Just thought I'd post this to help other looking to do the same, I searched for a few daysand did a lot of reading and every post says they are direct replacement or drop straight in units but they are not. However its still very simple and cheap to do.

First of all a little about the batteries.

Optima 35R is the red top, its 770CCA and is usually a little cheaper than the yellow top, not to be confused with the Optima 35 which has the battery posts on the wrong sides and will require replacing wiring with longer cables.

Optima D35 is the yellow top, it's 650CCA and is a deep cycle battery. I chose a deep cycle battery due to my Brant alarm being power hungry and if left for a long period the yellow top would charge back up without any negative effects on the battery. The D34 is the same as the D35 but has the battery posts on the wrong sides so make sure you don't get that one.

Now to the installation.

First of all you will notice the battery posts are too fat for your stock battery terminals (unless they have already been changed), so you will need some new terminals. I don't recall how much these cost but it was pretty cheap for 2 brass terminals, it was well under $10.


The stock negative terminals are crimped on, so you will need to cut the wires off as close to the terminal as possible then strip about 1.5cm of wire off each and use a terminal that will allow you to clamp the wires into position as shown.


The positive terminal had rings attached so there wasn't any wires to cut, just take off the old terminal and replace with the new.


Make sure to leave the positive terminal protector on when you swap the terminals or you will have to take the terminal off to put it back on again. The protector fits the new terminal very snug.


The battery tie down needed to be replaced, the Optima D35 is 172mm wide and I found a 175mm tie down for $4.95 at Bursons.

I am very happy with my new battery, next I'll upgrade from my 75A alternator to a 110A alternator.

*Unfortunately this site won't let me post in the DIY section, perhaps it needs to be moved there.

Brant alarm troubleshooting when reconnecting a battery.

This did not happen to me but for others after reconnecting the battery the alarm will sound and there appears no way to turn it off, here is what you need to do:

From what I have read the brant keypad has its own battery back up, however this can become flat over time. If it becomes flat then you will either need to reset it with the method above or with the override code provided by Subaru.

Luckily the previous owner gave me both the override code and the personal code for the car when I bought it, I haven't had to use the override code but I hear that Subaru will make you take the car to them then charge you for putting in the code.