I’m adding a 24v trolling motor to my pontoon boat.  My plan is to run two 12v batteries instead of a single 24v.  

 

How crucial is it that the two batteries are identical?  I have two marine batteries that appear to be good and charge up well but they’re different brands.

 

Thanks in advance for answers to what is likely a dumb question.  

 

 

The issue is you need marine deep cycle batteries, not automotive batteries, to be able to be recharged after draining the voltage down. Batteries in series are only as stronge as the weakest one, so it's ideal if the 2 batteries are identicle in age, size and power ratings. You can do whatever you want it will not harm the trolling motor.

Tom

 

Not silly at all.  First thing is that there is no such thing as a 24 volt battery unless you go with a lithium.  Even for my 36 volt TM I have 3- 12v batteries.  It's all in how you wire them.  This article will help.

 

https://www.batterystuff.com/kb/articles/battery-articles/battery-bank-tutorial.html

 

Your next choice is size and type.  For most boats either an AGM or wet cell battery is used.  Those choices depend on the spce you have and the type of charger.  Bigger is better in TM batteries as a rule.  More reserve and amp hours.  

 

 

They are both marine batteries, so that’s a good start.  I’ll have to check the amperage and see how close they are together.  

 

Thanks for the advice.  This is all new to me.  

12V marine deep cycle battery fully charged should 13.2-13.5V. You can't check amps without a load cell, Harbor Freight has a good inexpensive battery tester.

Tom