New battery -- any suggestion?

[JamieZ4C]

I) Don't know, I'm new to Z ownership, but it normally states the change procedure in the owners manual.
II) I don't think so. I don't have one on mine.
III) Not sure, but does an AGM cost more and what's the benefit? If it costs more for no benefit, then is it worth bothering?

Hopefully someone more knowledgeable will come along with better answers!

 

[obewan]

ii) Do I have to connect a vent tube on the battery to remove the gases produced?

I've never bothered in the past with previous cars, as the battery was always under the bonnet (Hood)
With it in the boot (Trunk) I was a little more wary.
The vent on my new battery was in a different position. I extended the vent by using fish tank air tube and a junction piece - Sorted :wink:

 

[skurup]

Do AGM batteries have vent?

 

[obewan]

Do AGM batteries have vent?

Apparently not
Courtesy of Google
AGM Batteries. A VRLA battery (valve-regulated lead–acid battery), more commonly known as a sealed battery or maintenance free battery, is a type of lead-acid rechargeable battery. Due to their construction, they do not require ventilation, can be mounted in any orientation, and do not require constant maintenance.

 

[Mr Tidy]

AGM Batteries. A VRLA battery (valve-regulated lead–acid battery), more commonly known as a sealed battery or maintenance free battery, is a type of lead-acid rechargeable battery. Due to their construction, they do not require ventilation, can be mounted in any orientation, and do not require constant maintenance.

You really don't want one of those - I had to have one in my 123d and by the time it was coded to the car it cost just over £250 in 2012. (It had to have AGM because it had stop/start).

Thankfully E85/6 ones don't need coding - my BMW Indy supplied an OEM battery for my E86 in late 2015 for £75 + VAT. I thought it would be Bosch, but he said they were Exide - but then the car was built in Spartanburg!

 

[Tinman6]

I had my AGM battery replaced with another decent make of AGM last year and it cost me £115 fitted. Solved a problem I had at the time with the engine and electrics intermittently going dead which turned out to be a duff cell in the original 13yr old battery !

As far as 70ah etc goes, that's the capacity of the battery, 70ah means it'll supply 70 amps continuously for an hour before being fully discharged.
Fitting a higher capacity battery such as an 85 or 90ah should not be an issue, just means it won't go flat so quickly, it'll be the same voltage.

 

[Ewazix]

You can't go wrong with a recognised brand like Bosche or Varta which are actually the same company making batteries worldwide in the same factories. Higher 'ah' rated batteries are more resilient and have an advantage if you leave your stood for periods as they have more in reserve after self discharging, Higher CCA indicated a battery will give more power at start-up.

Apparently our original BMW batteries may be date stamped on top of the negative terminal with a year/week code e.g. 03/25 being June 2003 and or have a number etched on the case which starts with the year/month e.g. 0306......... = 2003June. Mine is and this fits with the cars build date, but I don't know if it's the same with later cars.

 

[skurup]

Finally, I ended up buying this one: :wink:
Bosch Platinum series, Advanced AGM battery.
760 Cold Cranking Amps, 70 AmpereHour. It has a 4 year replacement warranty.
I also has my CTEK Battery sense connected to it. I draws only around 1 mA current which is pretty good.

I have to admit, the steering wheel has become easier to turn; it was harder with the previous battery. When I first started the car after the battery got replaced, I was like, what happened to the steering? Why is it so soft? Is it disconnected or what?
So much easier to turn.

 

[skurup]

And, yeah, I did one other change today on my car; nothing related to battery though (still posting it here).
I got the control arm bushing and bracket changed. It's pretty good to drive now.
Polyurethane -- a little bit stiffer than rubber -- but I don't have to worry about changing it again.
The old ones were in a pretty bad shape. It's sooooo much comfortable to ride now.