Charging batteries

[Nibor]

I have been using this boat for years using the battery setup it came to me with. Recently I began having troubles. I will admit I am a Luddite in these matters. He appears to have done it incorrectly. He mixed an AGM deep cycle with a flooded. I replaced the flooded last week with another flooded and of course had problems. I had the alternator checked and it works properly. Now I am looking at getting another battery. I was going to use the same setup but learned how that was a bad idea. I do not have large power requirements but want to put in some extra just in case. I want to use group 24 due to space issues. If I buy two AGM’s at the same time can I use one with more amp hrs as a house battery and a dual purpose for starting? I have a three stage smart charger for shore power. I can select AGM or Flooded charging. I am checking now to see how it is set. The other option is two AGM deep cycles. Marine how to says you can do that if the cranking power is within the engine makers specs.

[ranger58sb]

If you're meaning the two batteries are in separate banks... it's likely more important to pay attention to charging voltages than to type. IOW, if you want a flooded battery for starting and an AGM for house... that can work OK if one of your two charger settings is close to correct bulk/absorption/float voltages for both specific batteries.

Note that not all flooded batteries want the same charge voltages; ditto AGMs...

So it's often really a matter of specific battery brand/model... and the voltages that manufacturer recommends.

And then, note that most (although not all) AGMs are NOT "deep cycle" batteries. Most are really dual-purpose -- not a bad thing, if that's what the situation needs. Yes, a dual-purpose (or deep cycle, if you're looking at something like Lifeline) AGM that meets your engine's cranking requirements can be quite workable.

If you happen to be shopping Lifeline AGMs ($$$$) they do make deep cycle and starting variants. Not sure about the charging voltages for each, but that'll be on the Lifeline website.

If I understand your question...

-Chris

[GordMay]

Does your boat still have the original 30HP Universal Atomic 4 gas engine?
Keeping all batteries the same size and type can greatly simplify the process of managing the use, and charging process.
The low compression design of the Atomic 4 allows it to be started using any normal size deep cycle "house" battery.

[Nibor]

It has the M3 20 B universal. Minimum 400 cranking apps.