lithium ion car and motorcycle batteries

Just a smattering of observation in no particular order:

- The reserve capacity in a standard car battery has more to do with the ability to crank the car at very cold temps and when really hot and the engine compression is high... moreso than being able to run anything in normal operation. Batteries lose their ability to produce current when cold and a higher reserve will limit that reduction. Yes, I know, CCA means 'cold cranking amps', but unfortunately, CCA's have become a marketing number more and more and less of a useful rating (to me). The reserve has been a better reflection of this ability.

- Lithium batteries have a much higher discharge rate ability than lead-acid. So they can advertise very high CCA's versus reserve capacity. So judging a Lithium battery by CCA's is going to be VERY misleading versus our CCA standards for lead acid batteries. And which means they go like crazy for a bit and then just die with little warning.

- This high discharge rate also means more potential danger in a short circuit in the car. The lithium batteries can deliver a lot more energy into a short than a lead acid battery. If you do this, make sure you have a good fusing system in the car. Using a lithium battery with old wiring seems like a pretty bad idea.

- Lithium ion batteries have around the same max temp rating as lead-acid, about 40 C. But putting your batteries in a closed box may be bad; you'll need some real air venting in your fake enclosure.

- Computer and aircraft battery fires with these batteries are for real. But, lead-acid battery internal shorts are for real too, and can lead to a lead-acid battery fire. Both usually result form similar causes: internal shorts.

- You are correct to think that paralleling 2 or 3 batteries will double or triple the AH capacity (AH means amp-hours). It just involves more maintenance of the interconnecting cables so that part is less appealing.

- I would be most concerned with the charging system and how it will charge the Lithium battery. The voltage is not matched quite right for a lithium battery so I would expect it to never be charged right. Standard older car charging voltage fluctuations and limits are not right for Lithium batteries and you will be almost certainly overcharging the Lithium battery, stressing it, and risking internal ruptures. This alone makes this Lithium idea a non-starter, if you pardon the expression.

- In line with the above: Now, I do not know why these batteries are now being offered for motorcycles and cars so that bears some additional reading. Perhaps they are one of the different Lithium types, or take advantage of newer auto charging systems' tighter voltage tolerances.

- BTW, having a light load in the cars electrical system has less to do with this than the OP seems to be thinking. That load is mostly sourced from the alternator when running, except when very heavily loaded or idling a lot. So, unless you are running the lights and heater blower a lot or idling a lot, the battery is just sitting there.