Good idea to replace battery at 4 yrs.?

Dackelone · 11-11-2015, 01:28 PM

Quote:

Originally Posted by BrokenVert

Why? I'm in the same boat. Battery has a resting voltage of 12.5 and starts the car immediately.

Why should I change? It's a battery not a spark plug

I believe 12.8 volts is where the standing voltage should be at. Anything less and your battery is not fully charged. Doesn't mean your battery is done, just that it is on its way out.

When the engine is running you should see more than 13.4 (dc)volts across the battery terminals. Also... if you measure AC volts across the battery... anything more than ~1 ACvolt and your alternator is not working. Most likely the regulator inside the alternator is shot.

Dackel

BrokenVert · 11-11-2015, 01:51 PM

Quote:

Originally Posted by Dackelone

I believe 12.8 volts is where the standing voltage should be at. Anything less and your battery is not fully charged. Doesn't mean your battery is done, just that it is on its way out.

When the engine is running you should see more than 13.4 (dc)volts across the battery terminals. Also... if you measure AC volts across the battery... anything more than ~1 ACvolt and your alternator is not working. Most likely the regulator inside the alternator is shot.

Dackel

Well it is an 8 year old battery. Id expect it to show some signs of wear. But it still works fine.

Running voltage is over 14. Cant rember the exact number (14.3 or 14.4 I think)

Dackelone · 11-11-2015, 02:30 PM

Quote:

Originally Posted by BrokenVert

Well it is an 8 year old battery. Id expect it to show some signs of wear. But it still works fine.

Running voltage is over 14. Cant rember the exact number (14.3 or 14.4 I think)

When I worked at a VW dealership... VOA would have us replace any car battery of a new car in inventory - when the static battery voltage was under 12.8 volts. It was easy money for any PDI tech.

BrokenVert · 11-11-2015, 02:40 PM

Quote:

Originally Posted by Dackelone

When I worked at a VW dealership... VOA would have us replace any car battery of a new car in inventory - when the static battery voltage was under 12.8 volts. It was easy money for any PDI tech.

I still don't understand why you would change a battery preventatively when the electrical system still works fine.

Dackelone · 11-11-2015, 04:13 PM

Quote:

Originally Posted by BrokenVert

I still don't understand why you would change a battery preventatively when the electrical system still works fine.

Because the battery can not or is not holding a "full charge". First step is to measure static dc voltage. Then the tech has to charge the battery, and then load test it. IF it fails the test, the car gets a new battery under the new car warranty before the car gets sold to a customer. That is the way VW did things back in the day. Who knows how they do things now.

BrokenVert · 11-12-2015, 11:51 AM

Quote:

Originally Posted by Dackelone

Because the battery can not or is not holding a "full charge". First step is to measure static dc voltage. Then the tech has to charge the battery, and then load test it. IF it fails the test, the car gets a new battery under the new car warranty before the car gets sold to a customer. That is the way VW did things back in the day. Who knows how they do things now.

Why does it matter if it isnt full so long as the car starts without issue and the electrical system runs at the proper voltage while running?

My car sat for 3 weeks while my parents were on vacation and I drove my father's i3. They got back a few days ago, my car started quickly and without issue.

JimD · 11-24-2015, 07:19 AM

A couple thoughts. I wouldn't be too worried if a battery was at 12.5 static versus 12.8 IF I know that the voltage loss is spread evenly over the cells. If one cell is significantly low, then I don't think the battery is going to make it much longer. But I don't know how you can know this in any practical way. Cutting the battery up to test it is not, IMHO, practical.

But I would also be leery concluding that my multimeter's measurement of 12.5 is completely dependable. I don't know what their 95/95 confidence level is but I wouldn't be surprised to learn that a measurement of 12.5 could be anywhere between 12.3 and 12.7 on a 95/95 basis. I would want to understand that better before I bought a battery.

I like to test CCA with an inexpensive tester from HF (inexpensive like $20). I think it may help identify a bad cell. All the tester does is to put a resister across the battery to draw like 100A and you read the voltage. The meter has a scale to convert the voltage to CCA automatically. When I have concerns about a battery I use this meter. If the CCA is low, I replace the battery.

Last thought, I have had batteries fail quickly several times. Like within a year of purchase. I don't know why they failed, just that they did. I have also had batteries last very long (more than 10 years). As long as you have a backup plan for what you will do if you go to start the car and it doesn't start, I don't see why you can't wait for it to fail. But if the car not starting will be a major event in your life, then replacing it when you see signs of decline may make sense. My backup plan is another car (not my wife's my old SUV). Plus I have good cables and two chargers. But it is only a couple minutes to switch to the other car. Then I can deal with the car that won't start when I have time.

ok75 · 12-04-2015, 11:09 AM

The low battery yellow alert showed up in my 2011 135i.
I can replace it with a Exide BMW Battery or a Bosch which I've been told that it is better while the Exide cost $100 more.
Any recommendations for the Bosch?

11-24-2015, 07:19 AM	#51
JimD Brigadier General 368 Rep 3,547 Posts Drives: 128i convertible Join Date: Apr 2009 Location: Lexington, SC iTrader: (0)	A couple thoughts. I wouldn't be too worried if a battery was at 12.5 static versus 12.8 IF I know that the voltage loss is spread evenly over the cells. If one cell is significantly low, then I don't think the battery is going to make it much longer. But I don't know how you can know this in any practical way. Cutting the battery up to test it is not, IMHO, practical. But I would also be leery concluding that my multimeter's measurement of 12.5 is completely dependable. I don't know what their 95/95 confidence level is but I wouldn't be surprised to learn that a measurement of 12.5 could be anywhere between 12.3 and 12.7 on a 95/95 basis. I would want to understand that better before I bought a battery. I like to test CCA with an inexpensive tester from HF (inexpensive like $20). I think it may help identify a bad cell. All the tester does is to put a resister across the battery to draw like 100A and you read the voltage. The meter has a scale to convert the voltage to CCA automatically. When I have concerns about a battery I use this meter. If the CCA is low, I replace the battery. Last thought, I have had batteries fail quickly several times. Like within a year of purchase. I don't know why they failed, just that they did. I have also had batteries last very long (more than 10 years). As long as you have a backup plan for what you will do if you go to start the car and it doesn't start, I don't see why you can't wait for it to fail. But if the car not starting will be a major event in your life, then replacing it when you see signs of decline may make sense. My backup plan is another car (not my wife's my old SUV). Plus I have good cables and two chargers. But it is only a couple minutes to switch to the other car. Then I can deal with the car that won't start when I have time. __________________ 128i Convertible, MT, Alpine White, Black Top, Taupe Leatherette, Walnut, Sport Ordered 5/22/09, Completed 6/4/09, At Port 6/9/09, On the Georgia Highway 6/13/09, Ship Arrived Charleston 6/24/09 at 10pm, PCD 7/21/09
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12-04-2015, 11:09 AM	#52
ok75 Registered 0 Rep 3 Posts Drives: 2015 BMW 435i Convertible Join Date: Dec 2015 Location: CA iTrader: (0)	The low battery yellow alert showed up in my 2011 135i. I can replace it with a Exide BMW Battery or a Bosch which I've been told that it is better while the Exide cost $100 more. Any recommendations for the Bosch?
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