Installing an anchor winch battery

[Wigeon]

First time I've tried to instal an electrical anchor winch. Its a small 300W version. I have 2 no 135ah 12v batteries, but 20 feet away. There is not a huge demand apart from engine start, but my only charging is marina supply or engine use.
Am I right in that I have 2 options?
a) install rather hefty cables for 20 feet to control panel of winch, cable size..?
OR
b) put in another battery very near the winch.

My preference would probably be (b)
I have a position very handy for (b), but would like to keep it charged from equipment that connects to the other 2 batteries. Also what Ah size would I need. Max use probably 3 or 4 between marina.
I seem to vaguely remeber an article in PBO some time ago that explained how this is done with pretty thin cables from aft to forward new battery, but cannot acess search function.
Can anybody give me guidance please

 

[pvb]

The cheaper and better option is to just run cables from your main battery bank.

If you put a dedicated battery in the bows, you still need fairly hefty cables to charge it, as operating the windlass when the engine's running will cause a significant current to flow in the charging cables. You also have the extra expense of needing to fuse the cable at the windlass end, as well as at the main battery end. Then there's the problem of securing and ventilating a dedicated battery.

 

[vyv_cox]

Agree with pvb. The distance from my batteries to the windlass is about the same as yours. I used welding cable to install mine around 10 years ago. Heavily used since but no problems, no warmth detected in the cables.

 

[jdc]

A third way?

First time I've tried to instal an electrical anchor winch. Its a small 300W version. I have 2 no 135ah 12v batteries, but 20 feet away. There is not a huge demand apart from engine start, but my only charging is marina supply or engine use.
Am I right in that I have 2 options?
a) install rather hefty cables for 20 feet to control panel of winch, cable size..?
OR
b) put in another battery very near the winch.

My preference would probably be (b)
I have a position very handy for (b), but would like to keep it charged from equipment that connects to the other 2 batteries. Also what Ah size would I need. Max use probably 3 or 4 between marina.
I seem to vaguely remeber an article in PBO some time ago that explained how this is done with pretty thin cables from aft to forward new battery, but cannot acess search function.
Can anybody give me guidance please

I think there may be a third option (but havn't tried it myself). I don't necessarily make it a serious suggestion, but wonder what others think. One day I may dare to try it.

Why not do as the elctricity companies do and distribute HVAC? HV in our case might only be 110V or 230V, which is reasonably safe on board. The idea is to reduce copper losses, which are proprotional to I^2 * R. So if we reduce the current I by a factor of roughly 10 (110/12) will reduce losses 100 fold. Alternatively we can use thinner cable - ordinary electric flex will do in fact.

Some sums:

Distribute 230V
Power drain 600W (I note 300W above but lets allow for stalling)
so current = 2.6A rms

Voltage drop of full-wave recifier = 0.8V (I assume a centre-tapped xformer)

Thus efficiency of secondary = 12/12.8 = 94%

Efficency of inverter = 92% (approx, some are more)

Total efficiency ~86%

Total drain between charges = 4 x 200 x 300 / 12 / 0.86 = 23256 Amp-seconds
= 6.5Ah, ie next to nothing compared to the battery capacity.

(I estimate the duration of each anchor raising as 200 seconds, the load as 300W, and there are 4 between charges).

So what you'd need is:

- A 12V to mains inverter, of about 600W
- ordinary flex (20A say) to the vicinity of the anchor winch
- A transformer tapped 0-230, 12 - 0 - 12 secondary
- Two rectifiers in series with the two 12V secondaries to make a full-wave rectifier
- connected to the normal 12V reversing relay (if fitted or required)

Can be switched on / off at the pimary side or 12V secondary as you find convenient.

Anyody see a fatal flaw? Ones (but not fatal) I've seen include:
- RFI (emissions) may be bad during winching
- It requires a reasonably sinusoidal inverter (but most are nowadays)
- Shock hazard (but lots of people have 230V inverters on board, and you can always use 110V if worried)
- Regulation dubious if the transformer too small

On the plus side I think the overall cost may be no higher than that of an extra battery, the weight will be less and the reliabilty better provided it's well built, and as mentiond before cabling simpler and much cheaper. Eficiency just as good or better.

An even better method, but _much_ more complicated to arrange would be to use a 230V motor, eg from an electric drill, instead of the 12V DC motor.

