One or two batteries for Stock Elim.

[Danny Ashley]

In the planning stage for a new car and was wondering about battery choices. Since we have to run an alternator, would like pros and cons of the following systems.Which one do you have and why?Thank you for your input.

1. Conventional one 12 volt up front w/ working alternator. Most popular.
2. One 16 volt up front w/ appropiate alternator. Don't know anyone using this personally.
3.Two 12 volts wired in series. Alternator hooked to both. Very popular.
4. Two 12 volts. One for starting and ignition hooked to alternator and the other to power everything else.
5.Another that I might not have considered. But not the one with a fake battery up front and one in trunk hooked to alternator. Don't want to go that route . Although a good way to shed 32+ front end pounds

[Kenny Wigington]

Danny, I use option #2, but 2 or 3 will do just fine. What kind of car are you getting ready ?
Good Luck !

[Todd Bailey]

I hope this subject gets many responses as I am REALLY curious as to which route to take. I do, though, understand that car type/combo will dictate the number of batteries and the 12 volt versus 16 volt issue.

[magnumv8]

drooze.....you don't need a second battery just the right one for your application.....most stockers add it for the ballast not the extra capacity....if you take into consideration that a modern street car has a MUCH higher electrical demand than your race car, after all they have to be able to power everything in the car at once including A/C, interior blower fan, power windows,rear defoggers, high powered stereos and they are doing it with one battery.....yes the alternator in newer vehicles have a higher output, but they also rely on the battery reserve to start the vehicle after setting for one, two or longer number of days.....you will probably be throwing a charger on it between rounds and leaving it on a maintenance charger when not at the track....for your app, I would use a Braille battery 12v....they have one with 850 CCA @ 0 degrees (over 1100 CCA at 32 degrees)...it weighs 41 lbs. giving you a good compromise between power, weight and size....

Alternators take on average 1hp per every 25 amps of output that they are required to provide so as long as the battery (batteries) are at full charge the alternator will not go to full output, what hurts is when you have dual batteries and the alternator has to provide enough output to keep 2 batteries up instead of just one also if one starts to create a heavy current draw you have to figure out which one it is, you can end up with a performance issue that becomes difficult to diagnose and could be as simple as a battery that "pulls" more current to charge than the other even though they are the same....

To create a "rule of thumb" calculate your total current draw and size your alternator to provide just enough output to cover it, this way with fully charged battery (batteries) to provide the starting power once the car is running you will actually be running on the alternator so available power is a non issue with you race cars electrical needs....

The fuel pump voltage boosters are really only for cars with no alternator to keep the voltage constant at the pump while the voltage is being drained by the rest of the electrical items in the car.....alternators usually output between 13.5 to 14.5 volts constant during operation so the pumps output is usually fine....


D L RAMBO....

PS.....twrs2006.....for a "legal" stocker items #1 and #2 are good

#3 has to be PARALLEL or you end up with (again) 24volts which will cook most of your 12 volt accessories, also in parallel the alternator only has to be connected to ONE battery positive since both are connected together at the positive posts....

#4 and #5 aren't LEGAL in stock.....

[Chris "drooze" Wertman]

Check, and thanks for the advice.

The second battery was going to be isolated for accesory items, (Light and Tailight, Fan, Windows, YES the DP Actually has Power Windows, lexan but power....and POSSIBLY the Fuel pump since all the other items are pretty isolated.)

The "Accesory" items were going to run off the second battery but the input/and draw from the alternator will be isolated as I will run an inline switch to handle it aside from the elctronics package. So Im not charging the accesory battery when I dont want to.

I asked the old man to go grab me an underdrive pulley for the alternator, I thought he brought back a damm balancer...lol....but I can get a smaller pulley, the alternator is one of the 50amp mini denso's so......

And the ballast was a consideration as well depending on what the car scales out at.....My other buddy who is a circle jerk is back in town he stopped by the shop this morning, and theyve got 3 cars going south for some roundy round but hes gonna bring his scales over this week later so Ill have a better idea.

The battery is a marine deep well unit I have , high amp (950 @ 32f I think, if my memory is right) and not so heavy (odd for a marine battery but true) so ....

