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Old 22-10-2010, 09:08   #1
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Build My Electrical System

Through no fault of my own, I am somehow now the proud owner and chief electrician of a sailboat. She's equipped just as she was the day she left the showroom in 1982, plus or minus one (1) Truecharge 10TB mounted battery charger.

She currently has one D8 battery of questionable heritage that runs the whole show. The battery is mounted in the cabinetry next to the icebox, so not quite the ideal location, but as of yet I have no clever ideas for a new home for it or any potential new friends it might want to share the load with.

The alternator is apparently whatever's commonly bolted to Westerbeke 30s.

We will both eventually and perhaps live and work aboard, so we'll be powering two laptops. Replacing all lighting with LED is somewhere in the first 10 pages of our list. We're planning to leave the rest alone - pump water, no refrigeration, no watermaker - at least for now, so starting out we have pretty minimal power requirements. Eventual plans include cruising at least as far as Mexico.

The budget is limited, but we'd rather spend more than we want to and not have to think about it later than to fight not having enough power.

How would you approach this situation, and what else should we be thinking about?
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Old 22-10-2010, 09:23   #2
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A few things I would look at.

1. Condition of the existing wire and terminals. On old boats the wire tends to corrode, usually obvious and visible at the ends where a terminal is crimped on and attached to the load (light, pump, radio, etc). Bad connections and wire where the copper has turned green inside the insulation will give you fits. Might work usually and fail at the most inopportune moment. Also, depending on the expertise of the PO look at any new wiring and new electronics installations to make sure the wiring was done correctly.

2. Running lights. Don't want them to fail in a busy channel at night.

3. Bilge pumps. Condition, size, wiring, switches.

4. Go for at least 100 amp, heavy duty alternator. If the budget allows go for external, multistage voltage regulator.

5. I would have two house batteries and a separate starting battery.

6. If you will be at the dock often get a good, multistage, smart charger. If mostly on the hook dedicate the budget to solar or wind charger and a small portable generator for backup.
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Old 22-10-2010, 09:42   #3
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The existing wiring, including running lights, looks great. The ONLY non-factory wiring is the battery charger, which looks good to me as well.

Why would I want a 100 amp, heavy duty alternator or an external, multistage voltage regulator? My budget will just have to stretch if it's something I need, but I'm also not going to buy something because it's expensive. (It's an honest question - what's the tangible advantage over my ~60A?? internally-regulated alt?)

What sort of house batteries? D8? AMG? G27? Wal-Mart "Marine"?

A separate starting battery is on my list, but I have no idea where to put it or how to isolate it from the house bank.

I don't think a generator is something we want to consider.

Thanks!
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Old 22-10-2010, 10:26   #4
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What size is your boat? I had a 32 foot columbia with two 12v batteries and one charger and a battery selector switch which I would say is the minimum requirements.
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Old 22-10-2010, 10:33   #5
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Originally Posted by Dustymc View Post
Why would I want a 100 amp, heavy duty alternator or an external, multistage voltage regulator? My budget will just have to stretch if it's something I need, but I'm also not going to buy something because it's expensive. (It's an honest question - what's the tangible advantage over my ~60A?? internally-regulated alt?)

What sort of house batteries? D8? AMG? G27? Wal-Mart "Marine"?

A separate starting battery is on my list, but I have no idea where to put it or how to isolate it from the house bank.
Great Questions! I don't have all the answers, but let's look at some points.

I run Trojan T-105's as they seem to be the best bang for the buck I could find. 2 of them will fit in almost the same space as the 8D (a little taller) and give you 225AH of 12v deep cycle. I carry 450AH as this seems to suit our needs.

Trojan recommends charging at ~13% of AH capacity, so your 60amp alternator is more than adequate. The question comes down to the regulator, built-in vs. external multi-stage. I don't know the real answer but I find it amazing that all car batteries (starting batteries) are cooked at 14.2-14.4 volts the whole time a car is running and seem to last a reasonable amount of time. What I don't know is if holding deep-cycle batteries at a constant 14.2-14.4 harms them. I believe that your internal regulator on the 60a alternator could be disabled and you can then add a smart regulator like a Balmar. But again, I don't know if the bang for buck is there.

I do like the idea of a separate engine start battery, it's a good safety measure for that morning you decide to sleep in and run the house bank down. There are multiple options to let them charge from a single source, BlueSea comes to mind. I start my starboard engine from the house bank and have a separate starting battery shared by the port engine and generator. You can use deep cycle for starting, but you can't use a start battery for deep cycle. Deep cycle batteries won't deliver the same cold-cranking amps as a start battery pound for pound, but it won't harm them to start an engine.
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Old 22-10-2010, 10:35   #6
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Old 22-10-2010, 10:52   #7
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Quote:
Originally Posted by Dustymc View Post

Why would I want a 100 amp, heavy duty alternator or an external, multistage voltage regulator?
Its an interesting point. Grabbing my trusty Budget Marine Catalogue (2008) it says a 98 amp hour Alternator is $338 and a 90 watt solar pannel is $415

So, if and when you need more charging capacity you could look at buying a solar panel, then a second later if need be.
It would save you fuel in generating electricty too.

