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The benefit to AGM is that it will provide higher CCA (Cold Cranking Amps) in the same size case. But the drawback is that there is less free electrolyte (acid) so the battery is much more sensitive to overcharge, and will not last as long if it is abused. Also a AGM battery is much more temperature sensitive - you would not want to put it under the hood of a car next to the engine, but in our Porsches no problem in the frunk. Gel would not typically be used in a starting application - only deep cycle. Standard flooded batteries or AGM will both work fine in our cars as long as the charging voltage is good (should be around 14.1 - 14.2 volts on charge).
AGM also costs more than standard flooded batteries but that cost differential is decreasing as all three main manufacturers are moving more towards AGM for new cars with stop-start. My BMW with stop-start came from the factory with an AGM battery - they perform much better in repeated start applications. The next new thing that you will see soon is EFB - enhanced flooded battery - that will work well for start-stop but will handle under-hood temperatures. Again, not necessary for a 996 but will be a less-expensive option than an AGM battery in the next year or two.
Daryll
Great info! Based upon the above, independent of price, would you pick AGM or flooded for:
1) a 996 driven regularly
2) a 996 driven only on weekends and mostly stored during winter
I would recommend the AGM batteries for both scenarios. The old lead/acid batteries off-gas corrosive fumes, thus the little hose you attach to the vent on the battery. The newer AGM's do not do this and can be installed in a confined space. Newer technology, better technology...adapt and move on. They really are powerful and do not need any maintenance.
I would recommend the AGM batteries for both scenarios. The old lead/acid batteries off-gas corrosive fumes, thus the little hose you attach to the vent on the battery. The newer AGM's do not do this and can be installed in a confined space. Newer technology, better technology...adapt and move on. They really are powerful and do not need any maintenance.
Most of the new "wet cell" batteries are either SLA "sealed lead/acid" or VRLA "valve regulated lead/acid" and are considered "maintenance free", (no need to add distilled water). they do have a vent line but it is for extreme conditions/overcharging.
The AGM's do usually have a higher cranking amps, but give up amp hours. This is a product of the plates design, number and size of the plates determine the cranking amps and amp hours. AGM's are harder to manufacture and therefore cost more, no real magic, still lead and acid, just has sponges in it.
On all my vehicle's I run the Maxx Everstart from Walmart, very hard to beat for the price and warranty. under a hundred dollars for the H8 battery with almost 1000 cca and 3 year 100% replacement and prorated to 5 years. very easy to upgrade to the H8 battery, battery tray come out with couple bolts and place blind nut in the hole already there for H8 install. worse part of the whole ordeal was having to go into Walmart. LOL they even chain down these 50 lbs. plus batteries to prevent theft.
... then of course you have the lithium-ion batteries, very powerfull, light weight, and expensive.
Lithium-ion batteries are worrisome, due to the problem of overheating and fires during charging. (Boeing grappled with this issue on the 787 Dreamliner.)
Lithium-iron - aka LiFePO4 - batteries have performance close to lithium-ion without the nasty charging issues.
And they are less than half the weight of comparable lead-acid batteries. But definitely more expensive - though cost seems to be dropping.
Great info! Based upon the above, independent of price, would you pick AGM or flooded for:
1) a 996 driven regularly
2) a 996 driven only on weekends and mostly stored during winter
A number of people have made good recommendations for AGM for both of these scenarios. That is fine - a quality AGM battery will perform well for a long time. But - in my cars I use standard flooded batteries and just plan on replacing them after five years or so. The exception is my BMW with start-stop - will replace that with another AGM. Cost-wise it works out probably the same, and you have less concern of a dead car due to a battery failure. Today's batteries, both flooded and AGM, tend to fail quickly - they typically don't give a lot of warning - so replacing on a time basis makes some sense. This is especially true for a daily driver that you depend on to get to work.
Either way, as others have said keep a battery maintainer on a car that is going to be parked for more than a couple of weeks and your battery will thank you!
Daryll
A lot of Nope and more nope .. and a theory of operating only 5 years and then preventative replacement is fine until a few last nine months. Warranty? At Z2 am in the rain who cares. Want an AGM thats quality and made in the USA - not just rebranded junk like a bosch and everything else?
I had great success with my Optima AGM battery years ago - lasted 7+ years and back then I didnt have a trickle charger!
My 996 came with a Bosch which has been good so far but I do need to keep it maintained.
I've got an Opima adaptor plate from Yellowdog motorsports over in the USA so when the time comes i'll use that + Opima red top.
I did read some commentary around Optima moving their production to Mexico and the quality dropping - the one I bought was made in Mexico and lasted though. Maybe they send the good ones to Australia as its so expensive to get them over here haha!
I used a Costco battery for close to $130. I believe it’s an Interstate battery under the hood...
An important part of choosing a battery is the born date. You want a battery that’s no older than a month or two if possible.
I have an Interstate from Costco. It’s been fine for the 12 months I have had it. I park for a week at a time at the airport and never have an issue. It has a vent hole too. I bought the shortest one since it is a bit lighter and smaller. The mounting plate has theee hole to choose from.
On all my vehicle's I run the Maxx Everstart from Walmart, very hard to beat for the price and warranty. under a hundred dollars for the H8 battery with almost 1000 cca and 3 year 100% replacement and prorated to 5 years. very easy to upgrade to the H8 battery, battery tray come out with couple bolts and place blind nut in the hole already there for H8 install. worse part of the whole ordeal was having to go into Walmart. LOL they even chain down these 50 lbs. plus batteries to prevent theft.
You said it, the worst part is going to Walmart 😂. I️ go twice a year to buy Mobil 1 for another car. It’s a sh#%show indeed.
A number of people have made good recommendations for AGM for both of these scenarios. That is fine - a quality AGM battery will perform well for a long time. But - in my cars I use standard flooded batteries and just plan on replacing them after five years or so. The exception is my BMW with start-stop - will replace that with another AGM. Cost-wise it works out probably the same, and you have less concern of a dead car due to a battery failure. Today's batteries, both flooded and AGM, tend to fail quickly - they typically don't give a lot of warning - so replacing on a time basis makes some sense. This is especially true for a daily driver that you depend on to get to work.
Either way, as others have said keep a battery maintainer on a car that is going to be parked for more than a couple of weeks and your battery will thank you!
Daryll
In BMW's I find that most batteries don't last after replacement as most people don't realize they have an on board battery management system that must be reset after replacement. This system constantly monitors the condition of the battery based off its age and charges it accordingly. If the system is not reset it nukes the battery thinking its older. This system has been adopted by most manufacturers on late model cars now.
05-07-2019, 01:00 PM
