Put my 505 12.5 compression motor in after dyno testing. Battery is in back with kill switch. Had no problems with small block turning over. This motor I know is harder to turn over with high compression but it really draws the amps down and does turn slow after a few turns. Do I need a 2 battery set up?

I haven't used two batteries in over 40 years. Properly grounded system, good 12 volt battery, and 5 or so years ago I added an alternator and will never run a car without one again.I put a slow charger on my car at home every 3-4 weeks just to top it off.

Some good reading



https://board.moparts.org/ubbthreads/ubbthreads.php/ubb/showflat/Number/8385983/site_id/1#import

You need larger cable going to the starter.. if
you KNOW your battery is good then its not a issue
2 batteries gives you longer cranking.. doesnt change
the voltage... fix the starting system and you wont
need two batteries

If you have a good battery and the right sized cable, there's no need for 2 batteries. Unless you race w/ no alternator and don't take a battery charger to the track w/ you.
My car just has one battery and a 1/0 cable. Has always worked great w/ the 11:1 572" hemi and the previous 14.5:1 446" wedge.
FWIW...the Camaro I drive has a 14:1 436" sbc and has no alternator, but does have two batteries. It still cranks fine on just one battery, but lasts longer b/t charges when racing w/ two.

Me too. Its in the cables or connections. Two batteries is just adding time to how long the system can provide a certain voltage and amps. One battery is plenty if the rest of the system is up to it, ten batteries won't help if it isn't.

I run 2 gel batteries and love if for extra cranking(yes I have bad dog cable)and the added ballast plus car went quicker w/2..........

I run two batteries cause I have women drivers....

I run two batteries, for years we've had starting issues slow, lazy to turn over sometimes barely catching. So I put two batteries in there to help. still the same issues. I ran ground cables from the battery to the block still the same. I put higher cranking capacity batteries in there, still the same. Motor would spin ok when the batteries where charged so I put a bigger alternator in there, still the same. OK I thought thats just the way it is. Since I run an MSD grid, electric waterpump, fuelpump, fans, etc.I put up with it and made sure the batteries are charged before every run. I put a small logger system on it and the voltage would drop progressively to 12.5V by the end of a run. I also had a cheap battery charger that went faulty, it would damage the batteries when connected (the output wave form was incredibly coarse with a 6 - 20 V wave as seen on a 'scope)
I found out what the main problem was only a few months ago, I've always run a narrow alternator belt so it's sits low in the pulley. It was so narrow it was running on the bottom of the groove and slipping when hot, not charging. All the symptoms made sense, don't overlook the simple stuff as is my way sometimes I over complicated the problem.
The wiring is also a mess, not dangerous but unnecessary lengths / runs / borrowing lives done over the years as I've added stuff to the car. So a total re-wire is on the list for this winter, I'll be using some of the tips I've learned from here regarding wiring and grounds etc for sure

I run two batteries and an altrnator. Good insurance if you're going round robin in late rounds. Helps with cool down with high draw fans. Almost all cars are drivers side heavy. Mine has both batteries placed in the right rear. Car is still 54% on the nose but right to left balance is with-in 1%. Removing the forward placed battery (45lbs) resulted a pick-up of .02 on a good track.
Doug

We run a single 12v 1100 cranking amp AGM battery in the trunk, with a good alternator that charges ~14 volts at idle. The distributor is locked out at full advance and on rare occasions can cause the motor to turn hard. In those events we turn the ignition off, let the starter get a run at it, turn the motor a couple cycles to unload it, then turn the ignition on while its cranking and it fires. We have yet to be stranded or miss a round due to the battery with this setup, and only use the battery charger to top it off after sitting for a while.

For us the key has been having a good battery, alternator, and cabling. The current AGM is 3 years old and still tests out good, but we're swapping it out due to the abuse it goes through.

Oh - this is with a Mopar Performance mini starter too. Both the 13.5 580ci and now the 12.1 408ci.

Take care.

You need two if you want to hide nitrous in one.

Wow dvw that trunk is a mess, you really know how to make a guy fell flat, wish my 63 trunk was that nice