How many batteries do I actually need?

[Jobin 10+ year member]

Ill be running a modded RF Power 1500bd pushing 2200w+ at 1 OHM and a RF Punch 500x pushing 70w x4 in 2001 Lincoln Navigator. Ill obviously be doing the Big 3 with 1/0 gauge and a 220A alternator.

My question is how many batteries would be ideal for this kind of power? Thanks

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[Raven 10+ year member]

Just one. That 2480 watts is only 2480 watts at full output.

 

[helotaxi 5,000+ posts]

Unless you plan on playing it often with the engine off, you only need the one under the hood.

 

[Jobin 10+ year member]

Unless you plan on playing it often with the engine off, you only need the one under the hood.

hah, sound advice (tweeter) said i needed atleast 3. gotta love shops.

So I should be good with just one? I mean this thing has rear a/c, power everything, lights galor, and ill be adding a few TV's in addition to my alpine flipout.

 

[maxxguy1 10+ year member]

I would run two just to be safe.

 

[Hartman 10+ year member]

hah, sound advice (tweeter) said i needed atleast 3. gotta love shops.
So I should be good with just one? I mean this thing has rear a/c, power everything, lights galor, and ill be adding a few TV's in addition to my alpine flipout.

Let me guess, they sell batteries? //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

 

[Jobin 10+ year member]

Let me guess, they sell batteries? //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

Yep lol

I found this: http://www.cardomain.com/item/STISP1700

Maximum Peak Discharge of 3500 amps

5-Second Cranking Output of 1700 amps

Cold Cranking Output of 1200 amps

Worth my while?

 

[helotaxi 5,000+ posts]

The extra battery is just one more load on the alternator. The alternator is the source of all the current for your system. Putting another load on it with the idea of helping it out is like throwing a drowning man an anchor. With a 220A alt, you should be fine.

 

[knukonceptz 10+ year member]

With the anchor theory - its not quite like that. It seems no matter what I read, there is no right answer on any board. The guy has a 220A ALT, if it does what it claims I am sure it has ample head room to power two batteries.

A Battery is heavy like an anchor, thats where the similarities end. A battery has reserve capacity, it can hold a load X for Y hours before being dead (dead is defined as 10.5V) This acts as a buffer to the charging system. At idle your HO ALT may not put out maximum power, but that Battery can. A battery not RPM dependant. Yes, it does need to be recharged and UNLESS he is running Headlights, rear defrost, heater and stereo doing 50Hz sweeps at idle, his ALT or any decent sized unit will handle an extra battery or two.

Point being, you not going to draw full power from any system the ENTIRE time your car is running, Music will never cause that amp to pull its full potential....period. So the regulator tells the ALT what to put out to keep the system voltage, if that means working to maintain voltage on the first and the second battery - that is what its intended to do. Even a 130A Alt would suffice with 2 batteries, if you drive for 10 minutes on the phone - radio is not pulling any Amperage, your batteries are charged in that time. Ordering fast food, same thing. Police riding behind you.....well for you sake hopefully it won be a long stop //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

For the record I have run on a stock 90A Ford Alt - 5 batteries which powered 6 amps, four of which would draw about 110A each. Ran fine for a year, then added an external voltage regulator for some additional power in the lane //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[helotaxi 5,000+ posts]

Point taken, and I fully understand and agree with you but the question was, how many batteries does he NEED and the answer is just one. No number of batteries is going to keep the voltage at 14V which is where you really want it. Only an alt can do that, and he has quite a beefy one. If he's worried about output at idle, I would be more inclined to repulley the alt to up the output at idle than I ever would be to add a battery. I would even go so far as to put in a really big cap to stabilize the voltage until the regulator in the alt can catch up to a transient spike in demand before I would add another battery. The only time I would be worrying about batteries is if I was going to be sitting for a while with the engine off and the system on.

Point being, you not going to draw full power from any system the ENTIRE time your car is running, Music will never cause that amp to pull its full potential....period.

Agreed.

