While fishing yesterday it seemed like my trolling motor was a little sluggish. It worked all day with a lot on spot lock. First thought was batteries. After charging overnight I checked the battery voltage on the nine (9) year old Optima Blue Tops. One reading was 12.86 and the other was 13.33 volts. With that said, should I have unplugged boat charger? More accurate reading? I did this and plan on checking in an hour or so. Any help or suggestions much appreciated. Thanks.

2 minutes ago, Leeboy said:

With that said, should I have unplugged boat charger?

Never check a battery voltage while a charger is connected and powered up....what you're checking is how much the charger is sending to the battery.

1 minute ago, MN Fisher said:

Never check a battery voltage while a charger is connected and powered up....what you're checking is how much the charger is sending to the battery.

you the dawg snoop. thanks much.

Woof.

Those batteries don’t owe you anything if they’ve been used that long.

What they all said. 9 year old AGM? You got the usage from them. Start saving for replacements and depending on how critical having a not sluggish motor is decide when to pull the trigger. For $300 you can have a 24V50AH lithium and then you'll need another $100 for the charger (i assume you'll need one). That's not a bad shout for what you'll get out of it.

12,86 means it's finished.

24 minutes ago, Reel said:

12,86 means it's finished.

Again, the charger was connected - he was reading the charger, not the battery.

thanks for all of the responses. The batteries have been in a resting state for just over three hours. Voltage is pretty much the same. I thought 12.6 - 12.8 volts were good.

The voltage might be good - but batteries wear out. Old batteries that have been discharged/recharged numerous times will hold less AH than a new battery. If your batteries are that old, the 100ah listed might only be 60-70ah in reality....or even less.

1 hour ago, Leeboy said:

I thought 12.6 - 12.8 volts were good.

It is. Bring them to a shop and have them tested if you want to know how much life they have left in them. I have a Harbor Freight tester that I find is pretty accurate.

9 years is a good run. You're using them on borrowed time at this point.

6 hours ago, MN Fisher said:

Again, the charger was connected - he was reading the charger, not the battery.

Yes, a reading should be made a couple of hours after the charger was disconnected. Still, both batteries should give about the same reading. If one is much lower, that is something that should be investigated.

ran the trolling for about a minute. checked voltage...dropped like a rock. Guess I will start a new thread for batteries. thanks to all.