Originally Posted by magnumv8

drooze.....you don't need a second battery just the right one for your application.....most stockers add it for the ballast not the extra capacity....if you take into consideration that a modern street car has a MUCH higher electrical demand than your race car, after all they have to be able to power everything in the car at once including A/C, interior blower fan, power windows,rear defoggers, high powered stereos and they are doing it with one battery.....yes the alternator in newer vehicles have a higher output, but they also rely on the battery reserve to start the vehicle after setting for one, two or longer number of days.....you will probably be throwing a charger on it between rounds and leaving it on a maintenance charger when not at the track....for your app, I would use a Braille battery 12v....they have one with 850 CCA @ 0 degrees (over 1100 CCA at 32 degrees)...it weighs 41 lbs. giving you a good compromise between power, weight and size....

Alternators take on average 1hp per every 25 amps of output that they are required to provide so as long as the battery (batteries) are at full charge the alternator will not go to full output, what hurts is when you have dual batteries and the alternator has to provide enough output to keep 2 batteries up instead of just one also if one starts to create a heavy current draw you have to figure out which one it is, you can end up with a performance issue that becomes difficult to diagnose and could be as simple as a battery that "pulls" more current to charge than the other even though they are the same....

To create a "rule of thumb" calculate your total current draw and size your alternator to provide just enough output to cover it, this way with fully charged battery (batteries) to provide the starting power once the car is running you will actually be running on the alternator so available power is a non issue with you race cars electrical needs....

The fuel pump voltage boosters are really only for cars with no alternator to keep the voltage constant at the pump while the voltage is being drained by the rest of the electrical items in the car.....alternators usually output between 13.5 to 14.5 volts constant during operation so the pumps output is usually fine....


D L RAMBO....

PS.....twrs2006.....for a "legal" stocker items #1 and #2 are good

#3 has to be PARALLEL or you end up with (again) 24volts which will cook most of your 12 volt accessories, also in parallel the alternator only has to be connected to ONE battery positive since both are connected together at the positive posts....

#4 and #5 aren't LEGAL in stock.....

[Danny Ashley]

Kenny:
I'm leaving tomorrow for Charlotte,N.C. to pick up a 1976 Firebird purchased off E-Bay. Won't be out this season because I'm starting with a street car. I know it's a lot cheaper to buy a completed car but I enjoy building them . This may be my last racecar so I really want to do it right. Thanks for asking. I am leaning towards the 16 volt system right now. One of my Super Stock customers, who is really fast, said he would never go back to a 12 volt system and he only runs one 16 volt battery and no alternator. But I'm open to suggestions. Nothing is set in stone at this stage of the game except the color on the car which doesn't need re-painting. Danny

[Dick Butler]

It is my understanding that the Voltage of the battery(12 VS 16) wasnt the real issue it was the Amperage available to run it all. I had been told the Voltage of a 12 volt battery drops below the best voltage to run strong ignition systems if you power a water pump, fuel pump and Fan from the battery.
Alternator takes power to turn.
Two 16 volts in series will run it all with strength to Start, Run and cool without dropping below the voltage to power the ignition and fire the wide gap plugs.
If you Must run the Alternator use the 2 12volts as if they are well charged it will reduce the power draw on the alternator and therefore the HP loss turning it.

Run Parallel not series

[FED 387]

if you run a MSD box and the voltage gets below 10.5 volts YOU MIGHT GET high speed misses---- the more the battery is charged the better off you are--Comp 387

[Alan Warman]

What about the black boxes that keep the voltage at a constant 16V even if the battery
voltage drops below 10V. We have one in our bracket car and it seems to work good, I can't remember who made it though. But here is one like on this web site.

techwest@techwestracing.com,

[magnumv8]

drooze.....just remember that the secondary battery still has to be able to START the car as well as the primary battery (NHRA regs)....and as a side note... I personally won't use "deep cycle" marine type batteries anymore because they do not like to provide FULL cranking power on a start up...they are designed to allow as much power as possible while going to a full discharge of voltage.....I burned up 2 optima yellow tops before I found this out and now will avoid the deep cycle batteries for that reason....

D L Rambo....