Need help with High Output Alt and Lithium install

[DaftyOP]

I think I'll be one of the first people to try and install a 320amp alt and lithium in a 2 series and I just have a couple questions.

Question 1. With the alt im buying it has a built in regulator to charge at 14.6 and a a built in bms bypass. I know that Ill have a battery light after install, and im wondering if it can be coded out with bimmercode.

Question 2. Besides the install are there any wires that I wont be able to connect to the new alt, and will they cause any issues with the water pump, etc.

Question 3. Does the lithium battery need an isolator or anything to make sure there's no draw the the primary battery.

Question 4. Will running the big 3 upgrade damage anything in the car.

Question 5. Does anyone know of anyone who's run a high output for car audio.

Question 6. Does anyone have any other alt brands they recommend that dont need a bypass and charge at 260-320amp
Current system-
Custom built box 3.6ft^2 tuned to 32 hz
sundown audio sa classic 12s 1k rms each
D4S jb23 2300 watt rms amp
All ofc wiring from knukonceptz
LC2I pro line out converter.

Planning on upgrading all of this because I need more.



Products I plan to use for the upgrade-
https://js-alternators.com/products/...41638497517744
second choice alt
https://brand-x-electrical.myshopify.com/

[Sensawl]

I haven’t done a 2 series specifically with a 320 amp and lithium setup, but I’ve dealt with high output alternators and lithium installs on newer BMWs, so I’ll answer you like I would if we were just talking in the garage.

With the alternator having its own built in regulator set at 14.6 and a BMS bypass, you’re almost definitely going to see a battery light. BMW’s charging system is smart and it expects to control voltage through the IBS sensor. Once you remove that control from the car and give it a fixed voltage alternator, the car is going to know something isn’t factory anymore. BimmerCode might clear certain errors, but it usually doesn’t fully disable the intelligent battery monitoring logic. Sometimes people code out the battery type properly and leave the IBS plugged in just so the car doesn’t act weird, but on these cars coding can get tricky. I’d definitely make sure someone who knows BMW coding is available before you finalize everything.

As for extra wires, most newer BMW alternators are LIN controlled. If your new alternator isn’t using that communication wire, it’ll just sit there unused. It shouldn’t mess with the electric water pump or anything like that because the pump is controlled separately by the DME. The bigger thing is you’re basically removing BMW’s smart charging system. The car normally lowers voltage while cruising and raises it under braking for efficiency. With your setup it’ll just sit at a fixed voltage all the time. That usually doesn’t break anything, but it’s not how the car was designed to operate.

If you’re replacing the main battery with lithium, you typically don’t use an isolator. If you’re adding lithium as a secondary battery for audio, then yes, I’d strongly consider an isolator or a proper DC to DC solution so you’re not confusing the IBS or putting uneven stress on the primary battery. Also make sure your lithium battery is actually designed for automotive charging at 14.6 constantly. Some lithium batteries don’t like being held at that voltage long term.

Running the Big 3 upgrade won’t hurt the car if it’s done correctly. In fact with a 320 amp alternator it’s basically required. Just make sure your connections are clean, your grounds are solid, and your positive cable is properly fused. Don’t remove factory grounds, just reinforce them. Problems usually come from bad installs, not from the upgrade itself.

People absolutely run high output alternators for car audio, it’s just less common on newer BMWs because of how integrated everything is. Domestic cars are easier because they’re less picky electronically. It’s doable, you just have to accept you’re stepping outside factory logic.

As for alternator brands, JS and Brand X are both known in the audio world. Mechman and Singer are also solid, but I’d focus less on the name and more on whether they’ve actually built units that work properly with BMW platforms. Customer support matters a lot here because if the car throws weird electrical behavior, you’ll want a company that actually answers the phone.

Your current setup already pulls serious current. If you’re planning to go even bigger, just make sure the electrical foundation is fully sorted before adding more power. On these cars electrical stability matters more than just throwing in more amp.

If you tell me the exact 2 series chassis you’re working with and whether you’re fully deleting AGM or keeping it alongside lithium, I can think it through more specifically with you.

[DaftyOP]

Thank you for the response lol I have been needing help for awhile now, but it’s a f22 230i 2020 with the b46. I’m planning on running a second battery that’s lithium. Js alternators makes a factory replacement that doesn’t throw codes but it won’t charge at a set voltage to work with the lithium, but I feel safer with their company. Do you think with there 320amp alt, the big 3, and a second large agm battery I could get up to.5k watts rms?.