AGM and golf carts vs. Lithium Battery Test
I just happened across a "Mortons on the Move" YouTube video. "Don't waste your money on batteries". (Can't figure out how to link it on my phone.) Very informative info and test comparison between go...
Forum Discussion
These 'value comparisons' based on the cost of the battery/the number of cycle are kind of silly. First, I sincerely doubt that the manufacturers have actually done any where near the testing necessary to know what the cycle life of their cells are when those cycle lives are > 2-3000. They model it, and while these models could be accurate, they have a lot of parameters that need to be assumed.
Secondly, and most importantly, so called 'cycle aging' is only one of the ways that a battery ages. There is also something called 'calendar aging' which is the rate at which a battery ages as a function of time, regardless of whether it is being used or not. This is a factor for both lead-acid and lithium batteries. It is not so important for lead acid batteries as they typically degrade from cycle aging before calendar aging becomes an issue. However if you are going to advertise a battery with a 10,000 cycle life, then calendar aging is absolutely an issues. This had been researched for LiFePO4, and the rate of aging is a function of temperature (mostly) and storage state of charge (less so). For a 100% charged LiFePO4 battery stored at 30C the calendar aging is around 4% per year. If you take providing 80% of rated capacity as the metric for battery failure, then even an LiFePO4 battery will only 'last' 5-6 years, regardless of the number of cycles.
Assuming you are cycling your battery hard every day (365 cycles) then there is really not much advantage to a battery that provides more than 2-3000 cycles, as calendar aging will kill it long before cycle aging. For most of us here that may only deeply cycle our batteries 50 - 100 times a year, then 1000 - 2000 cycle is plenty.
Now there are plenty of other reasons to like lithium batteries, such as lower weight and volume, flat voltage curve, simple charging profile etc. But just dividing the price by the cycle life is not an honest or accurate metric.
Secondly, and most importantly, so called 'cycle aging' is only one of the ways that a battery ages. There is also something called 'calendar aging' which is the rate at which a battery ages as a function of time, regardless of whether it is being used or not. This is a factor for both lead-acid and lithium batteries. It is not so important for lead acid batteries as they typically degrade from cycle aging before calendar aging becomes an issue. However if you are going to advertise a battery with a 10,000 cycle life, then calendar aging is absolutely an issues. This had been researched for LiFePO4, and the rate of aging is a function of temperature (mostly) and storage state of charge (less so). For a 100% charged LiFePO4 battery stored at 30C the calendar aging is around 4% per year. If you take providing 80% of rated capacity as the metric for battery failure, then even an LiFePO4 battery will only 'last' 5-6 years, regardless of the number of cycles.
Assuming you are cycling your battery hard every day (365 cycles) then there is really not much advantage to a battery that provides more than 2-3000 cycles, as calendar aging will kill it long before cycle aging. For most of us here that may only deeply cycle our batteries 50 - 100 times a year, then 1000 - 2000 cycle is plenty.
Now there are plenty of other reasons to like lithium batteries, such as lower weight and volume, flat voltage curve, simple charging profile etc. But just dividing the price by the cycle life is not an honest or accurate metric.
