The maximum current from the battery depends on the model. For the T523/T524, it could be up to 2A. It's about 600 mA for the LTE Cat M1 modules.
The current consumption peaks are for battery, or for VIN if there is no battery attached.
The charge current is defaults to 896 mA. If powered by USB, this amount could be returned by DPDM, for example when connected to a 500 mA USB port, the input current limit is reduced, which also lowers the charge current. It can also be controlled in software, see batteryChargeCurrent.
The battery voltage is 4.2V maximum, VIN is up to 17V. How can the currents be for both the battery and VIN?
For T523/T524 what operating conditions cause 2A current spikes? What is the duration?
Sorry, the 2A is at 3.7V. You can convert that to watts and back for your VIN supply.
The spikes are short, milliseconds, though there could be a number of them over a period of several seconds. Connecting to a tower with 2G is high-current, and the initial connection to the cloud is as well.
Does this initial connection have to be done with 2G and is the cloud connection current high because of 2G? Is it just 2G and not 3G / 4G / LTE / LTE Cat M1?
Is there a way of determining in software if VIN in disconnected and if the cell connection is 2G?
The current is highest for 2G, then roughly descending for 3G, LTE Cat 1, and the lowest for LTE Cat M1.
The T524/T523 do not support LTE Cat M1, but it will generally connect to LTE Cat 1 if available, and if not 3G, then lastly 2G only if there is no other connectivity available. The preference order for connectivity type is managed by the celllular modem hardware. We don't recommend attempting steer the connection based on RAT (LTE, 3G UTMS, or 2G GSM) because it's hard to do it reliably and not all hardware allows it.