Shelling out for batteries

A couple of years ago while in the USA I purchased a FishMark 320 Portable Fishfinder, you know the one,
the screen sit’s on top of Power Pack case and the transducer comes with a suction-cup, its ideal if you want to change it from boat to boat very quickly.
It takes 8 large D batteries within the case and while it is relatively low on battery consumption I know it possible to have it running off one 12v rechargeable battery, It spends 90% of its time in an OSM 404 and I would like a more permanent setup in this boat for the power, any advice on how best to set this up, all advise gladly received taking in to account the size of the OSM 404 so no large boat or car batteries allowed I like to keep my boat on the surface if possible

Would getting a set of rechargable "D" batteries be a cost effective solution? 7dayshop do good deals on batteries from time to time.

get your self to an electrical supplies shop and ask for a 12v 7ah dry cell alarm battery for around 15euro
then all you need is a car battery charger or a golf trolley charger and away you go.
battery would only weigh about 1.5-2kg.
hope this helps.

You could try a motor bike battery to power your sonar, worked well for me on the last setup i had.

the problem with motor bike batteries is they are wet cell.
acid can spill from them if knocked over.
dry cell much safer and they are the same size.

Thanks for the ideas, at least now I have a choice, keep it very simple just buy rechargeable batteries or try the alarm battery idea .
Originally I was with alastairswilson on this one and had considered a bike or quad battery but it would get knocked around a lot in this tub.

Thanks for the ideas, at least now I have a choice, keep it very simple just buy rechargeable batteries or try the alarm battery idea .
Originally I was with alastairswilson on this one and had considered a bike or quad battery but it would get knocked around a lot in this tub.

What you're looking for is called a Gel cell.
It looks like the motor cycle/ride-on mower lead acid battery, but the alkalyte inside is jellified, and so it won't spill if knocked over, or the case gets cracked from a bump.
The rating is 12Volt 7Amp Hour. Also you will need a trickle charger so as to charge it at the correct (slow) speed.
Hobby shops sell them.

Beat me to it Tubenfish the beauty with these gel batteries is that you can attach them to the boat in any position as nothing to spill out. I have mine strapped on under the seat lying on it's side in a 17' lake boat. Bought it in the local motorbike shop.

Yappo

have a look at a solar charger viewtopic.php?f=12&t=17573

The only problem with the solar Stan is you need at least daylight never mind sunshine and looking out there today it looks more like a bad day in January out there. I don’t think I would even get a trickle charge.