Fish finder and power draw off

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    Posted: 25 Apr 2017 at 7:05am
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I use a Lowrance Elite 7 Chirp.
My power supply is a twin battery set up using a Blue Sea ACR and battery isolater.
I recently discovered that I can display battery voltage on the FF screen.
A useful tool.
However, after electing to use this display I have become concerned at the apparent power consumption of the FF.
The voltage displayed after I switched on the FF was 13.1v (system plugged into smart charger to maintain levels). But I became alarmed as I watched this voltage drop away until after about 15min, it had fallen to 12.1v
No other devices were on.
According to the manual for the FF, it draws .75amps.
I have to admit this means nothing to me and as much as I have tried to understand what this is in practice, I am none the wiser.
My question is; is this to be expected. Or is there a fault I am unaware of eg. bad connection somewhere, too small gauge wire for power supply etc.
This occurrence raises an issue of twice having a flat house battery following fishing trips where boat was at anchor and no motor charging batteries.
Any thoughts would be much appreciated
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Post Options Post Options   Likes (0) Likes(0)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2017 at 7:28am
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I turn my fishfinder off when anchored anyway but a healthy battery will power one for ages. Batteries (most boat batteries) are 12v and the 13.1v you are seeing is the remnants of the charging voltage. you certainly be concerned if the voltage continues to drop below 12.0v but 12.1 is fine. To check it try watching it at home with the nav lights and other loads on. Just turn the FF off and on to check voltage if you're concerned about your transducer.

When you test a battery with a volt meter even a flat one can show the correct voltage until you apply a load then it drops off real quick.

Having said that there must be a problem if the battery is going flat. It shouldn't drop below 12v with a light load like that. I'd get an auti sparky to test the batteries.
Best gurnard fisherman in my street
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Post Options Post Options   Likes (0) Likes(0)   Quote RaggedJoe Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2017 at 7:39am
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Smudge, do you turn it off to save battery or stop the transducer scaring fish? Never been sure of the reality of that...
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Post Options Post Options   Likes (0) Likes(0)   Quote AdAstra Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2017 at 8:28am
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Yeah. Thanks for that. Will get on with that check later today.
I guess what bothers me is that the house battery is near new. Bought end of Feb to replace one that I presumed stuffed.
It makes me wonder if it was OK and problem was/is something else!
Auto sparky would be the answer. But will make that the last resort.
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Post Options Post Options   Likes (0) Likes(0)   Quote Kevin.S Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2017 at 10:20am
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Most decent battery places will test a battery for free.  If they have the kit it only takes a few minutes to do.  At least that will confirm if battery is OK or not.
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Post Options Post Options   Likes (0) Likes(0)   Quote AdAstra Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2017 at 5:03pm
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Think I have it sorted.
Had sounder running near enough all day. Volt meter showed 13.3 at start. This was just after I disconnected charger.
Voltage quickly dropped to 12.2/3 then steadied.
Switched on nav lights which cause a drop to 12.1 but soon went back up to 12.3.
Left them like this for some time. No change.
Switched lights off. Voltage gained .1 then settled back to 12.3. That's where it remained until I shut everything down and reconnected charger.
So it seems that a battery when not connected to any form of charging will shed excess voltage quickly and then settle I suppose until it starts to run down!
I understand that a fully charged battery 'at rest' should indicate 12.7v.
The only thing that still puzzles me is an on-going issue of the batteries charge %.
As I said, voltage indicated 12.3 on the FF screen confirmed by that indicated on my charger. Yet the % shown was just 20%.
As said, this has been an unresolved issue. I think it must be a false reading by the charger!
Thanks anyway for all your input.
Cheers
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