Also you'd save on the external regulator.

My panels just go straight into the house battery bank so its not quite accurate that everyone needs a solar regulator.

A solar pannel would also give electricity if, at some stage, the 60 amp alternator goes bung. You would never be without electricity for your engine start. (Even if you had to jury rig if the alt fell apart).

One final point... we never need to hook up to marina shore power now we have solar! In the long run that saves good money too! Especially cruising where some marinas charge a huge amount to electricity (somehwere we were hit for $5 day flat for electricty!)
Hope this adds spice to your decision list!
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Old 22-10-2010, 10:59   #8
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Originally Posted by Dustymc View Post
The existing wiring, including running lights, looks great. The ONLY non-factory wiring is the battery charger, which looks good to me as well.

Why would I want a 100 amp, heavy duty alternator or an external, multistage voltage regulator? My budget will just have to stretch if it's something I need, but I'm also not going to buy something because it's expensive. (It's an honest question - what's the tangible advantage over my ~60A?? internally-regulated alt?)

What sort of house batteries? D8? AMG? G27? Wal-Mart "Marine"?

A separate starting battery is on my list, but I have no idea where to put it or how to isolate it from the house bank.

I don't think a generator is something we want to consider.

Thanks!
No use in buying an expensive 100A alternator unless you have a really huge battery bank. A separate starting battery though, is something you really should consider. Separate it from the house bank with an automatic relay that prevents you from draining your starter at the same time as it makes sure the startier battery gets charged first, and when full redirects the charging current to your house bank Starter battery needs to be in good condition oc, but no need for higher capacity than perhaps 65-75Ah since you will only be using it for short term loads and it will get recharged almost instantly.
I have a 75Ah "cheapo style" batt for starter and 3x105Ah to power my TV, laptop, lights, instruments etc. Alternator is 65A and it works perfect
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Old 22-10-2010, 13:24   #9
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1. Why 100 amp alternator?

Lots of reasons but the short answer is to get the most charge into your batteries with least amount of engine time. Not sure if I am explaining something where you are an expert so stop me if I am. A 100 amp alternator does not put 100 amps into the batteries. If the batteries are almost fully discharged then you might be getting close to 100 amps, but as the batteries charge state increases the charge going into the battery decreases. So you can't put 100 amps into a battery in an hour with a 100 amp alternator. So the bigger the alternator and adding the external smart, multistage regulator will let you dramatically reduce your engine running time.

2. Many different ways to isolate a starting battery from the house system. Of course the advantage is knowing that your engine battery is always charged and you won't accidentally run it down playing the stereo. The cheapest, simplest method it to use battery switches but that requires that you never forget to change the switch. You can also get automatic switches, relays, isolator diodes, etc. Each has various advantages and disadvantages.

3. A small, portable generator could be a really handy item. Can buy a really good one for a few hundred bucks and put it in a locker. If you do end up with dead batteries in the middle of nowhere you can crank up the generator and recharge. Plus you can run power tools, microwave, etc while you are away from a dock.
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Old 22-10-2010, 13:40   #10
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" it says a 98 amp hour Alternator is $338 and a 90 watt solar pannel is $415"
Mark, shouldn't that read "1411 watt Alternator" to compare watts to watts on the solar panel? <G>

15.6x more power coming out of the alternator for 22% less cost.
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Old 22-10-2010, 13:42   #11
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No, I'm far from an expert. If the answer is only "100 amps is more than 60" then it's a fairly arbitrary decision and I can do my own math. If the answer is more like "you'll fry your batteries/alternator/never get fully charged/etc." then that's another matter.

What's the "external smart, multistage regulator" have to do with anything? (Again, not an "expert" or trying to be a smartass - I really have no idea how moving the regulator outside the alternator case affects me, and I don't understand the difference between a "smart" and "dumb" regulator.)

What of the above changes if I go to AGM batteries, which are potentially appealing because I believe I might be able to stuff a couple of them down into my bilges? I'm sure it was written by someone trying to sell something, but Google tells me that AGMs can fry an alternator. Is that where the "smart" regulator comes into play?
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Old 22-10-2010, 14:30   #12
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"What's the "external smart, multistage regulator" have to do with anything? "
Internal regulators tend to be "automotive" regulators, designed to not overcharge an SLI battery during the course of a long day on the road. That means they quickly shove in enough power to compensate for starting (which isn't much) and then quickly ramp back to a slow charging rate, so that running all day on the highway won't overcharge the battery, but mainly will just pick up the load from the lights and heater fan.
In contrast an external regulator usually can be programmed (or has been programmed) to provide maximum output in order to feed a big hungry battery bank as quickly as it can, expecting that the engine will be shut down as soon as possible, and throttling back the charge only when the battery gets too hot or too fully charged. Totally different design philosophy.

