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Is there a way I can test if it is good or not?
I was also considering going dual batteries. Anyone know how I could do that? My battery is under the back seat so I have the other side of the seat for the other one. its just a matter of finding what wiring I would need to set it up. Thank you for your help/ideas.


Testing the battery?

With an acid densitometer(suction bulb with graded float), check the density of the acid in each cell. should all be within 0.02 g/cm3 of eachother. Do a couple of forceful suck/pumps in each cell and keep an eye on the color/clarity of the acid -should be clear.

Withh an artificial load (visit a good batter/car accessory shop,effectively an adjustable toaster running on 12V)you can pull a large current out of the battery (200-300A depending on capacity. Voltage shouldn't fall under ~9V. With a bad cell you'd see a sudden breakdown in voltage, and typically bubbling in the bad cell (protective goggles on!).

Adding a second battery

Do you want just larger capacity (effectively just a twice as large battery) or do you also want protection against running out of starter juice by extended music sessions with the car off?

First case: new cableshoe for the + terminal (must be capable of accepting 2 heavy guage wires, the existing+ a new one) of the existing battery and one for the new battery. a piece of heavy gauge (35-50 mm2 whaterver that is in AWG) wire between the +terminals. A gounding wire for the new battery and cable shoe for the - terminal.

For ttal security you would have a fuse (and associated holders) close to each attery on the new +wire (that wire will otherwise glow red hot and the isolation burn if either end of the wire shorts to ground - say the seat frame.) Depending on distances, wire routing, seat construction etc I personally might skip the fuses. But that really means playing the odds. I'd at least add some extra isolation. heat shrink tubing, rubber sheets/mats, plastic panels...I hope there's a fuse (might not look like one/be integrated in a cable shoe or wire as a "fusible link" near your existing battery. Ask your dealer/mechanic!)

second case: as above but you also need a high current relay (IIRC Stinger makes a 200A one, also gives you an idea of the fuse ratings required) ) + wiring (hin to control it so that it closes wiith engine on and opens with engine off) Your current hungry stereo gear should onnect to the battery "after" the relay, as seen from the alternator
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/Michael