Battery under hood for race car

I'm putting the battery under the hood in the Duster since it makes the wiring easier for the EFI system. I think I can also simplify things by getting rid of the master cutoff switch with the battery under the hood. I looked at the rules and for a 10 second car it looks like a master switch is only required if the battery is in the trunk.

I'll be running a half size battery that only weighs 18 lbs so I don't think there will be much of a weight penalty. Seems to me like an easier way to go but most cars I see still have a full size battery in the trunk. Guess we'll just see how it works out. Anyone else running a small battery under the hood in a bracket car?

In NHRA Stock Eliminator the battery must remain in the stock location....... So, there are plenty of surprisingly quick small tire cars running with the battery up front.

I see Lithium in the driver compartment all the time now, but yet to see one under the hood.

I've seen stock eliminator cars with a master disconnect on the rear panel. That seems really nuts to me unless there is something else going on with the wiring that I don't know about. If they are running a hot cable all the way to the back just for a disconnect switch then it seems like it is less safe than not having a disconnect.

With a battery up front and no disconnect switch there isn't a lot of hot cable. For my car I'm going to use a Ford type solenoid so the starter cable is only hot while cranking. So the only hot line when the key is off is the BATT feed to the fuse panel under the dash.

I haven't seen that. I wouldn't think that NHRA would allow a battery in the driver compartment. Do they put them in a sealed box or under the floor?

Stockers may have a small battery (possible decoy) up front and large capacity or 16volt in trunk to run everything.

You cannot run a decoy battery up front - but you can add a battery in back. A guy was suspended for doing this in NHRA.

The front battery must be able to start and run the car. Rear battery for ballast, suspension control and keeping the ignition system at a strong 12V.

There is some Solid State disconnects now that seem pretty neat. You would have the actual disconnect up front with just some small wires running to the switch in the back.

Like this one from Motion RaceWorks.
https://www.motionraceworks.com/store/p841/BatteryKillSwitchKit

I do not know about NHRA legality though since it is not a mechanical disconnect.

i don't have the wiring diagram handy to post. but there is a simple way to use a switch at the rear using ten gauge and smaller wire.. it just controls the relay mounted in the front. it has to be a snow plow constant power style relay.

Been that way for years

My battery in the rear is only 11lbs....

On a stocker, a battery has to be in stock location, no disconnect is needed. Add a battery in the trunk, disconnect is manditory. I'll be using the 3 lbs lithium in the front ($375) and if I need weight I'll use steel plate and lead where needed.

Could any of these lithium batteries be used for a street/strip car? Lot's of street miles, say 3,000 per year.

Good question. A friend owns and runs an RV operation, sells these batteries. He has a ex pro mod Stattis (? spelling) with an 800 cu Chevy engine, he has two batteries (3x5x5), one for starting and one to run the electronics. No problems even with his previous Corvette race car whitch had them also. Just saying with the vibration and extreme conditions the race cars had-have, street driving should be a breeze.
Might add, he has a bank of these in his trailer to run lights and AC with solar panels on the roof to recharge. I was amazed how well they worked

Battery at the firewall.

Exactly.

which begs this question. what about the "factory" location[s] on several newer cars with the battery in the trunk or under the rear seat ? disconnect mandatory even though this is a factory location[s] ?

I put mine up front also just for simplicity.

Not that its fast but some of the SRT's are... my wife's 2011 Jeep Grand Cherokee has the battery under the front passenger seat

I run the Braille battery in my NSS car. The 17# only lasted about two years, so I went with the larger 21# this year.

Challengers are in the spare tire well.

Some stocker guys put a master switch up front to shut the front battery off as well. 9.99 or quicker requires a shut off in the back, regardless where the battery is. The switch doesn't have to be back there. The shut off does so everyone knows where to look for it. It can operate the actual switch with a cable. Master switch is a safety device. I wouldn't have a race car without it. Especially with a lithium battery. I want everything off when the car is not being raced.

Not sure why a battery up front is any better than a battery in the rear with appropriate cables running up front to a set of terminals, studs or pass throughs.

Only if another is added. Why? Can't remember NHRAs rational on this, maybe we can't make as good a battery box as the factory?
Shut offs have to be in the back of car so running two cables front to back would be, lets say, weird. Them wanting battery in stock location is to keep the car "stock appearing" only.

