Parellel batteries of different size only. Yes or no?

[lqdchkn]

I ran an Optima Yellow top (AGM) and a standard OEM Panasonic lead acid in my FJ without any worry.
Personally I like to run my setup manually switched for the concerns mentioned so I could control each battery as I saw fit.
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Id combine them when winching with the engine running without issue.
Id run on each one independently for a few months in everyday driving to keep each in use and happy.
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I left my fog lights on once one morning and went in to work and came out to a dead battery on the OEM. Switched to the Optima and fired up and drove home with no issue. Put the OEM on the charger for a few hours, topped off the water in it and ran them combined for a few days before running it alone again and it came back to life fine.
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Since the lead acid will want a lower charge voltage than the AGM keeping them combined for long periods may result in a AGM that is not charged to it's full capability but it wont hurt it and you can always separate them to top it up independently
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*I hate this forum eliminates white space...makes formatting a bi7ch

 

[DiploStrat]

Since the lead acid will want a lower charge voltage than the AGM …

Check the tech manuals for your batteries; you may find that you have this backwards. Open lead acid batteries typically want a higher voltage and slightly lower amperage than sealed lead acid, aka AGM.

 

[lqdchkn]

Check the tech manuals for your batteries; you may find that you have this backwards. Open lead acid batteries typically want a higher voltage and slightly lower amperage than sealed lead acid, aka AGM.

Actually for general use it looks like they are the same. It's stand by float charge that AGM is lower

 

[DiploStrat]

As a practical matter, it is unlikely that your alternator will ever do much floating. Your shore/solar chargers, on the other hand, probably will. If your batteries call for dramatically different voltages, then you should probably lean towards the less aggressive float setting. I confess that I have my shore/solar chargers set for the specs of the larger, camper battery bank.