Can i add an extra car battery ?

 

New member
Username: Crusacargen

CA US

Post Number: 4
Registered: Feb-05
Can i ad an extra car battery to my car for the subs? If so, how do I wire it and does it have to be a special batery?
 

Silver Member
Username: Jeremyc

OK in less t... South Korea

Post Number: 611
Registered: Jun-04
Yes you can add a second battery, and no it doesn't have to be a special kind.

You need to run a wire from the positive terminal of the first battery, thru an isolater, and then to the positive terminal of the second battery. Then run a wire from the second battery - terminal to a chassi ground. The isolater seperates the batteries so you can't run them both down to the point your car won't start.

Keep in mind a second battery will not make up for an underpowered charging system. If your lights are dimming you need to look into a HO alternator.
 

New member
Username: Crusacargen

CA US

Post Number: 5
Registered: Feb-05
thx but what kind of isolator and where can i get one?
 

Silver Member
Username: Jeremyc

OK in less t... South Korea

Post Number: 612
Registered: Jun-04
Try your locale parts store, they should have one.
 

Bronze Member
Username: Goon

Post Number: 57
Registered: Feb-05
Can someone explain the benefits of having a seperate battery for the subs? it's not clicking for me...thanks.

goon
 

Bronze Member
Username: Hittmann

Adelaide, South Australia Australia

Post Number: 14
Registered: Mar-05
I have a matson dual battery charging kit, it came with all the wiring needed, enough to go from front of car to the boot. Terminals for the 2nd battery and an anti spike module (meant to protect car audio equiptment from voltage spikes when the car is started. When the main battery is charged the isolator then switches through to let the alternator charge the auxillary battery. I have an amp and a power inverter wich runs an xbox and a wireless lan connection. This is a good thing if you say go to a drive in and watch a movie with your amp running...... you will still be able to start your car at the end of the movie.
 

Bronze Member
Username: Goon

Post Number: 59
Registered: Feb-05
so the benefit is too spare the battery needed to start the car...so you arent always needing a jump....interesting. thanks

goon
 

Bronze Member
Username: Hittmann

Adelaide, South Australia Australia

Post Number: 21
Registered: Mar-05
pretty much..... and if you need more voltage..... it wont give you more amps but 2 batterys will gives you twice as much voltage
 

Silver Member
Username: Jeremyc

OK in less t... South Korea

Post Number: 621
Registered: Jun-04
WTF??? Two batteries installed the right way will not double your voltage. If it did you would fry your car. The way you conect the batteries dictated if the voltage or amperage is raised. When you go positive to positive your voltage is still the same, but your amperage is raised. If you were to hook it up negative to positive, and then positive to negatine it would raise your voltage, and probably fry every electronic component in your car.
 

Bronze Member
Username: Hittmann

Adelaide, South Australia Australia

Post Number: 30
Registered: Mar-05
two batterys dont give you 24v but gives you 2 lots of 12v is what i meant, and therefor doubling it. If you see what i mean.
 

Silver Member
Username: Jeremyc

OK in less t... South Korea

Post Number: 629
Registered: Jun-04
In other words it raises the amperage. It doesn't change anything with the voltage.
 

Silver Member
Username: Araknid

BOCA , FL U.S.

Post Number: 383
Registered: Nov-04
It helps if your competing and you cant get help from your alternator.
 

Bronze Member
Username: Nutshmeg

Post Number: 18
Registered: Mar-05
I just added a second battery to my truck, and I don't know if the primary battery is possibly damaged, but my system hits harder and sounds clearer at higher levels. I know it's not subliminal like sugar pills. I added an Exide Orbital by connecting the pos post of one battery to the pos post of the other and grounding the 2nd battery to the frame, using all pre made 2 gauge cables from the place I bought the battery. Adding a second battery doesn't boost anything as far as I know, it just gives you a larger reserve of stored energy or with an isolator allows you to drain a second battery without effecting the primary one.

I went to a site that is frequently referred to on this board, (can't recall the url, something with "beac" or some such thing in it) it detailed doing this, and I'm pretty sure it explained how the battery system is primary and the alternator only comes on when the voltage drops from lack of storage in the batteries. I'm going to pick up another Orbital to replace my current primary battery and replace all the cables with 2 gauge, the stock stuff looks like 4 gauge.