Flames please!

 

[pvb]

On the plus side I think the overall cost may be no higher than that of an extra battery, the weight will be less and the reliabilty better provided it's well built, and as mentiond before cabling simpler and much cheaper. Eficiency just as good or better.

I can't believe the complexity of that suggestion! What is wrong with simply running a couple of say 25 sq mm cables from the main battery bank? Overall cost - around £90, plus say £10 for a fuse. Overall weight - around 7kg. Efficiency - around 100%. Investment in time - minimal. Potential for things going wrong - zero.

 

[jdc]

I can't believe the complexity of that suggestion! What is wrong with simply running a couple of say 25 sq mm cables from the main battery bank? Overall cost - around £90, plus say £10 for a fuse. Overall weight - around 7kg. Efficiency - around 100%. Investment in time - minimal. Potential for things going wrong - zero.

Well, nothing really - It's what I did! But seriously, why don't boat builders use AC distribution? I think we're all a bit conservative and believe that 12VDC only is somhow more reliable or simpler. It's useful sometimes to challenge accepted ideas and establish if conditions or technolgy have changed. Is it Dag Pike who uses his boat as a test bed for new ideas? I applaud him.

So some numerate discussion is in order maybe:

Let's take efficiency: my example was for 600W, which at 12V is 50A. The cables will be 9m there and 9m back (bending around corners etc), 18m total.

25mm^2 cross section, 18m length, resistivity of copper (assuming perfect termination with no corrosion, which is dubious) 17nano Ohm Metres -> R = 0.012 Ohms (and probably 3x this from imperfect junctions). So I^2 * R = 30Watts, ie one has a minimum of 30 Watts of loss, and possibly 3 times this. NOT 100% efficiency but somewhere between 85 and 95% actually.

Cost £90: how much is an inverter? Especially if built-in and/or used already for other purposes. Mains motors are also cheap - look at the price of a power drill - so were winches to have 110 or 230VAC motors they would not be any more expensive and would probably be smaller than 12V ones. Relays would be smaller and cheaper also, and speed control would be trivial, like it is on a modern drill.

Better still, why not adopt aircraft practice and use 400Hz AC distribution? Light (smaller transformers), reliable, established track record...

So I don't think that we can dismiss the basic idea out-of-hand, even 'tho as I said it's not what I actually do or recommend to others but rather an idea for discussion.

 

[havandra]

Anchor Windlass Battery

I installed a new windlass 4 years ago, and because the electric cables are all ducted on my boat I decided to install a new battery next to the windlass (actually in the Anchor Locker, no ventilation problem there, it is on a shelf I built in the top of the locker). The charging cables installed were much lighter and I could put them through the ducting, you do not need heavy cabling for charging. As you should install a separate breaker switch for the windlass this can be near the windlass as well, mine is installed directly below the windlass on the forecabin bulkhead in an existing cupboard. All this keeps the heavy cabling to minimum, in my case about 2 metres in all (little or no voltage loss). The system has performed very well with no problems so far.

 

[nimbusgb]

My 39' boat has a 1.5kw winch right up in the bow. ( 120 am draw )

2 big cables run from the aft cabin and an isolator switch. Works fine.

Extra chargers, multiple batteries, extra electronics and bits and pieces ......... whatever for?

To run AC around a boat you need to generate AC, not efficient or inexpensive if the engine is not running, you also need step down transformers and regulators and rectifiers to get it back to DC to suit most of the stuff on the market.

You are adding weight, complexity, expense, potential failure points and a whole lot else like the fact that AC at anything above about 60 volts has the potential to kill you ...... dead!

 

[pvb]

The charging cables installed were much lighter and I could put them through the ducting, you do not need heavy cabling for charging.

You don't need heavy cables for charging as such. However, when using the windlass with the engine running, a surprisingly high current can be drawn through the charging cables. If these are enclosed in ducting, they do need to be substantial.

Also, with a battery mounted in the anchor locker, you need to put a fuse or a breaker at both ends of the charging cable.

 

[nedmin]

As suggested would use original batteries.Welding cable would be fine but make sure its copper and not aluminium.I would use 35sq/mm copper,which might be cheaper than welding cable.Volt drop for 35mm cable is 1.2mV per metre =42 mV at 40 amps =42X40=1.7 volts approx.If your engines running you will get nearly 14volts so you will get 12volts at winch.If you go to a decent stockist they will crimp the lugs on for you. I soldered mine.

