I'm new to these and I want to know how long my fishfinder will run. Thanks for the help.

1) My Lorance Hook4 fishfinder says it has a 1.1 amp current draw. My 12 volt battery lead acid battery says it's a 9 ah. In other words, one just says amp, and the other says ah or (amp hours). I think this means I can run this setup for about 8 1/2 hours on this battery? Is this correct?

2) I have read that people have made a battery pack to run these fish finders. Is this possible on my 1.1 amp current draw unit? If so, how many batteries of what size would I use?

Have you considered hooking up some type of solar charger to the battery. I know they make some pretty inexpensive ones. I don't know if they will charge that type of battery though.

SV
The 1.1 amp draw is probably a maximum current draw for that unit. It probably only draws that much current for a second during startup. I own a color Hook4 and if memory serves me correct I measured about 230mA average current draw. That would make your 9AH battery last 39 hours. Batteries usually do not live up to their full capacity but I would assume it would get you about 30 hours. I just finished a 10 day trip using
“Protected Panasonic NCR18650B 3400mAH LI-ION Button Top Batteries” and a set of 4 would run my detector for about 15 hours.

I bought a 10 AA batteries chassis off of Amazon for very cheap. Put lithium batteries in it which=12 volts. This is relatively lightweight and should last a week. I put it into a high quality ziplock freezer bag. Put a connection cable through the bag and sealed both sides with electrical tape and a little silicone sealant.

Shuz
If by Lithium Batteries you mean Energizer Ultimate Lithium that is the most power for the pound battery readily available. They are higher voltage and will deliver more current for longer than the alkaline but cost more. If you measure your 10 Energizer Ultimate Lithium batteries in series when new you will get about 16 volts not 12. Most fish detectors especially the older monochrome will run slightly longer on 8 Energizer Ultimate Lithium batteries rather than 10. The confusion comes when comparing Alkaline and Lithium batteries. Alkaline batteries deliver their current at a lower voltage and the voltage droops more as the battery is used. So if you use 8 alkaline batteries in series when they are ½ used up the voltage droops so low that the detector does not work properly. If you use alkaline batteries to use the entire energy in the battery before the voltage droops too much put 10 in series.

I just got a 9aH Lithium Iron battery pack this week to run my Garmin Striker 4 unit that also draws .23 amps. I am expecting a run time of 35 - 39 hours between charges. The battery weighs about 3.5 pounds. I mounted it in a drybox supported with foam rubber pads and ran the power cord through a hole that I drilled in the side of the box fitted with a rubber grommet. I will try it out once the weather clears up.

The Lithium Iron is a similar type battery to the Lithium Pi-Poly = Lipo. They have slightly different voltage but not enough to effect a fish detectors operation but enough to affect how they are charged and when to stop using them. The Lithium Iron is supposed to last more charge/discharge cycles but is a little heavier for a given energy level. Both types need charge discharge protection circuits that monitors the voltage on each cell.