What brand of battery?

All of the charger,magnum,300,Challenger have the battery in the rear. But it is factory so I am sure no disconnect is needed.

What is the largest lithium(CCA) that is reasonable
to buy

Personally I think having a driver accessible power cut-off is a good safety feature. This could be accomplished with either a cable or continuous duty solenoid. With the solenoid it would only take a single ground circuit to the rear to control it. A second switch could be mounted in the driver compartment.
Doug

The ignition key is a pretty good power cut off that is driver accessible. If you want something that kills all of the power then that gets a lot more difficult. Especially with EFI and/or other electronic systems that don't want to be shut off hot.

I'd be interested to see how various folks are wiring up the EFI computers in race cars. Holley wants the ECU connected directly to the battery without a cutoff switch. I don't know if NHRA allows that or not. I suppose it depends on the tech person.

The car can be shut off by turning off the switched 12v to the ECU but the ECU is still connected to the BAT so there are still hot wires inside the car.

NHRA has never defined the master cutoff very well. The rules just say it should turn off the car but they don't say how much stuff can still be connected to battery power when the engine stops running.

Does the rule book specifically say if they battery is in factory location and the car is faster than 9.99 it requires a disconnect switch?

I don't believe it does. I just clarified this with a NHRA div 6 tech guy...quite a few hellcat Challenger/Chargers running 9's now with battery in the trunk in the factory location.

Rule book says "must stop all electrical functions". The only thing I ever have on the battery side of the master is the heavy wire running to the one wire alternator. Everything gets shut off.

Andy, go to the Painless Performance Products web site . click on accessories. PN# 50105 high output solenoid shut off. I think that could be wired into your key switch for total shut off.

That is true for a carb car. I don't think EFI cars are going to work that way. At least they don't if you follow the Holley instructions.

I don't think I need a cutoff switch since I'm not aiming for 9's and I have the battery under the hood.

I'm just going to use the key to shut things off. I'm also going to use a Ford type solenoid so the starter wire is only hot during cranking. I think that is pretty safe setup and should be NHRA legal for 10's.

Andy, what p/n is the Ford type solenoid that you are going to use. I am aware that there are several different ones. I've been wanting to change the 64 over to the ford sol. thanks

Finding the right solenoid has been a bit of an adventure. I started off with a typical Ford solenoid but then learned that I should use a diode suppressed solenoid to protect the ECU. So I got a diode suppressed one and then I figured out that I needed some way to make the neutral start function work. So now I'm shopping for a third solenoid. Good news is these things are cheap. I give my mistakes away to a buddy who is a Ford guy.......

When I put my battery in the trunk a couple months ago I used a Ford (single small post) type solenoid along with a Painless alternator disconnect on a panel at the battery.

My starter cable runs from the solenoid directly to the starter so it's only hot when cranking. The factory solenoid was left on the fire wall with a hot wire from the disconnect switch in the back feeding power to the post that the + cable was on. Everything except the alternator and starter get power from there. There is a wire from the "start" terminal of the factory solenoid to the single post on the Ford relay in the trunk. My car still has the three post neutral safety switch and wiring, it starts great set up this way.

Have you thought about one of those cable shut offs the See Doos use when a person is thrown off? Break away on a trailer comes to mind to also, but maybe not enough amperage. Then there's the fuel pump shut off on vehicles in an accident, this would shut down everything if driver was incapitated, might make a difference till safety personnel could get there. Good to have backup systems.

Most Stocker's run the battery in the stock under hood location as well as one in the trunk where the disconnect is required.

For the most part all dragster have their batteries up front, many in the nose area of the car. They have to have a cutoff at the rear as the rulebook states, they all usually also have one in the cockpit as well. If you have a door car there are a few in cockpit kits for battery shut off like this one from Lokar that use a Morse cable

https://www.summitracing.com/parts/lok-1330023

I wouldn't have another door car without a cable/lever assembly to be able to turn the master on and off from the drivers seat.

Is that for safety reasons or for when you get strapped in and forget to turn the switch on

Both. Plenty of situations where I may need to turn power on or off without struggling out of the car first.

A buddy of mine always runs a cable to the kill switch too. He says if something goes wrong he'll be the first one there.