Thread: Why is my voltage dropping?

Get a bigger or "faster" battery. AGM batteries like kinetik are designed for audio systems. You could always get a bigger alternator too. You can probably get away with just some big deep-cycle battery though (I do just fine with a sears die-hard battery for audio).

It may not be a problem that the voltage is dropping like this though. 10.5 isn't THAT bad. Though 10.5 is considered a flat-dead battery. Check your batterie's voltage with nothing on. Try charging it to full capacity before doing anything and see what happens.

Originally Posted by PaulF

Get a bigger or "faster" battery. AGM batteries like kinetik are designed for audio systems. You could always get a bigger alternator too. You can probably get away with just some big deep-cycle battery though (I do just fine with a sears die-hard battery for audio).

It may not be a problem that the voltage is dropping like this though. 10.5 isn't THAT bad. Though 10.5 is considered a flat-dead battery. Check your batterie's voltage with nothing on. Try charging it to full capacity before doing anything and see what happens.

The battery is a little above 12v when the car is not running, plus its only a year old at this point and it has not been drained completely. How big should I go for with a new battery? The battery I have now has 690 cold cranking amps and 820 cranking amps. It is a superstart 75EXT. I am too low on money right now because things came up recently and I am broke so I dont want to buy anything that wont help. I would also like to avoid buying an alternator if a better battery will solve the problem.

I posted another thread about my amp clipping at low volumes, could this be part of the problem?

Define clipping. Also where is your gain/sensitivity at?

If you buy a battery locally, get one with some sort of return policy.

If you're in the US, I bet the sears batteries would be your best bet since they are cheaper than all batteries branded for car audio. I believe that they have something around the $120 price point that is massive. Get something with a reasonably high capacity ex. a reserve capacity of 80+, and the cranking amps to match your starter's needs.

950W means about 100A so your alt won't handle the peaks.
That will cause the alternator voltage (up to 14.4V) to drop to the battery voltage which should be ~12.7V fully charged (ignoring surface charge) less its {current x internal resistance} voltage drop .

But 12V on a good battery means it's discharged - certainly way bellow recommendations for a cranking battery (no less than ~12.4V) and borderline for deep cycle batteries (12.1-12.2V). That's rested and unloaded. A battery just off charge should be above 12.7V - up to ~13.6V (surface charge).
Otherwise 12V means a stuffed battery - collapsed or compromised cells etc


I'd say your battery is stuffed, though the alternator may be undercharging (ie, under 13.6V; they are usually set for ~14.2V and shouldn't exceed 14.4V long-term).


The cap would have been useless. In fact caps are generally useless - their main use being to protect AGM batteries in BIG systems - but yours is far from big.


I'd suggest replacing the battery with another cranking battery, and not AGM. You might however consider a second battery (AGM) next to or near the amp. You could try charging the battery separately to see if it's voltage does come up.
But have your alternator output checked. (Get a voltmeter for the dash, else a DMM.)

Flooded/wet batteries are just as fast as AGMs, but AGMs have a lower resistance - typically half that of wets. Hence AGMs have typically double the short circuit current of wets and can supply higher currents to loads. But they don't always like that - hence why caps are used, else cable resistance is enough to protect the AGM (ie - when it is up front as the cranking battery - assuming it tolerates the cranking current).