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  #11  
Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

Quote:
Originally Posted by paperbird View Post
Hmm - maybe this weekend I'll pull out the clamp-on ammeter and see what the windlass actually draws when hoisting the chain/anchor. It would be interesting to see the actual curve of how much the thing draws under various conditions.
More interesting would be to see what is left in the battery after one, two, or three anchoring attempts with retrieval. Windlass draw can be estimated easily. A 1000 watt windlass draws about 84 amps in normal use - I figure 10% or 100 amps to make it simpler.
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Re: Bow thruster - dedicated battery bank cabe

Thanks to everyone for posting. Maine Sail I especially appreciate your input and future input. Anyone who mentions good old W. Peukert has my full attention.

What I really need to know is "HOW MANY AMPS WILL RUN THROUGH THE CONNECTING CABLE ASSUMING A HALF CHARGED FORWARD BANK AND A FULLY CHARGED HOUSE BANK" once I flick the connecting switch. Having been there, I really hate the smell of burning insulation and rotten eggs.

My full install is as follows (I had simplified it in the original post);

"I have been undecided on the need for a forward battery bank for some time. I will have a windlass (Lofrans Tigres) and possibly a 4HP Vetus bow-thruster installed. I finally decided to bite the bullet and install two group 24 batteries (79AH each, installed in parallel) in the port locker in the vee-berth. I have connected the two banks (house and forward) with 1/0 cable via the Mastervolt DC Distribution 500. This cable is fused at both ends and has a switch at the forward battery end. Most of the time this switch will be off. The forward bank will be maintained by a Xantrex Echo Charger. This will ensure that the forward bank is charged anytime a charging source is charging the House Bank.


My logic is as follows.

1. The windlass needs a battery bank of a minimum of 100 AH - check. Its max draw is 125 Amps.

2. Under normal windlass operations I will switch the connecting switch ON. This will allow the alternator/house bank to pass this amperage to the windlass should it be needed. The 1/0 wire is far in excess of the minimum required for a 30 ft (round trip) of 125 Amps. This setup will permit almost continuous use of the windlass.

Circuit Wizard - Blue Sea Systems

The bow-thruster is another ball of chalk;

1. Interestingly it only needs a min battery bank of 108 AH. It draws 350 Amps for a max of 4 mins. In reality you use it far less that this or you are doing something wrong. I would have to connect both banks using 3/0 wire to facilitate recharging from the house bank. This was a non starter.

2. Under normal bow-thruster operations I will have the connecting switch to OFF. The bow-thruster will ONLY operate off the forward bank. This is acceptable in my book. Any current used will be recharged from the Echo Charge once a charging source (e.g. Alternator/solar/wind) is available.

All opinions welcome, speak now or forever hold your peace. "

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Last edited by gtod25; 11-20-2013 at 11:55 PM.
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  #13  
Old 11-21-2013
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Re: Bow thruster - dedicated battery bank cabe

The Blue Seas wizard figures 2/0 for a 3% voltage drop. That gives you only 13.97 volts at the forward battery bank when connected to the aft bank. 3/0 is not out of line for such a run even. As I posted the Echo Charge with its 15 amp max is light in this situation. An ACR would be a better choice.

As far as how much current will travel the route when the fore and aft banks are connected it depends - if the batteries are flooded not much - about 40 amps. If they are Agm, much more.

Another thing not mentioned - if you skip the forward batteries the heavy but expensive tinned wire you need will last an infinite time if properly crimped with heatshrink. The batteries if installed will have a much shorter life, especially if there is much voltage drop on the run to them. If they do not receive a full charge they will sulphate for quite a short life.

In addition a separate bank forward will increase maintenance over heavy wiring from the main house bank.

How are you planning on wiring the Echo Charge? What gauge wire will its run be?
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Old 11-21-2013
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Re: Bow thruster - dedicated battery bank cabe

Thanks mitiempo

The Echo Charger will be located next to the forward batteries and will be connected to the large connection cables before the switch. Its only job is to maintain the charge on the forward battery, not replenish it during use. It will operate automatically when there is a charging source on the house bank and mimic its charging process.

The batteries will be AGM.


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Re: Bow thruster - dedicated battery bank cabe

An Agm battery can accept in bulk stage C or greater. In other words a battery of 100AH can for a short time accept 100 amps plus. Lifeline has stated up to 5 x C. As the batteries have a high draw in use this very large acceptance can continue until the draw (windlass or thruster) is terminated and for a short while afterwards.
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Old 11-21-2013
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Re: Bow thruster - dedicated battery bank cabe

If I get the plan, there would be a switch allowing you to use the house bank, if the dedicated bank did not have sufficient charge. I thought I read that they would be interconnected. I would think you would want to simply by-pass the dedicated bank in this scenario, not introduce banks of different states of charge to each other.

You're still back to needing proper wiring from the house to the bow.

I've seen a few bow thruster failures. My buddy had his catch on fire last season. Thankfully he was aboard and it didn't take his boat. I've not heard of having insufficient charge being a problem. As long as you have a way to keep them topped, with the alternator, etc. and they are properly sized, it really shouldn't be an issue for a few blasts.

