My Tank 4000 and Yeti 4000 show different SoC in the App. Is my Tank broken?
TL;DR There is likely nothing wrong with your Tank or Yeti. The first time you connect a Tank Pro 4000 to a Yeti Pro 4000 they will not equalize to the same SoC(State Of charge) on their own even though their pack voltages have equalized to the same value. Connecting a power supply and charging the Yeti+Tank to 100% and then discharging to 0% will smooth out the SoC differences.
But Why? Pack voltage and SoC do not have a strictly linear relationship. Factors like which of the two packs was at a higher Voltage, how far apart they are in voltage, were either of the packs in a high enough SoC that CV mode applies instead of CC... will all influence how the SoC changes for each pack during equalization BETWEEN the two packs.
Equalization only ensures the Voltages are equalized. During equalization, the Yeti takes priority on receiving a charge over all other Tanks. This pre-charge is done at a low rate to protect cables from melting at what could be crazy high current flow.
Once a pack has been in pre-charge long enough to have the same voltage as another, it will transition to equalizing at full current limits so it does not take days to even out the power and have all packs in the system ready for use together as a unified battery.
Once the packs are equalized, running a few charge and discharge cycles will help smooth out the SoC differences because BOTH packs are able to hit 100% AND get full voltage and then drain to 0% AND empty voltage at the SAME CURRENT.
From there on SoC and Voltage should be very close for the Yeti and Tank.
If this FAQ does not seem to help you resolve an issue with your system, please visit our contact us page.
Comments
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On a related note. Here is a table that we put together to show when equalization will be fast and when it will take time:
Notes:
(1) Slow because the Yeti voltage is rising away from the Tank voltage
(2) Fast because the Yeti voltage is rising toward the Tank voltage
(3) Fast because the Yeti voltage is falling toward the Tank voltage
(4) Fast because the Tank will power the loads and its voltage is falling toward the Yeti voltage
