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Old 11 December 2007, 14:09   #21
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On his drawing he has connected the negatives on the batteries togethor, this is wrong? IMHO Or is it right? IYHO
But negative is common to both batteries and the electrical system, would be difficult to not have them connected together, otherwise you'd need an isolator and selector switch for the negative as well
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Old 11 December 2007, 14:23   #22
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Andy,

I thought you were only supposed to have the switch set to the "both" setting in an emergency when you need to parallel the batteries together in order to get a boost,

I may be wrong on this but leaving the switch set to both when you are running is not good.

I would speak to Merlin Electronics 01202 697979 . They sell Blue Sea stuff so could help.

Chris
My uptake was that I would either run the outward leg on one battery and the return on the other, however it's just more conveinient to put it on Both. As far as redundancy is concerned, yes that's why I fitted two batteries. And it obviously works as I've had problems with one of my batteries and still got the boat working, however I only found out when I tried to operate my systems when the isolator was set to position 1 and found out that way, so obviously a flawed system as I only found the problem by accident. But if I installed twin voltage guages to monitor each battery, well that wouldn't have worked in this instance either as it's a problem with load and not voltage as I think the battery terminals are shot as both turn, this was caused I think at the time the engine was rigged and was the result of an over enthusiastic Rigger that didn't stop the terminals from turning when doing up the cables on the studs resulting in internal damage.

The other reson I liked the Idea of twin batteries was because I can use the power of one battery when at anchor fishing and not be too worried about not starting the outboard.
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Old 11 December 2007, 15:14   #23
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Andy

Hi

I try to avoid the 'Both' position as much as possible.
In this position my opinion is that there is a possibility a duff battery will discharge the other one, or even another electrics problem will drain both batteries, then you've negated most of the advantages of having two seperate batteries.

I do exactly what you have suggested.
Battery 1 for the outward leg, and Battery 2 for the return.
It keeps both batteries topped up, and in use.

I have an 85AH halfords Battery of unknown age that came with the boat 4 years ago, and a 110AH Halfords Battery that I fitted during the rebuild process about 3.5years ago.
The intention was to replace the 85AH one with another 110AH one when it gave up the ghost, but despite being neglected for a month or even 2 at a time its still going strong, as is the 110AH one.

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Old 11 December 2007, 15:19   #24
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Andy, are you familiar with this thread?
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Old 11 December 2007, 16:19   #25
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I sure am Jeff, and a possible future addition to the gear on board, but for the moment I guess I'm happy doing it the manual way.
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Old 11 December 2007, 16:22   #26
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Andy

Hi

I try to avoid the 'Both' position as much as possible.
In this position my opinion is that there is a possibility a duff battery will discharge the other one, or even another electrics problem will drain both batteries, then you've negated most of the advantages of having two seperate batteries.

I do exactly what you have suggested.
Battery 1 for the outward leg, and Battery 2 for the return.
It keeps both batteries topped up, and in use.

I have an 85AH halfords Battery of unknown age that came with the boat 4 years ago, and a 110AH Halfords Battery that I fitted during the rebuild process about 3.5years ago.
The intention was to replace the 85AH one with another 110AH one when it gave up the ghost, but despite being neglected for a month or even 2 at a time its still going strong, as is the 110AH one.

Nasher
I did forget to mention that I always Isolate the electrics when I leave the boat, so unless there is a problem with the battery that affects both whilst under way I guess I'm covered, but agree with Jeff, that I need to consider a way of charging both batteries whilst underway without using both batteries, if you get what I meen.
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Old 11 December 2007, 18:15   #27
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Old 12 December 2007, 10:41   #28
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But negative is common to both batteries and the electrical system, would be difficult to not have them connected together, otherwise you'd need an isolator and selector switch for the negative as well
Think the drawing has made it a little difficult to see what the system is trying to do, appears to have two terminals marked 1 & 2, presumed these are for the power to his engine /systems, but perhaps not?
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Old 12 December 2007, 11:56   #29
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On his drawing he has connected the negatives on the batteries togethor, this is wrong? IMHO Or is it right? IYHO
No that's fine. It gives them a common connection, so the positives are (theoretically) at the same electrical potential, though isolated from each other. With the grounds connected, you only need to switch the positive lead to switch batteries.

Quote:
Originally Posted by Hightower
My uptake was that I would either run the outward leg on one battery and the return on the other, however it's just more conveinient to put it on Both. As far as redundancy is concerned, yes that's why I fitted two batteries. And it obviously works as I've had problems with one of my batteries and still got the boat working
If you fitted the two batteries for redundancy and are running on both, you're defeating your own purpose. On both, you do not have 2 batteries; you have one larger battery. And I think you're mistaken in your assessment: It doesn't "obviously work"; I think you just got lucky.

The outbound on 1 and return on 2 is good, except that you have the possibility of being at a remote spot, running 1 down, and finding out 2 hasn't been charged. Better is to run half of the outbound on 1, then switch to 2; that way you end up at your remote site with 2 charged batteries.

Bedajim's isolator/combiner (and similar) takes care of the problem of remembering to switch by charging both batteries even if you have the selector set to a single battery.

jky
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Old 12 December 2007, 12:26   #30
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No that's fine. It gives them a common connection, so the positives are (theoretically) at the same electrical potential, though isolated from each other. With the grounds connected, you only need to switch the positive lead to switch batteries.



If you fitted the two batteries for redundancy and are running on both, you're defeating your own purpose. On both, you do not have 2 batteries; you have one larger battery. And I think you're mistaken in your assessment: It doesn't "obviously work"; I think you just got lucky.

The outbound on 1 and return on 2 is good, except that you have the possibility of being at a remote spot, running 1 down, and finding out 2 hasn't been charged. Better is to run half of the outbound on 1, then switch to 2; that way you end up at your remote site with 2 charged batteries.

Bedajim's isolator/combiner (and similar) takes care of the problem of remembering to switch by charging both batteries even if you have the selector set to a single battery.

jky
I've got mine set up as a starter and a house, but the house is capable of starting the engine if required

The engine gauges show battery charge when running so I know what's happening with charging and I've got a meter for the house showing
charge/discharge amps, voltage and charge in the battery
I also routed the battery cables so that if it hits the fan you could swap cables to batteries etc to give me the maximum number of options to get home

James
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