I have a 5500watt amp that is 70% efficient which makes 3850watts to use. I have a 250amp alternator and my car uses up 27amps of that alternator so i have 223 amps from my alternator. i have replaced my BIG 3 with 0 gauge, and will have my system (an 18" Fi BTL dual 2) ran with 0ga and the speaker wire in 10ga. If i worked everything out correctly using 13v i should be looking for a 31ah battery but i know that i want to go much higher to run off of my battery and not my alt. What do i look for in a battery? and if possible what kind would you all recommend? should i use more then one?

Any 12 volt batt will rest at 12 to 12.8 volts normally. If you want to "run off your batt and not your alt " and still do that at 13 volts or more you will need to get 14 or 16 volts batts. IF you want to run off your batts and not go the 16 volt route you will need a batt with a high reserve capacity, and that will depend on how long you want to run with the car off.

So what brands of high reserve batteries should i be looking at and how high of a reserve? They should be deep cycle correct? and am i looking at only 1 for under the hood or probably 1 in the trunk as well?

not deep cycle. those discharge slower than AGM. You want AGM.

So an AGM battery that still doesn't answer the question of 1 or 2 and of what numbers to look for in the reserve power.

Please close/move this thread.

does not belong in this section.

This question is dealing with the 18"BTL fi in my car hence making this a "general Fi" question im sorry but i just would like to know a battery to go along with my sub.

What battery to get has nothing to do with the sub you have.

What battery to get has nothing to do with the sub you have.

It doesn't? Then y can i not just keep my stock battery to run my system? i guess i don't understand that? because im sure that if i put 2 type r alpines in my car then it would be 10x's different and there would be no call for an after market battery :/ sorry to say it but i think the fact that i have an 18" BTL dual 2 makes all the difference in the world. you see im running 3850 watts "roughly" through my 18" and that comes into play with how much power i need but that's the thing i don't know i have no idea how much power i should have because the BTL Fi could draw from that battery faster (which it will) then a normal subwoofer like the alpines. but how much is the question of which i do not know. so how much will the BTL Fi's draw is how much power i need. which comes to play with 1 or 2 batteries. and what size.

i am assuming the amp u have is a power acoustik 5500w amp or a board very similar.

They are only capable of around 3,000w.

Due to that, i'd say a single D2700 or a single D3100 would do fine.

What battery to get has nothing to do with the sub you have.

It doesn't? Then y can i not just keep my stock battery to run my system? i guess i don't understand that? because im sure that if i put 2 type r alpines in my car then it would be 10x's different and there would be no call for an after market battery :/ sorry to say it but i think the fact that i have an 18" BTL dual 2 makes all the difference in the world. you see im running 3850 watts "roughly" through my 18" and that comes into play with how much power i need but that's the thing i don't know i have no idea how much power i should have because the BTL Fi could draw from that battery faster (which it will) then a normal subwoofer like the alpines. but how much is the question of which i do not know. so how much will the BTL Fi's draw is how much power i need. which comes to play with 1 or 2 batteries. and what size.

Just for an FYI, the amp determines the battery(s) you will need and not the sub. Considering the sub does not make power it only accepts it, the amp makes the power so it takes power to make power. But the sub will determine what amp you will put on it, the only thing that will determine battery size is the amp(s) that will be used in the setup.

For a really good set up I would change out the stock battery with the brand of battery you are putting in back, preferably the same size.(front and back). Reason you want the same size type batteries is to make the pair act as 1 battery which is hard to do if they have different resistances/charge rates. Good brands to look at are Odyssey, Kinetik and if you are on a budget deka intimidators.AGM batteries can be deep cycle, some are not though and a prime example of one that is not is an optima red top.