I've generally preferred dual battery configurations for backup and extra juice to run things like snow plows or winches on my various vehicles.

I was curious though - why not use a lithium primary batter with 2-3 times the amp hours of a lead acid and the same weight and size, and back it up with a micro-start type miniature backup lithium battery. It seems like this would be a better solution for at least the later 5th gens like mine without a good place to locate a second battery.

Anyone using a lithium starter battery or have experience with them for winching use? Can they reliably deliver 400 amps for 20-60 seconds without failing?

And just to take this one step further out of the box - it could be very do-able to build a custom batter out of cheap 18650 cells and shape the pack to go just about anywhere - like in the rear side panel or even underneath the vehicle and eliminate the battery under the hood to make room for a nice compressor or similar.

Thoughts? Anyone go this route?

I doubt anyone has gone this route as my undestanding is the LI car batteries are 4x+ the price of a standard lead-acid. But I like the idea

I have to admit after looking around a bit - they are really $$$ for a pre-made drop in car battery. Pretty easy to spend $1,000 on a battery. Granted they are about equal to 3 lead acid batteries in capacity, that's a lot of cash. Probably much better to spend the money on a high output alternator and stick with what we've got.

It nerver hurts to think outside the box, but I am with you.....I think my ideal set up would be dual battery, maybe high capacity alternator......dont think I need it with current equipment, a shore charger for when camping in non remote areas and then the cats meow would be something like a honda 2000i or smaller generator dissabembled and built into the under carraige to run off the gas tank if you really really wanted extra power that 2 batteries couldnt give through the night....

Tesla, the company who make electric cars are getting into portable power battery packs. It seems they have a good business model and are working on storage for housing with solar electric. Maybe, they will eventually make something a little bit smaller.

How do the lithium batteries stand up to abuse? Can they take a beating like an AGM can?

I don't think it is as easy as just bolting something into the vehicle. Lion have a very different charge profile and I'm sure there would be at the least an electronic circuit required and possibly a completely different alternator and charging system. There is also the issue of crash worthiness as Lion are a potential bomb if the outer covering is broken. Without proper design, I would steer clear.

They are already available as direct swaps for regular batteries. Mostly used in racing and boating applications where weight is more important.

As for a custom pack somewhere underneath - probably would end up a lot like a hybrid. They all use the same cells. Sub-c or 18650's I believe. It would require the batteries plus a charge controller and a discharge disconnect - cant run em all the way to zero. Those are both readily available.

I do see a concern with safety, but IMO if they were protected and in a proper sheilded steel housing I think they could be made very safe. At least as safe as having 15 gallons of gasoline in a tank down there. It's also pretty dangerous. If you really wanted to get cute with safety you could attach the battery with a plastic hardware set so that in case of fire it would melt and drop free of the vehicle.

LI batteries are expensive that usually have some sort of microprocessor built inside of them.

The 2015 BMW M3/M4 comes standard with an LI battery (weight savings). I priced this battery and MSRP was $1200 for BMW OEM.

outside of the previous comments, what is the viability in temps below say 32F, 0F, -20F?

once November hits, we stay below 32F, some weeks we drop down in the single or negative single digits and hit snaps of 1-2 weeks of -20F.