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Old 10-13-2014, 01:41 PM   #1
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Perko Selector Switch Wiring

I spent the weekend trying to figure out what batteries do what on my boat and how that relates to the "Perko" selector switch on my electrical panel. The boat is a 1991 Ocean Alexander 44'.

According to the build sheet from OA, the switch should be wired #1 position 1-8D battery to start port engine, #2 position 1-8D battery to start strbrd engine.

How the switch is actually wired, position #1 - 2-6 volt Trojans wired to 12 volts used as house bank, yeah very small house bank. Position #2 wired to the 2 - 8D batteries which are used to start both engines.

Here's my concern; using up all of my starter batteries while at anchor by selecting position #2 on the switch or having about 4 hours worth of battery using the #1 setting for the "house" bank. I do have a generator to use to charge the batteries if I drain them.

One option I've thought of is going back to stock, and having 1-8D battery isolated for each engine. Then I could use 1 battery for my house bank and still have a fully charged one to start both engines. Then I started to wonder if the 2-6 volt batteries, currently in poor condition, would start my Caterpillar 3208's. This way I wouldn't have to worry about draining the 2-8D's or re-wiring the selector switch. All that would be necessary would be to replace the 2-6 volt batteries.

Any thoughts would be appreciated.
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Old 10-13-2014, 02:46 PM   #2
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I can't recall ever seeing a boat wired this way: "According to the build sheet from OA, the switch should be wired #1 position 1-8D battery to start port engine, #2 position 1-8D battery to start strbrd engine." That would be one battery switch choosing which engine to feed. 100% backwards! Something got lost in translation!
You should be using your house bank (GC's) at anchor not the starting batteries. If that is too small, either increase the capacity of the house bank or lower your load demand or both.
1- 8D is enough to start a 3208. 2 in parallel is a healthy extra margin of capacity.
Running the bank down until the gen is needed to recharge enough to start an engine is a bad plan.
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Old 10-13-2014, 03:11 PM   #3
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You identify the source for each position, but what is the destination? The 12 volt panel, giving a choice of which bank is the house bank(sounds like)? Do you have a parallel solenoid and switch to momentarily combine the banks if one start bank goes bad ? How are these batteries charged? I take it the two 8D's are wired to both engines?
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Old 10-13-2014, 04:32 PM   #4
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Anytime I see a battery selector switch question my advice is the same - Do away with the switch, have a starting battery (or two in your case and a separate house battery or bank. Use a battery combiner (automatic charging relay) to keep everything charged. You can run the house battery down completely and still start the engine(s). There's no manual intervention and nothing to remember or forget.
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Old 10-13-2014, 08:23 PM   #5
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First, thank you for the replies, I do appreciate your input, it gives me food for thought.

Let me clarify what I'm trying to accomplish, having separate starter and house banks so I can run down the house and still start the engines.

High Wire, I'll re-check what I read and make sure I got it right when I'm on the boat later this week.

CalTexFlanC, the destination is a round "Perko" type switch on the main electrical panel so yes I can chose either #1 or #2 as the house bank. Yes, there is a parallel solenoid and switch. From memory, it is a Pro Mariner 50 amp charger wired into the boat (big blue box).

Rwidman, if I have to call a professional in, which will be for most anything beyond replacing exactly the batteries that are in there, I'll look into a combiner.

So after thinking about his for a bit, why can't I add enough batteries to the #1 slot (where the 2-6 volt Trojans currently are) to use as the starter bank and then use the 2-8D's in the #2 slot as the house bank. So now my question is would 2-group 37's start the engines or will they need one of the 8-D's?

I've had my OA just a short time time. I came from a 34' sailboat and while it had similar systems, there is a big difference between the two. What I'm doing is thinking out load in a group of people who know what they're talking about. If my ideas are goofy, it's OK to let me know, that's why I'm posting here. Thanks again for your help.
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Old 10-14-2014, 06:02 AM   #6
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>You can run the house battery down completely<



Even real deep cycle batts have a far shorter life if >run down completely<.

Killing 2 golf carts in 4 hours means either there mostly dead ,or your loads are way too high .

Evereything you can do to reduce batt loads will be a huge help, but first install a SOC meter to be able to understand the loads you are feeding , and the charge going back in to the batts.

8D is a size , not a type , they can be starts or deep cycle .

>From memory, it is a Pro Mariner 50 amp charger wired into the boat (big blue box). <

The P-M chargers are sometimes set to do 4 batts at once , so that 50A charge will be 1/4 to each individual batt, which means overnight charging , not just a while on a noisemaker.
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Old 10-14-2014, 06:40 AM   #7
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http://www.perko.com/images/catalog/...(8500INS1).pdf

Perko's wiring instructions.

