is a lot smaller 25mm for part of the length but probably only 10mm for the last section from the relay to the windlass motor.

 

[prv]

At 31 feet I suspect the tradeoff between cable length vs space and weight in the bow will favour the cable. Certainly the cable option works better for me with 34 feet, albeit the batteries are under a seat at the aft end of the saloon rather than under a quarter berth as often found.

I regard the engine-start battery as dedicated to that job, and I frequently depart under sail without starting the engine. So my heavy windlass cables are wired to the far larger main battery bank.

Pete

 

[William_H]

I would go for the heavy cable option rather than another battery. olewill

 

[PaulRainbow]

I always wire my windlasses to the engine battery, for the reasons Onia cites, also never had a problem. My current boat is 33ft odd and the cables are 50mm sq, any less and voltage drop will be an issue.

 

[RupertW]

I always wire my windlasses to the engine battery, for the reasons Onia cites, also never had a problem. My current boat is 33ft odd and the cables are 50mm sq, any less and voltage drop will be an issue.

Mine is a 42ft boat and I inherited the same arrangement which works fine. I could not use the windlass unless the engine ignition is on (so either squeeling its alarm or actually running). I must be losing charging power to the domestics by not having a dedicated battery in the bows but that problem is negligible compared to the other drains on the batteries.

 

[PaulRainbow]

Mine is a 42ft boat and I inherited the same arrangement which works fine. I could not use the windlass unless the engine ignition is on (so either squeeling its alarm or actually running). I must be losing charging power to the domestics by not having a dedicated battery in the bows but that problem is negligible compared to the other drains on the batteries.

Mine is slightly different, as i only need the engine isolator on, not the ignition. I'd guess that you have a relay that is intended to prevent the windlass being used without the engine running.