Why don't replacement starting batteries last as long as oem ?

Many OEM batteries are fitted to imported vehicles from Japan.
The Japanese and some European makes have a philosophy of providing quality components, usually, and for them it is shameful to provide an item of inferior quality.
Batteries sold as replacements are from a battery maker who wants to sell batteries, so why does they want to make them last a long time and have less sales. Doesn't make economic sense to them. The OE battery is fitted under a different way of thinking.
Yes they are usually fresh batteries with a new car too.

Have seen OE motorcycle batteries last 8 years and the replacement 13 months.

Wicket - Regular lead-acid Batteries are kept fully charged in stock in many distribution centres for a maximum of 3 mths.
After that period of time, they are returned to the importer/manufacturer, and new ones are supplied to replace them.

The returned batteries are sold as "seconds", and you can regularly buy "seconds" batteries at a sizeable discount.
I have often bought "seconds" from my local Supercharge battery importer.

Lead-acid batteries are built with a "precharge" in them, with the lead plates being built with a lead oxide paste made from lead, sulphuric acid and water.

Batteries can be transported in this form with less problems, and their shelf life is a couple of years in this form (with no acid added).

Regular lead acid atteries are stored "dry" in the importers warehouse, and many distribution centres, and often filled with acid and charged prior to delivery, if there's time to do so.
However, many people haven't got time to wait, so they need fully charged batteries ready to roll. As a result, most distribution centres carry a range of fully-charged batteries ready to go.

OEM batteries are generally of superior quality to aftermarket batteries. The battery market is highly competitive, and you generally get what you pay for.
Most batteries are sold on price, and the price governs the quality. If you want a top-quality battery, buy a marine battery and expect to pay a premium price for a premium product.

Cheers - Ron.

Gday
There arn't many subjects that stir the juices in people and batteries is one of them.

I actually find the reverse. OEM usually last a bit over 3 years then I buy a decent replacement that goes for 6 or more. Especially in the past new vehicles could sit on the dock or in yards for months with little if any charge. When I picked up my new 100 series much to the embarrasment of the dealer it had a flat battery which no doubt contributed to it's early demise.
Biggest mistake people make is buying cheap relacement batteries often just because it was convienient. Save $50 only to last half as long.
Cheers Craig................

Thanks to those who replied...........

next question . what defines a top quality battery ( price seems to be a consideration ) ?
Are some brands more top quality than others, I want another 7 years from my next battery.

Wicket - Battery manufacturing is a complex process with many different ideas produced by different manufacturers.
There are differing physical design features, chemical design features, and metal type content and grain structure features.
Virtually all manufacturers have standard batteries, and superior quality batteries (that sell for premium prices).

Many batteries have specific useage design, with automotive/starting batteries needing different design to batteries used in other applications.
You won't go wrong buying a premium battery from a reputable manufacturer, that is designed for starting purposes.

The Marine batteries are regarded as a premium product and are designed to be particularly long-lasting, as many marine batteries are difficult to remove and install, and if you get a flat battery at sea, you can be a long, long way from any replacements, and it can become a life-threatening situation.

I'm personally tending towards the Century/Yuasa line after having had a so-so run from Supercharge batteries.
However, the Delco Marine batteries come highly recommended from many users as well.
There's some good info on the Century website about the various types and features (good & bad) of the various styles of battery construction (see Battery Talk newsletter).

http://www.centurybatteries.com.au/index.php/resources/battery-talk

Cheers - Ron.

i find batteries last much longer in petrol vehicles i guess due to the lower compression

in a diesal about 2 years is typical for a battery although good batteries will be more like 5 years

I wouldnt trust any battery in a diesal past 5 years

There are several things that will assist in improving battery life.

1. Keep your battery well secured in its tray or mounting. It's illegal, anyway not to have a battery properly secured.

2. Keep your battery cool. Heat in engine bays can be substantial, and prolonged heat kills batteries. Turbos produce vast amounts of heat. Install a heat shield for the battery, if one isn't fitted.

3. Install some insertion rubber under your battery. A battery mounted on rubber is isolated a little better from road shocks and vibration. Shock and vibration helps to wreck battery plates and separators, and shorten battery life.

4. Keep your batteries clean. Dust, salt and dirt build-up (particularly ironstone-gravel dust) combined with moisture leads to current being slowly but steadily trickled out of the battery. Keeping the battery clean, ensures there's no unnecessary current loss.

5. If your battery has caps for the cells that allows top-up, use only distilled water, and keep the electrolyte level about 10mm above the plates. Low electrolyte levels buckles and distorts plates and shortens battery life.

6. Use the correct size (adequate size) cables for starter and other power lead requirements. Too small diameter cables leads to excessively high amperage draw on batteries due to excessive resistance. Many OEM cables are too small. Manufacturers only fit the bare minimum diameter of cable.

7. Regularly clean up terminal posts, and all major connections. It's amazing how connections corrode, and corroded connection points leads to increased resistance and high amperage draw. Soldered connections are far superior connections where crimped connections are exposed.

8. Always make sure you have a good earth strap, with good, tight, clean, connections, between chassis/body and engine/transmission. This is an often neglected area that can create many electrical problems.

9. Ensure your alternator is always charging properly. Check to ensure that all alternator connections are clean and tight, and that the alternator is producing a minimum of 13.8V across the terminals and no more than 14.5V.

Testing Battery and Charging system - good info - http://www.w8ji.com/battery_and_charging_system.htm

Battery wiring techniques - good info - http://www.w8ji.com/battery_wiring.htm

Cheers - Ron.

Ive always had great service from aftermarket, like someone said you get what you pay for and I have bought batteries for all mine, my sons etc, usually buy a good strong overkill battery and they last 5 to 7 years on average.
As for OEM mostly they are good but my FG XR6 turbo is 15 months old and it winds over like its on its last legs, not real convincing at all.