Windlass Wiring and Battery Management

[tartansail]

I'm in the process of planning the replacement of my murdered LA batteries with an increase in capacity and solar charging. As I mentioned in another thread, one of the three G-27's was significantly deader than the others. (I guess murder is relative in battery land.) One hypothesis was that the batteries were not wired properly for balanced charging. I don't know, because I took the bank apart before noticing the voltage difference.

I was talking to someone who is generally knowledgeable who suggested that wiring the windlass into the house bank was shortening battery life and that the windlass should be wired to the start battery since, like the starter motor, it was a big load. That was the first I'd ever heard that recommendation. I understand that the windlass is a big draw, but it seems like the total amperage to haul the anchor would overwhelm the capacity of a cranking battery and destroy the plates in no time.

I don't have the space, at least, at the moment, to put a dedicated battery forward so I am trying to set up the wiring to be as efficient as possible. I always run the engine with the windlass on. The cable run is about 25 feet of 2-0 cable. What are thoughts on the suggestion of wiring to the starter battery? If not, are there best practices for wiring a big load like this to the bank? As always, many thanks.

[CharlieJ]

In general, windlasses use modified starting motors and they need a lot of energy for a short period of time...just like an engine starter.

I almost always wire a client's windlass to the starting battery and try to talk them out of installing a remote battery well up forward where it is out of sight and out of mind and never looked at.

I suggest that you run the controls separately back to the main panel and their own circuit breaker.

[tartansail]

Originally Posted by CharlieJ

In general, windlasses use modified starting motors and they need a lot of energy for a short period of time...just like an engine starter.

I almost always wire a client's windlass to the starting battery and try to talk them out of installing a remote battery well up forward where it is out of sight and out of mind and never looked at.

I suggest that you run the controls separately back to the main panel and their own circuit breaker.

Thanks, Charlie. The controls have a separate switch and breaker forward which works fine. Good point about the remote battery. The only places I could mount it would definitely be a PITA to monitor easily.

I'm still kind of surprised that a starting battery can handle the loads for as long as the windlass sometimes is working when we're pulling in 150' of chain from a 30' anchorage. I always thought they were designed for heavy load for a few seconds, not a few minutes. Live and learn.

[btrayfors]

David,

Since you said you always run the engine when using the windlass, the load on the start battery won't be all that great. It will be whatever the windlass motor draws minus whatever amperage the alternator is putting out (assuming the alternator output is wired to the start battery OR that you are using a battery combiner).

For example, let's say your windlass motor draws 75A on average when lifting the anchor. This is about typical for a 40' boat. And, if you have a 55A alternator, then the load on the start battery will be only 15-20A or so, depending on how fast the engine is running, resistances in the run up to the windlass, etc.

I chose a different path on my 42' sloop, because I often come to anchor completely under sail, and I like to sail off the anchor as well -- without running the engine. So, I installed two T-105 golf-cart batteries under the V-berth in the forward cabin. These are sufficient for 5-10 anchorings without charging (but I have a means of charging them efficiently). This has worked well for over 15 years now.

Bill

[ebaugh]

At the risk of disagreeing with Charlie....who is smarter than I am on this kind of stuff...I don't think it matters which bank the windlass is wired to so long as the engine alternator is charging the battery when your using it. On my boat, there is only one feed to the main panel, and it comes from the house bank. Difficult to rewire the windlass to use the start bank directly, and I don't think it matters.

[tartansail]

Thanks. The windlass doesn't run through the main panel. It was wired directly into one of the house batteries with a separate switch and fuse forward. Rewiring to the start battery or putting it on a bus bar from the house bank so that it isn't coming from a single house battery are both pretty easy options.

My alternator is a high output Balmar so it can put out plenty of juice. However, since the engine is usually idling when we're maneuvering around the anchor, I don't imagine it's putting out anywhere near its maximum charge.

[ebaugh]

Then in your case, the start bank is logical. Your stuck with low output of the alternator unless the wind is light and you don't need the engine to assist hauling it up.

Make sure solar, alternators or something fully charges the start bank periodically to extend the life of LA batteries.

[btrayfors]

How is your Balmar alternator wired now? Directly to the house batteries?

Mine is. With an EchoCharge to maintain the start battery.

My 100A Balmar alternator puts out a good 40A with the engine just above idle. With higher RPMs, it will put out >=80A for as long as the six T-105 batteries will accept that much current.

You may be fine, but you certainly want to draw equally off the house batteries, not just one, so a move to the bus might be just the way to go.

Bill

[LJH]

Originally Posted by btrayfors

How is your Balmar alternator wired now? Directly to the house batteries?

