Battery Use While Car is Running

[audiolife 5,000+ posts]

it can in but it alot of cases no if you charged up the rear first then after a week or 2 then checked them both it would tell you but haveing them both the same does help

 

[knukonceptz 10+ year member]

Got the video from the power supply test at a friends house. Turned out he uses a Battery Charger and it did not perform well for what we were trying to accomplish so the in car test will be better suited.

What we have - 8, yes 8 Batteries wired with aluminum rails, total cable length is maybe 5ft max so no loss there like we will see in the car. The charger wires are about 3ft long so in all we had 8ft from the charging point to the draw. I could not see any voltage loss with the minimal current we were drawing. We had to keep draw low ~ 20A as the charger has setting for 2/10/50/225, however the 50 and 225 settings put voltage over 16V so that really was not making a valid test of a car system.

So the 10A setting provided us with the most real world voltage, 13.9-14.1. We played a 35hz test tone (from a CD) using an Overdive as master volume control. We were able to establish a 18-22A load- double the power supply was putting out. We had two of every meter to make sure numbers were accurate and that the meters shown are correct. The charger is probably the weak link in the test, as we could only do 10A - its not exactly the high current test I was hoping for.

Video is a 30 sec clip of the 20A test, voltage stays at 13V for the majority of the time. Indicating the batteries are discharging above 12.6-12.8 nominal range.

When we really got on the system and draw 110-120A we would instantly see 12.8 and only once did it go below that but thats what 8 batteries will do. If we had less reserve, this number certainly would drop faster and over extended playing time would cause a very low voltage - but this is with a 10A power supply, Kicking it up to 50A did raise voltage, (also due to the fact is was trying to output 16V) but it would soon get back in the 12V range.

With this test, we did not get any voltage loss due to shortness of cabling (in car at 200A we should see near 1V in the rear) and very low load. What this shows is that if you have everything within feet of each other the HO ALT would be your best bet IF it can be made to match your entire system output. What this test does not include - variables such as engine RPM and the delay built into some regulators used in cars. No using regular music was used, it was just to hard to keep a consistant draw, made for too many variables added to the mix. To sum it up Taxi put it best - it is case dependant.

http://www.youtube.com/watch?v=r_w3_CO6oqw

(just uploaded so it may take a bit to be available)

 

[audiolife 5,000+ posts]

Got With this test, we did not get any voltage loss due to shortness of cabling (in car at 200A we should see near 1V in the rear) and very low load. What this shows is that if you have everything within feet of each other the HO ALT would be your best bet IF it can be made to match your entire system output. What this test does not include - variables such as engine RPM and the delay built into some regulators used in cars. No using regular music was used, it was just to hard to keep a consistant draw, made for too many variables added to the mix. To sum it up Taxi put it best - it is case dependant.
http://www.youtube.com/watch?v=r_w3_CO6oqw

(just uploaded so it may take a bit to be available)

thats a big if as in a high output alt is only slightly higher or even less than stock at idle. would anyone tend to agree that a ho alt with an extra battery would give you the best result?you would have less voltage drop by the amps, you would have the power of the alt/charging capabilities and the safty buffer for parked/idle times.couple other things with a more inconsistant load wouldnt the stock alt have time to recharge the extra battery?

*** also in db drag street classes while getting metered the car isnt allowed to be running ( i know this doesnt apply to everyone thats why i put it down here)

 

[knukonceptz 10+ year member]

As I said, IF everything is within feet of each other...... when we raise amperage and length, I think we'll see that the added batteries in the rear of the car will support the load better compared to a single battery and HO alt because of the resistance. For example, say we have the 200A load, it is known to exceed my 90A Alt so that should bring voltage down, add in the .8V loss at that length and we'll be very close to 12.0V. If we remove the loss from resistance, right there is .8V gained (back to 12.8V) adding double the reserve will add support to the 12.8V level giving us double the playing time before that voltage will drop.

Basically this shows that unless your ALT can output the max amperage at any given time you will need batteries to maintain voltage. Once we add in the resistance factor they will add more benefit

 

[audiolife 5,000+ posts]

i figured on what you were getting at lol truth be told i would do both an alt and a battery especially if i had over $1500 in my system. i always did it that way when i could, and back when i did it as such alts were 2x's the cost they are now and we didnt have a good selection of batteries. way i look at it you spend good $ to get the performance you do so the electrical just makes it perform and last they way you want it too.

 

[Thnking 10+ year member]

What we have - 8, yes 8 Batteries wired with aluminum rails, total cable length is maybe 5ft max so no loss there like we will see in the car. The charger wires are about 3ft long so in all we had 8ft from the charging point to the draw. I could not see any voltage loss with the minimal current we were drawing. We had to keep draw low ~ 20A as the charger has setting for 2/10/50/225, however the 50 and 225 settings put voltage over 16V so that really was not making a valid test of a car system.

So the 10A setting provided us with the most real world voltage, 13.9-14.1. We played a 35hz test tone (from a CD) using an Overdive as master volume control. We were able to establish a 18-22A load- double the power supply was putting out. We had two of every meter to make sure numbers were accurate and that the meters shown are correct. The charger is probably the weak link in the test, as we could only do 10A - its not exactly the high current test I was hoping for.

This doesn’t prove anything.

1. What is the charger’s maximum potential at 10A

2. What is the discharge rate of the charger

3. What are the batteries nominal paralleled potential

You jump to conclusions which defy physics, before understanding what’s actually happening.

