Fish finder for 2020 Outback

Thanks to all of you for taking the time to reply!  OK, I got a Lowrance HDS Live 9, which I know is total overkill for a noobie but it was a present.  Now I'm wondering, what lithium battery to get - max power consumption is 40.02 (2.9 A at 13.8 V DC).  Also, I've watched some videos and they use very different batteries, chargers and also some change out and waterproof the connectors, is that necessary?  Thank you for any advice you can share!

Go with Chet's battery... http://www.norcalkayakanglers.com/index.php?topic=87570.0

I run Lowrance HDS Live 7 with a Dakota Lithium 23Ah battery on my 2021 Autopilot 136. I called Lowrance tech support when I ordered the HDS unit and was told it is recommended that battery source be at least 21Ah for HDS Live units. Dakota Lithium, Amped Outdoors, FPV, Nocqua, etc. are some brands you can check out what's best for your needs and budget. Which ever battery manufacturer you decide on, Buy the battery charger from that company for battery reliability, longevity and or warranty.