I always test fire the thruster coming down the fairway. If it didn't work, I would have to approach our slip differently.
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Old 11-21-2013
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Re: Bow thruster - dedicated battery bank cabe

I am not a huge fan of batteries for individual components such as a windlass, unless 100% necessary. Sometimes forward banks are necessary but all too often they simply result in wasted weight in the ends of the boat where you want it least.

Keep in mind that it is often cheaper for a builder to slap in a bow battery than to use large enough wire and pull off the pathetic house bank they installed.. They may not be doing you any favors by using bow batteries, just keeping costs down. The average boat show consumer also thinks they are getting more not less when they see a "dedicated" bow battery.....

Bow batteries, when not 100% necessary, leads to the phenomenon I call "dead lead"...

For example your start battery is already 98% - 99% dead lead but is an unfortunate "must have" item. This means that 98-99% of the lead in this battery goes unused and you simply carry around 98-99% of this battery in dead lead weight.

A windlass battery is usually well over 90% dead lead, even when correcting for Peukert..

This capacity is put to far better use if added to the house bank, where it won't be dead lead. It in-fact becomes beneficial lead when added to the house bank as opposed to sticking it up in the bow for use on one device or perhaps two....

By adding the lead to the house bank you;

*Increase house bank capacity - always a GREAT thing

*By increasing capacity you reduce depth of discharge (DOD)

*By reducing DOD you increase cycle life - Longer battery life is ALWAYS good

*By increasing bank size you reduce voltage sag under load - Motors like the least voltage sag you can give them. The bigger the bank, the less sag.

*By increasing house bank size you capitalize on Peukert effect. - The only way to minimize/reduce high load Peukert effects is to increase bank size..

*By increasing house bank size you have usable & beneficial lead not dead lead....

*By increasing bank size ALL DC devices benefit from less voltage sag!!!


Voltage sag at the motor can come from four places, the batteries, battery cable, terminations & over-current protection. With small windlass banks up forward the largest sag comes from the batteries themselves. With a much larger house bank and longer wire runs the cabling, terminations and OCP can add some sag but not to the level of creating problems when compared to the sag the bow battery gives up.

While proper sized battery cabling is expensive, up front, you do it ONCE.. With forward batteries they are an every 4-6 year expense plus the installation costs, over current protection, boxes etc. etc....

By running both large cables, and the batteries to the bow, you will now need OCP at both ends, vs. just one end, which also costs more money... You also have an opportunity for HEF or human error factor with the ability to forget to turn off the combine switch.

By using only the house bank and straight large cable runs your alt has a direct path to the windlass for the least voltage sag. By using a combiner or Echo they will simply drop out if not mechanically combined... If you've mechanically combined, and done it properly, this means your wires can handle the work on their own so I'd recommend putting the lead into the house bank where it will be beneficial not more dead weight....

I generally do not choose Echo's for banks like that and prefer the high amperage capabilities of the large Blue Sea ACR's, a Balmar Duo Charge or a Sterling battery to battery charger....

Course on a boat like that I would most likely add the capacity to the house bank and then send some big pipes to the bow and call it a day. A simple one time expense and one that can serve to benefit ALL systems not just a windlass that is used 0.1% of the time....

By far and away the biggest cause of "voltage sag" in thrusters or windlasses is from the batteries, not the cable. This can only be mitigated by using a much larger bank. Interestingly enough most boats already have one, it's called the house bank........

Even at 50% SOC a single large house bank will have less voltage sag than two G-24's....

If one must install bow batteries, the best of the best LA batteries for this use are Odyssey TPPL AGM's.. They will have less sag than any other LA battery and can be sized smaller and with less weight than other LA products....
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Last edited by Maine Sail; 11-21-2013 at 12:51 PM.
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Old 11-21-2013
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Re: Bow thruster - dedicated battery bank cabe

Maine makes excellent ponts, as always.

I have Oddessey AGMs running both our windlass and thruster. In fact, separate for each of those too.

I like knowing, regardless of the state of my house bank, they are always topped and fully ready. In fact, the ground buss for my house bank shorted out this past year and several systems went offline while at anchor overnight. I spent hours tracking it down to a leak that corroded some connectors. Nice to know they were independent, because I had to get back to the slip to figure it all out.
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Old 11-22-2013
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Re: Bow thruster - dedicated battery bank cabe

Maine's advice is excellent as always.

When we had the 52, it had a 24 volt bow thruster with a couple of D8's forward. The rest of the boat was 12 volts. To charge the 2 12 volt batteries, there was the relay box that would parallel the 2 batteries when the thruster was not in use for charging, and then when you keyed the truster, put them in series. Needless to say there were LOTS of Cole Hursee relays in a box to make this happen. When that box went bad, we reverse engineered it to figure it out, and came to realize if it failed the wrong way, it would short the batteries together.

I ended up chucking this pile of relays and putting in a 24 volt AC charger, and only charged the thruster batteries by shore power or genset. That actually worked out, as we would tend to operate the genset enough for other reasons easily keeping the bow batteries charged. Although you don't have the 24 volt problem, this might be a solution for you if you have a generator.

That said, personally I like Maine's suggestion better.

Owning the 52 for 10 years taught us the value of simplicity, and when we finally built the 38, no thruster, no unnecessary systems. Now we actually go sailing for weeks at a time without fixing something
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