Amp-hour
Also called Ah, amp hours, amp-hours
What is an amp-hour on a battery?
A battery's capacity: how many amps it can supply for one hour. A 10 Ah battery can feed a 1 A load for about ten hours.
Amp-hours are the number that tells you how long a battery lasts, and the arithmetic is simple. Divide the amp-hours on the label by the current your device draws, in amps, and you get the hours it can run in theory. A fish finder drawing 0.2 A on a 7 Ah battery works out to about 35 hours on paper.
The real figure is always lower. A sealed lead-acid battery lasts far more seasons if you only use about half of its rating before recharging, cold weather cuts what any chemistry delivers, and a bright screen draws more than a dim one. That is why a sensible budget doubles the draw times the hours before choosing a battery.
Do not confuse amp-hours with watts. The watts printed on a fish finder box are usually sonar transmit power, what goes into the water, not what the unit takes from the battery. The current draw in the manual is the number that belongs in the sum.
Find your fish finder's current draw in its manual, multiply by the hours you fish, then double it. Buy the next battery size above that number.
Common questions
How many amp-hours does a fish finder need?
Usually fewer than ten. Small units draw well under 2 A, and Garmin pairs its STRIKER Plus 4 ice bundle with a 7 Ah battery it rates at up to 11 hours. Size up for a large screen, a cold day or several days between charges.
Where this comes up
The guides that use amp-hour and show it on real gear.
Last reviewed . Amp-hour is one of 224 terms in the fishing glossary.