Placement of windlass battery

On another forum, I replied to a question about where to place a windlass battery. I know that some of the participants on this forum also participate on that forum but not all do. I decided to post my response here:
——-

Please allow a current powerboat owner (former sailboat owner) provide a comment to this knowledgeable group. We sell our anchors to sailboat owners and I always try to ask about their entire ground tackle set-up. I learn a lot and can also then offer some suggestions and recommendations.

Some of my sailboat customers have found a separate dedicated windlass battery below the V-berth area to be quite good in not losing voltage over a long cable run from the rear of the vessel. The challenge then is how to charge the battery? Options typically include either solar panels, wind generators, or alternator charging from the engine. I did not mention shore power because it is probably understood that if docked and plugged in to shore power, some sort or battery charging system would include charging the dedicated windlass battery.

Solar and/or wind power can work to charge batteries underway. However, lots of my sailboat customers on the Chesapeake Bay and on the ICW of the East coast of the US admit they spend a lot time under power and not sailing. Unfortunate but happens that way. In those cases, when there is no auxiliary generator on the vessel that can charge battery banks while underway either with the main engine running or the sails up, the following system seems to work well:

1. The windlass is tied into the house bank.
2. Heavy cabling (0000) is run from bank to windlass to minimize the drop in electricity.
3. The main engine, while running, first charges the house bank then some combiner type device or relay switches the power supply from the alternator to the house bank to the start battery (when the house bank is satisfied). Typically the start battery does not require a lot of charge on a properly tuned and functioning engine. Also, some of these folks have their solar and/or wind generator charging tied into to charge the start battery.
4. Minimize the electric draw from the windlass: utilize more of a “free fall” when deploying the anchor and use the main engine to help reduce the strain on the engine motor (and electric draw) by powering forward to create a slack chain or rope rode and not using the windlass motor to pull the boat toward the anchor. Also use the main engine to “break the anchor free” from the bottom and not the windlass motor. These steps minimizes the electric draw of windlass (there still is a significant draw) and saves the windlass motor.

On my prior vessel, Willard Trawler, I had this setup with a large as possible house bank of 6 volt batteries in series and parellel and a dedicated start battery. There was a 000 cable to the bow thruster and the windlass (never operated both at the same time). There was a combiner that directed the alternator charge first to the house bank then to the start battery. Never a problem with power to the windlass or the bow thrurster.

Now a new boat (power) to me. Came with an undersized house bank to safely anchor all night with sufficient power and a start battery that supplied power to: main engine, generator start, windlass, and bow thruster. The battery banks and arrangements were not to my liking so I re-did to a simlar arrangement of my prior trawler.: large house bank serving house, windlass, bow thruster, and inverter devices. This bank has a dedicated charger/inverter. Dedicated start battery to just the main engine. That alternator charges the start battery first and then supplies the house bank. Dedicated generator start battery. New charger just for the two start batteries.

I know this system might not work for sailboat owners but the concept might work. I know it does from some of my customers.

Steve:

Bowthrusters often have a separate battery in the bow of the boat as the current required can be very high- as much as 400 amps and that much current will cause a significant voltage drop on a long run up to the bow, even with 4/0 cable.

Windlasses draw less current than bowthrusters, often less than 100 amps and some less than 50 amps. In that case a long run to the bow, even if just 1/0 cable will result in a reasonable voltage drop. A round trip length of 50' and a current draw of 100A results in a voltage drop of only 0.5 volts with 1/0 cable. So most installations power the windlass from the house battery with 1/0 cable up to the bow or even smaller if it is a smaller windlass.

A word about secondary battery charging. If you use a combiner, ACR, Echo Charger or similar to charge your starting battery then when the house battery gets mostly charged, any charging source tied to the house- solar, wind, engine alternator, shore power charger will cause the two systems to be combined when the voltage on the primary system rises to 13+ volts.

David

In short, all charging should be directed to the house bank. An echo charger(DC to DC charger) or a SACR (smart automatic combining relay) should be used to direct current to the start battery an additional one for the windless battery. Since these devices max out at 25 amps you only need to use 4 gauge wire instead of 0000 gauge(this is an estimate, length of run determines guage).

David,
I do not disagree the bow thruster cannot does draws a lot. However, that draw can be managed as well (for a different topic). The yard who did my battery arrangement and the bow thruster manufacturer agreed with the current setup as being acceptable. Part of my rationale is that when the bow thruster is used:
1. After running for a while the house bank is completely charged. In the docking process, I use the thruster, tie up, and plug in. Whatever discharge occurred is handled by plugging in to shore power. I have checked house bank voltage after docking and before plugging in and it has never been a discharge of the bank where I become concerned in the least bit.
2. Leaving a dock. Batteries are fully charged and I use the thruster to exit. Of course there is a discharge (usually less than docking because I typically dock stern in so the exit is easier). Again, since I am now running the engine, the alternator is charging the house bank. No issue there.

I do not use the bow thruster in anchoring.

