I am fitting an electric windlass on my Prout catamaran. I have located a battery forward to be close to the windlass. The system is a house bank and a starter battery separated by a battery isolator. Power being supplied by the engine [30amp] alternator as well as 150 watts of solar. My plan is to use #8 awg wire from the battery isolator starter battery terminal to the remote windlass battery (25 ft. away) and #6 awg for the short run from the battery to the windlass (1000watts). I just realized that this may be a problem because the starter and windlass batteries will try to equalize and the #8 wire may not be of sufficient size. How do I deal with this possible problem if there is one?
If wired correctly a DBI (dual battery isolater) will prevent the batteries from 'trying to equalize'.
A DBI unit is pretty rugged but like anything man makes it can sometimes fail. Add a fuse or resetable breaker near the battery terminal. This will provide some protection in case the wires get accidently pinched or shorted.
As set up the DBI splits the charge to the house bank on one side and the starter battery and windlass battery on the other side. The possible problem is these two are located 25 feet apart and connected by an 8awg wire.
If a "DBI" is what I would call a "split charge unit", that will prevent the starter battery )or "house bank" powering the line to the windlass battery. The maximum current that could flow under normal conditions would be around 30A from the alternator. 8 gauge is around 0.6mohm per ft - so 25ft at 30A is going to drop around 0.5v. Personally, I'd wire it with something thicker, as those 15W come expensive in solar panels and the OP may want to recharge the windlass battery faster or use shore power to recharge it.. Whatever cable size is used, it should have a thermal trip in circuit rated to protect the cable, just in case of fault.
The wire to the windlass is another matter. Rated at 1000W and 12v - its stall current, should the anchor snag, could be several hundred amps. Plus, a replacement windlass, one day, may be even thirstier.
Personally, if it were my boat, I'd be looking to run a really, really heavy cable forward, so that, in an emergency, I could power the windlass from the "house bank" and/or from the starter battery, in addition to the windlass battery, if I fitted one. The engine will usually already be running when the windlass is in use - so can be left running until the starter battery has recovered. I hate losing anchors (and cable) and have spent hours recovering one. A 1kW motor will discharge a 100AH battery in a very few tens of minutes. The only thing to be wary of is that the windlass motor probably has an intermittent use rating - not much point melting the thing.. I'd rather spend the money on a really heavy cable running the length of the hull than on a windlass battery..
As set up the DBI splits the charge to the house bank on one side and the starter battery and windlass battery on the other side. The possible problem is these two are located 25 feet apart and connected by an 8awg wire.
Another reason for thicker wire is termianl corrosion. Bigger wires just last longer in harsh conditions.
Assuming a solar panal that 'trickle charges' the battery at an amp or so under bright sunlight I wouldnt think a large wire is indicated for that... however: the sad fact is batterys go bad, often enough when you least want them to be bad. I guess the windlass has an "armstrong' backup system but being able to quickly jump batterys is a big plus in my book. you may even want to use that battery to start the engine sometime.
Are you familier with the 4 position dual battery switch? if not search for 'marine battery switch'.
| Another reason for thicker wire is termianl corrosion. Bigger wires just | last longer in harsh conditions.
Is that due to the larger contact area of the terminal? If so, why not large stranded wire (e.g. where the strands themselves are at least 14 AWG) fan out into multiple individual contact points? Or if not that, then at least taper the bundle of strands and have decreasing widths in a longer terminal to make better overall contact.
On Sun, 10 Feb 2008 18:54:58 GMT Palindrome wrote: | snipped-for-privacy@ipal.net wrote: |> On Sun, 10 Feb 2008 11:32:51 -0500 Tim Perry wrote: |> |> | Another reason for thicker wire is termianl corrosion. Bigger wires just |> | last longer in harsh conditions. |> |> Is that due to the larger contact area of the terminal? If so, why not |> large stranded wire (e.g. where the strands themselves are at least 14 AWG) |> fan out into multiple individual contact points? Or if not that, then at |> least taper the bundle of strands and have decreasing widths in a longer |> terminal to make better overall contact. |> | There are so many mechanisms at work, eg surface corrosion, crevice | corrosion, akin effect, vibration, work-hardening, etc, etc, etc. | | However, I'd suggest that the most important thing is to use a terminal | designed for the cable being used, or vice versa. | | This particular application is "only" a few hundred amps. It gets more | interesting once another zero or two is added..
What I have seen in applications of several hundred or more amps is multiple wires and very large terminal blocks with multiple lugs. But those are wires that stay separate all the way. The following I recall was 4200 amps at 416 or 480 volts (based on the colors):
The red stuff that the Interstate Battery pros use seems to work best for me.
Having spent several years at one point doing 2-way mobile service I feel I have gained some insight on problems involved in attaching wire to care/marine batteries.
My suggestion: use the largest practical connector that will fit on the terminal lug. Crimp and solder the connection (depending on type of connector). On occasion I have brazed larger conductors with copper phosphorous. Replenish the corrosion preventive goo annually (more or less depending on local conditions) Secure wire in such a manner as to minimize the effects of vibration. The mass of large inline fuse and holder assembly can vibrate the connection apart over time, especially when the connection point is weakened by corrosion. Secure it in some manner such as tape, wire ties, or clamps.
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