Battery drain - m50 swap?

[Ritt]

So, I did the M50 manifold swap. The car sat for so long (more than 6 weeks) that the battery was close to dead when I tried to start it. I jumped it and went about my business.

Since then though it's been doing it somewhat regularly. If I don't drive the car for 5-6 days it doesn't have the juice to start, though all the idiot lights etc come on like they should. It won't crank or click and if I try more than a couple times the wipers move - no idea what that's about.

I doubt that any part of the manifold swap has resulted in a voltage drain, so I'm focusing on the battery. I don't know how old the battery is though. It's possible it's original (I doubt it, it'd be 15 years old), and it's certainly OEM 'cause it's got German text on it. What I can't figure out is where there's a date code on this battery - there's nothing obvious on top. Is it on the side, meaning I'll have to pull it out of the car to see how old it is, or is there some way of deciphering the manufacture date from the info on top of the battery

OR: is there something that might have happened as a result of the manifold swap? I can't imagine what, but if anyone's got ideas I'd appreciate hearing them.

[MasterKwan]

Don't know how cold it is where you are but, if you let a battery discharge, it can freeze in cold weather and damage itself. That's why I keep the battery minder on my battery when I have the car on stands.

If the battery is more then 5 years old, it's due for replacement anyway.

I'd throw the battery on a real charger and charge it up. You can see if you have a current drain by using a volt meter set in current mode and putting it in series with one of the battery cables. Any draw over 1/2 amp is probably a problem.

[das borgen]

have autozone load test the battery to see if it's good usable life....that's by 1st step

2nd step is trace power draws

[Ritt]

Autozone tested the battery and told me it's "weakening," whatever that means. The little window that should show green if it's OK shows black with a yellow tinge (to my eyes) so that supports their conclusion. The fact that my trickle charger thinks it's full, when the window doesn't show green, also backs it up.

So, new question: what battery do you guys like for an E36 M3?

That is, STOCK FITMENT. Optima, Odyssey, etc need not apply. My criteria are that it fit in the stock location, and use the stock mounting/tie-down hardware.

I did a ton of searching and I know there are several that are near-stock size and will work fine, that's OK with me. Just curious what some other folks might have bought recently, or maybe within the last couple years, and what issues may have arisen.

[das borgen]

whatever battery.....it's all the same difference

[Schultz28]

buy an interstate!