Regardless of whether the battery is charging or not, it can be connected to the battery.
12 Volts Lead Acid Battery Maintainer & Desulfator Life Black
40A Car Battery Charger,6/12/24V Lead-Acid,Lithium,LiFePo4 Smart Battery Charger
Mercedes-Benz US 3300 Battery Charger for 12 V Lead Acid Batteries
Portable Carbon Pile Load Test Alternator Tester for 6 or 12 V Lead-acid Battery