 

[pvb]

As suggested would use original batteries.Welding cable would be fine but make sure its copper and not aluminium.I would use 35sq/mm copper,which might be cheaper than welding cable.Volt drop for 35mm cable is 1.2mV per metre =42 mV at 40 amps =42X40=1.7 volts approx.If your engines running you will get nearly 14volts so you will get 12volts at winch.If you go to a decent stockist they will crimp the lugs on for you. I soldered mine.

Your calculations are adrift! Voltage drop for 35 sq mm cable is only about 0.6mV per amp per metre. The return cable run is 2 x 20ft - say 13 metres. So at 40A current, the voltage drop will only be about 0.3V.

For a 300W windlass, I'd use 25 sq mm cable, which would give about 0.5V drop.

 

[nedmin]

Have redone calculations for 25mm copper cable. 25mm voltdrop/meter/amp =1-6mV Cable length =14meters approx=14X1.6=32.4mV at say 40amps allowing for overload = 32.4 X 40 = 1.3 volts approx.so 25 sq/mm cable would be OK.

 

[pvb]

Have redone calculations for 25mm copper cable. 25mm voltdrop/meter/amp =1-6mV Cable length =14meters approx=14X1.6=32.4mV at say 40amps allowing for overload = 32.4 X 40 = 1.3 volts approx.so 25 sq/mm cable would be OK.

I don't know where you're getting your figures from, but they're wrong! The voltage drop for 25 sq mm copper cable is about 0.8mV per amp per metre - not 1.6mV!

And 14 x 1.6 doesn't equal 32.4!

 

[nedmin]

Not in my book.35 sqmm is 1.2mV/amp.meter 25sq/mm is 1.6.mV/meter.But really we are talking about peanuts in this instance.

 

[pvb]

Not in my book.35 sqmm is 1.2mV/amp.meter 25sq/mm is 1.6.mV/meter.But really we are talking about peanuts in this instance.

You're looking in the wrong book then, or you're misinterpreting the data. Perhaps the data you're looking at is already doubled to take account of the return run (in which case you'd only use the actual distance between battery and windlass).

See here for example.

 

[nedmin]

Bl--dy H--l, Will have to go back to school! Got grand kids round so doesnt help!!

 

[VicS]

Aw you're both wrong, although PVB's source doesn't differ much from mine

AWG 4 (21.25mm²) is 0.8 ohms/1000m

AWG 2 (33.62mm²) is 0.5 ohms/1000m

A little bit of arithmetic and you get

25mm² is 0.68 ohms/1000m (That'll be 0.68 mV/amp/metre)

35mm² is 0.48 ohms/1000m ( ie 0.48 mv/amp/metre

 

[pvb]

25mm² is 0.68 ohms/1000m (That'll be 0.68 mV/amp/metre)

Don't know where your figures are from, Vic, but they don't agree with the figure usually quoted by cable suppliers. Look here, here, here, and here. They all quote around 0.79 - rather more than your 0.68. I rounded it to 0.8 for simplicity.

 

[KREW2]

I've just installed a loframs 1000watt windlass. After much disscusion on here I ran cables from the main battery bank, all works fine. Here are some guides as to what you will need.
http://www.safety-marine.co.uk/Anch...Battery-Cable-(sold-per-meter).htm?P1354-S38-

 

[jfkal]

Battery or cable or both

I did the same. Works very well for me. And no worries running the starter battery down too much. Hooked up for charging to the shore power charger as well as to the alternator using a VSR.

Happy Anchoring.

Alternatively you could install a fuel cell at 3,000 Pound and fill it with 400 bar of Hydrogen.
Just kiddin'

I installed a new windlass 4 years ago, and because the electric cables are all ducted on my boat I decided to install a new battery next to the windlass (actually in the Anchor Locker, no ventilation problem there, it is on a shelf I built in the top of the locker). The charging cables installed were much lighter and I could put them through the ducting, you do not need heavy cabling for charging. As you should install a separate breaker switch for the windlass this can be near the windlass as well, mine is installed directly below the windlass on the forecabin bulkhead in an existing cupboard. All this keeps the heavy cabling to minimum, in my case about 2 metres in all (little or no voltage loss). The system has performed very well with no problems so far.