Curious what to set my auto shutoff voltage to, currently I'm using a YakAttack 10ah 12v lithium-ion battery and its set to 12v

https://www.yakattack.us/yakattack-10ah-battery-power-kit/

I love the battery and the unit, but I find when using my Garmin striker 4cv, it didn't last past a day.

From the website the draw is 0.4ah and the minimum operating voltage is 12v. But this really only gives me fishing from 12.6v to 12v.

When I got home I plugged the battery in thinking it was dead, but it was still +75% battery.

Does anyone know how low I can go with this battery?

I've been playing around with my Striker 4 (not cv).

First, the specs on the Stiker are for operation from 10-20V.

I built a portable battery pack out of 8AA batteries. I ran those batteries down until the unit powered off. The unit finally powered off when the voltage hit 9.6V. I only got 4-5 hours out of those 8AA batteries, though.

I also tried it with a 12V seal lead acid battery. Fully charged it was at 13.6 volts. I ran it for 14 hours and the battery was still at 12.5V. I didn't run it down any further, but I would guess it would go down to under 10V like it did with the portable pack that I built. If so, I suspect I would get at least another 10-15 hours, meaning that I'd be around 30 hours or more, total. I'm planning to bring a lithium battery with 10-12Ah along with this lead-acid and figure I should have all the power I need for a full week.

I'd love to hear if you have any experiences that could help me understanding improve.

The issue you are experiencing is related to the battery design. The yak attack battery is likely only 3 lithium cells in series, so low reserve is about 9 volts. Other manufacturers are 4 cells in series, so low is 12 volts.

Ok, so if I understand correctly, since the lowest discharge voltage per cell should be around 3v - 3.2v I should be fine setting the voltage warning to 9.6v - 10v rather than the 12v it was at originally?

On the official Garmin website I'm seeing an amp draw of 0.4ah for the garmin and a minimum operating voltage of 12v, would this still be safe considering the above?

Yeah, I'd go with setting it @ 10volts and see how your runtime works out. I can't imagine low voltage harming the sonar head unit, but it might effect the transducer's performance a wee bit. The transducer side of sonar is analog and typically prefers higher voltages. You should start seeing noise in your signal as the voltage drops before anything on the digital side shuts down.

I use a milwaukee 12 volt 3 amphour battery for my garmin 4cv.
The unit starts to beep and screen flicker around 10.4-10.6 volts. A full 12 volt milwaukee will get me about 2-4 hours of fish finding. I think i am going to switch to my 18 volt milwaukee to not have to worry about battery life while fishing. I noticed it drains the battery faster on the higher frequency settinging also.