Help with HO alternator and AGM batteries

[dcornelius08]

Ok, to start off im electrically stupid so i am here to ask for a little advice. i purchased a HO alternator 300a upon recommendation of the manufacturer (fairly certain i was just up sold on it big time), i will be running a 2.3k watt @2 ohm mono and a 500w 4ch. i have a 80ah agm under hood and was going to buy another identical batt for trunk it is just an automotive agm, should i consider a marine deep cycle for the trunk or keep them matching? I am trying to keep batteries affordable for the time being. But no need to fret i will be getting some lithium as soon as that second stimulus check hits the bank

now i have another question about the alternator, my comprehension of how the whole thing works is you want to have as much reserve batt as possible to reduce strain on the alternator so you are only keeping them " topped off" and help compensate for high amperage draws from the amp not trying to charge drained batteries with the alternator. So my assumption that is why i would want as much batt reserve as possible to keep from running the batts to a low Voltage. would two 80ah be enough to prevent that? And can you tell me if my understanding is even remotely accurate? Lmao
I attempted to ask these on facebook and reddit but most of the comments were "if you gotta ask you shouldn't be in car audio" type ****. then got bashed for my choices in amp/sub so hopefully y'all will be a little more hospitable for an idiot such as myself.

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[Popwarhomie 5,000+ posts]

Lithium for 2k watts before rise? Waste of money.

80AH of AGM with a 300 amp alt is plenty.

 

[dcornelius08]

Lithium for 2k watts before rise? Waste of money.

80AH of AGM with a 300 amp alt is plenty.

Oh i know the lithium would be extreme overkill for 2k BUT i am trying to future proof, I want to have headroom for whatever i may want to do in the future. that's why i went with an amp that dynod(i know not real world results) over 4k at 1ohm so that way i have headroom for a second sub. My ultimate goal is to eventually have 4-6 woofers with 2-3 of this mono amp. Granted that wont happen for a while buying piece by piece but i wanna plan for my end goal not in the moment so i don't have to continuously replace items in the end costing quite a bit more money than just going overkill from the git go. I really just wanted to go with a temporary agm for peace of mind, then i can then put it into my other vehicle as a starting battery so no money wasted in the end.
But thank you for the assistance, i just hear SOO many conflicting opinions as to how many ah of agm is enough. ive seen some extremes from 110ah isnt enough for 2k to 50ah is enough for 2k

 

[BCotrell]

Additional Batteries will be used when you are listening to your vehicle with engine off. Once engine is on, alternator does all the work and will recharge your batteries. Based on planned size of your System, a rear lithium would allow you to run in demo mode for a significant period of time.

I recommend running the ho alternator for now with your agm up front, ensure that you complete a big 3 wire upgrade, and avoid trying to Run your system with engine off for Longer periods. Why waste $200 on a heavy 80ah agm when you’re only $300 away from a decent size lithium. And lithium bank can be build as you need versus replace.

 

[dcornelius08]

Thank you for your help, i will give it a shot with just the agm up front worst case scenario i gotta spend a little bit of time hooking up another battery in the back. I'm just unsure how things go with a HO alternator this is my first one and want to make sure everything is up to snuff i do a lot of driving in the middle of nowhere Texas and just been paranoid of killing the battery where i get no cell service. I do have a dewalt emergency jumper but better safe than sorry in my opinion, been stranded in 108 degree heat for hours before someone drove by due to **** box Honda dying and dont wanna go through that ever again. But I will for sure being doing big 3 when installing my alternator all 1/0 ofc everywhere.

 

[BCotrell]

Easiest way to avoid that is dont run your system with the engine off for long periods of time. A couple minute parking lot stunt won’t cripple you by any means but no batteries are going to last a long time if they are continuously emptied and recharge. Agm are obviously better for this task. If you don’t know your timeline check letgo or OfferUp for a used agm of any size. I got My group 78 for 50$ still had price tags on it.