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Old 23-04-2009, 11:52   #1
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House Bank or Genset-Engine Bank?

I'm upgrading my electrical system capacity by 50% (440Ah to 675Ah) as previously pointed out in another thread.

It has been recommended to me by a very knowledgeable Marine Electrical Engineer, that I have my power (i.e. hydraulic) winches, boom furler, etc. be instead connected to my Genset-Engine Bank (I have a separate battery for each) to avoid "voltage spikes" that could impact electronic instrument performance or potentially damage my electronic instrumentation (doing a major, i.e. "expensive" upgrade to that too).

A Kiwi Cruiser I respect has serious reservations about making this type of change, and while it is an accepted rule (at least I think it is) to never have anything connected to your Engine battery that could potentially risk it not being able to start your engine, I supposed I could have the above mentioned equipment powered in some way to my Genset-Engine Bank (BTW, I'm also upgrading this Bank as well as the House Bank).

I'd appreciate the views of "those I believe are in the know", i.e. Rick ... and even you GordMay , and of course others with similar levels of expertise.

Thanks in advance.

William
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Old 23-04-2009, 12:15   #2
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For what it's worth, here's what we're set up on mobetah:

1. House bank of batteries = 8 Trojan T105s ( 880ah)
2. Starting battery (for engine and generator) = 12v deep cycle cranking battery
3. Everything except the starters and engine instruments are powered by the
house batteries.
4. I do have an off-1-both-2 switch so if the starting battery fails, I can use the
house batteries to start the engine or generator.
5. The engine has a 125 amp alternator (wired through an isolator) to both battery
banks (senses off the house bank)
6. There is a 2500 watt inverter (with 135amp charger) wired to the house bank.
7. There is also a 40amp charger (with another off-1-both-2 switch) primarily as a
backup.

Our system works well for us. note: we don't have power winches or furlers. We do have a 12v windless that we almost always are running the engine when it is being used (remember that 125 amp alternator on the engine). We have the 880 amp house bank because we have a 120v AC ref/freezer (Rich Beers coldplate) and a small 120v AC watermaker which we ofter run using the inverter. We have the large chargers and alternator to recharge the 880 amp house bank.

Hope this helps, Bll A.
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Old 23-04-2009, 12:24   #3
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Modern marine electronics

I am not aware of any piece of modern marine electronics that could be damaged by spikes from windlass, thruster, inverter or other high energy users causing voltage spikes or current inrush.

Old Loran units were susceptible to noise yet even they were not damaged. Source everything to the house batteries using good wiring practices. Keep your starting batteries connected to their engine electrics without tapping off of them which, as you might guess, could decrease the reliablity of starting in dire need.
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Old 23-04-2009, 12:25   #4
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Thanks for the input, however the power winches and a power boom furler do make all the difference in the world. That's why I started this thread.

That aside it sounds like you have a highly functional set-up.

I will run my water-maker off my Genset, while also charging my batteries and cooling down my refrig/freezer, all which will be done 2x a day (another thread topic I started a short time back)
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Old 23-04-2009, 12:39   #5
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My last post was directed at mobetah, not you Rick. Thanks for your recommendation Rick. It does follow what I was taught.

I will request a further, more in depth expanation behind this marine electrical engineer's recommendation and share it with you when he gets back from overseas (on a overseas job ... like I said he's highly regarded)

William
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Old 23-04-2009, 13:47   #6
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FWIW, all of my electrical and electronic loads, except engines, come off of the house bank. Dedicated engine start batteries and the ability to parallel to start the engines in a pinch. This sounds like what you have now - and is most common.

2 issues I've had with this setup:
- when the house bank ran down I could not start the generator

- when I put heavy loads on the winch I sometimes get "Low Battery Alarm" from the GPS Chart plotter.

So yes - any / all equipment fed off the main bank will see the voltage transient spikes / under-voltages. How risky that is - well, that's an entirely different question. Even some 'modern' systems are affected by what I'll call 'dirty' input voltage. Everything from Splendide Washer/Dryers (need pure sine wave) to LED lighting (if not current-limited).

I would prefer to have a dedicated bank for the windlass / furlers. That way if one 'function' drains its power source, you still have options. I would want the ability to cross-connect all sources of course. You never know when you'll need to start the genset using the windlass bank, ya know?

Since you've already started your upgrade project, now might be the time to design a 3-tier system. I'd consider it to be worth the effort.

Good luck with the project whichever course you steer.

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Old 23-04-2009, 16:00   #7
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Thanks so very much Mark. As I'm living up to the cliche "a boat is nothing more than a hole in the water you pour money into" so well, as you have suggested it would be worth while exploring your suggestion, even if it means pissing away a little more $.

Regards

William
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Old 23-04-2009, 18:31   #8
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Proper wiring

William,
If you start with a low-resistance battery bank, correctly sized cables and low resistance power distribution points you will not have voltage dips caused by peak load currents that can allow dips to 8V or below at any other load.

A proper heirarchy of load terminal attachments to a distribution point (a star arrangement is superior to buss bars) the highest current sources and loads stack together in the center and the lighter loads/sources stack on both sides from "center" outward on a stud. This heirarchy minimizes voltage drops caused by parasitic resistance.

One company flew me to a truck OEM to troubleshoot a production problem whereas a power inverter for the sleeper kept shutting down on low voltage. All I had to do was reconfigure the cabling to the individual batteries in the bank and restack the heirarchy of attachment and the problem was solved. Each battery in the bank needs to "see" the same parasitic resistance as the others in getting to the load. Same argument for sources.

One can calculate just how much parasitic resistance is tolerable for each cable, connection and battery for any given peak load so that no other load ever sees a voltage that does not meet its minimum operating specified volage. One does not need to overspecify beyond assumption of normal time degradation due to thermal heating causing annealing of copper in the attachment points. Periodic tightening of all components prevents that.
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Old 23-04-2009, 18:45   #9
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Quote:
Originally Posted by Rick View Post
A proper heirarchy of load terminal attachments to a distribution point (a star arrangement is superior to buss bars) the highest current sources and loads stack together in the center and the lighter loads/sources stack on both sides from "center" outward on a stud. This heirarchy minimizes voltage drops caused by parasitic resistance.
Rick, could you explain this STAR arrangement?

My system which I put together has a very large "main" BlueSeas buss for all the large loads : windlass, inverter, battery switch for house ALL house switched loads, alternator and to an "always on" circuit for radio mems, 12v cig plugs, gas alarm etc. The cables are not arranged in an special order on the buss. Does it matter?
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Old 23-04-2009, 18:48   #10
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I suspect this is similar to what Rick was referring to:

PowerPost Plus Cable Connectors - Blue Sea Systems

But I could be wrong.
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Old 23-04-2009, 19:23   #11
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I use those as well. My question was more about the arrangement of large cables 2/0 etc which are on a 4 post 600amp buss - does the order of the cables matter?
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Old 24-04-2009, 16:11   #12
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Star vs buss

A "star" arrangement consists of all conductors meeting at one point in space. Obviously not practical unless one uses a stud from which all terminals are stacked (using the aforementioned heirarchy). The cables wind up exiting the stud radially due to the usual way that the terminals are formed which do not allow room for the cables to ride on top of each other well.

Attachment to buss bars should follow the same heirarchy with the highest current carrying conductors in the center of the bar and the othes falling to the sides with lower current ratings.
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