What type of battery do I need for my car stereo system?
Question by theguyversh: What type of battery do I need for my car stereo system?
I need an auxillary battery for my car stereo system. What amount of cranking amps/maximum output do I need for my system? I have a 1,000 watt Kenwood amp and the lights are dimming and I’m running through alternators like mad.
Best answer:
Answer by andrew
Kinetic or shuriken, they both make nice batteries. I am currently running the small shuriken on 2000 watts.
What do you think? Answer below!
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Starting Batteries are measured in Cranking amps, and this measures battery power for starting an engine, in under 15 seconds. (aka short it, for 15 seconds, read minimum amps = cranking amps). This process should unload a sizeable amount of power from the battery as well. Unless your stereo is on for 20 second intervals, this measurement is irrelevant to you.
Deep Cycle batteries are measured in Amp Hours. This means that you can run amps through them for hours at a time; aka several CDs worth. Make sure you buy AGM or SEALED at least. AGM batteries are far more efficient (extends run time), safer (90% less h2o to Hyrdrogen which is explosive), can be installed at angles or upside down, require no maintenance, and they won’t corrode your expensive electronics, upholstery, or interior. Add to this a UL rating, and it makes sense to spend for the better batteries. AGM batteries are usually 85% efficient at high amps, whereas flooded varieties are usually under 60% efficient.
100ah x 85% efficient = 85 ah to drive the stereo…
100ah x 60% efficient = 60 ah to drive the stereo
WHAT SIZE?
Batteries are power tanks, so the bigger the better, within reason. Just pack them in until you reach size or weight requirements. The amp hours can be directly correlated to your stereo, at full power, based on the size. Watts = amps x volts so we just solve this little equation for Y.
1000 Watt Stereo = 12 v * Y amps
y = 83 amps
83 amps is needed by the stereo, note that this is an instantaneous measurement.
Should your stereo remain on all hour, you ran 83 amp hours through it.
But you have to overcome a bunch of inefficiencies to get the power there….
First we multiply to overcome the inefficiency in the battery..
83 * 1.15 = 100 ah battery per hour
Depending on how efficient the wires to get the power to the stereo are, you are losing even more power. (wire voltage drop increases with amps –manifests as heat). So when you have that stereo blasting, you are pulling 83-95 amps, depending on the setup. To make sure your wires are good, use the calculator on the bottom of this page, and keep the loss to under 5%. Since you already have it wired, you can see what the voltage drop is by percentage. Then you only need to multiply;
83ah * 1.05 = 88 amps per hour @ 5% wire voltage drop
83ah * 1.10 = 91 amps per hour @ 10% loss
http://www.bdbatteries.com/wirerules.php
Next thing you need to take into consideration is depth of discharge. Since batteries are electro-chemical, they aren’t quite perfect. When they go through a charge cycle, they lose some life. The harder you charge and discharge them, the less long they last. Look at the last page of the manual here for the graph.
http://www.lifelinebatteries.com/manual.pdf
Basically:
1 GPL-27T (100ah) will run your stereo, full blast, for one hour, 300 times.
2 GPL-27Ts (200ah) will run your stereo, full blast, for one hour, 1000 times.
By only discharging the batteries 1/2 way, you get 3 times the lifespan, not double.
Here is a list of UL listed, high quality AGM batteries that will do what you want.
The AGM batteries from Lifeline are 85% efficient at high amp loads, like what you will be doing (GPL-27T is second from top).
http://www.bdbatteries.com/marinebatteries.php
(flooded batteries are like 50-60% efficient by comparison)
Lastly, let’s talk about your alternator:
All power under the hood originates at the alternator. Batteries store the power the alternator makes. Batteries do not make power. Therefore, you need to get a big alternaotr, the biggest one your engine will take.
The stereo and batteries are currently chewing alternators up because they run at full tilt, or “REDLINE”, whenever we can hear you coming. Based on the size of your stereo, you are chewing every available ounce of power from a standard 80 amp alternator when at full power with a bass heavy song. If you had a 150, or a 200, you would be better off, as it would work less hard. If you tackle the wires and battery, that may take care of it though, so do that first. Bass doesn’t hit at full blast throughout the song….
Should you be unable to upsize the alternator, you run down to 3 very bad power generation options.
1. nightly plug your car into a battery charger (power from the grid).
2. Install an onboard generator (like an RV, to make more power).
3. Solar panels or wind generators (yes you add a lot of drag with a wind generator.)
The alternative is to turn it down.
January 19th, 2013 at 1:21 pmThat defeats the purpose of having that nice a stereo in the first place.
I suggest you ensure the wires are up to snuff first (less than 5% drop).
Second, upgrade to better batteries; 25% efficiency will help you out a lot (60% vs 85%)…
Third, up size the alternator if you still need to. The system will work less hard due to #1 and #2.
Kinetic is best performing for my car.
January 19th, 2013 at 2:15 pm