Ian.... I also was not aware of the extended life aspects of AGM. Is this typical or maybe a bit of exageration? Are you saying I could expect to get 12-15 years from one of these batteries (typical)???
From what I can tell from this forum and elsewhere, production standards for modern batteries with liquid acid and plain lead plates is that anything past three years is a bonus. Sure, they might last longer, but don't count on it. Additionally, because of plate fragility, a cracked plate can lead to a battery that tests fine on the bench but sporadically fails in a vehicle.
With a premium AGM battery, if you get less than six years from it, consider yourself cheated. My oldest one is an Orbital Extreme (spiral cell) that is almost 7 years old, on deck to be in its third vehicle, and can still spin over a cold V6 engine FAST at -30 degrees Celcius after sitting for three months. I'm going to call that a win at $200.
I have now purchased two Northstar batteries as well. I put a 24F in my Ridgeline early last winter and just replaced the failing 4yo OEM one in a relative's CX-7 (a Group 35 battery). These were $300 each.
My expectation with each of these purchases is that it will be the last battery ever needed for each respective vehicle. So far, so good, though only the one has been tested for long enough to say that it was worth it.
If so, I too will change my outlook on AGM. I used them for my Diesel boat batteries (talk about expensive!), but have never considered them for my cars. Please clarify on the longevity question if you can. Thanks
FYI my wet cell maint. free conventional car batteries have lasted me about 4-5 years typically.. I've had some last 6 or 7, but those were the exception.
Both my OEM & 1st replacement in the Ridge lasted just over 4 years. The one in my S2000 lasted 8.
Let's say that an AGM would last 10 years. In each case, that's once or twice that, with cheap batteries, you were probably operating a vehicle with a battery for quite some time in a risky situation, where a temperature drop or an accidental drain (leaving a light on) could lead to an embarrassing or even dangerous stranding. Sure, an AGM will eventually wear out. However, your amount of time operating the vehicle with a weak battery will be a fraction of with the cheap ones. Plus, if YOU installed an AGM battery after the original one failed, chances are that you'll sell the vehicle before the AGM needs replacement, because by then the vehicle will be 13+ years old.
Here in sunny Ottawa, there is a rash of strandings every winter (or even autumn) as people didn't realise that their batteries got weak over the past year. They started fine all summer. Every day that is a few degrees colder than previously in the season, a few hundred (or thousand) more vehicle won't start. If they can't get a boost from a friend or neighbour, they call for service. Those service vehicles have multi-hour backlogs because it's all happening at the same time.
Sure, you can remember to bench test a vehicle before winter every year. However, that test will be done before it's cold, and probably in a warm mechanic's garage! Or, you can just put in the last battery you'll ever need and never worry about it again. I've gone with the second option.