Windlass wiring

[firstascent2002]

Hi guys,

Putting in a windlass next week. The plan is to have a seperate battery in the bows and connect it to the windlass with 40A wiring. Obviously I need to connect this battery intot eh main system to charge it. Currently I have a single domestic battery (100AH) and a single cranking battery (85AH). They are charged from the engine alternator and via a rutland 913 throught the rutland cleaver box. Should I attatch this third battery in parrallel to the domestic battery?

Please someone tell me how its done!

J

 

[pvb]

What you’re proposing isn’t really the easiest (or indeed the cheapest) solution. By far the easiest way is to add the new battery to your domestic bank, in parallel, so you then have the benefit of a bigger domestic battery capacity. Then simply run suitably heavy cables from your domestic or starter batteries to the windlass. You’ll need a circuit breaker as close to the battery end of the circuit as possible. That’s all you need.

In contrast, if you go for a bow battery, you can’t just use thin wire to charge it. The windlass will usually be used when the engine's running, and the windlass will draw current both from the bow battery and down the charging cables. To prevent overheating in the charging cables, they must be heavy enough to carry a significant current. You’ll also need to protect the charging cables against overload with fuses or breakers. But, remember that, as there's a battery at each end of the charging cables, you’ll need a fuse or breaker at both ends. And you’ll need some way of isolating the bow battery - perhaps by having a VSR to feed it. The other thing to bear in mind is that a bow battery will get shaken about a bit more than the main batteries, so it needs to be very securely fitted, which probably involves a purpose-built glassed-in box with a tie-down facility (and it will also need some means of ventilation). Add up the cost of that little lot and, all things considered, it's probably easier not to have a dedicated bow battery.

 

[vyv_cox]

If you search the forum you will find a long thread on this subject from a couple of months ago, and doubtless numerous others. I think the consensus of opinion is as pvb says: you are better off running a pair of cables forward than trying to put a dedicated battery up there. I used welding cable when I did mine, cost reasonable and plenty big enough.

Adding a second domestic battery alongside your existing one is a far better option. Just connect it to the other in parallel, the only problem being that it is normally recommended that batteries in parallel should be of the same age. There is a risk that the old one will drag the new one down and shorten its life. I have no experience of this but others can probably advise.

 

[Billjratt]

Have to say I went for the third battery option. Thick cables between battery and motor/switchgear, heavy mains cable (like on your water heater at home) back to the charger area, where there are three big diodes on heatsinks to split the charge from the alternator and mains charger. Remember that when winding - yes the charger will be replenishing the battery, but most of the oomph will be from the battery it'self. the long cable doesn't need to carry more than the chargers can supply (less the amps that are being stolen by the other batteries). Once the lump is up, all the batteries share the available power. A voltmeter is a handy guide for charge level if you intend to run the engine for a while.