2nd battery for audio

(sangerlover) · (sangerlover) **Join Date: Sep 2005** 10-27-2005, 8:44 PM

My boat currently has 1 full size interstate battery as primary with a smaller MK power battery as a secondary battery with a relay switch contoling them . I read that both batteries should be the same size amperage ect.. A stereo shop installed my 2nd battery during the install of my stereo , amps and speakers so I assumed the smaller battery was Ok . Should I change this setup to 2 batteries of the same size ?
Thanks,
Jeff

(chas) · (chas) **Join Date: Feb 2002** 10-27-2005, 10:13 PM

Yes, batterys charge and discharge different.

(rodmcinnis) · (rodmcinnis) **Join Date: Sep 2002** 10-28-2005, 1:32 PM

If the batteries are of the same type (both flooded lead acid or both AGM) then size doesn't really matter for your application.

How the battery charges is going to be primarily a function of the overall condition/age of the battery. Unfortunately, calendar days is not a good way of measuring the age of a battery. If your stereo battery gets deep cycled a lot then it will age a lot faster than the starting battery.

If you are using the batteries independantly (starting on one, running the stereo off the other) then you will be able to tell when one of the batteries is going bad and thus the age/condition issue is minor. On the other hand, if you were permanently connecting two batteries in parallel and using them as one unit then it is really important that the two batteries be as matched as possible: size, age and manufacturer.