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Discussion Starter #1
Car wouldn't crank so I had the battery tested. It shows to be bad. The OEM battery is rated for 850 CCA. The aftermarket battery they say is made for the M5 is 800 CCA. Is there a problem using a battery with lower CCA than the original?
 

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Depends...what kind of battery do they want to sell you? There are very few good replacements other than another BMW battery. I bought a Red Top spiral wound and it is much smaller than original. Battery Plus has a decent replacement from what I understand for about 170 bucks. As long as the CCA (cold cranking amp) is close you should be ok.
 

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Doug is correct of course. The problem is selection. There are only a handful of batteries available (reasonably priced) that equal the battery BMW uses, let alone batteries that exceed it! I don't know why they use such a powerful battery to start with- don't get me wrong, I'm glad they did, but I've cranked big block Chevy's with more compression and so much advance and cam that they shouldn't run with smaller! If your dealer will work with you, go OEM BMW, but I have seen prices stated here on this forum from $179-$300+ for the same battery-just different dealer. Shop by phone first if you can and tell them you won't pay "list". G/L at least the batteries are so good you probably will never buy another!
 

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Hey BMWx2 -- The biggest difference is that your big blocks didn't use oil to control their cam timing - once you add in the additional "sludge factor" of thick oil you run into a tough engine to start. At least, that's my thought :)

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The 34R Optima RedTop has been used successfully be several folks here, and is what I was planning on getting when I thought my battery was dead.

I'd love to find a deep cycle (blue or yellow top), but they don't have one with appropriate CCA and reverse terminals.

I think I may just wire up a new ground cable to solve that issue since reverse terminals are a PITA, in which case I'd get a Yellow Top D31A...

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The 34R Optima RedTop has been used successfully be several folks here, and is what I was planning on getting when I thought my battery was dead.

I'd love to find a deep cycle (blue or yellow top), but they don't have one with appropriate CCA and reverse terminals.



d-

I use a deep cycle Odyssey 1700. I believe you have to get the one with reverse terminals.

I let the car sit for 4 weeks, and while not completly draining the battery, I did not have enough juice to start. But after a quick jump, all was good.

I had the car unlocked in the garage, not sure if locking would have used less juice over that time period.
Regards,
Jerry
 

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I went with the Optima 34R (reverse tap) red top. I keep my garage at 40 degrees in the winter so it's hard to say how long the battery will last, but it's a damn good battery-I too wanted the deep cycle, but between price and reverse terminal availability chose the red.

I do not like the fit Doug. You have to slide the battery all the way to the right and remove all the plastic crap on the bottom to get the cover to close. I used some foam material to fill the void on the left which of course covers the vent hole. Optima supposedly doesn't need venting, but it was a little weird. The cover fits now, but it's not molded to fit any thing but an OEM.

There are compromises, but I think a red top will do you very well service-wise. If I had dealers close by that would work with me, the OEM battery is MASSIVE compared to the red top.
 

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Discussion Starter #9
Thanks for the input. There is about a $20 difference between the cost of the 800 CCA battery at Battery Plus and the OEM one (after my 10% BMWCCA discount). I'd really like to have the higher CCA and probably will go with the OEM since the price difference is so little. Works out to less than $5 a year difference over the life of a battery.

What I'm wrestling with now is why the battery tested as bad. After I got home from testing it, the battery showed 12.45v and it stayed at that level all night with no additional charge. This morning it was still 12.35v and I was able to start it 3 times straight with the lights on; the voltage only dropped to 12v after the 3 starts. In thinking back over the events from yesterday, I seem to recall one of the back doors was open. Doesn't the M5 supposed to cut the inside lights off if the door is left open too long? Also, I'm wondering now if the test was valid. I plan to let the dealer run a test as well on Monday. I don't understand why it should continue to perform as it does if it is truly bad; however, I don't want the get stranded being cheap.
 

