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Old 01-08-2012, 02:38 AM   #1
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Default Battery Switch Relocation

Hi all, I have a 1997 2700 SCR, the battery switch is located in the engine compartment. It is a real pain in the #$s to get to and switch to a single battery or to switch to both. I am always worried that I am going to forget to switch to a single battery and end up with two dead batteries because of the difficulty in changing.

I am thinking of relocating the switch out of the engine compartment to the storage area directly above. Would mean new cables and some other modifications. Is this a bad idea?
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Old 01-08-2012, 04:38 AM   #2
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first, never run your boat on BOTH batteries.... that is 80 amp, only for emergency starts with half dead batteries. In says that in the first 5 pages of your mercruier manual.

The Searay's have a nice battery switch in the storage locker, so if it was a weather proof switch it would be easy to cut one into the side of the storage box, and connect the battery wire inline.

I thought about doing it myself, but in the engine bay it forces you to look in there to check it out before every trip.
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Old 01-08-2012, 06:05 AM   #3
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Is there ever a time when the battery switch should be on both ??? Except for the half dead batteries thing, just wondering.
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Old 01-08-2012, 06:03 PM   #4
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pascavone,

Good point on the forced opening of the engine compartment. I have a habit of doing that before every start regardless of the battery situation. Seems that it would a good idea before thinking all is good for the night anyway. The question of rather or not to have the switch on both whaile running the engine seems to depend on which expert you listen too. From doing a search on the boatus website the "experts" say this ok. Makes me wonder. From some of the information use of a combiner may be the best approach to ensure that both batteries get charged and lessen the chance of draining both. So just leave the switch in the engine comparment if I am going to open it up anyway.
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Old 01-08-2012, 06:21 PM   #5
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hai floaty,

welcome aboard.....i also have two batteries with a switch but i always let my boat run on battery 1 and have the 2th for reserve, loading both go's automaticly. once a month i check if battery 2 is in good shape...and thats it...never turn the switch of....than i have to open the motorhatch......just leave my boat always under power......risk of theft......i lock my boat at the front and at the back in my dockingplace with this locks.... http://www.doublelock.com/site/index...d&product_id=5

greatz, ed
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Old 01-09-2012, 12:25 AM   #6
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From everything that I have read, it is okay to have your switch on both with the engine charging if you have two of the same batteries at the same level of charge. If you have two different batteries, or they are at different charge levels, you should never run the engine with the switch in the both position.

So go out and buy two of the same new batteries and make sure they are at a full charge. Then you can just leave your switch in the Both position.
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Old 01-09-2012, 12:52 AM   #7
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Electricity always follows the path of least resistance ..... so leaving the position on both isn't the best idea.

When charging, electricity will flow to the better of the two batteries, since that is the least resistance, just the opposite of what is really needed. Since keeping two exact batteries seems improbable, I think it makes the most sense to have it on one or two and switch back and forth on a regular basis. This would force your charging system to charge each battery separately.

Just my two cents.
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Old 01-09-2012, 09:49 AM   #8
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I believe switch location from the factory probably has more to do with cost/time savings than anything else. Far easier and less expensive to locate the switch closer to the batteries and cables than it is to extend all that cabling to a more convenient, accessible, location.

While there is merrit in locating the switch inside the engine compartment to force a looksie, when I installed a 2nd battery and a switch I elected to install the switch outside of the engine compartment. A pre-flight check should be performed regardless of where the switch is. Really though, how many people raise the hatch before each and every re-start? I only check at the first start of the day and when I fuel up. Typical outing for us, and assuming both batts are mostly charged: Start on B1, let engine warm then switch to Both. Run the usual 30 or 60 minutes to where we're headed - thus ensuring both are charged, shut down and switch to B2 to run the lights, radio, etc. I'll normally re-start on B2 then run back on it only. Otherwise, switch to B1, start, and then switch to B2 to charge it. If we're going to several places to hang out there'd be lots to switching. If the switch was in the EC and there are 1/2 a dozen people on the boat I'd have to get them out of the way to open the hatch way to often.

