Windlass Charging

[4arch]

Economy has been put forward as a reason for having a separate windlass battery, but I don't see the cost savings on a boat where the one-way cable run between the house bank and windlass is about 40 feet or less. The cost of the heavy gauge cable compared to a separate battery, battery box, combiner, etc. is about even. Once the cable runs get longer the equation does start to flip. But then there’s the fact that the windlass battery will have to be replaced from time to time while the cables should last 20+ years. I think what it comes down to is that it can be much easier said than done to run large cables aft (especially when it’s best to keep them out of low-lying bilges). The ups and downs/twists and turns can also eat up that 40 foot run pretty fast.

[Horror Hotel]

Just because some people choose to mount a bow battery for a windlass in no way makes it "best practice". I'd go as far as saying the opposite, worst practice. Keep the bow light, sure $800 of tinned wire is a bummer, thats yachting for ya.

[Cheechako]

There have been a lot of pros and cons discussed on this in a past thread on a new installation. I think the result was a pretty split opinion. I guess one question is, if you set it up right, do you really need very big cable run to the bow if you have a bow battery? I would think not. Not much differnt than a travel trailer with a couple batteries being charged off the main truck engine. Just dont run them flat and expect to recharge quickly. always keep the bow battery topped off.

[Horror Hotel]

Once the big wires are in the thruster install is that much easier. I went with 0/0 gauge, might do a thruster, but have a freeze wired to the windlass circuit .

[sailinglegend]

Originally Posted by djmarchand

...The Yandina website at How to add a remote battery bank on a boat. shows one approach...With this scheme you can use 10 gauge wire from the house to the bow battery....

You just have to do some math(s) to see how stupid this advice is using only 10 gauge wire.

If you want to rely on the alternator to supply some amps to the windlass battery then 50 amps current down the wire is going to help when raising the windlass AND charge quickly whilst motoring. 10 gauge wire will cause a 4 volt drop over a winding 40 foot run from the battery to the windlass. That's a 33% drop. For motors a 3% drop is considered "Best Practice", which means a 2/0 cable or 70mm². This figure has been checked on 3 voltage drop calculator sites.

A friend of mine had a very similar problem and I gave him the same answer. He didn't believe me and emailed a reader's letter to the UK Yachting Monthly magazine and got exactly the same answer from Mr Nigel Calder.

So you might as well move the battery further back and combine it with the house bank, and gain from having a much bigger bank, and still use 2/0 wire to feed the windlass. That's how my boat was supplied.

[Cheechako]

Hmmmm... not so sure you're "asking the right question". So lets say the actual run time to retrieve your anchor is at most 5 mins of windlass run. That may use up what..... 6-8 amp hours out of the bow battery? You now will replenish that while you are motoring. You might be motoring 20 minutes or you might be motoring 12 hours.
If 10 gage, or 4 gage or whatever smalli-sh wire doesnt work for this ... why not? As I mentioned earlier.. it does work for travel trailers.
The down side I see is if you have a entangled anchor or something like that.. once you mess around for an hour and use up your battery ,... you are SOL.
Just trying to figure out what's wrong with this thinking...?

[sailinglegend]

Originally Posted by Cheechako

Hmmmm....You might be motoring 20 minutes or you might be motoring 12 hours....If 10 gage wire doesnt work for this ... why not? As I mentioned earlier.. it does work for travel trailers.

Just trying to figure out what's wrong with this thinking...?

Travel Trailers would tend to motor long enough to charge the battery, and then at the end of the day most might plug back into a power socket. A boat might just motor on and off their mooring and anchor for two days, then 20 minutes of charging is not going to do much good as the volt drop along the cable will be so great they will never get a proper charge. Motor for 20 hours and they may get fully charged, but batteries like to be charged at their correct voltage to help stir up the electrolyte and stop stratification - not just put Ah back into the battery - that's what is wrong with your thinking.

My reference to a friend and his problem was because his windlass battery never charged up properly and finally the solenoid contacts failed and the windlass stopped working because of the chatter caused by a low battery voltage. He had a 10 gauge wired from his house bank to his windlass. QED.

[smac999]

Originally Posted by Cheechako

There have been a lot of pros and cons discussed on this in a past thread on a new installation. I think the result was a pretty split opinion. I guess one question is, if you set it up right, do you really need very big cable run to the bow if you have a bow battery? I would think not. Not much differnt than a travel trailer with a couple batteries being charged off the main truck engine. Just dont run them flat and expect to recharge quickly. always keep the bow battery topped off.

yes you need big wires. if the engine is running and you start drawing 80a for the bow thruster you are going to have 80a from the alt (assuming it's 80a or bigger and you're using something like an acr) going back into that battery while the windlass is running.

unless you are using a current limiter like an echo charger


plus if you run small wire you need small fuses at both ends. which might blow if the charge current spikes when starting the windlass. large cable = larger fuses = more reliable and less nuance blowing.

I don't know how a car trailer charger is set up. it must have a current limiter circuit it in otherwise it would be unsafe. considering most truck alts are over 100a now. if it was only relying on the wire resistance to keep the amps down that would be crazy.

[sabray]

My solution is run the cable. Use a solenoid for the on off. Fuse the battery links. The cost is nominal compared to the batts, cable run and work.


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