what size alt.

[Mat Dope 10+ year member]

how big of an alt. will i need for running 1200rms class d and 250rms class a/b

i can only get 150-180a for my car. im leaning tward the 150a because its like 100$ cheaper.

will a 150 support this my stock alt is 80a. if i get the 150a id probly have to add some batts. id go with kinetic but how many/ what size would be apporpriate

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[iceteebone 5,000+ posts]

150 should be enough, but i'd still like to go bigger, especially if you upgrade later

 

[helotaxi 5,000+ posts]

Until you install everything there is really no way of knowing if a simple additional battery will be enough with your stock alt. If you have the money, get a bigger alt but before worrying about that I would make sure that all your wiring is good, all connections are solid, you have a good battery etc. Whether or not your will need an alt or what size you will need is going to depend a lot on how loud you listen to your music and what type of music it is.

 

[Mat Dope 10+ year member]

thanks ice tee and jman if i did go with the 150a i would be more then likly getting a kinetic with it.

helo - i think you misunderstood me. im definatly getting an HO alt just dont know what size i need. and of corse big 3 in 1/0 and maybe a kinetic if i need it.

 

[iceteebone 5,000+ posts]

thanks ice tee and jman if i did go with the 150a i would be more then likly getting a kinetic with it.
helo - i think you misunderstood me. im definatly getting an HO alt just dont know what size i need. and of corse big 3 in 1/0 and maybe a kinetic if i need it.

i think what he is saying is do your big 3 and all that first before you buy an alternator, to see if you really need an alternator

 

[Mat Dope 10+ year member]

yeah i have done that, my stock alt was only 80amp. and i was trying to run 1200rms class d and 250rms class a/b and now my alt. is definatly dieing.

so i wanted to know what size HO alt i need to go with. for running the amount of power i am.

 

[helotaxi 5,000+ posts]

Get ahold of a clamp meter. Measure the current coming from the alt with the stereo off and the headlights and AC on. That is the amount of current that your car was spec'd for. There is a bit of headroom beyond that as well which your audio system is using. Now turn off the headlights and AC and turn on the system. Turn it up to the level that you normally listen to it playing what you normally listen to. Clamp the power wire going to your system and see what the average draw is, not the peak, the battery in the trunk will handle the peak. Add the average draw of the system to the current from the alt with the system off. Add a few percent for headroom. The chances of you really needing more than 100-120A are small. The nice thing about smaller alts is they put out a larger percentage of their rated power at lower RPM unlike really big alts.

 

[Mat Dope 10+ year member]

thanks although i cant get ahold of a clamp meter and dont have the extra cash to buy one at the moment.

when i had 650rms on my stock alt (80a) it was fine no dimming or anything. but after i a little more then doubled the power thats when i ran into problems which i expected. so hopefully ill be ok if i get the 150a alt.

 

[questionaire 10+ year member]

thanks although i cant get ahold of a clamp meter and dont have the extra cash to buy one at the moment.
when i had 650rms on my stock alt (80a) it was fine no dimming or anything. but after i a little more then doubled the power thats when i ran into problems which i expected. so hopefully ill be ok if i get the 150a alt.

Is there a specific number of watts(from amp) when alternator needs to be changed? My stock is 130 if I got a BXI1606 would I need to change it??