not super light. i needed something with reserve to run fans and stuff at track. this is designed for high compression motors, with a 74 minute reserve. 4.75 x 6.5 x 7 20# cool thing about this one is it has real deal 3/8 threads so you can bolt side post terminals right up. i really didnt like the designs of the others that use a 6mm thread. im sure they are fine, im just paranoid. saves me 13# over my redtop optima.

I don't even want to know the weight of my 31 series truck battery but the 180 minute reserve sure is nice.

haha, yea. thats a huge battery.
they arent light. hope its in the back of the car. im sure it is.
im always adding weight to the car for bracket and index races, but its nice to go fast when i wanna run all out.

ive been tossing around the idea of getting a 16/12v battery from batteriesareus.com and ditching my alternator. (for now)
it would be super nice to make a 3-4 passes without even having to worry about the battery!

If I ever get around to installing my belt driven vacuum pump, the alternator goes because I don't have the room for both. I have a small generator I can use to keep voltage up while the fan and water pump are cooling the engine down between rounds. It's still nice having full voltage while going down the track

i dont care if i raced a rail or an altered, i would have some kind of alternator too keep the battery charged.
charging batteries between rounds is not for me.
i like low maintenance. crank and go. already enough going on and stuff to do to worry about the car not starting.

I have a mini alternator but don't know where I could mount it. My home made front motor plates prevent me from putting it low beside the block.

On the driver's side is the belt driven fuel pump. On the passenger side, I have a 10SI alternator mounted backwards and down low enough that the idler arm doesn't interfere. Each has it's own belt and the water pump is electric so I can't use it as an idler to run another belt up higher for the vacuum pump. There isn't enough room to use a single belt for the alternator and vaccum pump without installing at least one idler somewhere so that a belt covers more than 90* of any pulley.

I also like having an alternator but unless a solution can be found to have the vaccum pump and alternator, the large battery will win out and the alternator will go. I probably won't get around to doing more fabrication work until after the race season now.

go buy a mandrel and run it off that, it'll move the alternator 5" forward easily.

it is my understanding that those 16/12v batteries can be run 10-20+ passes and STILL read 15v! if thats the case, i could just charge the thing when i get back home.... would drop the ~10lbs of weight as well as the drag on the motor, and the battery would still be hitting the electronics with the same amount of juice or more than the alternator would be.

as far as charging, best thing ive seen to use is the quick disconnect mounted under the bumper or whatever. pull in the pits, and plug it up to the charger in 5 seconds.

Another facet to considered is that ignition systems are not light bulbs-on or off. Instead the output of an ignition system is greatly affected by the voltage available on the primary side. A 12V battery fully charged is 12.6 volts. ( Higher readings from post to post are obtained after heavy charging, but this is called surface charge and disappears in seconds after a load is applied.) The window of performance for most electronic ignition is 12 to 16 volts with performance advantages at the higher voltage, Performance drops dramatically below 12.0 volts. Running without an alternator (battery only) starts the electrical system out at 12.6V and it goes down from there which, in turn, operates the ignition system at the low end of the performance range.

Some very good reading here: http://www.hotrodssuperstore.com/faq.html

I do run a mandrel. The fuel pump is on the outer pulley because it won't fit anywhere else. With the 10SI alternator flipped around, it uses a pulley mounted right beside the balancer.

As for voltage and ignitions, we're not talking long term use like in a street vehicle. Take off the alternator belt of a street vehicle and providing you're not using a lot of accessories, you can drive for at least an hour just on battery power feeding the ignition.

Although it's better to have charging voltages, most ignition systems will work fine down to about 10 volts. My delay box starts flashing numbers at me if voltage drops below 10 volts.

That's why you want a battery with a high reserve capacity. It will maintain a higher voltage for a longer time. Even if you have to constantly start and stop the engine going through the staging lanes, there will still be adequate voltage to run the electrics for 5-10 minutes to make a run and get back to the pits.