I have a Thunderbolt 100W solar panel from Harbor Freight, and I'm wondering if I can connect it directly to my dead car battery using the clamps it comes with, without a charge controller, in case of an emergency. If this is possible, how long should I leave it connected in full sun?
2 Answers
Honestly, it's not a great idea to connect the solar panel directly to the battery without a charge controller. The manual suggests using one, and it's really there for safety—you could risk overcharging and damaging your battery. For a 48Ah battery, it might take about 6 hours to charge it fully, but that’s if the panel’s output is at max and the battery is completely dead. Definitely better to get that controller for around $20, trust me!
Please don't do this! Hooking the panel up directly poses serious risks. If the solar panel outputs 18V, it can overheat your battery, potentially leading to an explosion. I've seen it happen. If you really need to charge a dead battery, make sure it's disconnected from the car’s electrical system before trying anything. You don’t want to fry the car’s electronics!