From everything I read running on Both is not a problem as long as both are fairly charged already - the alt doesn't see much of a load. If one is significantly discharged then switching to both actually sucks power from the charged battery and delivers it to the discharged battery.

Combiners and isolators are probably the right way to do it as they take the guess work out of charging the batterys. Of course, all that stuff adds cost, complexity, and failure points. Everthing is a trade off. I opted for simplicity. I have 1 lead acid, 1 AGM, and one switch. The lead acid and AGM have similar charging characteristics (Gel's are the one's that don't play well with others). AGM's are nice because they only loose approx 3% of their charge per month from just sitting whereas LA's loose like 10%. Soon as the LA I have bites it I'll replace it with another AGM.

Dan
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Old 01-09-2012, 02:21 PM   #9
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battery on both provide 24 volts....... this will burn your starter motor, and the 80amp fuseible link holds that amp and current back from your harness, until it melts.



There are two basic ways to wire multiple batteries together, in "Parallel" or in "Series".

PARALLEL
Wiring two batteries which have the same output voltage in "Parallel", the output voltage of the combination stays the same but the amp/hour capacity of the combination is equal to the sum of their individual amp/hour capacities.

Wiring: Battery 1 Positive to Battery 2 Positive and Battery 1 Negative to Battery 2 Negative is Parallel wiring, retaining the voltage rating of either one of the batteries.

WARNING
It is not a good idea to wire two batteries which have different voltage ratings in parallel because the one with the higher voltage will immediately send current to the other one with the lower voltage to try to make their voltages both the same. The very high current which will flow between the two batteries is likely to make the batteries get very hot. IF THEY ARE CAR BATTERIES THEY COULD EXPLODE!


SERIES
Wiring two batteries which have the same output voltage in "Series" makes their combined output voltage equal to the sum of their individual voltages but the amp/hour capacity of the combination will be no greater than the amp/hour capacity of the smallest battery of the two.

Wiring: Bat 1 Positive to Load, and Bat 1 Negative to Bat 2 Positive, then Bat 2 Negative to the other side of the Load is Series wiring and the total voltage of the combined batteries is the sum of both individual voltage ratings.

So, assuming you want to get 24 volts out of two similar batteries, you could wire two 12 volt batteries in series.

NEVER OPERATE A 12 VOLT ELECTRICAL SYSTEM as in CARS or most BOATS with 24 VOLTS. YOU WILL BURN UP YOUR COMPONENTS AND SOME WIRING.

<><><>

Common Flashlights are simple examples of series wiring. Flashlight batteries are usually 1.5 volts whether they are AAA, AA, C or D size. So flashlights with with 1 battery are operating at 1.5 volts, 2 batteries are 3 volts, 3 batteries are 4.5 volts, etc.

Read more: http://wiki.answers.com/Q/How_do_you...#ixzz1iyFPbU6x
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Old 01-09-2012, 02:43 PM   #10
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Quote:
Originally Posted by pascavone View Post
battery on both provide 24 volts....... this will burn your starter motor, and the 80amp fuseible link holds that amp and current back from your harness, until it melts.
Correct me if I'm wrong but having the switch on Both/1+2 does not result in 24V IF the batteries are wired in parallel.
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Old 01-09-2012, 05:10 PM   #11
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Quote:
Originally Posted by ss3964spd View Post
Correct me if I'm wrong but having the switch on Both/1+2 does not result in 24V IF the batteries are wired in parallel.
Connecting in 'Series' = Double Voltage, Same capacity in amp hours (ah)
Example: Batt.1 (100ah/12V) + Batt 2 (100ah/12v) = Battery Bank (100ah/24v)

Connecting in 'Parallel' = Same Voltage, Double amp hours (ah)
Example: Batt.1 (100ah/12V) + Batt 2 (100ah/12v) = Battery Bank (200ah/12v)

The battery switch should be wired so it is in Parallel when switched to BOTH. If it is wired so it is in Serial when switched to both, that would make the 12v system a 24V system. I would not expect a 12v device to appreciate being on a 24v system and would think it could potentially be a costly mistake.
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