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Discussion Starter #1
My battery went flat last week so I pulled out my multimeter and got to work.

According to my plugging and unplugging of fuses in the engine compartment the ECU B-1 (25A fuse) has a battery drain of 0.19A when the car is shut off completely and HAZ (15A fuse) about 0.10. I know that MR2s have issues with parasitic battery drain and that it's not good to leave it for weeks without recharging or starting the car (this is my second spyder, my previous 2 would empty the battery if it sat for 3 or 4 weeks), but is such an immense drain by ECU normal? Especially HAZ draining battery when the button is not even pressed? Am I understanding correctly that ECU B-1 is the constant power to ECU that is like that from factory? But is this charge correct or too high? Does anyone know what the normal battery drain should be? Thanks!

I hope I'm not being paranoid about this, but I bought a new battery, installed it in car and tested it works, then just disconnected the leads while waiting for paperwork so I can get the car insured and on the road, to avoid draining the new battery as well.
 

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Parasitic battery drain is normal and your measurements are reasonable since it takes power for the immobilizer/alarm, radio, clock, etc... to retain their settings.
 

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It is likely that the battery is just worn out. Lead-acid batteries tend to lose any capacity that is left uncharged. That causes them to deteriorate over time, because you can't use the battery without taking charge out. Hence, any battery found dead for no clear reason is probably scrap regardless of the cause. The one thing that you want to watch out for is a weak alternator. If that is the case, then it will go ahead and kill your new battery also.
 

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Discussion Starter #4
Thanks for the replies, guys, that's definitely a load off my heart! :)

Should probably regularly check the voltage in case it's alternator?
 

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You should check the charging circuit when there is a problem. Alternators do go bad and driving a car with a bad alternator will drain the battery. Just picking an item to replace without diagonsing the problem can get expensive. I have had a bad alternator after a few years in a new Corolla. The alternators in my 2001 Tacoma and 2001 Spyder are still original.
 
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