I ran the batteries together, rather than using an isolator because having the whole electrical system draw from both batteries made more sense to me than isolating them from each other, and the isolator is just one more current bottleneck in the system. I guess if I found myself frequently with a dead battery from my truck being parked with the system up, I would add an isolator and a 3rd battery, giving the system 2 batts ganged up and a 3rd to start the truck.

I have no idea yet if running the two batteries ganged up has any negative effect on my stock alternator.


 

Silver Member
Username: Fishy

Tamarac Ft.Laud, FL USA

Post Number: 848
Registered: Sep-04
and I'm pretty sure it explained how the battery system is primary and the alternator only comes on when the voltage drops from lack of storage in the batteries.

You've got that backwards. When your car is running your alternator is responsible for providing ALL of your vehicle's electrical needs. The only time your battery provides energy is when system voltage falls below that of the battery(~<12volts) such as when the vehicle is off or the alternator is unable to keep up with current demands.

Yes, adding extra batteries or caps can be a problem if an alternator is already sorely taxed to begin with. The extra charging requirements just puts that much more strain on it.

Unless one plans on running their system for extended periods of time with the engine off adding extra caps or batteries isn't a very smart move and can just make a bad situation that much worse. A HO alternator solution should come first.

-Fishy
 

Gold Member
Username: Carguy

Post Number: 2181
Registered: Nov-04
I'd like to challenge the theory that capacitors cause more strain on the alternator. Everyone says it but I haven't seen much proof.
A capacitor is like a condenser, stores electrical energy and discharges rapidly at high speed. So in theory, it will recharge faster than the load (amp) could require. I can see the possibility of a little strain on the alternator in certain conditions, but not like the way everyone makes it out to be.
It is not a load waster like a light bulb, so I can't see how it will have much impact in current loss/waste.
I know a lot will argue, but I'd like to see solid proof on current exchange. If it's less than 1% loss, then the benefits outweigh the negatives.
 

Silver Member
Username: Fishy

Tamarac Ft.Laud, FL USA

Post Number: 852
Registered: Sep-04
Its not merely about power loss. Its also about current demands. If you already have an adequate alternator you're right, no big deal, but in a system where there are significant voltage drops I'd think a good deal of current would flow into that cap as the alternator strains to regain a 14 volt potential.

Lets find out:

From Kirchoff's rule for charging a capacitor you get:

I(t) = V/R*(e^-t/RC)

where t = time

V = potential difference

R = resistance of power wire and ground

C = capacitance

at t=0 that equation simply becomes

I(0) = V/R

In other words your stiffening cap acts like a short for a very small amount of time. Assuming a voltage drop of say 2 volts(to battery level ~12v) and a resistance of .0044 ohms(equal to about 15 feet of 4 gauge or ~10 feet of power wire + chassis resistance) you'd have an instantaneous current demand of over 450 amps! For a 1 farad cap you'd have at t=1msec, 360A; t=10msec, 47 amps; and after t=100msec(a tenth of a second) it would essentially be zero. With a higher resistance the initial current would be less but this decay could take much longer. It takes along time for that light bulb(resistor) to dim when charging a cap doesn't it.

Of course no alternator is capable of imediately providing 14 volts in this situation, but you get the idea. Charging a capacitor does provide an additional load to the alternator.

As far as being a "load waster" well in actuality every time you charge a cap half the energy required is converted into heat through the resistance in the wiring regardless of its value and is equal to

1/2*C*V^2

from here:

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng.html

To completely charge a 1 farad cap from 0 to 14 volts would "waste" about 100 joules of energy. To charge the same cap from 12 to 14 volts would require 4 joules, half of which would be dissipated as heat. To give you an idea what this means 1 watt = 1 joule/sec, so if you charged or discharged this cap between 12 and 14 volts every tenth of a second(see above example) it would be analogous to having a "silent" 20 watt amplifier running full bore in your system.

Is all this significant? It depends a whole lot on the individual system. Might wanna ask Glass what he thinks, but yes, stiffening caps do require an alternator to work a bit harder and if its struggling, give up the ghost that much sooner.

