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new amp in car, need some suggestions.

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Member - Posts: 13
Joined: September 25, 2010
Location: Alabama, United States
Posted: June 24, 2011 at 12:28 PM / IP Logged Link to Post Post Reply Quote anoble1
I have a USA-2000 amp. I am pushing 2 Orion H2 subs. I have a 98 Honda Accord 4 cylinder. I talked to someone and they told me that I would need a rear battery with a "Pack 200 setup"? Don't have a clue what that is. The guy told me that the amp will kill any battery I put in there unless I did the pack 200 with a rear battery.
I am running a 2 gauge to the back of the car now. The amp is not hooked up yet, but the amp has 4 power terminals on it.
Any better suggestions better than this guy I talked to?
Copper - Posts: 71
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Joined: March 17, 2011
Location: Tennessee, United States
Posted: June 24, 2011 at 4:45 PM / IP Logged Link to Post Post Reply Quote sthrnbmpn
thats alot of power for a stock alternator, people will say get a h.o.alt which is a gd choice.
ive been contemplating adding a rear batt too, which is probly more of load on your alt but it should help the main batt power the amp, less voltage loss!
ive heard talk of a battery isolator to which i think is a device that keeps the main batt fully charged an the charges the aux batt
maybe someone will chime with some better advice on the right way to add a second battery other than hook it up directly to the alt then power the amp from the rear battery
also a distrubtion block would help you with going from 2ga to 4ga
1000 watts of lp, now need sum hp an mids
Copper - Posts: 121
Joined: January 27, 2006
Location: United States
Posted: July 10, 2011 at 12:55 AM / IP Logged Link to Post Post Reply Quote ac0j

Adding a second battery will make a bad problem worse.  You need to have enough altenator output to support the current needs of the amp as well as the existing needs of the rest of the car.  IF you dont, the voltage will drop and amp problems are probably going to occur.  If your altenator cant keep up with one battery, it will have even a worse time trying to keep up with two.

i am an idiot 
Platinum - Posts: 12,135
Platinum This member consistently provides reliable information
Joined: September 21, 2006
Location: Louisiana, United States
Posted: July 15, 2011 at 4:36 AM / IP Logged Link to Post Post Reply Quote i am an idiot
Copper - Posts: 121
Joined: January 27, 2006
Location: United States
Posted: July 19, 2011 at 10:25 PM / IP Logged Link to Post Post Reply Quote ac0j
That is in fact an isolator, BUT it still wont do much to add a second battery if the charging system cant keep up.  All this would do is insure the amp goes low voltage faster and the car will still start.
Gold - Posts: 4,934
Joined: November 03, 2008
Location: Australia
Posted: July 20, 2011 at 12:43 AM / IP Logged Link to Post Post Reply Quote oldspark
Ah, the usual crap - except for the advice given by the other 12volters above. That's IMHO of course!
#1 should be an alternator with adequate output for at least your average consumption, or your max consumption if you want (say) 14V - 14.4V for your amp (and system).
That's after #0 which is the BIG 3 which ensure you will not melt inadequate grounds and will reduce voltage drops.
Then comes a 2nd battery near the amp. Being internal (ie, in the boot/trunk or passenger compartment) it has to be a sealed type which means AGM. (Gel-cells are not usually suited.)
Unfortunately AGMs are more prone to damage from high-current peaks than flooded/wet cells, but that depends on what battery life you want. Usually people add more batteries though even then, a cap may be required.
[ Yes - I am anti-cap, but the one thing they do is lessen AGM damage from high-current surges. As for increasing power (LOL!) or being a substitute for an alternator or battery - that is all crap - a battery will out-perform a cap, and neither is a substitute for an adequate alternator (except perhaps to reduce voltages dips). ]
An isolator is used for 2 main reasons.
The first is that batteries should not be paralleled when not in use. (That can be a contentious issue/opinion, but those in the know know, and I won't repeat my previous rants now.)
The second is independence - ie, isolation when not charging so that the amp may flatten the aux batteries, but you still have a normal main battery and cranking capacity. (And aux batteries can be used to jump-start the main battery if the main dies...)
Then we get in to the types of isolator. Ignore crap about "smart isolators" that charge the main battery before the aux batteries - that is merely a time delay. Smart Isolators are merely voltage-sensing isolators and they require various delays to guard against bad operation, and depending on what is delayed determines what they are best suited to.
The voltage sensing is usually used to determine if the system is charging. But many vehicles have that information already - it's call a charge light.
Hence many simply use a relay which is controlled by the charge light. (It's the alternator's (regulator's) D+ or L output - when not charging it is low (ground) which lights the charge lamp. When charging, it goes to +12V and extinguishes the charge lamp (whose other side is connected to IGN +12V). That +12V D+ or L output can supply enough current to energise a relay.)
The latter "charge light" controlled system has been affectionately dubbed the UIBI (Ultimate Intelligence Battery Isolator) and I have oft described it here on the12volt and on
In your case, assuming the USA-2000 means 2kW output - hence ~200A, you probably want a 250A or larger isolator - ie, enough for peak amp supply PLUS aux battery(s) recharge current.
I'd be tempted for a 300A or 400A isolator and distribution (the 2 fuses and cable required between the aux battery(s) and main battery/alternator) since AGMs can take 100A as an initial recharge current. I have a 38AH AGM that takes 45A when about half discharged, but that drops to under 10A within 60 seconds.
Boosting isolator current is no problem irrespective of the isolator used (UIBI or Smart) - merely have the original isolator relay energise the bigger isolating relay. (Big 200A - 400A relays may need 2A or more to energise. This can be too much for many alternator charge-light circuits whereas normal automotive 30A relays (~250mA energising current) is usually not a problem. Hence the alternator D+/L drives a 30A relay which in turn drives the larger relay(s). I say relays because the isolator may also isolate multiple aux batteries from each other, though they often have a override (from the amp or a switch) when the amp is to operate when the system is not charging.)
Of course, if you don't have a charge lamp or equivalent charge/not-charging indicator (as with stator systems used in marine and some RVs. motorbikes, etc) or some sort of charge-current sensing system, then you have to use a voltage sensing isolator.
BTW - the PAC-200 is merely a voltage sensing circuit that actuates a 200A relay. Disconnect the voltage sensing output and substitute the D+/L signal (preferably via a smaller relay) and you have UIBI instead. Of course, you would just by the (200A) relay itself if that's what you wanted.)
Howz that for a short reply?

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