How can I test a 24v system for my trolling motor?

Question

I originally bought a 4 battery energy gauge/tester from Bass Pro. It has a dial #1-#4. I want to know how much juice I have left in my two deep cycles and my starting battery- total of 3 batteries on my boat. My original thought was to run a set of wires #1 & #2 to each deep cycle battery. Run #3 to the starter battery. Battery wire #4 would won't be used obviously. This way I could test each battery individually by turning the dial to the selected battery.

But then I got to thinking. Could I've bought the 2 battery energy gauge/tester instead? Hook one tester up to the starter battery and the other to the 24v system? By putting the positive wire to the one deep cycle battery and the negative wire to the other battery. Not sure how to word this exactly.

Answer 1

if it's a digital tester that tells you voltage to the nearest tenth or hundredth it'll work.

if it's a needle gauge that measures state of charge as zero to 100 percent, then it won't work cause the 2 deepcycles in series will always be over 12 volts.

but, it'll test your 24V system as is, you just have to average the readings of the 2 batteries -- most of the time they should be pretty close to identical.