AGM battery

[copaco]

Would it make sense to replace two lead-acid 12 V batteries by one AGM for my 8hp diesel?Mainly for starting engine.

[Wotname]

You can start your 8hp Yanmar with a lemon and two dissimilar metal nails .

OK, maybe not but it doesn't take much battery energy to start your SB8 engine.

The AGM is a sealed battery and usually mounted in any position. It has a low self discharge provided the battery is fully charged initially. It is intolerant to PSOC.

I suggest the cost is a more important factor in your application unless you need a spill proof battery or if you are leaving the battery unattended for many months.

[Ded reckoner]

You can get low cost AGM's (likely not as low cost as conventional lead acid batteries, though) at an auto parts store instead of a marine chandlery. AGM's are sold there for commercial vehicle applications. But, they are fine for marine purposes and are good quality. We only have AGM's on our boat now after one conventional battery leaked and we had to replace our wooden battery box.

[copaco]

The boat is in Canada unattended from November to May.PSOC ?Over charge?Thanks both.

[copaco]

OK PSoC Partial State of Charge.

[Pete7]

Originally Posted by copaco

The boat is in Canada unattended from November to May.PSOC ?Over charge?Thanks both.

So at the moment do you have two batteries one for the engine start and one for the house loads like lights etc?

On a small yacht one AGM could work, providing you don't discharge it down too far so you can't start the engine. Unless you have a hand start mechanism. Some form of battery monitoring would be really good like this:

https://www.nasamarine.com/product/b...ttery-monitor/

If its only one battery, no reason why it couldn't be taken home each winter to keep warm and top up occasionally.

[Adelie]

PSOC - Partial State of Charge, more specifically using the battery when it has not been fully recharged. AGMs really like to be fully recharged each cycle.

Overcharging: leaving a battery on full recharge voltage indefinitely. It does permanent damage to Gels and AGMs. At some point when the battery is “full” the charger should drop to a lower “float” voltage that will not damage the battery or allow it to self-discharge over the long run.

[copaco]

My Honda Fit is pretty full when I head for home, but with one leak-proof I could find room.

[Mirage35]

I, like many others, leave AGMs on the boat over the Canadian winter. I just make sure they're fully charged and then disconnect them before leaving.