Battery Size?

"And guys, I've already figured out you can't drill holes in a battery..."

Spoilsport.  We could have an entire thread on that...

Ok, Bob, you just made my evening!                                                                                 And I'm not going to tell you how I know...

While I hate to interrupt this frivolity with a serious answer, I'm a strong advocate of Odyssey gel-cell batteries in Speedsters (and dune buggies).  They're small (7.2"L x 3"W x 6.6"H), light (~14lb), and can be placed in any orientation except fully inverted.  As they are AGM they do not outgas toxic fumes so they can be placed in the passenger compartment.  I had great luck with them lasting years.  What's not to love?

@Lane Anderson posted:

What's not to love?

The price tag?

I believe @DannyP uses a U1 lawn-tractor battery. They're tiny and dirt cheap, and available in Lithium Ion for about $125 (if that rocks your world). They're all over with 300+ CCA.

Use a gear reduction starter and it'd be more than enough for whatever you're trying to do. I'll be buying this one next time I need a battery. It weighs 3-1/2 lbs.

If you can find something lighter, Al -- go for it. If you're dead set on spending Odyssey money on a battery, this one has 900 CCA, weighs 9 lbs, and costs $280. The general rule of thumb is that you need about 2 CCA for every cubic inch of displacement, so this one should turn over a 12:1 BBC with a tired starter.

i remember buying a high torque starter that fits into this thread somehow.

A very good point, @Stan Galat and @barncobob- a gear reduction starter brings the starting power requirement down considerably and and as such allows a smaller battery to be part of the package.  I'm guessing a stock Type 1 alternator as well?

@Lane Anderson- that's alright, we had to get to the task at hand sooner or later!    That's exactly the kind of info I'm looking for.  Were you running driving/fog lights or anything drawing extra power in your Speedster (which still comes to mind when I think of the classic red Speedster)?

Stan- that Ionic battery you linked to is wicked!

Any one running an agm battery- is a diode for slightly higher charging voltage necessary?                                                                                                                                  And any one running driving lights- halogen or led?  Any issues with power draw on halogen bulbs?

I guess I’m lost what you’re looking for, Al.

The total (constant) current draw on any electrical system should never exceed the capacity of the alternator. If lights or any other constant load draws less that the alternator can put out, then it really doesn’t matter how tiny the battery is, because the battery is just acting to absorb the peaks and fill in the valleys of load and capacity. It’s just an energy sink, if you will It obviously needs to be able to crank the car over, but as long as it’s big enough to do that and absorb peaks and valleys, it’s fine. An analog car will run on the alternator, without any battery at all  

If loads exceed what the alternator puts out, you better have a battery big enough to carry the loads without the ability to recharge for as long as the loads are on.

Big ol subwoofers (only drawing peak load occasionally): fine, get a big battery. Headlights (drawing continuously more than the alternator can put out), no battery in the world will work well.