Lights dimming, adding bat?

[01 S 10 10+ year member]

to OP, i had a SAZ1500 running full tilt @ 1 ohm... with a 200 amp alt, red top under hood, and 2 Batcap 800's inside, i had NO dimming while driving, all 2/0 wire for Big 3 and to the back batts. At idle, voltage would drop to to MAYBE 13.1 at the lowest. HO alt and more battery reserve with large wire for better current flow will help you tremendously, none of this is cheap, thats just the way this hobby is... there is no easy/cheap way out of dimming.

 

[helotaxi 5,000+ posts]

Your alt only needs to cover your average current draw. Also your stock alt can charge as manny batteries as you want to hook to it as long as it can cover the average current draw os the car+system, it won't have any problems.

There has to be a voltage drop below a certain threshold (the drop is what causes the dimming) before the regulator ups the output of the alt. With a good sized bank of batteries, the batteries absorb the shock load of the transient current demand and minimize the voltage drop. Then the alt merely need replace the charge from the battery. With very transient music, the transients are shorter than the breaks between them and as such the average demand from the alt isn't really all that high. The system might draw 200A for a fraction of a second (guess what, your 200A alt won't do jack during this period) but the alt has a second or two to replace the amount discharged during that brief spike. It doesn't matter if the amount discharged is taken from one battery or 10, the amount is still the same and that same amount needs to be replaced.

 

[dakotap 10+ year member]

Your alt only needs to cover your average current draw. Also your stock alt can charge as manny batteries as you want to hook to it as long as it can cover the average current draw os the car+system, it won't have any problems.
There has to be a voltage drop below a certain threshold (the drop is what causes the dimming) before the regulator ups the output of the alt. With a good sized bank of batteries, the batteries absorb the shock load of the transient current demand and minimize the voltage drop. Then the alt merely need replace the charge from the battery. With very transient music, the transients are shorter than the breaks between them and as such the average demand from the alt isn't really all that high. The system might draw 200A for a fraction of a second (guess what, your 200A alt won't do jack during this period) but the alt has a second or two to replace the amount discharged during that brief spike. It doesn't matter if the amount discharged is taken from one battery or 10, the amount is still the same and that same amount needs to be replaced.

Which is why people love the Yellowtop, because of a large reserve? It keeps steadier voltage under a higher load and the HO alt can keep a deep cell battery like that charged constantly?

 

[SethPhillips 5,000+ posts]

how are you guys charging your batteries that are in the back?

when you wire 2 batt's in series they act like one big 12v batt.

so in line with the alt, both batt's get charged.. a smaller amp alt will just take longer to get the voltage up while the car is running.

 

[lostdaytomorrow 10+ year member]

when you wire 2 batt's in series they act like one big 12v batt.so in line with the alt, both batt's get charged.. a smaller amp alt will just take longer to get the voltage up while the car is running.

Parallel, not series. + to + and - to -

Ohm's Law and all.

 

[jrwalte 10+ year member]

I've seen some guys say running them in series will actually give you 24 volts? Is that true?

 

[dakotap 10+ year member]

I've seen some guys say running them in series will actually give you 24 volts? Is that true?

Of course it will, you dont wanna do that though. It will fry your s##t

 

[jrwalte 10+ year member]

Of course it will, you dont wanna do that though. It will fry your s##t

Obviously //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[helotaxi 5,000+ posts]

a smaller amp alt will just take longer to get the voltage up while the car is running.

A battery or bank of batteries draw the amperage that they require to be charged. If the stock alt can provide that current, you will not see any benefit to upgrading the alt. Adding a bigger alt will not decrease the time required if the stock alt can cover it.

 

[jrwalte 10+ year member]

You'd still see an overall lower voltage because the smaller alt can't supply the power to the amp as much and the bat has to be used more, hence your voltage stays lower longer and more often.

 

[helotaxi 5,000+ posts]

You'd still see an overall lower voltage because the smaller alt can't supply the power to the amp as much and the bat has to be used more, hence your voltage stays lower longer and more often.

If the alt can provide the AVERAGE current demand of the system, that's all that matters. For most really dynamic music the alt simply will not up the amperage quickly enough to keep the voltage from dropping and by the time it DOES up its output the transient is over and the demand is only there to charge the battery. Depending on the size of the system and what is being played, the continuous draw might be high enough that the stock alt can't meet the average current demand, but the overwhelming majority of normal systems (sorry if you have 4kW on the subs, you're not normal) don't need an upgraded alt and won't see any real benefit from running one. At idle, you may even create problems because the bigger alts don't usually put out as much as the stock alt at lower RPMs.

 

[UNDERGROUND_BUM 10+ year member]

If the alt can provide the AVERAGE current demand of the system, that's all that matters. For most really dynamic music the alt simply will not up the amperage quickly enough to keep the voltage from dropping and by the time it DOES up its output the transient is over and the demand is only there to charge the battery. Depending on the size of the system and what is being played, the continuous draw might be high enough that the stock alt can't meet the average current demand, but the overwhelming majority of normal systems (sorry if you have 4kW on the subs, you're not normal) don't need an upgraded alt and won't see any real benefit from running one. At idle, you may even create problems because the bigger alts don't usually put out as much as the stock alt at lower RPMs.

ok so say i have an 80 amp stock alt on my civic, and im running a kicker kx1200.1 (150A) and a small orion amp (25A). would putting a batt in the back help my diming problems? and would my alt beable to charge boths batts? also is it bad to mix and match batts? i was thinking of running my stock batt up front and a yellow top in the back, would this cause problems?

 

[helotaxi 5,000+ posts]

ok so say i have an 80 amp stock alt on my civic, and im running a kicker kx1200.1 (150A) and a small orion amp (25A).

I'm assumung that those are the amp ratings of the fuses? Fuse ratings are not any kind of indication of the current that the amp actually draws

would putting a batt in the back help my diming problems? and would my alt beable to charge boths batts?

Probably on both counts.

also is it bad to mix and match batts? i was thinking of running my stock batt up front and a yellow top in the back, would this cause problems?

Usually not a big problem unless one battery is kinda old, then you're better off replacing the fornt battery as well as adding the second.

 

[jrwalte 10+ year member]

Since you still have the stock battery under the hood you're probably better off replacing it with a deep cycle (like a yellow top) before placing one in your trunk.

 

[trebor 10+ year member]

Lot's of good info here from helotaxi!

UNDERGROUND_BUM, assuming those amps will do 1500W and 250W, gains properly set...then your looking at an average current draw of around 38A with music. If your amps wattage is lower then expect that average to be lower.