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What I'm wrestling with now is why the battery tested as bad. After I got home from testing it, the battery showed 12.45v and it stayed at that level all night with no additional charge. This morning it was still 12.35v and I was able to start it 3 times straight with the lights on; the voltage only dropped to 12v after the 3 starts. In thinking back over the events from yesterday, I seem to recall one of the back doors was open. Doesn't the M5 supposed to cut the inside lights off if the door is left open too long? Also, I'm wondering now if the test was valid. I plan to let the dealer run a test as well on Monday. I don't understand why it should continue to perform as it does if it is truly bad; however, I don't want the get stranded being cheap.

Just as an FYI, a "12V" battery is actually 6 (six) 2.1V batteries in series. As such, a battery with no load should measure 12.6V to be considered "good". If you were at 12.4 or 12.3V then you probably need a new battery.

Yes, we do have a battery saver, and if it weren't working in your car you wouldn't have been anywhere near 12.4V - you'd be in the high 11's with nary a squeak from your car...

There is no way to "start your car with the lights on" - like many other high electronics content vehicles, the car disables lights, HVAC, etc when you turn the key to engage the starter...

It is still worth getting the battery tested at the dealer, but based on the voltages you listed I'd be surprised if they tell you anything other than you need a new battery...

d-
 

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Thanks BMWx2 - good to know on the fit. Since my battery is apparently missing the factory hold down, I'm looking to fashion a new way to hold it in place anyway :)

I wouldn't worry about the drain hole - your Odyssey is completely sealed, so all the hole would be is a way for water to get in your trunk...

I like the Optima's, so maybe I'll try a 31A and re-wire my Ground. Of course, my stock battery needs to hurry up and die first!

Or, just maybe I'll win the lottery and then I can wire up 2 of the Voltphreaks batteries in parallel and mount my sub amp in there with them. :)

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I had no tie down on my battery EXCEPT the molded cover which was plenty. Any of the Optimas will just look tiny by comparison-physically in the space. I'm sure battery technology allows for as much battery in a smaller footprint
 

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I don't know why they use such a powerful battery to start with
There are a lot of electrical accessories not to mention the juice needed to run the engine. Just park your car for a few weeks with nothing "on" (and yet, something is always draining something) and you will appreciate the need for the capacity. The weight also helps balance the car to give you close to 50/50 wt distribution :blink: , though I'll bet mine is more front weighted (52/48 or 54/46?) because I replaced by OEM exhausts (they weigh a ton) with Tubis.
 

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Discussion Starter #14 (Edited)
Just as an FYI, a "12V" battery is actually 6 (six) 2.1V batteries in series. As such, a battery with no load should measure 12.6V to be considered "good". If you were at 12.4 or 12.3V then you probably need a new battery.

Yes, we do have a battery saver, and if it weren't working in your car you wouldn't have been anywhere near 12.4V - you'd be in the high 11's with nary a squeak from your car...

There is no way to "start your car with the lights on" - like many other high electronics content vehicles, the car disables lights, HVAC, etc when you turn the key to engage the starter...

It is still worth getting the battery tested at the dealer, but based on the voltages you listed I'd be surprised if they tell you anything other than you need a new battery...

d-
Thanks.

I plan to show up at the dealer first thing tomorrow morning. On the headlights, I'm sure mine aren't disabled when I turn the starter. They don't even dim like they would on my old car; thanks in part I guess to the huge battery. In the darkened garage with the light switch on "auto", I notice they're on when I first turn the key and they remain on when I start it. I try to remember to turn them off before I start it to limit battery drain. Do yours go out as you turn your key? Could that be a programmable option?

Also, good point about the battery saver. That's probably what's keeping it as high as it is.
 

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Discussion Starter #16
I got the Batteries+ replacement with the vent tube....and a three year warranty for about 100 bucks..It fit perfectly.

Great deal. Batteries+ wanted about $169 for the one they quoted me. I just picked up an OEM one today and installed it. The dealer verifed Batteries+ test that the battery was bad. Borderline bad, but it was on it's way out; low cranking amps.

Douglas was spot on about the 12.6v. The new battery measured 12.6 on the nose before I installed it.

And don't fit to remove the black vent hole connector from the old battery. I didn't forget mine but could see how it could easily be done.
 
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