Need some assistance

[bmwking]

Hey all,

So I'm getting ready to start purchasing equipment for my wall and I have a quick question. I'm looking into HO alts for my 99 bmw 528, but they are a little price prohibitive at the moment. I've contacted Mike and he has the best options so far and is who I will be going through, most likely. However I see more and more topics with people using battery banks or multiple batts to stabilize voltage. I have a factory sized agm in the stock location, and a shuriken bt20 to help it. cca 1/0 throughout too. My sub amp is an AB ph4000md and while it beats the daylights out of my xfl 12s, Ill run into it shutting down due to low voltage after beating on it for over an hour while driving. I usually have to wait a minute or two for it to kick back on but I have no other issues than that. So my question is, How do I figure out how many batteries I'll need If i stick with my stock 120amp alt? I see batteries rated 35aH and such. Does that mean I need 10 of those batteries if I'm pulling 350amps? I plan on adding another identical sub amp and 2 more 12s in a 9.6cu ft ported c pillar wall. I was thinking about getting like 5 xs xp750s and hoping thatd keep my voltage solid. any thoughts? criticisms? relevant ideas?

TIA

[06RTCharger]

I think the idea is that a alternator keeps the battery full, but cant "recharge" a battery. Without an alternator your battery/batteries will be completly drained over a shorter than normal time. So if u try to get the alternator later, your new batteries might already be close to dieing by then.

If i was to spend money on new batteries, id want to be sure i have an alternator that will keep them full first. So id say the alt is priority over more/new batteries.

Also im assuming youve already done the Big 3 wiring upgrade or even the big 4. Tho I am just a noobie here tryna helpout with what i can, goodluck man

[bcbrassard]

Get a bigger HO Alt. Stock wont keep system charged enough IMO. I have a Singer 220 amp alt with 4 Battery's and it beats the stock voltage drop from low 11's to 12.6 while charging at 14.1

[bmwking]

so thats the general consensus then, get the alt then the batteries. not the other way around

[06RTCharger]

Yes. Generally you'd want to upgrade alt first, or if money wasnt a factor both alt and batt at the same time. But if you can only do one at a time, HO alt first.

[DLHgn]

A couple of batteries might help for a while but would probably drain eventually if you're alt isn't able to recharge them in time. You would have to make sure you stop playing music for a while before turning off the car to make sure the batteries could be recharged. And the alt is probably the same price as a couple decent batteries. I think it would be in your best interest just to get the HO alt before anything else that way if/when you decide to get more/better batteries they can be charged properly. Just my two cents and in the end it's your decision.