I recently bought a new boat, it came with 2 batteries only ( it’s a nitro z17). 1 battery for the motor, and 1 battery for the rest of the boat. So I’m going to be looking for another battery or two. I’ve had my boat out 5 times since buying it, every time I use the trolling motor/graphs for roughly 4 hours and my battery only has 0-25% remaining.
 

my question is  how much better are lithium over lead acid batteries? Will a 100 AH lithium last longer than the 100 AH lead acid battery?
I understand that 2 batteries isn’t enough, but before I invest in buying more should I just switch them all to lithium? 

3 minutes ago, Jmay1002 said:

my question is  how much better are lithium over lead acid batteries? Will a 100 AH lithium last longer than the 100 AH lead acid battery?

If you're dropping to 25% charge regularly - then go with Lithiums. Lead acid (Flooded, Gel, AGM) doesn't like going below 50% charge often - it shortens the lifespan.

 

The lithiums won't last longer per outing - you'll still drop to 25% charge - but they can handle going to 5% or less charge regularly without shortening the lifespan...so they are better in that respect.

 

If you get two batteries and connect them in parallel - then you'll have basically 200AH - or you can just get a single 200AH battery.

2 minutes ago, MN Fisher said:

If you're dropping to 25% charge regularly - then go with Lithiums. Lead acid (Flooded, Gel, AGM) doesn't like going below 50% charge often - it shortens the lifespan.

 

The lithiums won't last longer per outing - you'll still drop to 25% charge - but they can handle going to 5% or less charge regularly without shortening the lifespan...so they are better in that respect.

Thank you. 

Get you one of these, not particularly this model but one the that will check battery capacity.  It's the only way to conveniently check sealed batteries.  Amazon.com: ANCEL BA101 Car Battery Tester 12V - Digital Automotive Batteries & Alternator Diagnostic Tool, 100-2000 CCA Load Capacity, Charging & Cranking Analysis for Motorcycle, Truck, Boat, RV, Marine & More : Automotive

Amp hour capacity is amp hour capacity, Just make sure they are using the same rating system.  Most use the 25 min rating system, but there are several, and it makes a huge difference in numbers.  Some of the imports will just plain lie about them, just to make theirs look better.  

The first thing I noticed in your post is the setup.  You should not have anything else hooked to the trolling motor battery.  You should have a strong enough cranking battery to start your engine, run your pumps and electronics unless you have some seriously powerful electronics.  If that is the case then you might need a house battery.

 

It sounds like you have a 12 volt trolling motor so a good strong battery is a must.

 

If you switch to lithiums you may also have to buy a new charger.