I have a friend who always turns his generator on prior docking or exiting a dock or anchoring or retrieving an anchor. He feels having the additional charging provides more assurance of minimizing the discharge when using these two big draw devices.

To each their own.

Steve

djmarchand said:

Steve
Bowthrusters often have a separate battery in the bow of the boat as the current required can be very high- as much as 400 amps and that much current will cause a significant voltage drop on a long run up to the bow, even with 4/0 cable.

Windlasses draw less current than bowthrusters, often less than 100 amps and some less than 50 amps. In that case a long run to the bow, even if just 1/0 cable will result in a reasonable voltage drop. A round trip length of 50' and a current draw of 100A results in a voltage drop of only 0.5 volts with 1/0 cable. So most installations power the windlass from the house battery with 1/0 cable up to the bow or even smaller if it is a smaller windlass.

A word about secondary battery charging. If you use a combiner, ACR, Echo Charger or similar to charge your starting battery then when the house battery gets mostly charged, any charging source tied to the house- solar, wind, engine alternator, shore power charger will cause the two systems to be combined when the voltage on the primary system rises to 13+ volts.

David

Click to expand...

agree with David....no need to make it harder than simple.

as usual, it does depend on individual installs and boat/windlass/thruster size.

needing the genset on to thrust or anchor to me is a failure in system setup and management.

I think the windlass batt should be OK for most anchor drills with no assist from the house bank , so monster cable is not required.

What ever output there is from the main engine alt will help a bit , and when operating keep the batt to 100%.

KISS!

Thrusters are different , but the short ON time usually allowed is a great assist to battery use..

On a MS34 I put an 8D AGM under the V Berth. 2 or 3 foot wire run to the thruster a bit more to the windlass. For charging, a small solar panel on the eyebrow handled the charging nicely. No large gauge long wire runs for charging or operation. Worked seamlessly, very happy with it.

psneeld said:

needing the genset on to thrust or anchor to me is a failure in system setup and management.

Click to expand...

Not all vessels are the same. Many vessels benefit from running a genset when hoisting anchor. A larger all electric vessel may well be running the genset to charge the house bank after an overnight of drawing 100s of amps and then doing wash and cooking in the AM.

I much prefer to start the day's cruise with a well nourished house bank with a couple of big operating chargers with the genset running while hoisting 300 feet of chain. The BMKs can well tell the story as to best options for house bank replenishment.

sunchaser said:

Not all vessels are the same. Many vessels benefit from running a genset when hoisting anchor. A larger all electric vessel may well be running the genset to charge the house bank after an overnight of drawing 100s of amps and then doing wash and cooking in the AM.

I much prefer to start the day's cruise with a well nourished house bank with a couple of big operating chargers with the genset running while hoisting 300 feet of chain. The BMKs can well tell the story as to best options for house bank replenishment.

Click to expand...

Sorry, forgot to include all vessels, heck some setups are hydraulic off genny or AC.....

However I would say that it would be the rare smaller trawler thatyou would "have to"....running the genset for many is for many reasons, if it helps the anchoring process, then its a plus, especially if it keeps you from making a bigger, more complex electrical system.

Interesting comments. I did not initially post this inferring that “this is the way to do it!” Rather, it was an opinion of an option (or options). There are good ideas presented and I believe the best solution is the solution that best works for each boat owner. I personally thought I would like to have a dedicated windlass battery and a dedicated battery for the bow thruster. However, my situation does not permit that and therefore I sought a different solution. The previous owner of my bot felt one AGM serving to start the Cummins 660 hp, Northern Lights genset, Side Power bow thruster, and Muir windlass was acceptable and worked for his needs. I didn’t accept that and looked for different solution that best met my needs, budget, and situation.

I sought out the opinions of many I respect on this list serves, other lists, personal fiends, recognized experts, and ABYC Electrician (who eventually did the work). One, higher respected boat owner who many of you know, actually ultimately suggested I have two banks: one single start battery to start the genset and as large a bank as possible to start the main engine, service as house bank, and power for windlass and thruster. The theory was that with a large house bank, with proper monitoring , one can supply power to start the main engine and if somehow you can’t due to a lack of power, start the generator and charge the bank. I did not go that direction.

I agree that starting a generator may not be necessary for all prior to approaching or leaving a dock (and using a bow or stern thruster) or prior to deploying or retrieving an anchor but I am certainly going to tell that captain that he should not do it. If that is the security that a Captain need to be confident with the charge in his batteries, so be it. I have run my genset in the morning after a night at anchor to re-charge or top off batteries. I often run the genset for a while after leaving an anchorage. I do not run the genset while anchoring because as I said, I use more of a free fall using less power. Also, I do not run genset while docking or leaving a dock knowing the thruster takes more power. I have shore power to replenish batteries after docking and the alternator on the main engine to top off (already fully charged house batteries from the shore power plug in) upon departure.

System works for me.

Steve

"I have run my genset in the morning after a night at anchor to re-charge or top off batteries.

The batt for the anchor is usually not part of the house bank , so would only be down about 1% per anchored day from internal losses.

Charging from any source would not change its operating voltage very much.