-Fishy
 

Gold Member
Username: Carguy

Post Number: 2197
Registered: Nov-04
That's a good informative post. I did say under certain condition it would make a difference but I was talking about a normal use. 90A alternator with a 500w amp being driven 65% - 75%.
I could not find any significant evidence on added stress in my tests.
Of course it doesn't apply to extreme conditions.
Lot of people purchase system for everyday use, and in those cases, a properly sized capacitor's benefits will outweigh the negatives.
 

Silver Member
Username: Fishy

Tamarac Ft.Laud, FL USA

Post Number: 856
Registered: Sep-04
Yeah, kinda pulled that one out my @$$, hehe, but a lot of people think a cap is a voltage problem cure-all and a good replacement for an inadequate alternator when its not.

You're probably right about the severity of the added load in most cases, especially if compared to adding another battery, but its often helpful to get the point across if its mentioned that adding a cap can actually worsen a situaition, however slightly, instead of making things better.

Some people claim that caps don't even help the way a system sounds, but I thought mine sounded a bit punchier after installing a 2F Tsunami.

:-)

-Fishy
 

Silver Member
Username: Fishy

Tamarac Ft.Laud, FL USA

Post Number: 857
Registered: Sep-04
Since you seem to like testing things out a lot Isaac you oughta get hold of one of those clamp meters and wrap it around your cap's ground(assuming its separate from you amps' grounds) and measure the current with some periodic test tones and then with some material that has a lot of transients. I've never used one of those clamp dealies and am not sure you'd get very accurate readings with the wildly varying current, but you might get a good idea of just how "hard" your cap is working.

You could try it with the engine off, at idle, and then at different RPM's. Could get some neat results.

Hmmmmm..... a few 12 volt bulbs wired in series across a low resistance, high wattage dummy load might even work better. Not sure one of those clamp meters would react fast enough to give you a good idea of what the current was but you could probably tell pretty easily how "bright" those bulbs glowed.

Just a thought.

:-)

-Fishy
 

Silver Member
Username: Fishy

Tamarac Ft.Laud, FL USA

Post Number: 858
Registered: Sep-04
Of course it would probably just be easier use an analog meter to measure the voltage at that cap, duh, but lights WOULD look cool.

Its gettin late and I think I'm beginning to wear out the few functioning synapses I have left.

:P

'nite

-Fishy
 

Bronze Member
Username: Hittmann

Adelaide, South Australia Australia

Post Number: 32
Registered: Mar-05
having 2 batteries hooked up with an isolator, you can play music, xbox, etc with car off without worrying about the car not starting when its time to leave. Good for drive-in movies where you see many cars sitting there waiting for jumps when all you need to do is crank and go.
 

Gold Member
Username: Carguy

Post Number: 2210
Registered: Nov-04
That'll only work if you have deep cycle battery as your aux.
 

Unregistered guest
I need help:

I have a '03 corolla ce w/a pair of infinity 9603i's (6x9 @100 rms)in the back and a pair of infinity 6002i's (6.5's @60 rms)in the front. In the trunk is an alpine mrdm301 to power an alpine sws1042 sub (300 rms). I need a recommendation for an amp to power all the speakers and the subs (1 extra sws <2>) and a recommendation on a source of more power as far as capacitors, batteries, and alternators. My system shuts off when I try to turn up the base, and even did so when I only had one sub and nothing else. I believe the car only puts out 12v. Do I need more volts? Do I need another battery? Do I need a capacitor? Do I need an alternator? All help is appreciated, but if you don't know what you're talking about...please don't give advice. HELP ME!
 

Gold Member
Username: Carguy

Post Number: 2354
Registered: Nov-04
Are you currently powering the Infinitys with HU power?
If you want to power all of your speakers then get a 4-channel amp. As for your sub, if 300w rms is enough, then you don't need to upgrade.
Since your are having power problem, get a HO alternator from 4alterstart.com. I'd get something in the 150A-200A range. After that, you can get a 1F capacitor for tighter bass.
No need to get another battery with the above upgrade.
 

Webby87
Unregistered guest
ok i have a question. Im going to put a 1500 watt RMS amp in my truck. Now. what should i do as far as power. I believe my Alternator powers at 95 amps. Should i just get a bigger alternator and if so what size?? or should i get a bigger alternator with a cap??? or should i get another battery. And if i do get another battery..I will have to upgrade the alternator anyways right? What would you guys do?
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