Fishfinder Battery

I'm really thinking of taking Charles's advice and using the 12V battery out of one of those multi-million candle powered spotlights to power my fishfinder.  They have what I think is probably a really REALLY good light down at Costco right now.  It's 15 million candle power for only $29.  My big concern is that I might accidentally fry the guts out of my Cuda Eagle 260.

Is voltage the only number that I should be looking at, or is amperage a big deal too.  I've never been any good with electicity, but isn't amperage just the measure of power available from the battery.  I mean if the sonar is rated at about "A" amps and the battery is rated at 10 x "A", doesn't that mean that the battery has a potential to deliver 10 x "A" but the sonar only actually uses "A"?   

Fishin-T

Hey go over to Norcal and access the archives cause Sean "sqwafish" has a good set up he uses made from rechargeable lithuim batterys size AA. He built a holder out of parts from radio shack and a water proof box with plug-ins and everything. Actualy a nice set up. Not sure how long it last but you can also carry extra batterys. He has them wired in series to create 12 volts.
As for me I use a 12volt lead acid battery from radio shack used to power home alarmsystems. It is very nice I just have to secure it some how. I usualy just put in an old shoe when I got it in the yak. Re charges quick on a trickle charger and last for a couple trips before I have to recharge. It is about 2"x4"x5" roughly and weighs about a pound and a half.

You should look at the voltage number.  Actually, the rating on most batteries you see will also have a Ampere-hour rating.  Roughly speaking, a 7 Ampere-hour battery could drive 7 Amperes for 1 hour, IF the device actually drew that current. The same batter could also drive 3.5 Amperes for 2 hours, etc.  I believe a fishfinder draws much less than 1A.   Here's a trick as well if you need more juice to last a longer time.  Some fishfinders, while rated for 12 V, can take 18V (check the user's manual).  Instead of using a bunch of AA's in series to get 12V, you may shoot higher.  Note, don't go all the way up to 18V as there is some headroom in the charge.  You'll notice this in that you may think you have a 12V source, but un reality you might have 13.7V.

Lost yet?  Short story ... you should be fine with any batter that has a 12V rating.

BTW, I design semiconductor chips that go into battery powered platforms.  So I know a thing or 2 about batteries.

-Allen
 

Hello,

I just picked up a nice little battery from a place called Batteries Plus. They have a store less than a mile from my home. It is a 12V 5 amp per hour. Dimensions are 3.5" x 2.75" x 4". Pic attached. Not sure how much it weighs but it is light. It should run my little Piranha Max 20 FF for about 20hrs without charge.  They also had a variety of other 12V batteries some smaller and some larger. This one cost me $18.45 after tax.

Here is their website http://www.batteriesplus.com/. Looks like they have a store in Tacoma and Olympia as well as 2 in Spokane were I am at.