"but Google tells me that AGMs can fry an alternator. " I think you've misconstrued something. A large battery bank, combined with a bad regulator design, can cause an alternator to overheat but AGM per se has nothing to do with that, it is a bad regulator design. The design can be bad, and cheap, and IF the original battery and alternator were matched by design--it'll still work.
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Old 22-10-2010, 16:50   #13
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Im still not convinced that the 100A alternator is to prefer on small battery banks.
I say the single most important thing when it comes to boat and electricity is the cables/wiring. Start off by checking all wires and connections. Make sure they are dimensioned correctly acc to length and load, and that theyre not corroded. If you dont have this basic thing right, then you can go buy as many alternators as you wish, and still not get anything out of it.
Also, figure out what your power need is. Maybe youre better off by just getting one or 2 more batteries for the house bank? If you dont have more than about 225Ah (plus start batt) then you really have no use for a 100A alternator.
Do some math and then decide, using the energy balance scheme you get, is my suggestion. As an example:

If you use per 24 hrs (rough figures and just as an example)
Lights: 8Ah
Fridge: 12Ah
Pumps: 1Ah
Laptop: 24Ah
Others: 5Ah
You get a total drain of 50Ah
Now, with a FRESH electrical system, using good sized wires and connectors, a system with just a 50Ah alternator will generate 45A in one hour. Not taking into consideration that you probably have some of the above already covered with a solar panel you wont have to motorize more than an hour to have your batteries recharged. I just cant see why one should pay good money for something that you can achieve just by making sure your wiring is ok. Someting you must do anyway.

As far as the AGM frying: As said above, no you cant fry the alternator if you use AGM`s. However, you CAN fry your AGMs with your alternator. Why? Because some AGM`s wont like 14.4V charging power. Older batteries more common than newer ones and Im not sure its even a problem with todays batteries but it might have been this you could have misread when googling the AGM? And this problem might be solved using an external regulator too.
EDIT: I made a mistake in translation between engl and swe. I was talking about Gel-batteries NOT AGM`s, so the above is incorrect,

My advice: See how much power you are likely to use. Get batteries to accomodate it and if more than about 225Ah, you may be well off with a more powerful alternator. But in either case: Make sure your wiring is in perfect condition.
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Old 22-10-2010, 17:54   #14
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Internal regulators tend to be "automotive" regulators, designed to not overcharge an SLI battery during the course of a long day on the road. That means they quickly shove in enough power to compensate for starting (which isn't much) and then quickly ramp back to a slow charging rate, so that running all day on the highway won't overcharge the battery, but mainly will just pick up the load from the lights and heater fan.
In contrast an external regulator usually can be programmed (or has been programmed) to provide maximum output in order to feed a big hungry battery bank as quickly as it can, expecting that the engine will be shut down as soon as possible, and throttling back the charge only when the battery gets too hot or too fully charged. Totally different design philosophy.
No disrespect, but......
Hmm, please explain how the regulator works when all it does is sense battery voltage and excite the field accordingly. Regulators don't sense how much current the alternator is putting out, they simply measure the battery voltage and crank the field voltage up until they can see the battery voltage rising. IOW, if an "automotive" regulator is set to 14.2v, he'll crank the field voltage up proportionally to the difference between the battery voltage and 14.2V. He doesn't regulate the current the alternator is putting out, that's a function of the capacity of the alternator. Use the same regulator on a 60A alternator or a 200A alternator, guess what, the regulator doesn't have a clue how many amps the alternator is putting out.

I also see a dicodomy between 'use the big alternator so you don't have to run your engine as long' and the battery manufacturer asking for a longer slow charge rate. Again, Trojan recommends a 10-13% of AH capacity charge rate. On my 450AH house, that's ~50amps.

Why is Trojan asking for a lower charge rate? Could it be because it affects the longevity of the battery to continual burn it with a higher charge rate??? Hmm, I'll take the advise of the manufacturer's engineers.
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Old 22-10-2010, 18:10   #15
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No disrespect, but......
Hmm, please explain how the regulator works when all it does is sense battery voltage and excite the field accordingly. Regulators don't sense how much current the alternator is putting out, they simply measure the battery voltage and crank the field voltage up until they can see the battery voltage rising. IOW, if an "automotive" regulator is set to 14.2v, he'll crank the field voltage up proportionally to the difference between the battery voltage and 14.2V. He doesn't regulate the current the alternator is putting out, that's a function of the capacity of the alternator. Use the same regulator on a 60A alternator or a 200A alternator, guess what, the regulator doesn't have a clue how many amps the alternator is putting out.

I also see a dicodomy between 'use the big alternator so you don't have to run your engine as long' and the battery manufacturer asking for a longer slow charge rate. Again, Trojan recommends a 10-13% of AH capacity charge rate. On my 450AH house, that's ~50amps.

Why is Trojan asking for a lower charge rate? Could it be because it affects the longevity of the battery to continual burn it with a higher charge rate??? Hmm, I'll take the advise of the manufacturer's engineers.
First, a proper, smart regulator will not shorten the life of a battery. In fact I believe data shows that a well charged battery will outlive a constantly undercharged battery.

Either way, I would rather risk the early demise of a $200 battery than putting a lot of extra hours on a $20,000 engine.

Then there is the aggravation of listening to the engine run for hours every day to charge the batteries.
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