Fixes multi-cell chargers (#27357)

* Update multi_cell_charger.dm

* Update wall_cell_charger.dm

modular_skyrat/modules/colony_fabricator/code/appliances/wall_cell_charger.dm

@@ -7,7 +7,7 @@
 	circuit = null
 	obj_flags = CAN_BE_HIT | NO_DECONSTRUCTION
 	max_batteries = 3
-	charge_rate = 750
+	charge_rate = 900 KILO WATTS
 	/// The item we turn into when repacked
 	var/repacked_type = /obj/item/wallframe/cell_charger_multi
 
@@ -33,7 +33,7 @@ MAPPING_DIRECTIONAL_HELPERS(/obj/machinery/cell_charger_multi/wall_mounted, 29)
 
 /obj/machinery/cell_charger_multi/wall_mounted/RefreshParts()
 	. = ..()
-	charge_rate = 750 // Nuh uh!
+	charge_rate = 900 KILO WATTS // Nuh uh!
 
 // Item for creating the arc furnace or carrying it around
 

modular_skyrat/modules/multicellcharger/code/multi_cell_charger.dm

@@ -10,11 +10,12 @@
 	power_channel = AREA_USAGE_EQUIP
 	circuit = /obj/item/circuitboard/machine/cell_charger_multi
 	pass_flags = PASSTABLE
-	var/list/charging_batteries = list() //The list of batteries we are gonna charge!
+	/// The list of batteries we are gonna charge!
+	var/list/charging_batteries = list()
+	/// Number of concurrent batteries that can be charged
 	var/max_batteries = 4
-	var/charge_rate = 250 KILO WATTS
-	var/charge_rate_base = 250 KILO WATTS// Amount of charge we gain from a level one capacitor
-	var/charge_rate_max = 4000 KILO WATTS// The highest we allow the charge rate to go
+	/// The base charge rate when spawned
+	var/charge_rate = 375 KILO WATTS
 
 /obj/machinery/cell_charger_multi/update_overlays()
 	. = ..()
@@ -93,15 +94,27 @@
 	if(!charging_batteries.len || !anchored || (machine_stat & (BROKEN|NOPOWER)))
 		return
 
-	for(var/obj/item/stock_parts/cell/charging in charging_batteries)
-		if(charging.percent() >= 100)
+	// create a charging queue, we only want cells that require charging to use the power budget
+	var/list/charging_queue = list()
+	for(var/obj/item/stock_parts/cell/battery_slot in charging_batteries)
+		if(battery_slot.percent() >= 100)
 			continue
-		var/main_draw = use_power_from_net(charge_rate * seconds_per_tick, take_any = TRUE) //Pulls directly from the Powernet to dump into the cell
-		if(!main_draw)
-			return
-		charging.give(main_draw)
-		use_energy(charge_rate / 100) //use a small bit for the charger itself, but power usage scales up with the part tier
+		LAZYADD(charging_queue, battery_slot)
 
+	if(!length(charging_queue))
+		return
+
+	// since this loop is running multiple times per tick, we divide so that the total usage in the tick is the expected charge rate
+	// 4 batteries can no longer magically each pull 4MW per tick (16MW total per tick) out of thin air like in the old system
+	var/charge_current = (charge_rate / length(charging_queue)) * seconds_per_tick
+	if(!charge_current)
+		return
+
+	for(var/obj/item/stock_parts/cell/charging_cell in charging_queue)
+		use_energy(charge_current * 0.01) //use a small bit for the charger itself, but power usage scales up with the part tier
+		charge_cell(charge_current, charging_cell, grid_only = TRUE)
+
+	LAZYNULL(charging_queue)
 	update_appearance()
 
 /obj/machinery/cell_charger_multi/attack_tk(mob/user)
@@ -115,14 +128,9 @@
 /obj/machinery/cell_charger_multi/RefreshParts()
 	. = ..()
 	charge_rate = 0 // No, you cant get free charging speed!
+	var/charge_rate_base = 250 KILO WATTS
 	for(var/datum/stock_part/capacitor/capacitor in component_parts)
-		charge_rate += charge_rate_base * capacitor.tier
-		if(charge_rate >= charge_rate_max) // We've hit the charge speed cap, stop iterating.
-			charge_rate = charge_rate_max
-			break
-
-	if(charge_rate < charge_rate_base) // This should never happen; but we need to pretend it can.
-		charge_rate = charge_rate_base
+		charge_rate += (charge_rate_base * capacitor.tier) / 4
 
 /obj/machinery/cell_charger_multi/emp_act(severity)
 	. = ..()
@@ -137,6 +145,8 @@
 	for(var/obj/item/stock_parts/cell/charging in charging_batteries)
 		charging.forceMove(drop_location())
 	charging_batteries = null
+	return ..()
+
 
 /obj/machinery/cell_charger_multi/attack_ai(mob/user)
 	return
@@ -163,7 +173,7 @@
 	if(charging_batteries.len > 1 && user)
 		var/list/buttons = list()
 		for(var/obj/item/stock_parts/cell/battery in charging_batteries)
-			buttons["[battery] [battery.percent()]%"] = battery
+			buttons["[battery.name] ([round(battery.percent(), 1)]%)"] = battery
 		var/cell_name = tgui_input_list(user, "Please choose what cell you'd like to remove.", "Remove a cell", buttons)
 		charging = buttons[cell_name]
 	else
@@ -186,7 +196,7 @@
 	name = "Multi-Cell Charger (Machine Board)"
 	greyscale_colors = CIRCUIT_COLOR_ENGINEERING
 	build_path = /obj/machinery/cell_charger_multi
-	req_components = list(/datum/stock_part/capacitor = 4)
+	req_components = list(/datum/stock_part/capacitor = 6)
 	needs_anchored = FALSE