So the regulator tells the ALT what to put out to keep the system voltage, if that means working to maintain voltage on the first and the second battery - that is what its intended to do. Even a 130A Alt would suffice with 2 batteries, if you drive for 10 minutes on the phone - radio is not pulling any Amperage, your batteries are charged in that time. Ordering fast food, same thing. Police riding behind you.....well for you sake hopefully it won be a long stop

The problem with this statement is that if you have managed to discharge the batteries at all, they are a load on the alt until they are fully recharged and even then they require a maintenance current to keep them charged (given this amount is nominal but hte higher the capacity of the battery the higher it is). If your system is placing such a strain on the alt that the batteries are being discharged, adding more batteries is exactly like throwing a drowning man an anchor.

In this guy's situation I would be inclined to actually add a BIG (20+ farad) cap and an overdrive pulley for the alt if he is regularly sitting in traffic or driving at low RPM.

The bottom line of what I'm saying is if you are worried about powering a system with the car running focus on the alt and have a battery adequate to start the car. If you want to run the systme with the engine off, then start worrying about batteries or external power supplies.

 

[knukonceptz 10+ year member]

If your system is placing such a strain on the alt that the batteries are being discharged, adding more batteries is exactly like throwing a drowning man an anchor.

Right there, the second battery is holding the ability to discharge 500A (and thats a small one) Which would you rather have on reserve - 1000A or 500A? Does a larger battery make for more of a load on the ALT then two small ones? If both units are charged equally upon installation, the ALT only sees them as one load.

By having the additional reserve, the ALT needs to work less to over come the spike. Large fluctuations are what is hard on a unit and Ford Regulators actually have a delay in some called Load Response Control. What this does is delays the ALT repsonse to prevent the motor to bog at idle, it gradually comes on. If you have this regulator in your ALT it can not be swapped with an instant type, it can cause driveability (PCM is prgrammed to see a delay and a spike could trigger CEL)

Back to topic - Sure if you have One dead battery that is hard on the ALT and TWO dead would be even worse, but it is not physically possible for this to occur with the car ON and a everything installed and working properly unless you have an extreme SPL car. The ALT is constantly making power

In this guy's situation I would be inclined to actually add a BIG (20+ farad) cap and an overdrive pulley for the alt if he is regularly sitting in traffic or driving at low RPM..

Large caps are not great solutions, you are better off using multiple small caps - lower ESR. Over drive pulley is harder on a unit then adding a second battery since it is full time. The battery only adds a load under draw. You can only go so small before the belt may start to slip (lack of area to grip the belt under load) trust when I say it has been looked into //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

The bottom line of what I'm saying is if you are worried about powering a system with the car running focus on the alt and have a battery adequate to start the car. If you want to run the systme with the engine off, then start worrying about batteries or external power supplies.

Again- the second battery adds reserve capacity and will actually help by reducing spikes. If both batteries are equally charged, the ALT will not see any diffrence.

PS - to answer the OP question - I would check your voltage with car on and stereo running. That info was never actually established. At most any normal install would need is a second battery.

 

[Jobin 10+ year member]

Thanks for the advice guys. I guess I wont need to run multiple batteries afterall.

But what about one BIG battery? Would this be overkill? http://www.cardomain.com/item/STISP1700

 

[Jdizzle 10+ year member]

well...you'd need around 46 (not including the 4 you have to have under the hood) haha im j/k im in a smartass mood, i agree with what mr knukoncepts said....looks like knowledgable stuff i personally have no time for reading it

 

[helotaxi 5,000+ posts]

Right there, the second battery is holding the ability to discharge 500A (and thats a small one) Which would you rather have on reserve - 1000A or 500A? Does a larger battery make for more of a load on the ALT then two small ones? If both units are charged equally upon installation, the ALT only sees them as one load.

It sees them as one load but the maintenance current of multiple batteries is cumulative and if they are wired in parallel (which they have to be to be of any benefit) the ESR is lower and that load is higher than it would be for a single battery.

By having the additional reserve, the ALT needs to work less to over come the spike. Large fluctuations are what is hard on a unit and Ford Regulators actually have a delay in some called Load Response Control. What this does is delays the ALT repsonse to prevent the motor to bog at idle, it gradually comes on. If you have this regulator in your ALT it can not be swapped with an instant type, it can cause driveability (PCM is prgrammed to see a delay and a spike could trigger CEL)

Problem is your working voltage is 14V and your reserve is 12V. Every time you dip into that reserve, your system voltage drops. Not a problem, per se, but dimming lights is really annoying and the additional load of the headlights makes this more likely to occur. This is why capacitance is nice IMO because it is reserve as well (given not as much as a battery but you will never use 95%+ of the battery's reserve anyway) and it will start at 14V and slowly decrease to a lower voltage. The lights will still dim but it will be a more gradual fade rather than a sharp flicker, ie no disco effect. Once the voltage regulator on the alt notes the drop in voltage, it ups the current output and all is happy again. For stopping headlight flicker with music, a battery will simply not help.

