I already have a trolling motor and I'm thinking of getting a fish finder. If (okay, when) I get the fish finder, is it okay to run them both off of the same marine battery? How badly will that affect the life of the battery and will it affect either of the electronics? Right now, I have a 55lb thrust minn kota that uses pulse technology to extend the battery life (and quite well). Basically, I'm considering either a fish finder that attaches to the marine battery or one that runs off of a bunch of AAs or similar. Thanks for any advice.

--Bank Angler

Deep cycle marine batteries supply a relatively low amount of current for a long period of time. They are designed to power electric trolling motors and other electrical accessories in boats and RVs. Unlike ordinary car starting batteries, they can be run down and recharged (deep cycled) repeatedly with minimum loss of capacity. Do not use a fast boost charger. A slow/trickle charge is best for a deep cycle battery.

In order to understand how long your battery will last, First you need to establish:
1) The loading of each piece of electrical equipment. This is expressed in watts and is stamped into the
compliance plate attached to the electrical item.
2) The length of time (in hours) that it is intended to operate each piece of equipment between recharges.
3) The system voltage (6v, 12v or 24v).
Probably 12 in your case.

The first step is to determine the total number of Watt Hours involved. Calculate this by multiplying the loading of each piece of equipment (watts) by the number of hours you intend to use it between recharges and then add them all up.

The next step is to determine the Ampere Hour (AH) requirement that the battery must accommodate. You calculate this by dividing the watt hours by the system voltage.


example:
500 Watt Hours/12 volts = 42 Ampere Hours.

Take a look at what your battery is rated at and you should be able to figure it out from there.

Also Make sure you run an inline fuse between your battery and any expensive electronics.