Anchor Windlass- Which Battery

[Jon W]

I'm installing a new electric anchor windlass. The windlass has a 600 W motor connected to a 50A breaker/isolator. I have a choice of using either my 4 golf cart battery ~450 ah house bank, or my ~80 ah 650 CCA reserve battery. The reserve battery uses an Echo Charger to stay fully charged.

Is my reserve battery a viable choice for this windlass or will it drain the battery and not get back to full charge without running the engine for a long time? Ron Hill what size is your start battery?

Thanks for the help everybody.

[KWKloeber]

Jon

Let the math decide. 600w is 50 amp (less w/ engine running and alt pushing out more than 12 volts).  Or 0.83 amp-hr for every min you run the winless. It's likely less because 600 is probably the peak (they wouldn't have you fuse it exactly at the operating amps).  Say it's 40 amps or 0.7 amp-hr used per min of windlassing.  If you consider the magnitude of that vs the capacity of either your house or reserve, it's an insignificant percentage. 

JTSO but your reserve is better suited for higher amperage, short bursts than a house battery.  Even if you never replaced the amp hrs used, it wouldn't affect the reserve- starting requires an insignificant amount of energy, in the neighborhood of 1 amp hour.

What's the relative cable run (i.e., voltage loss) both ways?

Another way to use the math.  If you're pulling 40 amp per minute, what's the replenishment time?  Since the reserve is theoretically topped off, the recharge amps will be low and decreasing until fully charged.  Say it's 8 amps averaged (to make the math easy).   So for each minute of winlassing, it would take 5 min of recharge time.  Not a deal killer.

Ken

[Noah]

Don't know the math. Do know best to keep your engine running when anchoring or pulling the hook.

[mark_53]

I would connect a windless to my house bank simply because my start/reserve battery is for starting which is priority #1.  But, it wouldn't be to difficult to put a switch in to use either.

[J_Sail]

There are valid arguments for both, and both will work, but in your case I would be inclined to put it on the house battery.

Why? Because you are using an Echo charger (rather than combiner ACR relay) to recharge the reserve battery. While the Echo will recharge it just fine, it will not allow the alternator to help hold the voltage up during windlass operations (presuming you have the motor running as recommended), as the windlass will draw more than the rating of the Echo charger.

That could matter in the future if the reserve battery is getting old and you engage in heavy windlass operation. In that scenario it would be nice for the alternator to carry the lion's share of the load while pumping out current at 14+ volts, versus your battery at just 12v (or less if on it's last legs).  That would make for a happier, more powerful and faster windlass, and thus a happier skipper.

Might be interesting to see if MaineSail weighs in with an opinion.

[Jon W]

The engine will be running when I use the windlass.

[Ron Hill]

Jon : I connected my windlass to a "starting type" battery!!
Yes, my engine is always running when I breakout the anchor.

A thought

[Jon W]

Thanks Ron. Is it charged by a dual output alternator, echo charger, ACR relay, or?

Thanks Ken. I don't have the total run length yet, but if I use the house bank instead of the reserve it adds about 8 feet to the total cable circuit. The positive and negative cable on the battery side of the up/down solenoid will be 1 AWG. The motor cable is metric equivalent to 6 AWG. I'm not sure I understand where the numbers come from in your last paragraph and how they relate to the earlier paragraphs. Can you give a layman a little more detail?

Thanks Jeremy. Although the engine will be running when I use the anchor windlass I wasn't sure the run time would be enough to top off the reserve. I plan to add Solar which will help, but until then I only have charging when the engine runs.

Thanks for the help.

[mainesail]

Windlass to house bank....

[KWKloeber]

Windlass to house bank....

RC.  And the reasoning?

Ken

[mainesail]

Windlass to house bank....

RC.  And the reasoning?

Ken

Pretty simple really, windlass performance will be better with windlass durations with the larger house bank. Start batteries are rated for very short duration use then voltage starts to fade rapidly. We also can't forget Peukert in this.

#1 A 450Ah GC2 bank puts a 50A windlass load at approx .11C or 11% of Ah capacity in load. This is really an insignificant load for a 450Ah bank of GC2 batteries. Even with Peukert we're not really affecting the battery by all that much. These batteries can typically deliver anywhere between 450 minutes & 480 minutes at a 25A load and 110 minutes to 125 minutes at a 75A load. Now build a 450Ah bank and you're doing roughly 900 minutes at 25A and 230 +/- minutes at 75A. These batteries are designed to run high current electric motors for hours on end including in-rush after in-rush (stop and go golf cart use) all day long. 

#2 An 80Ah start battery would be seeing a load of approx .67C or 67% of Ah capacity which is a significant load for such as small battery especially when we hold that load for a few minutes, not just for a few seconds. If we then consider Peukert this banks capacity is essentially chopped in half at a load like that..

#3 Most cruising boats, with a well designed DC system, are feeding the alternator directly to the house bank for optimal charging performance.. When running the windlass the alternator is often supplying the majority of the windlass load and the battery is barely breaking a sweat.. If you pull the windlass off a start battery, via a combiner or Echo it simply can't keep up because as the voltage sags the relay will open or the Echo will max out at 10-12A (yet to see one actually deliver 15A).. Even without the alternator running, a bank of 4 GC2's will do this with ease even at 50% SOC.

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 routinely correct and re-wire windlasses that boat yards or DIY's have wired to a start battery. After the fix the owners are usually shocked at how well their windlass now performs. I've measured everything from Rolls (the worst of the deep cycles in high load applications due to very high Peukert) to large L-16 type Trojan's and even these big deep cycle batteries beat starting batteries for longer term windlass use... They hold a higher voltage to the motor for longer than will a typical starting battery.