A lot of what you need for a house bank depends on how you use your boat. If you spend a lot of time on the hook using house bank power vs marina to marina with a little anchor time in between calls for different needs and power options.

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Old 10-14-2014, 08:15 AM   #8
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Quote:
Originally Posted by FF View Post
>You can run the house battery down completely<



Even real deep cycle batts have a far shorter life if >run down completely<.

.........
Yes they will. I am not suggesting that anyone run their batteries down completely, just that with a combiner, accidentally running the house batteries down completely won't leave you stranded somewhere needing a jump start or a tow.

Is it clear now?

The real advantage of a combiner over manual switches is, you don't have to think about your batteries (except for checking the electrolyte level if applicable) and you don't have to worry about forgetting to switch a switch. And they are not expensive.
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Old 10-14-2014, 12:18 PM   #9
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I agree with Ron. The Automatic Charger Relays really make battery management a no brainer.

I've had very good luck with the Blue Sea brand.
https://www.bluesea.com/products/761...12_24V_DC_120A
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Old 10-14-2014, 02:32 PM   #10
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For me, the ideal setup is with battery switches installed in an accessible area (preferably out of the ER) and a combining relay to tie batteries together for charging. The manual switches will allow you to turn off the source of power to house or start circuits in the event of a fire.

I have both on my boat and the switches will only be needed in an abnormal or emergency event. The charging is routed directly from the alternators to the batteries so switch position will only affect the loads...not the charging. If I need to remove alternator charging, I can turn off the key to kill the field or turn off the engine.

I don't need to touch the battery (load) switches during normal boating operations. If my start battery dies, I can use the switches to connect my house bank with the start battery for engine starting. If an electrical fire starts, I can immediately remove power from the affected circuit without entering the engine room.

My boat was originally wired to provide the charging current through the start cables. The wiring from the alternator to the starter was woefully undersized for modern alternators. Also, there was no way to switch charging without switching loads. If I wanted to charge the start bank, my loads were also shifted to the start bank. If I wanted to charge both start and house banks, the batteries were tied together manually at the switches and loads were shared, too. When I'd forget to move the switch back to house on anchor, the loads would draw down both batteries. I felt this was a poor system design and I changed it to separate the charging circuits from the load circuits with properly sized cables.

Just my guess, but I would think you could start those Cats with a pair of Group 31 batteries...one for each engine tied with a switch to allow you to parallel the pair for additional power if needed. Then you could use the 8Ds for your house (they're deep cycle, right?) until they need replacement. You'll gain about a 50% battery capacity increase if you replace the 8Ds with six 6V golf cart batteries in parallel/series to give you a 660AH 12V bank.

I have a single 8D start battery for both engines and used to keep it on my multi-bank charger. It really didn't need that constant charging so when I replaced the charger, I went with a single-bank charger and a Yandina combiner with a small single control wire ON/OFF switch to allow me to control the charging from the helm with the flip of a small switch. It's hardly ever turned on, but it's there if I need it. The start battery gets plenty of charge through the port alternator and has zero demand while at the dock or on the hook. My SOC meter monitors its voltage so I get a good look at its condition at all times. If I come to the boat after a month of non-use (rarely happens) the start battery might be sitting at 12.4 or 12.5V. I'll flip the combiner switch on while prepping the boat just to top it off. I have little doubt that the battery could still start the engines at that voltage, but I do it anyway.

Here's a pic of the panel with the Combiner ON/OFF switch just after installation.



On my boat, the ~50A port alternator charges the start battery and the stbd 120A alternator smart charges the 660AH house bank. The 55A Iota shore charger is wired to the house bank and, through the combiner to the start bank. When the combiner is selected on, once the house bank reaches 13.1V (+/-), the combiner closes allowing the charging current to be shared with the start battery. I use a small Honda generator to provide charging at anchor through the boat's shore power outlet and the Iota charger.

I'm not saying this is the best configuration for your boat, but it works well for my little boat. When my 8D start battery finally dies, I'll replace it with a single group 31 to start my pair of Perkins 4.236 engines and add 2 more golf cart batteries to increase my house bank capacity by 220AH.
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Old 10-15-2014, 06:39 AM   #11
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>The Automatic Charger Relays really make battery management a no brainer.<

Thats why RV.s have been using a solenoid wired to the ACC position of the key switch, for 6-7 decades.

$18.00 and no need to understand anything , the house charges automatically., after every engine start.

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