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First recorded activity by BoatBanter: Jul 2006
Posts: 1,301
Default Alternator size vs Windlass current

Would you really use the windlass for 5-10 minutes? Probably more
like 2 minutes usually. And the current won't be 90 Amps just lifting
the anchor (unless its huge and you're in 500 feet of water), the max
draw would only be if you straining, something that almost always
unnecessary. In wind you should drive the boat up over the anchor,
but in light air you can pull the chain tight, then let the weight of
the chain pull the boat up - repeat a few time until you're over the
hook and wait for the bobbing of the boat to work it loose. The net
result may be more charge in the bank than when you started

And the shortfall isn't really that bad, since running the engine for
a few more minutes is going to recover it. This is what batteries
are for. You're talking about 10 Amp-hours even in your worst case
reckoning. If you have a large DC fridge, you could consider turning
it off - we do that on occasion if we need to run the engine at top
RPM to make a bridge opening, etc. But more often than not, I've set
my regulator down to 30 amps if I'm expecting to use the engine long
enough to charge the bank.

I wouldn't worry about this at all. As for the wire, the WM catalog
has the chart - that should tell you if the size is right, but it
seems a bit small. Some people add an extra battery at the windlass
that can be charged with low current, but that seems complicated. If
you want to add, enlarge your house bank - that's always a good thing.

GBM wrote:
I am still trying to decide on a windlass for our boat. Perhaps some the
experienced cruisers can help?

Our alternator output, is nominally 55A, but likely actually quite a bit
less. Max size alternator recommended for Yanmar 2QM15 engine is about 80A)

Some suitable horizontal windlasses for a 32 ft boat draw as much as 90A
(e.g. Quick Eagle 500/700)

If we have the engine running at say 1500rpm while pulling up the anchor, we
may be putting about 35A into the 200AH house bank, if we are lucky. At the
same time, the windlass is drawing up to 90A and other items like the refrig
unit are still drawing current. We could have a shortfall of 60A for 5-10
minutes.

Question: Would I be better to buy a somewhat undersized windlass that might
only draw 35A? (e.g Lofrans Dorado with gypsy on wrong side ) or buy the
larger unit and draw a bigger current?

GBM

(PS: I have 6 Ga wiring already installed, but will change if need be)




 
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