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Old 16 November 2005, 05:48   #11
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Quote:
Originally Posted by MadMat
Except a split charging diode has a voltage drop across it so neither battery ends up being fully charged.
From Here
'Typical voltage drop @ 120Amp models ~80mVolts (new models).'
Hardly worth worrying about considering
'With common machine sensed alternators, batteries are, in most cases, charged to only 60 - 70% of their capacity, however long the engine is running.' from here but then Mandy Rice-Davis comments might apply.

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KISS!
Agreed
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Old 16 November 2005, 06:56   #12
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so does 2 x 60 amp battery give you a 120amp feed , curious as i have 2 x 60amp batterys on my optimax and i now know it state's being or recomended 100amp for the engine?
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Old 16 November 2005, 07:16   #13
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so does 2 x 60 amp battery give you a 120amp feed
Yes, just make sure the wiring is capable of the higher current.
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Old 16 November 2005, 07:21   #14
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thanks for that i normally start it on both batterys first time in water then switch to one for the rest of the day, and next outing switch to the 2nd battery that way i have allways got a good charge in both,
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Old 16 November 2005, 07:29   #15
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Yes, but look at the price you're paying for the 80mV priviledge.

Quote:
Originally Posted by Nick Thompson
From Here
'Typical voltage drop @ 120Amp models ~80mVolts (new models).'
Hardly worth worrying about considering
'With common machine sensed alternators, batteries are, in most cases, charged to only 60 - 70% of their capacity, however long the engine is running.' from here but then Mandy Rice-Davis comments might apply.

Agreed
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Old 16 November 2005, 08:07   #16
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Originally Posted by MadMat
Yes, but look at the price you're paying for the 80mV priviledge.
Of course it's expensive. It's a 'marine' product, what else do you expect ?.
Although (providing it could handle the environment) a cheap relay would do the same thing.

As to whether it's worth it would depend upon the user, IF you use the boat regularly, can remember which battery was used last & the batteries are in good condition it's probably a waste of money.
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Old 16 November 2005, 11:25   #17
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Its horses for courses.

You can make it idiot proof, but when something does go wrong it will take an expert to fix it.

Brian,
Quite agree, but a yacht engine is not an outboard.

Nick,
Very true, but the first warning I would have had of a problem would have been too late. 2 flat batteries!

Two 80 Ahr batteries in parrallel does not make a 160Ahr battery. There are losses involved (Sods Law?) and it should be de-rated to about 85% making about a 140Ahr.

And back to the point, if you are going for belt and braces, where would you put the blocking diode? It needs a volume of air to dissipate the heat, so would probably have to go inside the console. Then it would need long cables that are very thick (battery cables) and so on. Like MadMat says K I S S...

Sorry Andrew, seem to have ommitted the obvious. As regards choice of batteries, you have many options, cheapo car battery for about 40, Pukka marine battery for 80+. Differences are numerous but in my experience its cheaper to use car batteries and replace them every two years than to buy the marine versions which are overpriced because they are ... Marine!

Tim'mers.
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Old 16 November 2005, 11:31   #18
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Two 80 Ahr batteries in parrallel does not make a 160Ahr battery. There are losses involved (Sods Law?) and it should be de-rated to about 85% making about a 140Ahr.

An

Tim'mers. [/QUOTE]

so the recomendation of 100amp makes me safe then,,,, as i am runing approx 140a,,
Ohh its all getting stress full
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Old 16 November 2005, 11:38   #19
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Quote:
Originally Posted by Swifty
Two 80 Ahr batteries in parrallel does not make a 160Ahr battery. There are losses involved (Sods Law?) and it should be de-rated to about 85% making about a 140Ahr.
Exactly where do these losses occur? Lead acid accumulators are very efficient and have a very low internal resistance, hence their suitability for supplying high currents.
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Old 16 November 2005, 11:48   #20
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Quote:
Originally Posted by nugent
so the recomendation of 100amp makes me safe then,,,, as i am runing approx 140a,,
Ohh its all getting stress full
Looks like you have enough there to crank over a big diesel
My Searider runs on 2x 60 Ahr car batteries. Admittedly my engine doesn't need as much power as an opti.

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