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I've been experiencing some slow cranking on some mornings on My 98 forester. Currently I'm running and my second battery and is probably due for a new one. I also noticed the other night as I was going home from work the lights dimmed a little and the wipers slowed down while sitting at a red light with my turn signal on. I'm assumming the battery is worn out. But is this a sign of the alternater going bad. I'm planning on getting an Optima blue top D34M for a replacement. I due run allot of extra electronics. I currently have a high wattage stereo system, scanner radio, CB Radio, GPS, Radar dectector with amplified speaker, sirius and XM radio receivers. I am planning on getting a winch, and high power off-road lights as well. the Optima blue top D34M is just like a yellow top deep cycle except has a couple extra 5/32 threaded posts. I was wondering if these extra posts can be used to hook up some of the extra accessories. Also I've been considering replacing the alternator for a higher amp one. Does any have any recommendations on higher amp Alternators.

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Originally posted by Forester_Ranger

I've been experiencing some slow cranking on some mornings on My 98 forester. Currently I'm running and my second battery and is probably due for a new one. I also noticed the other night as I was going home from work the lights dimmed a little and the wipers slowed down while sitting at a red light with my turn signal on. I'm assumming the battery is worn out. But is this a sign of the alternater going bad. I'm planning on getting an Optima blue top D34M for a replacement. I due run allot of extra electronics. I currently have a high wattage stereo system, scanner radio, CB Radio, GPS, Radar dectector with amplified speaker, sirius and XM radio receivers. I am planning on getting a winch, and high power off-road lights as well. the Optima blue top D34M is just like a yellow top deep cycle except has a couple extra 5/32 threaded posts. I was wondering if these extra posts can be used to hook up some of the extra accessories. Also I've been considering replacing the alternator for a higher amp one. Does any have any recommendations on higher amp Alternators.

 

You are probably killing your battery by demanding more power than the alternator can deliver. Your alternator produces about 40-60 amps of "spare" power for things like audio systems, heated seats, etc. 40-60 amps is not enough for you.....

 

When you repetitively drain cranking batteries more than 10% of their capacity you destroy them. Cranking batteries have thin plates that allow for much higher cranking power, while deep cycle batteries have thicker plates for durability to allow regular deep cycling.

 

The Optima Yellow Top is an awesome battery, and will suit your needs perfectly.

 

I would suggest an voltmeter and ammeter to monitor your battery charging. You should not be drawing on battery power on a regular basis.

 

Change the battery since it is toast, and consider getting a larger amperage alternator. The Subaru alternator can be rebuilt with some high amperage kits that fit Nissan alternators, find a good auto electric shop and see if your 85 amp alternator can be rebuilt into a 140 amp one. You will have to upgrade the the following wires as well: Battery negative terminal to chassis (ground), engine to chassis (ground), alternator positive to battery positive (I think this is a fused link?), and maybe a few other wires (all wires responsible for charging the battery MUST be upgraded to handle more current).

 

I don't know much about the Optima blue top.

 

Watch the terminal orientation, some Subaru's are reverse terminals, I tried to transplant a battery from my 85 GL to my 93 Legacy and could not because the terminals were in reversed positions on either car.

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