Super Small Battery

[JET]

Look at your voltage when you are under power with and without an alternator. If you have a very strong battery you will see 12.3 volts or so without the alternator. With the alternator you will see about 14 volts. Which do you think is going to supply the ignition with more power? We already know the effect that the voltage has on the fuel pump, that is why we rewire them.

There is a way around that though. Jacobs makes a product called the Accuvolt that will bump the voltage up to 14.4 volts no matter what the incoming voltage is. If you put one of those on the ignition and fuel pump, you would be set! They aren't real cheap, but it is a good option.

[Shane@DBPerformance]

We run 16volt batteries on drag cars that don't use an alternator.

[Raptor]

That sounds like a smart option. I know there are companies like Taylor that manufacture altenators that cut out the charging function if the car is at WOT and the batteries have adequate charge. Running without altenators in drag racing is not a new concept, it has been done for years even on cars without magnetos. the 16 volt battery does sound like it would be a good idea.

One of the reasons the small battery thing kills me is the guys who have put them in heavy cars with no real other weight reductions. I can see running one in a car that has been well thought out and lightened, but running one in a heavy boat is pretty much pointless other than if there is some space requirement.

That is not pointed at anyone who posted in this thread yet. I saw a few that fit that description on Uni last year.

I remember looking up the Jacobs thing last year when you mentioned it JET. It is pretty expensive and designed mainly for sound systems, but it could work. I would bet the higher voltage battery/charging system is probably the best method if finances are not an issue though, considering the extra complexity/weight of additional equipment with the Jacobs setup.

[Raptor]

After further reading, the 16volt battery would be good for race only for the simple fact that without serious modification to the charging system, you would need to keep it charged with an external charger and at that level not bother with an altenator at all.

I am still going to dig on this since I know there are always a lot more things to consider than just the basics. Ideas like JET mentioned are things that are worthwhile to look into. Either way, it boils down to the facts that every system on the car must be up to par to be competitive.

[JoeGengsta]

the small battery is NOT a practical choice, for instance, lets look at Kirchhoff's law that states
L(dI/dt) +RI + (1/C)Q = E(t) where voltage drop across the resistor is IR, voltage drop across the capacitor is Q/C, and lotage drop across the inductor is LdI/dt, comined you have the relationship of 1 volt * 1 ampere = 1 coulomb/1 farad = 1 henry * 1 ampere/1 second. The comibination of all of this resembeles the electrolytic behavior of your circuity within the car. Now, take something with 1/3 the electrolytic capacity, the small battery would certainly power the car, run the radio, and your sparks for the plugs.. but wait... what would happen if you plugged in something that requires 12 volts and a few amps, or perhaps what do you think would happen if your car didn't have the electrolytic potential to power the cominbation of your highbeams, your factory stereo and what not.. oh i guess intra charge < forced charge which means that your car may not be able to make it home. anyway, electrical physicts and ciruit board engineers created a BIGer battery for a reason, why mess with it? anyway, my name is Joe and i fart a lot.

[-GSX-Falcon]

L(dI/dt) +RI + (1/C)Q = E(t) where voltage drop across the resistor is IR, voltage drop across the capacitor is Q/C, and lotage drop across the inductor is LdI/dt, comined you have the relationship of 1 volt * 1 ampere = 1 coulomb/1 farad = 1 henry * 1 ampere/1 second.

I must be stupid. 90% of that sounds like a different language....I still kind of understand....

[Shane@DBPerformance]

Originally posted by JoeGengsta@Mar 6 2004, 02:51 PM
the small battery is NOT a practical choice, for instance, lets look at Kirchhoff's law that states
L(dI/dt) +RI + (1/C)Q = E(t) where voltage drop across the resistor is IR, voltage drop across the capacitor is Q/C, and lotage drop across the inductor is LdI/dt, comined you have the relationship of 1 volt * 1 ampere = 1 coulomb/1 farad = 1 henry * 1 ampere/1 second. The comibination of all of this resembeles the electrolytic behavior of your circuity within the car. Now, take something with 1/3 the electrolytic capacity, the small battery would certainly power the car, run the radio, and your sparks for the plugs.. but wait... what would happen if you plugged in something that requires 12 volts and a few amps, or perhaps what do you think would happen if your car didn't have the electrolytic potential to power the cominbation of your highbeams, your factory stereo and what not.. oh i guess intra charge < forced charge which means that your car may not be able to make it home. anyway, electrical physicts and ciruit board engineers created a BIGer battery for a reason, why mess with it? anyway, my name is Joe and i fart a lot.
Alternator?

[JoeGengsta]

yes, the alternator flows like dX/dt, where X is the charge input and t is time. (change of charge in respect to time), but remember, i'm saying if there is a burst of electrical withdrawl, the SYSTEM will die.

in addition, remember that the entrance of frictionally created charge by the alternator is all in respect to the cycles of the engine, more RPMS = more cycles = more charge that the alterantor generates through its supercoil. so, what happens at a stop light when all your electronics are on? hmm... the charge can be distributed inadequetly/unevenly to your componenets which can cause misreads on your electrical gauges, misreads in your audio equipment, misreads in your sensors, and so forth. so why bother doing it?for the 7 pounds or what not saved? maybe people should just go on a diet and stop worrying about how much faster 7 pounds can get u, besides, think of the accelatory coeffienct that powers 7 more pounds.. i dont see the benefit.

[JET]

We are talking about fast cars here, not normal daily driven cars with enough neon lights to light up the sky and a sound system that knocks the body kits off of honda's. If you require more power than the alternator puts out, you are in trouble. The batteries in question are gel cells too, so their capicity is larger per pound than the bigger batteries. They are still smaller capacity though.

The difference is actually 30 pounds, not 7.

[Goat Blower]

Originally posted by Raptor@Mar 6 2004, 11:01 AM
Notice a trend here?

I have the same old battery in my car that it came with, I just moved it. It is probably 4 years old and still holds a charge just fine, hasn't needed a jump once in any weather. I am also confident that it can support my ignition system at high RPM without the aid of the altenator. I can't say that about the small batteries. I am assuming that everyone is running them mainly to save weight and get the associated power savings that goes along with it. Consider this though, if you are saving 20 lbs going with that battery, and the statement is true that a 100lbs is worth a tenth in the 1320 you are less than a 2HP advantage from the weight loss. If you kill your altenator for the run and go from the batteries power, you are probable closer to saving 3-5HP and possibly more, I have heard alot of different numbers on that over the years. Also, by moving it to the back, you have more even weight distribution and can place it directly over the most significant tire (RR).

I am interested in anyone elses opinions of what I am talking about. Try and shoot holes in what I am saying if you can, I am always open for a better way of doing anything.
The only bad thing with a rear mounted battery in our cars is using the chassis as a ground. There's a lot of interference in a unibody chassis and that could hurt your battery's performance. If you're running a large power and ground cable(0-1awg), things should be fine.

I had a rear mounted battery, I didn't like the extra complication so I put the mini battery up front directly on the subframe. Does exactly what I want, saves me 20+ lbs and they're cheap. So I have to replace it each year at $20 a crack, fine with me.