I'm thinking of replacing one of my 2 batteries to an AGM (glass matt). I would use my lead acid cranking battery for starting and use the AGM deep cycle for the house while sailing. Are these types compatible or do they have to be the same kind? Can they be charged together? Etc. etc. Any experts in batteries out there?
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no
They're (AGM & Flooded Lean Acid) NOT compatible, in that they cannot be charged together (different voltages).
They're (AGM & Flooded Lean Acid) NOT compatible, in that they cannot be charged together (different voltages).
Batteries
If you do not have a charger or regulator specifically designed to the AGM battery, I think you are asking for trouble. The charging voltage needed for those it different from the lead acid you now have. In my humble opinion, I don't think that any advantage the AGM's have over lead acid is offset by the price difference, and the alway easy availibity of a plain old lead acid battery. The lead acid is good for several years, IF you take care of it.
If you do not have a charger or regulator specifically designed to the AGM battery, I think you are asking for trouble. The charging voltage needed for those it different from the lead acid you now have. In my humble opinion, I don't think that any advantage the AGM's have over lead acid is offset by the price difference, and the alway easy availibity of a plain old lead acid battery. The lead acid is good for several years, IF you take care of it.
OK to do, with 1 caveat
I just purchased a "blue top" AGM battery. Don't know if thats similar to your AGM battery, but the literature by the manufacturer specifically states that battery charging voltage is NOT critical. There obviously are limits but any typical charger you are using now for the lead acid should work ok for the AGM. To be sure, check the manufacturer for the specific model. When charging, I would think that charging each seperatly would be perferred, i.e., do not use the "both" switch on your battery selector.
I just purchased a "blue top" AGM battery. Don't know if thats similar to your AGM battery, but the literature by the manufacturer specifically states that battery charging voltage is NOT critical. There obviously are limits but any typical charger you are using now for the lead acid should work ok for the AGM. To be sure, check the manufacturer for the specific model. When charging, I would think that charging each seperatly would be perferred, i.e., do not use the "both" switch on your battery selector.
Roger, Just talked to my neighbor who is a boater--he agrees with you, however,his opinion is to go with both AGM's to avoid differences in charging rates between 2 different battery types. Can anyone else confirm any of this? BTW, I'm looking at getting the Bluetop also.
Can be done.
It depends upon the type of charger and how you wire the batteries. It sounds like you have separate systems like battery switch #1 to wet cell and #2 to new AGM. Most newer chargers have settings for gel, wet, and AGM. You could set the charger for AGM but it might never charge the wet cell to capacity. Some chargers have two outputs with a setting for each, that would be ideal. Now you have to be concerned about your alternator. The older 35-amp and 55-amp Hitachi alternators cannot overcharge a gel or an AGM so no worry there. If you have a newer alternator with separate regulator there is probably a setting that will work regardless of where you have the battery switch, again using the lower AGM setting. My own charger is set for the three house gels. It seems to keep the AGM starter battery topped off(via a combiner).
It depends upon the type of charger and how you wire the batteries. It sounds like you have separate systems like battery switch #1 to wet cell and #2 to new AGM. Most newer chargers have settings for gel, wet, and AGM. You could set the charger for AGM but it might never charge the wet cell to capacity. Some chargers have two outputs with a setting for each, that would be ideal. Now you have to be concerned about your alternator. The older 35-amp and 55-amp Hitachi alternators cannot overcharge a gel or an AGM so no worry there. If you have a newer alternator with separate regulator there is probably a setting that will work regardless of where you have the battery switch, again using the lower AGM setting. My own charger is set for the three house gels. It seems to keep the AGM starter battery topped off(via a combiner).
Careful
Check it out. I know my charger is wired to charge both banks at the same time reguardless of the switch setting (1-2-both). The switch setting will control which batteries the alternator is charging. If thats the case you will have problems mixing batteries.
Check it out. I know my charger is wired to charge both banks at the same time reguardless of the switch setting (1-2-both). The switch setting will control which batteries the alternator is charging. If thats the case you will have problems mixing batteries.
Get 2 New Wet Cells!
Jack, You have not shared with us the details of your boat and how it is equipped, but why not get two new quality wet cells. One small starter battery and one larger deep cycle for your house load. No worries about charger or alternator compatibility and you will spend about the same as one AGM. If you have some extra money burning a hole in your pocket, upgrade your charging system to multi-stage charge controller. Batteries die from improper charging, not because they are wet cells. Jon
Jack, You have not shared with us the details of your boat and how it is equipped, but why not get two new quality wet cells. One small starter battery and one larger deep cycle for your house load. No worries about charger or alternator compatibility and you will spend about the same as one AGM. If you have some extra money burning a hole in your pocket, upgrade your charging system to multi-stage charge controller. Batteries die from improper charging, not because they are wet cells. Jon
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