Batteries

RumRunner · May 10, 2021

I stupidly left my battery switch turned on for several weeks. The Batteries were less than 6months old. Naturally they didn’t start, but I jumped them with a top of the line NOCO charger. The engine ran while I did some work. Next time I came to the dock to fish, the batteries barely turned,so I jumped them again. Went out...ran the boat for several hours. When I got to my dock, I charged one of the batteries overnight, with the NOCO, then the other one. Have not tried to crank it again. What do you guys think? Did I do enough, or shouldibe safe and replace these relatively new batteries? Appreciate any insight you may have. Most of you have forgotten more than I’ll ever know.

pelagic2530 · May 11, 2021

RumRunner said:
I stupidly left my battery switch turned on for several weeks. The Batteries were less than 6months old. Naturally they didn’t start, but I jumped them with a top of the line NOCO charger. The engine ran while I did some work. Next time I came to the dock to fish, the batteries barely turned,so I jumped them again. Went out...ran the boat for several hours. When I got to my dock, I charged one of the batteries overnight, with the NOCO, then the other one. Have not tried to crank it again. What do you guys think? Did I do enough, or shouldibe safe and replace these relatively new batteries? Appreciate any insight you may have. Most of you have forgotten more than I’ll ever know.

You're probably ok. Keep in mind that "running the engine while you did some work", at an alternator output of 50A and charging two batteries, is only putting 25A per hour back into each battery. Depending on how deeply discharged your batteries were, recharging them to full would likely require a couple hours at idle. Jumping them does nothing to recharge the batteries, it just provides enough starting current to crank the motor.

If after being charged, the batteries crank the motor, you likely escaped damage. I would test them both independently. If they're still sluggish, you could have a problem. If you're really concerned about it you could have the batteries load tested at nearly any automotive center or most likely wherever you bought them.

If you've got a multimeter and some electrical knowledge, there are some tests you can perform that will give you an indication of how they're performing.

RumRunner · May 11, 2021

Thanks very much. Very helpful.

baker · May 11, 2021

Are they flooded or AGM?

RumRunner said:
Thanks very much. Very helpful.

What kind and size are these batteries?

warthog5 · May 12, 2021

After the overnight Charge......Have them Load Tested.....Then you will really know where you stand.

sydngoose · May 26, 2021

Agree with Wart. I would remove the batteries, bring them to a reputable battery shop, drop them off to be load tested and charged. Often they will keep them overnight. Then, the next day they can tell you if the battery's dead or was resuscitated.