The other day I was out in my kayak and my Hook 4, which has been working flawlessly was giving readings of 100+ feet depth no matter what the actual depth was for the first few minutes.  Then it started working right.   After about an hour it started back at the 100+ depth again.  Shortly after that it turned off.  I hadn't charged the battery the last couple times out. 

It's all freshly charged now but it's driving me crazy not knowing if the weak battery caused the problem. It's going to be a few days until I get back out and was wondering if the battery can do that or do I have bigger problems? 

Always charge your battery after every use. 

I have not noticed inaccurate depth readings as the batteries get low, but I have noticed the depth finder simply turns itself off.  "cuts out."  I expect that about anything can happen with different brands reacting differently to low voltage.

 

Fully charged battery and no issues today..