Power to a depth sounder

Installation of instruments and electrics in the Cape Cutter 19

Power to a depth sounder

Postby MickMitch » Thu Mar 13, 2014 6:30 pm

I acquired my Cape Cutter from the brokerage at HM last June, and now I'm looking to fit a depth sounder. I have bought a NASA Clipper depth sounder complete with the fixing kit and I am wondering what is the best way to provide power. I was thinking of getting a 12V sealed lead acid battery as sold by Maplin with a 7 amp/h rating. Would anybody know if this would be sufficient, as I may want to add some LED cabin and Nav lights at a later date.
I would also be grateful if anyone could send me photos of a similar installation, to give me an idea of what other components I may need, and how to go about installing them.
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Postby Ru88ell » Thu Mar 13, 2014 7:41 pm

Hi Mick
My first tip would be to avoid putting the transducer too close to the centre line. Mine was, and the thickness of the hull caused problems. Off-set by about 4".

The NASA system only draws 20mA, but if you plan to add more electronics you should think about what they will be now. A 7Ah battery won't give you 7 amps for an hour, or an amp for 7 hours. Only a fraction of the Ah rating is useful - this is why people oversize. And as batteries age they become less efficient.

There is a battery shelf under the cockpit with more than enough space for a 100Ah battery. I'm sure someone more proficient than me will be along soon with better advice.

Russell

ps - Are you coming to Mylor?
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Postby Dennis » Thu Mar 13, 2014 7:45 pm

Hello Mick

I used a 7ah lead acid battery on my previous boat to power a NASA duet (log/depth) instrument.

Proved fine for the purpose. I usually removed the battery half way through the season to recharge it.

It would also be suitable for use with LED cabin and nav lights but would need charging more frequently. Solar panels are reasonably priced nowadays.

It would not have enough capacity for VHF radio or a tiller pilot though.

As Russell has suggested, a larger capacity battery is easily sited on the shelf under the cockpit. I use a 26 ah (standard golf trolley size) battery and keep it charged with a 20 watt solar panel.

Best bet is to list everything that you might eventually fit, and size the battery on that.

Amp Hour ratings on batteries are given at the 20 hour rate. That means a 7 ah battery will give 350 milliamps for 20 hours. However if discharged at a higher rate the capacity is reduced, typically a 7 ah battery would only produce 3.5 amps for one hour.
Cheers

Dennis

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Postby erbster » Sat Mar 15, 2014 12:50 pm

I would agree with Russell and Dennis; the unit uses very little power, but you might find (as I did!) that when you start adding some electrics, you'll want more!

I think, if you are sure you want no more than sounder and led cabin lights, then a very modest battery would suffice backed up with a solar panel.

The advice to oversize the battery is important- you can't use more than about 50% of the capacity and the actual capacity is less than the manufacturers statement (and declines with age).

If you look at the photo albums on this site and people's blogs, you might get some ideas.
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Postby MickMitch » Thu Mar 27, 2014 8:41 am

Thanks for the help guys. Things are becoming clearer now. I am now getting more ambitious and I am considering cabin lights and nav lights. Has anyone used cordless cabin lights before or is it better to run them from the main battery?
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Postby Dennis » Thu Mar 27, 2014 10:47 am

MickMitch wrote: Has anyone used cordless cabin lights before or is it better to run them from the main battery?


Hello Mick

I have both. :D

When I first fitted out Mary Ann, LED lamps were not easily available. I wired in two lamps to the battery and fitted them with LED relector bulbs.

Since then, self contained, battery powered, LED lamps have become widely available. They are also (now) very inexpensive. Consequently, I have fitted (double sided adhesive tape:rolleyes:) a multi LED lamp to light the forward end of the boat. It is very effective. I also use a couple of lantern style battery powered LED lamps for localised illumination. The batteries seem to last forever. I have had the same set of batteries in one of these lamps for five years now.

The choice is yours. ;)
Cheers

Dennis

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Postby erbster » Thu Mar 27, 2014 11:58 pm

I too have wired LED lamps, which are convenient, compact and arguably tidier than battery operated units. However, I always have a battery operated LED lantern on hand in case the boat battery goes flat or there is some other electrical problem.
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Re: Power to a depth sounder

Postby Adrian Langford » Mon Apr 13, 2015 10:50 pm

Meisje came to us with two 80Ah leisure batteries (!) which I suspect were used to power a fridge when she was kept on the Med (-itteranean, not -way). I have just tested them, finding a 5 watt car bulb lasted around 72 hours, giving a working capacity at room temperature of approximately 25Ah. I suspect this means we're carrying around a lot of 'dead' weight.

We have engine charging on our Mariner 6, which generates around 1 amp, also a 1 amp solar panel. We have LED nav lights, internal LED cabin lights and, of course, need to provide charging power for the usual mobile phones and tablets, which I reckon can easily draw 1 amp. We also have a tiller pilot, which uses around 2 amps when shoving the tiller about.

What capacity do others use? We will probably only use the boat for a maximum continuous period of a 1 week cruise at a time, then the rest of the season leave on her on her mooring and use her for just a day at a time at Kielder.

Any suggestions regarding capacity and suitable types of battery would be most welcome.

Kind regards,

Adrian.
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Re: Power to a depth sounder

Postby erbster » Sat Apr 18, 2015 8:01 am

Sounds like your batteries might be due for replacement. What charger do you use? You might be able to recondition the batteries if they have not been properly charged (or left flat). I think two batteries is overkill for a CC (too heavy).

I fitted a 110Ah battery to Aurora. We have LED cabin lights, GPS, VHF, nav lights (rarely used), depth & log. The VHF is pretty thirsty, but doesn't get a great deal of use. Might fit a tiller pilot. The biggest drain for us is gadget charging. An iPad draws 2A when charging! Consequently, I have fitted two "roaming" (ie not permanently fixed) solar panels.

My initial plan (before solar panels) was to go about 4 days without needing shore power. That was fine. We had nearly 4 weeks in Sweden last year and did not use mains at all- the solar panels were used intermittently (not usually whilst sailing) and there was never any worry about low battery, despite constant use of iPad whilst sailing and major gadget charging by family.

In summary, it depends on how you want to use the boat. You might be on a mooring, in water all season (in which case, a small battery, easily removed for charging might be best). If you use marinas most of the time, then you can use shore power and a large battery is not needed. If you want to be away from mains often (nights at anchor anyone?), then a big battery is an asset.

I told my wife it makes the boat heel less....
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