Back to topic - Sure if you have One dead battery that is hard on the ALT and TWO dead would be even worse, but it is not physically possible for this to occur with the car ON and a everything installed and working properly unless you have an extreme SPL car. The ALT is constantly making power

Or a fairly large system with a really small alt and other electrical loads on the system, I agree, not really likely though.

Large caps are not great solutions, you are better off using multiple small caps - lower ESR.

Of course low ESR works on both the discharge (good) and charge (bad) when the alt does catch up, a battery of small caps with relatively lower ESR will present a larger current load on the alt.

Over drive pulley is harder on a unit then adding a second battery since it is full time.

On a large engine this load is nominal, and the load is still in proportion to the demand placed on the alt. The only difference is that the potential of the alt is available at a lower engine rpm.

The battery only adds a load under draw.

Barring maintenance current, true.

You can only go so small before the belt may start to slip (lack of area to grip the belt under load) trust when I say it has been looked into //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

If you are really desperate, you can increase the size of the other pulleys and effectively decrease the size of the alt pulley without decreasing the contact patch. Might require some custom work but is a solution if you really care enough.

 

[knukonceptz 10+ year member]

Problem is your working voltage is 14V and your reserve is 12V.

So your batteries are not @ 14V with the car running....thats not correct....You know this.

Every time you dip into that reserve, your system voltage drops. Not a problem, per se, but dimming lights is really annoying and the additional load of the headlights makes this more likely to occur. This is why capacitance is nice IMO because it is reserve as well (given not as much as a battery but you will never use 95%+ of the battery's reserve anyway) and it will start at 14V and slowly decrease to a lower voltage. The lights will still dim but it will be a more gradual fade rather than a sharp flicker, ie no disco effect. Once the voltage regulator on the alt notes the drop in voltage, it ups the current output and all is happy again. For stopping headlight flicker with music, a battery will simply not help..

Ok so you think a battery has no capacitance? What do you think fills a capacitor ? When you first charge one - is the car usually on ...... No. A battery and cap are similar - one holds a reserve and by adding a second you doubled the reserve (assuming both batteries are equal) Adding a cap just adds capacity to hold power that is already in the system. Its like an air tank for airbags - it did not make the air but will hold it and release upon demand.

A battery will certainly stop any disco light or slow fade. You have to look at the whole picture, not just one part. Everything works as a system. With the car on the entire system operates at 14V. You cant say that this burst came from the ALT or this low note was powered by the battery (unles car is off, we know that) All parts are daisy chained together and therefore react together.

Of course low ESR works on both the discharge (good) and charge (bad) when the alt does catch up, a battery of small caps with relatively lower ESR will present a larger current load on the alt. .

Again, second battery - the ALT does not need to catch up. You see the ALT and batteries are directly connected, so while the ALT creates the 14V operating voltage, large spikes come from a battery and the ALT adjusts to reload for the next burst. More reserve means less to reload.

On a large engine this load is nominal, and the load is still in proportion to the demand placed on the alt. The only difference is that the potential of the alt is available at a lower engine rpm. .

I meant it is harder on the ALT but it will add a load to the engine, if you do over drive your ALT it could cause premature failure. If in a car that is taken to redline often, you could possibly exceed the bearings rpm tolerances (this is not likely, but in extreme cases like we seem to be talking about - could really happen) Bearings go on units all the time just from time, excessive heat could break the grease down premature.

You have a system in your car - turn it on start your car and play some music. See what the voltage does at the front battery (not of a block or cap - a real DVM on the battery). with MUSIC it will bouce around, but never drop conitously. Have a friend pull up next to you, connect his battery to your car with jumper cables. Let your car run for 30 seconds with his connected to make sure both batteries are equal - see what happens to the voltage now. Its easy and free learning //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif