Replacement Battery REBATE

[lanbrown]

Originally Posted by TiAgX5

Just picked up the Bosch battery.

It's a tank. 49lbs, 185 minutes reserve capacity, 1080 cranking amps @ 32 deg F!

This thing is more commercial truck battery then SUV battery.

It is made by Exide which can also sell a BMW battery for the dealers to sell.

[josiahg52]

I did not design these Bosch batteries either but I assure you the flooded battery is not 'sealed' by any industry definition. Likely the sealed term is used to describe the presence of a valve or plug in the vent line and to communicate the maintenance free aspect.

As these batteries do not benefit from the recombination cycle as do VRLA batteries, they must be vented outside the vehicle so that potentially explosive or flammable gases do not build up in the cabin during operation.

[PAX5]

Originally Posted by TiAgX5

Bosch 900CCA is under $115 TOTAL (with tax/fees), when purchased online/store P/U with 35% online discount code applied and after $15 core refund. Pep Boys site.

OE battery is only 740CCA.

CCA (Cold Cranking Amps) is NOT the same as Ah (amp hour) capacity.

BMW batteries are rated in Ah.

Research it and you'll be surprised how significant the difference is!

[TiAgX5]

Originally Posted by basora

CCA (Cold Cranking Amps) is NOT the same as Ah (amp hour) capacity.

BMW batteries are rated in Ah.

Research it and you'll be surprised how significant the difference is!

AH rating is used for deep cycle batteries.

I don't understand why BMW uses a rating that applies to a battery that won't see regular usage (boats/planes/motorhomes).

Most all automotive battery manufacturers use an RC rating, how many minutes it takes a 25 amp load to drop voltage to 10.5.

Not very useful to know what a 1 amp load does to an automotive battery. Automotive batteries have a high draw at start up, alternator carries the draw from there.

[PAX5]

Originally Posted by TiAgX5

AH rating is used for deep cycle batteries.

That's a true statement, but it says nothing about the appropriateness of the battery for its application.

Selecting a battery for a BMW based on CCA is incorrect.

[TiAgX5]

Reserve Capacity (RC) is a very important rating. This is the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts.
An amp hour (AH) is a rating usually found on deep cycle batteries. The standard rating is an Amp rating taken for 20 Hours. What this means, say for a 100 AH rated battery is this: Draw from the battery for 20 hours and it will provide a total of 100 amp-hours. That translates to about 5 amps an hour. 5 x 20 = 100. However, it's very important to know that the total time of discharge and load applied is not a linear relationship. As your load increases, your realized capacity decreases. This means if you discharged that same 100 AH battery by a 100 amp load, it will not give you one hour of runtime. On the contrary, the perceived capacity of the battery will be that of 64 Amp Hours.

Understanding that, the RC rating applies to automotive apps, & AH rating apply to apps such as mooring lights on boats (on and low amp draw, when motors are off and alternators are not operating).

Couldn't care less what a 1 amp constant draw does to an automotive battery, I shut everything off, and trickle charge whenever it will be parked over 72 hrs.

I posted the 185RC info in post 12, what applies to automotive applications.

If this was a marine of aircraft forum, the AH would matter.

[PAX5]

Originally Posted by TiAgX5

Reserve Capacity (RC) is a very important rating. This is the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts.
An amp hour (AH) is a rating usually found on deep cycle batteries. The standard rating is an Amp rating taken for 20 Hours. What this means, say for a 100 AH rated battery is this: Draw from the battery for 20 hours and it will provide a total of 100 amp-hours. That translates to about 5 amps an hour. 5 x 20 = 100. However, it's very important to know that the total time of discharge and load applied is not a linear relationship. As your load increases, your realized capacity decreases. This means if you discharged that same 100 AH battery by a 100 amp load, it will not give you one hour of runtime. On the contrary, the perceived capacity of the battery will be that of 64 Amp Hours.

Understanding that, the RC rating applies to automotive apps, & AH rating apply to apps such as mooring lights on boats (on and low amp draw, when motors are off and alternators are not operating).

Couldn't care less what a 1 amp constant draw does to an automotive battery, I shut everything off, and trickle charge whenever it will be parked over 72 hrs.

Good!

You've "almost" defined Peukert's law ...

Back to my original point when you recommended that specific Bosch battery without giving the Ah rating ...

[TiAgX5]

I posted the 185RC info in post 12, what applies to automotive applications.

If this was a marine of aircraft forum, the AH would matter.

Knowing the AH rating of an automotive battery is like knowing the MPG at 2 mph, you may have the info, yet never actually need or use it.

[josiahg52]

Absolutely. The ampere-hour capacity is only a useful specification if the discharge rate is given and is incomplete otherwise. The A-hr. capacity will actual be different depending on the discharge rate. The batteries that I deal with range in A-hr capacity from several thousand to several tens of thousands depending on the discharge rate.