(just uploaded so it may take a bit to be available)

 

[ngsm13 5,000+ posts]

This doesn’t prove anything.1. What is the charger’s maximum potential at 10A

2. What is the discharge rate of the charger

3. What are the batteries nominal paralleled potential

You jump to conclusions which defy physics, before understanding what’s actually happening.

(just uploaded so it may take a bit to be available)

Well, come sit in my truck. Come see with your eyes, and a clamp meter and a DMM... my truck will defy physics.

nG

 

[knukonceptz 10+ year member]

Did another test today but again my load was not as high as I previously had wanted. A quick over view 90A alt (stock wire) Standard car battery (Interstate MT-35) with constant 55A draw on 18ft of 1/0; nothing else. At idle start voltage was 14.47 under load voltage shot to 12.4(Front)/ 12.16(rear) instantly and continued to fall below 12V. This with only 55A at idle......cable should cause a .2V loss according to our wire calculators - those look to be spot on. Alternator only put out 40A at idle with the one battery. At idle the stock unit could not keep a 55A load above 12V, a HO alt will have similar issues on large loads.

We added a second battery (SLA type posted earlier) - voltage stayed at 12.8 at the Front and 12.56 at the Rear (again we only did this at idle) There was a much slower drop this time.

Next I might try at higher rpm with a smaller wire to demostrate resistance with the same 55A load, wont be this week though.

At idle - the battery makes a big difference, keeps the voltage higher and stable. A HO alt, if it can make the 55A at idle would make a bigger difference (sustain 14V most likely) In some instances, your HO alt will not always meet the demads of the system at idle or even at max output.... It is at this point voltage will begin to drop and continue to fall until the battery reserve holds it from dropping further down (small reserve will drop quick, large reserve will maintain and slowly drop). The battery will always add support in the 12V range - If you drop to far, that is when you will damage the amplifier power supply.

so its back to square one and comes down to what your needs and budget are. An SLA battery like I used is roughly $100-120, the HO alt will range from $200-$600 - best option is both, but thats not always realistic when the bills are due......

 

[qtipextra 5,000+ posts]

I would like to bring this back up again. Thanks for the tests provided, KnuKonceptz.

So have we found out if, in an actual application, the battery provides current above it's operating range? It did out of car, with the 10A power supply. I didn't really pick up if it did in the car or not.

 

[qtipextra 5,000+ posts]

Where is everyone at? Knu? Audiolife?

 

[audiolife 5,000+ posts]

umm its operating range is higher than 90% of what people say (its a gray area where both alt and battery are working. this can be 13.5-13v). also why its good to have a battery that can "rest" at a higher voltage. if your alt keeps up to your listening habits a battery helps. meaning you keep it down at times so it can charge or your alt is flat out large enough. will a better battery power 100 amps at 13v? no but its better than having it dip FARTHER to even start to kick in. when power is called upon the power goes to what is called for (equipment) that is why if you have a smallish alt and go rambo on the volume all the time it eventually weakens the battery.....

 

[Justintoxicated 10+ year member]

umm its operating range is higher than 90% of what people say (its a gray area where both alt and battery are working. this can be 13.5-13v). also why its good to have a battery that can "rest" at a higher voltage. if your alt keeps up to your listening habits a battery helps. meaning you keep it down at times so it can charge or your alt is flat out large enough. will a better battery power 100 amps at 13v? no but its better than having it dip FARTHER to even start to kick in. when power is called upon the power goes to what is called for (equipment) that is why if you have a smallish alt and go rambo on the volume all the time it eventually weakens the battery.....

Voltage drop = more current pull = Harder on electrical, and battery = Not good.

 

[audiolife 5,000+ posts]

show me an alt with no voltage drop when the system is actually doing the power it claims....300 amp alt is doing 300 amps at 12.5v MAX rpm

 

[jmoreno150 10+ year member]

Well I could be wrong, but I think it acts as a reserve when driving. The alternator does most of the work when the car is driving, but if your system draws more amps than the alternator can supply, then the battery provides the extra juice.

thats correct man. once u exceed the amps of the alty you start to damage it and drain ur battery.

 

[audiolife 5,000+ posts]

damage it? it is how it was designed to do. what damages it is the stress when maxxed at full tilt or used in such a way you kill a battery. the load of the severally drained battery will kill the alt. that isnt from regular use either. an alts voltage will drop rise drop rise while in use. a hi amp alt under heavy load is also VERY hard to turn. that causes stress to the belt,alt and eats hp (but if you need it you gotta do it). main point I'm talking about though is where a battery will kick in. lets say you have a 200 amp alt at idle it does 120 amps. if your system is 2000 watts (real power) at idle it will have a drop .people will argue just like when people talk about "grounding a second battery" there is alot of MISINFORMATION . best place is BACK UP FRONT

your audio gear is meant to work (in about every case i can think of) between 11.5 v-15v (some can go up to 20 v but ill leave that alone because its not a typical "daily set up") the equipment will run cooler when you stay in the sweet spot between 12.5 and 14.4. less volts needs more current to do same amount of power. more current builds up the heat. in electronics heat does = bad. some people state that too big of voltage drop is a serious loss of power. per 100 amps of power drawn the difference would be negligible at best to your ear. 200 or so watt difference between 12v and 14v that is maybe .1-.3 db and perfect hearing can MAYBE tell the difference in FULL db differences.when i say this .1-.3 db means alot while in competition but in every street class org i know you get metered with the engine off.....not dogging alts just saying the better the battery you have (condition to float voltage) can make a notiable difference