Purchased a LiFePO4 12.8V 8AH battery to use on the go kart as it is light weight.
Fully charged using a LiFePO4 charger, but is not able to crank the starter motor of a go kart.
Smaller 12V 7AH lead battery from century has no problem starting the kart. Can someone please advise if this is common across all Lithium batteries ?
“Lithium” batteries actually encompass quite a few chemistries and compositions. For instance, a LiPo pack designed for low internal resistance is rated for 75C continuously, where C is the capacity in Amp-hours:
So that tiny little 4Ah pack can output 300A! (though I wouldn’t be game to try it)
To contrast that, the LiFePo4 (also called “Lithium Phosphate”) cell you purchased is only rated to 28A for 30s, with the BMS (battery management system) cutting off the power at 28-38A:
That info was pulled from the datasheet on the product page.
A comparable lead acid cell is rated at about 100A for short bursts like starting an engine:
Generally, car starters need about 50-250A to crank depending on the size of the engine, so even a small go-kart starter may overwhelm a LiFePo4 cell.
Please let me know if this spurs any followup questions for you
To get into perspective a small 1.6L car would probably have a battery with a CCA (Cold Cranking Amps) of some 450 and probably require 200 or so amps to start. My car (2L diesel) requires a battery of 750CCA or at minimum 650 Although I think it is only about 80AHr it is still quite a large battery. What I am getting at is the important number here is the CCA, irrespective of AHr.That is the number of Amps that can be delivered for a short period.
As James says, Horses for Courses.