Mine is. With an EchoCharge to maintain the start battery.

My 100A Balmar alternator puts out a good 40A with the engine just above idle. With higher RPMs, it will put out >=80A for as long as the six T-105 batteries will accept that much current.

You may be fine, but you certainly want to draw equally off the house batteries, not just one, so a move to the bus might be just the way to go.

Bill

I have my windlass hooked up to my house battery bus through a switch and circuit breaker. I have a high output Balmar connected to my house bank, but no secondary charging. I have had no problems with this setup affecting my batteries.

Is your start battery is much further away from your windlass than you house bank? Mine are 15 feet apart. If you go that route make sure you re-size the windlass cables appropriately.

Lyndon

[noelex 77]

There are pros and cons of attaching the windlass to the start battery or the house battery.
IMHO it makes little difference. If the system is well engineered both work very well and I would not attempt to change it.

The argument that the house bank cannot is not designed to supply current is not valid. A typical house deep cycle battery bank is not stressed supplying the windless, especially if the alternator is running.
All other things being equal "Start batteries" provide better short term current delivery ( is the windlass short term? It requires high current for much longer than start motor?) than deep cycle batteries, but the house battery bank will typically be much larger than the start bank. This size difference means that generally the house bank is better at suppliing the high current over 5mins or so that the windlass needs.

[sailinglegend]

Originally Posted by noelex 77

There are pros and cons of attaching the windlass to the start battery or the house battery.
IMHO it makes little difference. If the system is well engineered both work very well and I would not attempt to change it.............

Agree - but one other point to consider is that if you put ALL your charging sources to the house bank and take the windlass load from your house bank then you could replace your existing starter battery with very much smaller Odyssey or Red Flash AGMs which can be placed anywhere - even on their sides. The space where the starter battery was can be used for another house battery. The more Ahs you have the longer the house bank will last you.

[tartansail]

Thanks all.
@btrayfors -- The Balmar is wired through a switch which allows me to select which bank to charge. It is always charging the house bank. A combiner allows the start battery to be charged. Good to know it puts out that much juice at idle.
@LJH -- The start battery is in the same space as the house bank. However, it may not fit when I replace the three G27 with four six volts. If it moves, it will be further away which will lean me towards your setup.
@Noelex -- Thank you. That was what I had thought. The max current for the starter and the windlass may be similar, but the total draw is much greater with the windlass.
@sailinglegend -- Interesting point about the starting battery. Doesn't charging via a combiner equate to mixing battery types? My solar setup is going to be floating at 14.3 volts. Wouldn't an AGM be a pretty unhappy camper if the combiner let that through?

[Maine Sail]

Originally Posted by noelex 77

The argument that the house bank cannot is not designed to supply current is not valid.

Spot on. These batteries can usually supply ample current for the durations of either an electric bow thruster, a windlass or starting loads and do so with ease, with a sufficient "bank" and will hold a voltage better than most starting batteries during these loads.

Originally Posted by noelex 77

A typical house deep cycle battery bank is not stressed supplying the windless, especially if the alternator is running.

Even without the alternator running they should do this with ease, if they are in good shape.. Batteries in bad shape of either type will cause issues. In most cases boats with windlasses also have rather large multiple battery house banks. These banks even if deep cycle can have multiple thousands of motor cranking amps available at cruising temps..

I have had the ability to analyze many starting and battery systems with my Midtronics analyzer. I have yet to come across many house banks that perform worse than a single starting battery during any of these high load exercises. I've measured everything from Rolls (the worst of the deep cycles in high load applications) to large L-16 type Trojan's and even these batteries beat single starting batteries for longer term durations... They hold a higher voltage to the motor for longer than will a typical "starting" battery.

Originally Posted by noelex 77

All other things being equal "Start batteries" provide better short term current delivery ( is the winless short term? It requires high current for much longer than start motor?).

Average starting durations range from about 0.6 seconds to about 2 seconds, on a motor that "starts hard". These starting batteries are designed for that type of inrush not the 4 - 12+ minutes of running a windlass that folks often do.

Below are screen shots from a house bank starting a 4 cylinder diesel at 24F.

This first screen shows the bank CCA at an actual battery case temp of 32F. These were three "deep cycle" group 31 batteries.. It also shows the voltage before starting.


This screen shows the in-rush at 24F ambient temp (batt cases were at 32F) and the cranking current.


This screen shows the voltage screen during starting. Note that the lowest dip at 32F batt case temp was still well above where any electronics would "drop out"... Three group 31's are a fairly common bank of boats sub 36 feet.


