Basics of Lithium conversion... I'm lost!

I think you are starting with the assumption that a lithium battery is necessarily a much higher up front cost than a lead acid battery, which is no longer really true. A pack assembled from cells is around $650 - $750 for 280Ah. Without even getting into the 50% vs 100% DOD and number of cycles, this is about the same upfront cost as 300Ah of mid-grade AGM batteries, and is clearly much less expensive over the lifetime of the battery. Even the drop in batteries can be had for as low as $500 per 100Ah, which is about 2x the cost of AGM, but then if you do consider usable capacity, the upfront cost is still about the same.

I have had no issues with my small battery BMS, just as I have had no issues with my solar controller or battery monitor. Unlike a BMS for a car that is using lithium cobalt batteries and charging/discharging at rates up to 10C for 200,000 miles, these small controllers are not complicated devices - so I am not sure why you would think there is an issue here. Furthermore, if you go the DIY route, replacing the BMS if it were to fail would be around $70.

In my case the justification is not 'heavy continuous cycling' but weight, lifetime cost and simplicity. If you can get a McClaren (with Toyota reliability) for the same price as a Kia, who wouldn't want one?

MEXICOWANDERER wrote:
Have you examined a battery management system for an automobile versus a battery management system for a six hundred dollar lithium battery? Apples and oranges. Better said a durable circuit versus chew and spit.

The navy and air force refuse to replace AGM batteries in military aircraft because it is not feasible to construct chew and spit management systems for small batteries with extreme high reliability.

A half dozen years of actual use is a ridiculous claim for reliability. Lithium batteries are said to yield six thousand or more cycles of usability. Tell me, how many years of service is that? Like with vaccines or tires or light bulbs, only real life and real time consumer testing and use are going to reveal the durability of small battery BMS systems after six years, after ten years after twelve years. If you cannot get six thousand cycles out of an expensive battery then what is the use of spending thousands on a battery bank? How many cents per cycle is rational or irrational?

I view this the same way as I do 19.5" four hundred dollar tires on a daily commuter car. They give far less mileage than a conventional tire, are more easily punctured, more difficult to service and spend 0.000% of the time at the rated limit.

What the hell good is a lithium accumulator in a weekend warrior or even 2-week campout RV? They may (or may not) last ten years. In 10 years RV's may have something akin to wall packs making conventional batteries ridiculous.

Immediate use involving heavy continuous cycling is the sole justification for spending thousands of dollars for a specialty battery bank.

Of course there will always be folks who glad hand others into thinking a thousand horsepower McLaren is absolutely necessary for 5 mph stop and go. My lights will shine just as bright as yours :)