James, I am using 5ah AGM batteries that weigh 3.8 pounds. They measure 4'' x 3.5'' x 2.7''. I have 4 of these that I have used for years, they predate the popularity of lithium. I could buy much smaller, lighter and more powerful batteries but my boats have custom mounts in the pockets that hold these so I stick with them. One of them also powers the water for the sink in the back of my truck so I always have at least 3 with me. They last more than all day with my Striker 4, I have never run one down in a day's fishing. They also power the electric hoist in my barn that raises my boats to the ceiling, they are very useful. They currently sell for $15-$20 , back when I bought mine I probably got 4 for around 50 bucks. They obviously last a long time, I use them every time I go out and have never had a failure, it has been years since I bought them.
To keep them charged I use something called the Accusense X-Citer that is a 5 stage battery charger/maintainer. I have seven 12v batteries in my shop for different things including a trolling motor and riding lawn mower and I maintain them all winter with just the one maintainer. I just rotate through the group whenever I am in the shop and since it is warm in there the batteries all stay up.
Not necessarily relevant to this discussion but if anyone owns a modern car that sits for long periods of time-especially in winter-I would recommend keeping a battery maintainer on it at all times while it is out of use. The parasitic drain of all the electronic bullshit on the new vehicles can completely drain the battery in about a month leaving you stranded. Yeah, you can always start it with jumpers or a lithium battery pack but running a lead acid battery down to zero will probably shorten battery life significantly.