12V Trolling Motor – Adding a 2nd Battery

I know that you a can use 2 batteries for a 12v trolling motor by putting them in parallel, but my question is more on the battery types

I have a 3yr Interstate group 27 deep cycle battery used for the trolling motor now, someone gave me an Alphacell gel 165GXL today that is next to new. When looking at the companies website, this model battery is also a group 27 and the physical size is the same as the Interstate that I have now.

Would there be any issues with putting this Alphacell battery in parallel with my existing battery?

I also have a single bank charger in the boat, I would expect that will work just fine, it just would take longer to re-charge since there would be 2 batteries.

The boat was wired for a 24V trolling motor from the factory so I’m not worried about the wire gauge

Thanks

They should be equal in age, size, and condition. Ideally just buy 2 new group 27’s and hook them in parallel from the get-go.

Charger will charge fine, just slower.

Both batteries should be the same type and age. You are proposing to mix an old lead-acid battery with a new gel cel battery. Not a good idea on two counts.

Do not mix any factors concerning the batteries. They could discharge (run your equipment at separate load voltages). If this occurs one battery will be powering the trolling motor and tickle charging the second battery at the same time. Your 2nd battery will behave as an undesired load. Eventually it will likely catch up but most of the work will-could have been performed by the battery with the ability to store more charge by that time. This largely defeats the reason for having the 2nd battery. Use a heavy AWG wire to parallel up the 2 batteries to avoid voltage drop between the 2 while under load.

Thanks for the info. Maybe ill just put the 2nd battery in there and use it as a backup, hook it up if the primary runs out of juice and keep the seperate