What battery should i be installing in my 96 xj12? My supplier is saying a type 47 but it is less than half the size of the old battery . My engine will turn over but quite slowly and the starter motor cuts in and out as if its not getting enough power. I assumed the battery must be dieing but only marine batteries seem to be around the size of the battery im replacing. I took my type 47 out of my xj6 and it seems even weaker than the original xj12 battery .

 

The group size in my car is H8 aka 49. Should be 95 amp-hours or so. HTH.

 

Most USA auto parts stores show only the Group 47 for all the X300s. But that one is not really appropriate for these cars. You want the 49 or the 93. Big, powerful and heavy. 800 or 900 CCA. You can get a Napa 93 for $139.

My one year old Napa 93 must have been an old stock turd. It is down to 11.8V after only 2 days parked. Hopefully that's an anomaly. 18 months free replacement so I'll see about that. It replaced an O'Reilly Superstart that lasted for six years! Check that your new one is fresh before you carry it out.

 

Thankyou to all for your help.

 

I put a new group 49 battery in my car yesterday. The first time i turned the key the engine fired up immediately. No nasty metal chanking sounds just instantly started. Every time since then it sounds like the battery is weak and the starter motor releases and re-engages the flywheel causeing a clanking sound just as the engine fires up. Im thinking weak starter motor. This car has been sitting as it only has 76000 miles on it.

 

Could be the starter, but don't rush into that job until you've checked the simpler things first! Namely, the starter relay, power feed to the starter, engine ground strap, and ignition switch operation, in that order. Starter relay is the innermost of the row of 4 behind the left headlight assembly.

I don't recall exactly where the engine ground strap is located (lower left?). I'll have to look around for it next time I'm down there. I bet it needs cleaning.