This screen shows the "averages" during the starting event. Average voltage during "starting" the diesel at 24F ambient temp and 32F battery temp was still 12.04V! This particular "deep cycle" house bank kicked the a$$ of the single group 27 starting battery, even at at these temps, holding both a higher voltage and also starting the engine slightly faster in "duration"....

The "average" cranking current during the "duration" was 286A. The "duration" or the time it took from the first engagement of the starter until it "unloaded" was just 0.75 seconds at 24F...... I have also measured this boat in summer temps and these numbers for "cranking" are considerably lower. This is the type of "duration" starting batteries are intended for. They were never intended for 4 -12 minutes of 100A+.... This screen also shows the "resistance" in the cabling. This is very good reading....

Originally Posted by noelex 77

than deep cycle batteries, but the house battery bank will typically be much larger than the start bank. This size difference means that generally the house bank is better at suppliing the high current over 5mins or so that the windlass needs.

There

I agree 100% but I would shorten that to "over 30 seconds". This is perhaps the one instance where Charlie and I will actually disagree. I have spent countless hours analyzing, measuring and comparing deep cycle banks vs. starting banks for such things as starting, windlass, inverter and bow thrusters. I have not seen the "conventional wisdom" that the starting battery will handle these loads better for longer or have it bear it out and back it up as measured, as installed.... With instruments capable of doing so I suspect anyone would find the same thing...

In nearly every instance when the batteries are in comparable condition the house bank wins. This is aided of course by the sheer size of a house bank but we can't just discount that. That large bank is there and it is real and available current....

I have even done this testing on my bench supplying a 130A load to deep cycle batteries and starting batteries. The 130A mimics a windlass quite well. For the first few seconds, and I mean seconds, like 15 - 30 or so, the start battery holds voltage better.

Once beyond 15 - 30 seconds the starting batteries begin to suck wind and the deep cycle battery levels out voltage wise. These are simple head to head tests with actual batteries that have come right off customers boats. In most of these cases the "start battery" has little to no cycling and the house battery has "use/cycles" on it.

What got me started on this?

I am often seen in boat yards or working on moored boats carrying around my inverter/battery box so I can run my heat gun & tools while re-wiring spars, boats etc. or in areas of a boat yard where an extension cord would need to be 400 feet long. My battery/inverter, while heavy, is a LOT easier to move about than my Honda EU2000 or a mulch-hundred foot extension cord. I also don't have to listen to it run, even in "ECO" mode, or breathe the exhaust all day long.. I don't have to pull start it either I just flip a switch and fire up my tools..

I began years ago using a thin plate "starting battery" for this application relying on "conventional wisdom"... It was also slightly lighter in weight to carry up & down ladders and on and off moored boats.. Even with a full charge the inverter would trip out on low voltage after just a hand full of "shrinks" with my Milwaukee heat gun. Even if I switched to low power it would trip because it just took longer to complete the shrinking.

I then switched to a deep cycle 12V battery. It used to be a Trojan SCS-225 now it is a US Battery group 31. In contras to the thin plate start battery I can go an entire work days worth of "heat shrinking" or tool use with my single group 31 "deep cycle" before it begins tripping the inverter on low voltage....

I am not bothering to care about how deeply I have cycled it just that I can use my tools and not have to use my obnoxious Honda. The battery gets re-charged to 100% after each use and last me quite a few years.. That is a huge difference to me in high current performance from the DC battery to the starting battery... .

Not all my customers want to run the motor to make popcorn, or to leave an anchorage, so I usually route to the house bank...

Many ways to skin the cat and each can do what works for them. All I can do is present what I see, touch feel and measure...

[tartansail]

Many thanks, Maine Sail. Great stuff. BTW, I'm planning to get my golf cart batteries at Sam's Club based on your note elsewhere. I hope they'll be there after the Christmas rush. Also, I saw your Solbian installation on your site. I'm putting two of the 125W on my bimini with zippers, but the velcro looks like a nice setup, too.

[Matt sachs]

From what little I know, the cranking battery sould be fine for the windlass and bow thruster applications, however, mine will be wired into the house bank for 2 reasons 1) the draw from the windlass/ thruster will be a smaller % of whats in the bank than from the single battery . ie even though the deep cycle batteries have thicker plates and the surface voltage drops faster under a large load, the house bank likely will be drained less than the cranking battery 2) I want to know if all else fails I can crank up my engine. The cranking battery will only be used to start the engine. I'm taking it one step further. The engines alternator will only supply the cranking battery much like the setup in an automobile, and either a high output alternator or a seperate gen set will be used on the house bank.
If this is crazy, I hope some will let me know....