Only needs to run continuously for maybe 2 minutes, which a decent car battery will do just fine. But at the end of 2 minutes the battery is pretty spent. I then need to run it for another 2 minutes maybe 5 minutes later. I will need to do ~10 runs. I'd prefer not to do it over 10 days (recharging 1 battery) or use 10 batteries.
Is this a one time thing (10 runs total) or will it be 10 runs per day for ever?
Probably not one time, but rare. Once or twice a year maybe.
Maybe its time for a mule, block and tackle. ;)
Better check the duty cycle of the motors! They may tell you you can run back to back pulls that quickly.
44
It's hard to design with a bunch or maybies and probablies.
what is your load? what is the duration of your load?
At the risk of being accused of stating something redundantly, Marine starting batteries are cheap and way the heckfire more appropriate for what you say you probably want to do rarely than "car batteries". I am curious, and I do not mean to pry... can you tell us?
"What's he building in there? What the hell is he building In there? He has subscriptions to those Magazines... "
Tom waits 1999
If you can stand the extra time and maybe space, why not ad a pulley or two and cut your load in half or ....
Pulling a 10,000# pound load for ~ 2 minutes.
Can't cut the load - it's a motor test. It has to be loaded.
I still think a bank of batteries is the cheapest, easiest, most appropriate way to get that kind of DC power. Using big batteries (such as deep cycle boat/semi/tractor batteries) with a charger on them, it seems like you could get by with less than 10 batteries. If you can't afford a better battery charger and feel like rigging something up, you could always do the AC motor-> car alternator method and get pretty fast recharge times. More batteries or more charging, pick your poison.
Bryce
This method should be good for 1.21 GigaWatts.
DILYSI Dave wrote: Pulling a 10,000# pound load for ~ 2 minutes. Can't cut the load - it's a motor test. It has to be loaded.
That sounds cool!!!
Look up something called the "Bad Boy Charger". Its the DIY simplist crudest battery charger you can imagine. Its possible it could be used to charge the battery bank for quick recovery.
Ten run once or twice a year, just borrow/rent a diesel truck. Fords run dual batteries in a lot of theirs. The alternator on them charge a 140 amps. That should be enough to get your runs with out buying anything.
Rent an electric fork truck..Big battery high curent and not yours..
Forklifts run at 36VDC. Already checked. :)
DILYSI Dave wrote: Forklifts run at 36VDC. Already checked. :)
wrong! some are 36v, but others are 24v, and electric walkie pallet jacks frequently have a 24volt power pack made of 4 6volt deep-cycle batteries in series, with a built in charger.
rent one of these or something similar, take the cover off of the battery pack and have at it. If you do rent one, specify lead acid batteries, not industrial of maitanace free batteries. maitance free batteries wont hold up well to that kind of use, and an industrial battery will be difficult to tap 12v out of. If you were going to be doing this frequently I would sugest just buying a used battery pack from one of these 
Alright - Four Optima Deep Cycles and a stout charger have been sourced. Thanks for the input!
DILYSI Dave wrote: Alright - Four Optima Deep Cycles and a stout charger have been sourced. Thanks for the input!
Good Choices! T the risk of stating the oblivious, Something like 1 or even 0 gauge cable and Fuse the batteries away from whatever those suckers could make molten. I used a similar set-up: 8 600 amp deep cycle batteries in parallel with a honda eu1000 gennie as the recharger to rock the sound system at out door dance parties. When not in use, I had the whole thing hooked up to a 20watt solar panel with a deep cycle battery charge controller keeping everything right. You can have batteries grouped and they will charge back up together if they all go on-line together from new. I found that I needed to move the + and - around every now and then because the battery terminal connected directly to the load would draw down a little faster than the other ones. Mayby i was doing something wrong, but i would move the positive occasionally and it worked. If the battery charge levels get away from each other you can damage them and the whole system cascades into a battery ruination frenzy. I eventually put voltmeter on them permanently to make sure everything was cool. I ruined a few hundred dollars of batteries to learn these rudiments, there is, of course, lots of good info on-line: http://www.windsun.com/Batteries/Battery_FAQ.htm#Major%20Battery%20Types
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