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johnhup

Anyone else done Zenon's under-seat battery? (just ordered)

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Well I am still getting ready for my ITB EFI system and am just realizing that I will need the engine bay clearance so I am looking into relocating the battery. I came across Zenon's site where he put 2 sealed batteries under the rear seat. Anyone else done this?

My big question is, would one battery be enough? They are relatively cheap on eBay: http://cgi.ebay.com/ebaymotors/ODYSSEY-PC680-EXTREME-BATTERY-NEW-PC-680-AUDIO-0-SHIP_W0QQcmdZViewItemQQcategoryZ34284QQihZ010QQitemZ200025847356QQrdZ1QQsspagenameZWDVW

Keep in mind I dont live in a cold climate.

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I did it with one under the rear seat (mine's a touring, but that only means a little difference).

Here are my impressions from limited use, as the car is just back on the road: There is less of cranking power than with a standard size battery, I think. But, it is not horrible. As I use the car somewhat infrequently, I have a battery tender on it and there is enough juice to start it if all is tuned decently. But when I messing around with the MSD install, etc., after five minutes of cranking (not staright, mind you), the battery was not happy. Overnight with the tender and it was fine again.

Now, the motor it is cranking has pretty high compression (10.5:1), so it needs more juice and I'm in the Inner Sunset, so it might be cooler than where you are (a little S.F. weather joke for those who do not know S.F.).

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Crap. Maybe I will go with dual batteries. Its not about money, just time. Mind you I will be running HID's MegaSquirt, two amplifiers, and sloo of other electronics. I will also be upgrading to the 65 amp 320i alternator.

Anything I should worry about? I have never series'ed two batteries together before. Is everyone else using the PC-680 Odyssey?

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Here's a write-up on how I did my rear seat battery installation. I was pretty pleased with the results.

http://markstumm.com/76BMW2002.html

Thanks,

Mark

P.S. That 1976 is now in London, England. I wish I would have kept it, but a 1976 in California is not the ideal car to own.

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Thats some great information Mark. It appears that your Genesis, the Dyna-Batt, and the Odyssey PC-680 that Zenon used are exactly the same but rebranded. From what I have read, it appears that one battery will do just fine for my purposes. Also, with EFI I am not going to have to wait long at all for the fuel rail to reach its optimal 40 pounds of pressure.

I figure I may as well start with 1 and see what that road leads me. If I need to add one in the future it wont be hard. Cheers!

P.S. Mark, where did you get that battery tie down? I was gonna fabricate one but this seems a lot easier.

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ive got an optima red top sitting on its side under the back seat. ground is a seatbelt anchor bolt and a 1/0 gauge welding + cable goes to a custom power block under hood.......... ;)

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The red top will fit? What about when someone sits on the seat?

Also, anyone know a good place to get welding cable to run to the engine bay? West Marine maybe? Something cheaper?

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...pretty much exactly to Zenon's writeup with two Odyssey batteries. I can't answer your question about the single battery, but with two it's awesome. You can listen to the stereo for hours, or forget and leave your driving lights on for most of the day at work with no worries at all. Cheers!

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Crap. Maybe I will go with dual batteries. Its not about money, just time. Mind you I will be running HID's MegaSquirt, two amplifiers, and sloo of other electronics. I will also be upgrading to the 65 amp 320i alternator.

Anything I should worry about? I have never series'ed two batteries together before. Is everyone else using the PC-680 Odyssey?

Use two batteries. You'll want them when you're parked and listening to your music, when it's raining, the lights, heat, wipers, blower, radio, etc. are all on. I know you're in a warm climate but just throw in the extra battery. If not you'll just give yourself the opportunity to do it right the second time.

TJW

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So I just ordered from Odyssey Batteries here in CA (odysseybatteries.com) and they matched the price I found on eBay! I got one for 93 dollars and free shipping. I also ordered their battery tiedown box that should work nicely under the seat.

I am going with one for now and we'll see how that goes. After I install my new alternator I will probably order another one. I will have a writeup in the future so stay tuned if you are interested.

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So I just ordered from Odyssey Batteries here in CA (odysseybatteries.com) and they matched the price I found on eBay! I got one for 93 dollars and free shipping. I also ordered their battery tiedown box that should work nicely under the seat.

I am going with one for now and we'll see how that goes. After I install my new alternator I will probably order another one. I will have a writeup in the future so stay tuned if you are interested.

I used their box, too. Works good. Try it with one and see if it works. It's not hard to add one.

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Yes in parallel. I actually had to look it up to make sure I was doing it right. (Hey, I'm a software engineer).

Series

tworesistorsseries.jpg

Parallel

tworesistorsparallel.jpg

Thanks again to everyone.

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