I've been looking at batteries thinking of some new projects I want to try out... got me thinking, now many CCA do we really need to turn over the v6 and v8 engine? Referring to a healthy starter and motor, regular working conditions. What type of peak currents are we talking about here?

What about the same thing starting in cold/freezing conditions? Or perhaps an unhealthy starter?

Id actually measure it myself BUT my DC clamp meter doesn't actually have a peak hold function ... this is what I get for being frugal when buying tools.

I want to downsize the starter battery to the smallest size possible... perhaps a battery relocate or to just create some room under the hood for other things.

for smaller size battery, i would do a deep cycle agm. but bigger means more power.

That was the plan from the get-go...

The starter side of the system doesn't need to do anything other than start the truck...

I was trying to get away with a Odyssey PC680 (170 CCA) for the starter and the PC925 (330 CCA) for the house.

Perhaps dual PC925s if there is room in the tray but I want room for the ACR as well.

If I can confine my entire dual battery setup into one tray, then I can free up room for some other items I really want, specifically some air compressor(s).

Up here in Canada where is can get crazy cold, we use batteries that average 700-900 CCA's

you need 550 CCA with these vehicles . however in the cold north the battery used most preferred is 800CCA. reason is at zero F temp the battery output drops and the engine requires more amps to crank.

if you live in a warm area of cali perhaps 200CCA will work but the battery will get slowly damaged from the surge in amps on crank. the lead plates will get hot and will distort and short out over time so a shorter life.

I just had my battery tested, and it measured 473 CCA. I think the tester extrapolates CCA since the measurement was done at 68 degrees F, and the tester measures the battery temperature. It starts fine in moderate weather, but it was taking a long time at 0 degrees F a couple weeks ago. I use synthetic oil, so that helps make it easier to start.

I don't think battery size is something I would compromise on. I want the biggest possible starter battery, and if I ever go with dual battery I'd also want the biggest possible secondary battery. But I understand wanting to fit an air compressor and other things.

There must be an upper limit for the starter current, though. Does it have a fuse and/or relay? Does anyone know the rating for those parts? That might give some insight about it.

I just looked up replacement starters, and there are 1.4KW and 2.0KW options. 2 KW is 167A at 12V. If we assume the voltage drops to 10V when starting then 2KW is 200A. Of course depending on how it's rated, the peak current could be higher since the starter is basically a stalled motor momentarily until the engine starts turning.

To successfully start the battery needs to supply enough current to overcome the initial stall and friction of the engine being stationary, and then it also needs to supply enough current to get the engine turning long enough and fast enough for it to start. To cover all conditions the battery should be able to run the starter for a lot longer than it normally takes to start the engine. And it should have enough stored energy to start it several times without time to recharge in between.

Does anyone know how to tell if we have the 2KW or 1.4KW starter installed? Rock Auto lists both for the V8 engine.

Factory V6s use a 575CCA battery if I recall and all V8's and V6 Limiteds came with 710CCA units. As for actual cranking amps? That's a bit tricky because your initial strike amperage could be easily in the 500+ amp range, sustained cranking is probably between 150~200amps if I recall; but it's been a long while since I played with that kind of stuff.

I would find a better way to relocate the batteries or something rather than downsizing reserve capacity or cranking amps; it's better to have a larger margin with batteries than not enough when you need it.

BlackWorks' numbers seem about right to me. Car manufacturers size their batteries and starters for reliable starts down to at least -20F, so if you live in sunny California and are willing to live a little closer to the edge, I'm sure on most 70 degF days 150CCA would get you going, but I personally wouldn't cut it that thin.