The Grin Technologies Satiator used to charge the batteries was set to the same Amps and Voltage values as the OEM charger. For the 36V Easy Motion 11.6 Amp*Hour battery, the fully charged voltage was 42V and the charge current was 2 Amps. The Satiator uses the common 2 stage charging scheme to achieve a full charge for a Lithium Ion battery. In other words, it charges at constant current, 2 Amps in this case, until 42V is achieved and it then applies a "saturation charge," by gradually decreasing the current while maintaining the 42V. The maximum voltage, charging amperage and battery type can be set by the user. Charging is complete when the current drops below a pre-programmed low value. If one were to cease charging immediately after the voltage reached 42V, then the battery would be expected to contain only ~85% charge, as described in the Battery University website above by
@Ann M. However, that is not the case here, as a saturation charge was applied by the Satiator automatically, ensuring a "full," charge.
The table below shows the cumulative Amp*Hours of charge accepted by the battery at each voltage value. As can be seen from the table, the highest value, 9.7 Amp*Hours, is ~84% of the stated capacity. The battery was ~7 months old at the time of testing. The other Easy Motion battery evaluated yielded nearly the same result, 82%, and was ~3 months old at the time of testing.
It seems like possible explanations based upon the feedback above are some combination of the following:
1.) Not all of the capacity is usable because of the low voltage cutoff of the BMS, as mentioned by
@JoePah
2.) Stated capacity assumes a "full," charge above 42V.
3.) Degradation of battery after 3-7 months of use.
4.) Ideal case/nominal, ratings for battery.
5.) cell to cell variation tripping the low voltage cutoff, as mentioned by
@George S.
I'm curious if others have observed the same phenomenon with their battery packs. Per the video above and the Kinaye website, the Sonders and Kinaye batteries delivered 94% and 92% of their stated capacities respectively when discharged from 42V to 32.6-32.7V. This represents a discharge of ~1.6V more than the Easy Motion battery, so could explain some of the lower actual vs stated capacity of the Easy Motion battery. However, the video tests represent the capacity delivered, vs the results in the table above which only show the amount of charge accepted by the battery. During discharge there could be losses due to heat etc., so that the Easy Motion batteries tested could deliver even less than 82-84% of stated capacity.
Regarding the Satiator question from
@Jonah it can be used with a wide variety of battery types: Li Ion, Lithium Iron Phosphate, Lead Acid etc. However, it only comes with XLR and Anderson connectors. If your charger port is of a different type, the Satiator will not work out of the box. However, it is fairly easy to cut the wires on an OEM charger and solder male and female XLR connectors to the resultant wires ends of the OEM charger. In this way, either the OEM charger or Satiator can be used.
