I wonder why we got different search results?
And sorry - my
google comment reflected frustrations with those that don't search. Of course people on this forum are a different class all together! Hence my "jest", though partly too a potential for further education (myself included!).
Just beware of what you read from other forums.
I have seen so many incredulous statements - many IMO the total OPPOSITE of what should be done.
Then there are strange rules like 100AH per 1kW of audio (I suspect a corruption of the 100A per 1kW - ie, from input current ~= Power/10 for 12V systems (where power is audio or inverter output etc).
Or that bigger/more batteries are better than a bigger alternator (usually its the other way around, though it does depend on what is desired - eg competition versus street and longer lasting batteries at full volume).
I was aware of the above previously from audio forums in particular, though the recent need to find certain info (due to lost data) has shown an abundance or ridiculous statements, conclusions, and debunks from people that seem to be knowledgeable. (Their readers are praising their incorrect writings, and I presume following their expensive conclusions.)
The worst part is that these are RECENT!
But it supports my hypothesis that there is more bad info than good, and both grow exponentially, hence as web "eduction" continues, we get worse (as an
educated population! (IE, the proportion "correct info" - and hence the chance of finding it - diminishes as time progresses. But I know that started even before the web became populous.)
Back to Duralast...
I could be wrong (I'm going from yesterday's memory which is still in RAM and not ROMmed - ie, my short term memory can be bad. And I am talking about my brain cell, er, cells - not my PC!)... but my memory & logic is:
Another battery looked like the Duralast, but one was Deka (I thought Duralast) and the other not.
The other was (IMO from other resources) an inferior brand.
Now, I associate the inferior with Johnson Controls, but that is from a professional experience many moons ago (an attempt was made here in Australia to supply crappy UPS batteries at a lower price; they may have been Apollo batteries (litigious crap) but that may have been a different incident.
The point of this in case Johnson is not Deka etc. But it could be my confusion.
But from what I gathered, Duralast seems ok. (I got far more hits about bad Optimas.)
I was somewhat concerned over an 8 year warranty for an apparent new type of battery (Platinum), but being a pro-rata warranty explained that (ie, the company cannot lose).
I'll leave my usual tips about standard wet cells for the cranker with audio AGM(s) next to the amps - via an isolator(s) of course, and I suggest the simpler, cheaper, and generally superior UIBI type (alternator charge-light controlled relay) over expensive "smart" or voltage-controlled isolators - that's easily found by googling UIBI or UIBI battery isolator (which are typically my posts, and cover isolation of multiple auxiliary batteries and why or when that is desirable).
The other main issue is whether a deep-cycle or cranker for the amps.
If thumps are the concern, the crankers. If it's a big system, the crankers, though it may be that a big capacitor is required to protect the AGM (typically systems above 3kW).
If they will be heavily discharged (as in DOD - Depth of Discharge), then deep cycle, but they do not handle the thumps as well (life-cycle wise) - but they could be up-sized to compensate.
As to underpowered systems (small alternators), well take your pick. You won't have full voltage (14V etc), and the extra battery discharges and insufficient or delayed recharge take their toll on the batteries as well as a thump versus DOD issues.
You'll note that there is no single universal answer. And most forum answers seem to plug a solution without even ascertaining the system or desire - eg, performance with 6-month replacement of batteries; amplifiers whose output varies with supply voltage...
LOL - I just recalled one of the biggest jokes of all time: Place your audio battery in the engine bay - the extra heat gives you more capacity! That shows very ignorant
single-minded advice.
Good luck.