8D Battery Explodes

The charging profiles for flooded and AGM are the same.

I've had a few batteries grenade over the years when trying to start an engine, a few were AGM's . It sounded like a bomb going off. The ONLY cause of this and in every situation is that the battery charger leaked AC voltage into the batteries. Check the batteries with a multimeter with a setting for AC voltage with the charger on. If you're getting an AC voltage reading, the charger has a bad diode and leaking AC voltage into the batteries which causes them to explode when you hit them with a big draw. One of the boats I measured 67 volts AC on the batteries.

Deka's are a good compromise for the money. AGM Lifelines are great, NorthStar are very good also, Interstate are better than DEKA in my experiences and about the same money as Deka.

FWIW, the charge profiles for Odyssey (13.5-13.8V) and Lifeline AGMs (13.3V are different enough that it suggests checking a battery manufacturer's specific recommendations.

-Chris

I had a 8D blow apart last winter while stored in the water. Only thing I can figure is that it went try from the charger, even though it wasn't getting any real use? Don't recall the manufacturer.
I usually wind up replacing one 8D a year....

I usually replace them all at once. Usually when the first bank shows any signs of weekness. You can cut the label on the "maintenance free" flooded batteries and add water to them. Deka's anyways.

So I test the remaining batteries and they are strong. Why change them all?

Because they all tend to last about the same length of time on the same boat. Other boats,when I've had owners just change the bank that fails, it ends up being a battery changing circus. You change this bank now, then 2-3 months later the other bank goes, then another month later the generator batteries, then another month or two later the house bank. etc. etc. and the cycle just keeps repeating itself. Nobody seems to know how old each bank is. And, a bank almost always seems to go bad on a trip when it's seeing the most demand. Then you end up frying the battery charger because one of the older banks is always taking more juice. In order to test the batteries you have to break the battery bank apart and test each battery individually. You tend to have constant disruption and battery issues and batteries going in and out of the engine room. If you get a hole in one shoe, do you just replace one shoe or buy a set of shoes.

I have been successful in changing only the bad battery. I have a date of installation on each and they seem to fail chronologically. I can almost pick the next one to go, and it's 4 years old. Do you know a place were I can buy one shoe at a time? Buying a pair is a marketing gimmick....

Don't know what the heck I did wrong on the above so I'll just repeat what I wrote.

2 batteries per bank, 2 banks per side, genny has its own battery. My system has been working, dunno. Should I be changing both batteries in the bank when one battery fails? I have a separate charger for each bank. Been using my system for the wonderful 19 years I have owned her.

Yes, you should always change all batteries in the same bank when 1 in that bank fails as they work together. Whether or not you want to change all of the banks is up to you, but you should always change 2 at a time.

I've never examine that. I assumed they were independent 12/24 per side. 24 for the starters?