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Old 30 July 2009, 17:34   #11
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Sorry, forgot to mention that they only cost a tenner or so.
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Old 30 July 2009, 18:21   #12
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Hi Polwart

I suspect the figures that you are quoting are not accurate. If our battery had run out of steam after only 6 hours, I'd either have bought a regulator for the motor or a bigger battery.

Without hunting for my manuals, I have had a quick search on the net for power consumptions of my electronics.

VHF quoted as 0.5A, GPS 0.8A at max power.

Presuming 1.3A and the 25 AH figure you quoted, this should give give me at least 19 hours operation for those two.

The sounder uses 0.8A at max power, very unlikely in a shallow North Sea, and is switched off except when motoring.

I suspect the pump uses a fraction of what you think. When testing the efficiency of the PWM, I had it pumping water for over 24 hours on a 7Ah alarm battery before I got tired of hearing running water outside and switched it off.


Having checked, the battery we are now using is a Leisure 685L. It seems that this is not 50AH but 85 and costs / weighs in at about the same as a 50. That said, we had quite happily been using Halfords 50A batteries in our boats up until we replaced them at the start of the summer. The old ones lasted for over 3 seasons before noticeably tailing off.
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Old 30 July 2009, 18:29   #13
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The pump was a total guess - since I have never really looked at one, and obviously you have taken steps to reduce its consumption. But I think I understand what you are suggesting - that a big battery may be fine without charging.
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Old 30 July 2009, 23:28   #14
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Worth a look - very efficient batteries for their size & weight that can be deep cycled.

http://www.odysseybattery.com/battspecs.html
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Old 31 July 2009, 09:34   #15
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Quote:
Originally Posted by m chappelow View Post
once towed a boat back in ,this young lad no experience had bought a speedboat with no electrics ,so he fitted lights radio ect ,wired up engine straight to a battery ,,,no rectifier ,,,and 20 mins later boom went the battery .acid everywhere ,,,,his tart wasent to impressed when her clothes started to disintergrate later on.
That's one way to get her clothes off...
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Old 31 July 2009, 09:42   #16
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Quote:
Originally Posted by Polwart View Post
not sure what you mean by that or what you would consider reasonable. IIRC my 20 HP engine's "charging" output is rated a 7 A. (I would guess it probably does less at tickover/trolling speed). Since you have a 50 Ah battery I'll assure that is "reasonable". In reality it will only usefully give 25 Ah of power.

Your VHF and GPS are probably drawing 1-2 Amps (except when VHF transmitting). I guess the bait pump uses a similar power to a bilge pump so is drawing another couple of amps.

So the net draw is probably similar to the net input at trolling speed, and the battery should remain charged throughout. On the other hand your 50 Amp battery - with no "topping up" will probably give a maximum of 6 hrs operation until its output reached inadequate levels and by being continually "deep cycled" will not last very long.
All of this sounds too complicated for me. I'll probably just keep things as is and be safe. Maybe get a portable Hummingbird and forgo the lights. I don't usually go out at night anyway. M Chap's story is really scary! thanks for all of the great advice though!!!
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