#4 Coulombic efficiency is worst at high SOC's. Even if you remove just a few Ah's from the start battery you're now looking at 4-5 hours to get it back to 100% SOC due to the horrible acceptance rates and extremely poor charge efficiency in the high 90's.. It is bad enough that we have to do this to the house bank but to create two on-board banks that need hours of absorption charging to get back to 100% is probably not the best practice.

#5 I have spent countless hours analyzing, measuring and comparing deep cycle house bbanks vs. starting banks for such things as starting, windlass, inverters and bow thrusters. I have not seen a case where the starting battery will handle these loads with better voltage, or for longer duration than the house bank will.

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, because it is already there. That large bank is there, it is real and it means immense available current to drive high amperage loads.

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

Once beyond 15 - 30 seconds the starting batteries begin to suck wind and the deep cycle battery levels out voltage wise and continues to chug right along. 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.

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 multi-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 incorrectly assuming this type of battery was best suited to fairly short duration large loads.... 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 GC-12 battery after a customer switched to GEL and gave me his four used 12V US Battery Golf Car batteries.. In contrast to the thin plate start battery I could easily go an entire work days worth of "heat shrinking" or tool use before it began tripping the inverter on low voltage. I don't recall it ever tripping out on low voltage. Now days I use an Odyssey TPPL AGM battery that is spill proof.

Not all my customers want to run the motor to make popcorn (inverter), or to leave an anchorage (windlass), so I usually route to the house bank, on boats that don't require a bow bank, usually sub 45' or so. Many of my customers are also world cruisers so they are not always anchoring in 10' of water where even a garden tractor battery might work. When we get into deeper anchorages, or hard setting bottoms, the windlass may need to be run for as many as 15 + minutes. I have customers in Alaska and the PNW who anchor in 100' or more of water depth. In those depths the weakness of using a starting battery in this application really exposes itself.


#6 Windlass performance is directly related to the voltage at the motor end. Most windlass manufacturers suggest that a 10% voltage drop is OK. Why do they do this? The bottom line, direct from one of the more honest manufacturers, it saves the customer money so they don't get scared off the windlass purchase. Unfortunately 10% VD on top of battery voltage sag, really inhibits your windlass performance and makes the windlass a rather lethargic performer. I prefer to see voltage drops in windlass circuits of 5% or less and this leads to excellent windlass performance.. We also need to keep in mind that its not just the wire length that adds to the voltage drop but every fuse, termination etc.. Aiming for a 10% voltage drop, based on wire only sizing, usually lands you closer to 11 or 12%.

Keep in mind that a windlass can draw more than the face value 50A (in this case) when loaded. Windlass manufacturers are famous for stating "nominal" or calling it "normal current draw" but then not specifying the "under load" figures.

For example last fall I was testing a customers Lewmar 1000W windlass, and using Ohm's law 1000W/12V = 83.3A However a DC motor, when loaded, can draw more than the "normal" unloaded rating would suggest. Lewmar specs a "normal current draw" of 85A. Start-up current (called in-rush) using a Fluke 376 was 295A or more than 3X nominal, and this is to be expected. The current drawn, when simply lifting the 44 pound anchor and chain, straight up from a 40' depth, (not unsetting it just lifting it through the water) was pretty steady at 122-126A. This is for a motor Lewmar says only has an 85A "normal current draw". With no load the motor did draw about 87A.


There are many ways to skin the cat and each can do what works for them. I would not personally wire a windlass to a starting battery unless it was TPPL AGM and had a latching relay to use available alternator power.

[KWKloeber]

I'm not sure I understand where the numbers come from in your last paragraph and how they relate to the earlier paragraphs. Can you give a layman a little more detail?

Jon

The math was just comparing pulling energy out at a given amp rate vs replenishing the battery at a lower amp rate due to the battery acceptance. 

To make the point even simpler, say you pull 1 amp during every minute of use, and you recharge at an average 1/10 amp.  Then to replenish what you pulled out, it takes 10 times the number minutes to replenish what you used.

The example was using something that pulls 40 amps, and recharging 8 amps.  40/8 = 5, so it takes 5 times longer to replenish whats used.  (i.e., use equipment for 1 minute, recharge for 5 minutes.) 

As I said though, the recharge rate was just theoretical to make the math easy.  The rate of recharge would depend on the SOC and the alternator/regulator used, specific battery brand and chemistry, etc.   RC probably knows a typical recharge rate given a high SOC (I don't) but I suppose that's something one could easily measure for their specific battery bank, cabling (v loss), internal or external regulator, etc.

ken

[KWKloeber]

I began years ago using a thin plate "starting battery" for this application incorrectly assuming this type of battery was best suited to fairly short duration large loads....

Rod,

I too had thought the opposite of your real-world testing and experience.  I see what you mean -- short duration is really short duration, not "minutes."

I thought that the house was best suited for low-rate drain over a long time (lighting, etc.), rather than a high-rate drain?    Maybe it's that there's not a "good" supply, only a better than "worse" supply?  Then again, I'm used to wet cells and not golf carts, that I guess would be more similar to windlass use (have no idea how many amps a golf cart draws, but understand it's like 100 amps @ 36 volts.)

I hadn't even thought of applying this to a deep anchorage!  Defo that would kill a starting battery.

Ken

[Jon W]

Thanks for the great responses and experienced advice. I"ll be connecting to the house bank.