Battery.
- Thread starter acer54
- Start date
acer54 said:
Get it from Tanya batteries, cheap as chips and next day delivery! This what I bought
http://www.ebay.co.uk/itm/Powerline-096-Heavy-Duty-Car-Van-Battery-12V-fits-many-Audi-BMW-Citroen/251410202004?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Had the same in my previous Z4 too
Just drops straight in nothing to register just need to reset the clock and the windows literally 10 minutes from opening the boot to having the new battery in and installed
If you order from that link it'll be with you tomorrow
^^^^This^^^^. No silly battery registration requirements on E85 / E86.
Powerline is a good budget option and will be fine. If you wanted to spend a littler more the Varta Silver Calcium has lower leakage (so will self discharge more slowly when left standing) and has about 20% more cranking power. http://www.ebay.co.uk/itm/096-Bosch-Equivalent-Silver-Calcium-Car-Battery-S4008-4-Yr-Wty/252662697206?hash=item3ad3deccf6:g:3ZQAAOSwbtNaGA2T
Powerline is a good budget option and will be fine. If you wanted to spend a littler more the Varta Silver Calcium has lower leakage (so will self discharge more slowly when left standing) and has about 20% more cranking power. http://www.ebay.co.uk/itm/096-Bosch-Equivalent-Silver-Calcium-Car-Battery-S4008-4-Yr-Wty/252662697206?hash=item3ad3deccf6:g:3ZQAAOSwbtNaGA2T
If you check realoem, there is a choice of three capacities dependent on vehicle spec. The tray in the boot has a removable plastic insert which can be taken out to fit the larger of the three. If it were me, providing you can be sure to keep it charged I would go for the largest one.
http://www.realoem.com/bmw/enUS/showparts?id=BT52-EUR-10-2004-E85-BMW-Z4_30i&diagId=61_1612
http://www.realoem.com/bmw/enUS/showparts?id=BT52-EUR-10-2004-E85-BMW-Z4_30i&diagId=61_1612
Indeed. The capacity is almost irrelevant but they do seem to go hand in hand with CCA (cold cranking amps) which is more important.
From cold, the typical pull from the starter is around 200A + approx 10A for ancillaries on a 6cyl n/a petrol, so still way less than the CCA rating of even the smallest of batteries. The CCA is just another way of stating the internal resistance of the battery. It is the current that can be provided for 30 seconds at 0'C whilst maintaining a battery voltage of 7.2V.
So for example, taking the figures from above - if you chose a battery with a CCA of 200A, you would get 7.2V at the starter motor when turning the key (ignoring cable losses). That's OK, but it wouldn't turn the starter particularly fast. A battery with a CCA of twice that (400A) would turn the starter at 10V. The starter would spin around 40% faster.
Generally speaking, the CCA rating is a good indication of the quality of battery. Certainly more than any other factor. That's why calcium / silver batteries tend to have higher CCA ratings. AGM even more so. They also have far lower self discharge rates when left stood.
Given that once the car is running all the power is taken from the alternator (apart from occasional very large transitory spikes), the only real requirement for capacity (Ah) is how long the battery will last while the car is stood. In 'sleep' mode the current draw is well below 0.1A, so even a 50Ah battery would last 500 hours (or 20 days).
To summarise, always go for the highest CCA rating. You can pretty much ignore capacity.
From cold, the typical pull from the starter is around 200A + approx 10A for ancillaries on a 6cyl n/a petrol, so still way less than the CCA rating of even the smallest of batteries. The CCA is just another way of stating the internal resistance of the battery. It is the current that can be provided for 30 seconds at 0'C whilst maintaining a battery voltage of 7.2V.
So for example, taking the figures from above - if you chose a battery with a CCA of 200A, you would get 7.2V at the starter motor when turning the key (ignoring cable losses). That's OK, but it wouldn't turn the starter particularly fast. A battery with a CCA of twice that (400A) would turn the starter at 10V. The starter would spin around 40% faster.
Generally speaking, the CCA rating is a good indication of the quality of battery. Certainly more than any other factor. That's why calcium / silver batteries tend to have higher CCA ratings. AGM even more so. They also have far lower self discharge rates when left stood.
Given that once the car is running all the power is taken from the alternator (apart from occasional very large transitory spikes), the only real requirement for capacity (Ah) is how long the battery will last while the car is stood. In 'sleep' mode the current draw is well below 0.1A, so even a 50Ah battery would last 500 hours (or 20 days).
To summarise, always go for the highest CCA rating. You can pretty much ignore capacity.
ph001 said:
Great post.
For Info, just took my ///MR out to top up with petrol, not moved for 13 days and the battery was clearly feeling it. Another day and I think I would have been getting a text from the tracker, to tell me to plug the charger in. The cold weather won't help at the moment either.ph001 said:
That depends upon how many devices you have in the car that draw quiescent current. If you have a standard Z4 I agree, but I have accessories that need to be permanently powered and draw 105mA on top of the car quiescent current. I want the highest capacity possible so I have the best chance of starting the car if I have parked it up for any length of time and forgot to hook up my CTEK trickle charger.
Given the difference in price is generally not that great I would still go with the battery with the highest capacity.
Magicarcher said:
Most people drive their car at least once a week or put a trickle charger on it. Even with a few aftermarket accessories you would still be in the mA range unless it’s something really odd which isn’t really designed to be wired on permanent live. I stand by my statement that capacity is pretty much irrelevant.
ph001 said:
I have a single AM accessory that draws 105mA and it is designed to be permanently wired. It is a GPS tracker that has to be permanently wired to provide vehicle location on demand. It is horrendously inefficient in terms of current draw, but sadly that is the state of AM accessories that are not designed to OEM specs. It is a bitter pill to swallow given that when I used to design vehicle electrical systems I had a whole vehicle quiescent current target of 80mA but I choose to swallow it because a friend had his Z4 stolen 2 miles from where I park mine every day at work and I like the comfort of knowing that if anyone steals my car I will know exactly where they are.
A big problem with batteries not in regular use is plate sulphating, I forget the exact chemistry but the build up of lead sulphate stops them working properly. The calcium type batteries do not suffer from this problem or at least suffer much less so are generally a better choice for cars not in daily use.
Rob.
Rob.
Bertz4 said:
Yes - this is the number one cause of battery degradation. Significant plate sulphation starts to occur when the battery terminal voltage drops below about 12.2V (so about 70% discharged), but it is quite soft and easily reversed with a full recharge if done within a few days. Let the terminal voltage go much below this for a number of weeks though and the sulphation crystals harden so much they they can never be recombined back into the electrolyte. I would be putting a trickle charger on anything left standing for more than a couple of weeks.
It's also important to do a full equalisation charge (i.e. 14.4V) until the battery is 100% charged at least once a month to remove any soft sulphation. If the car is doing lots of short journeys it probably never gets to 100% charge from the alternator and this is a big killer of batteries over time.
Below is a typical state of charge characteristic. The C/100 curve one is the one most applicable when the car is stood...
