Selecting a battery for your kayak
Battery selection depends on what equipment you intend running off it
The type of battery you need is an SLA ( Sealed Lead Acid) , these are most commonly found as backups for emergency lighting or alarm systems
It has to be a sealed unit .. unless you want battery acid sloshing about inside your yak ?
The more equipment the bigger the battery
Lights , fish finder , GPS all have a draw on the battery , a black and white fish finder has a low draw . A colour one will have more and a colour unit combining a GPS will have even more
What does your fish finder draw ?
Lets take a popular model the Garmin 90 , according to The tech spec on their website
The Voltage is 10-18 volt
The Power output: 100 watts (RMS), 800 watts (peak to peak)
So we’ve established that the unit has an average power rating of 100 watts (100 watts (RMS), )
Batteries capacity is measured in Ah (Amp hours) usually over a twenty hour period
For example this Battery pictured below is rated as 12 volt SLA 7.5 Amp/hr 20 hours
So this battery will ( with a full charge ) deliver 7.5amps to an appliance for a duration of 20 hours
So how do we calculate from the info above what the Amp hour draw of our fishfinder will be
Quite simple Amps = Watts divided by Volts
So taking the average of 14 volts and an average of watts of 100 , divide 100 by 14 = 7.142
So on average the fish finder draws 7.142 amps per hour from the battery
This is not set in stone … its an average calculation, when you start your fish finder up the power could increase to 800 watts fro a short time ,
The battery in the picture is a 7.5 amp/hour . So in theory it will run our fish finder for twenty hours
Although allowing for variable lets say sixteen hours ., so you should get two fishing trips out of a 7.5 Amp/hour battery battery
Some tips for keeping your battery in good condition
Get the right charger for your battery . Do not use a car battery charger , some of the older models might cause your battery to explode
Always store your battery fully charged
Keep corrosion off the terminals. When cleaning the terminals avoid bridging the positive and negative or sparks will fly
