Dedicated windlass battery forward

kappykaplan · Nov 15, 2013

Bob, when I bought my boat in 2008, there were two group 27s under the v-berth for the anchor windlass. During my first refit, both cables from the aft bus bars were replaced with new heavy gauge copper since the sheathing on the originals were compromised. You'll have less voltage loss if the windlass battery is forward.

Stu Jackson · Nov 15, 2013

Bob, first you need to get rid of the isolator, which imparts an almost 1.0V drop just when you need charging. Second, you have to deal with this non-uncommon "system design issue" of determining the trade-offs and options between, as you said, copper, weight and battery location.

From a truly simplistic electrical system point of view, the largest house bank running the windlass off that would be the preferred scheme. Why? 'Cuz you're running your engine when the windlass is running, so the house bank is being charged. If your house bank is close to the center of the boat, as most are, then you have to run heavy cables to the bow. It's a one time effort and well worth it.

Having a separate dedicated battery for any use on a boat (some thought having a separate battery for the electronics, another for the fridge, etc. was a wise move) has been shown to be an incorrect choice.

Benny17441 · Nov 15, 2013

First of all test the windlass for the minimum required voltage that will allow it to operate properly. Older winches might require more than rated for. Second see if you can supply that voltage with the longer run wires. I concur with Stu, it is best to keep it simple. A large battery bank will store more power than a single battery and will run a load for longer. You can keep your current recharge configuration.

Bill Roosa · Nov 15, 2013

If you do decide to go with a battery forward I'd wire it in parallel with the starter battery. The amount of Ah you are going to suck out of the forward battery is easily replaced (almost like a car battery application with the engine running) by the alternator. You would still have to have the cables rated for the windlass however as the potential for most of the amps coming from the alternator exists. In fact that was the reason we just used the starter battery (located under the galley sole) and heavy cables and only run the windlass when the motor is running. You really can't get around the heavy cables unless you have some sort of fancy isolation/charging device (don't know what that would be either)

Mark Maulden · Nov 15, 2013

Stu is right. I did it last Spring.

Ron20324 · Nov 15, 2013

Stu Jackson said:
...Having a separate dedicated battery for any use on a boat has been shown to be an incorrect choice.

If you have that "dedicated" battery up front undercharged - or dead- then you've got nothing for the windlass. Better to cable the windlass to the main bank. Also, it's better to lessen the weight in the ends of the boat, and have it as mid-ships and low as possible- usually.

Maine Sail · Nov 17, 2013

I am not a huge fan of batteries for individual components such as a windlass, unless 100% necessary.

It leads to the phenomenon I call "dead lead"...

Your start battery is already 99% dead lead but an unfortunate "must have" item. This means that 99% of the lead in this battery goes unused and you simply carry around this dead lead weight.

A windlass battery is nearly 96% dead lead. This capacity is put to far better use if added to the house bank where it won't be dead lead. It in-fact becomes beneficial lead when added to the house bank..

By adding the lead to the house bank you;

Increase house bank capacity
By increasing capacity you reduce DOD
By reducing DOD you increase cycle life
By increasing bank size you reduce voltage sag under load
By increasing bank size you capitalize on Peukert effect
By increasing bank size you have usable & beneficial lead not dead lead....

Bill Roosa · Nov 17, 2013

instead of a diode to isolate the battery you can use a solenoid. WM has examples. It's control circuit senses when the alternator is on and then connects the battery (with almost no voltage drop). Course this is another machanical thing to fail (at the worst time) that gives no warning so having some way to check wither the batter is seeing charging voltage is helpful. A volt meter and rotory switch to each bank works. Mount it on the nav station then run the small wires from each bank to the switch and then from the switch to the volt meter. Then you can check all the banks with little fuss. If you only have two banks you need to check a pushbutton momentary contact switch could be used. This prevents leaving the rotary switch in the "wrong" position and reading a good windlass battery when you think you are reading the house battery state of charge. And yes, I know using voltage as an indication of SOC is not what most folks on this site think is a good idea but it works for me. In any case you are only looking for wither the windlass battery is seeing charging voltage and not its state of charge.

Bill1565 · Nov 17, 2013

BobT said:
it. I'd prefer to use the existing cables for charging, install a grp 27 deep cycle in a box at the foot of the V berth (needs a step up anyway), and have nice fat, short runs of cable to the windlass. Battery charge management becomes the issue. Currently, the alternator feeds a Guest isolator box and the 65w solar panel feeds a Morningstar Duo controller. The banks are 2 grp 27 for house and 1 grp 27 for reserve/start. Could another controller be stair-stepped behind the single battery? Ideas and suggestions appreciated.

If , against all this advice, you elect to put a battery forward, make It a starting battery, not a deep cycle. Windlass s draw lots of current for short periods , just like starters

,

Maine Sail · Nov 17, 2013

Bill1565 said:
If , against all this advice, you elect to put a battery forward, make It a starting battery, not a deep cycle. Windlass s draw lots of current for short periods , just like starters

,

The "short period" rating for thin plate start batteries is 30 seconds before dropping to 7.2V. All things being equal, G-27 S to G-27 D, a deep cycle battery will hold a higher voltage for longer when using a windlass.... Some folks anchor and re-anchor multiple times before actually getting a good set, or the right location or swing room, and this can mean 6 to 10 minutes of off and on use...