How do you correctly charge a 12V lead acid battery using a 5V phone charger and step-up converter? Answered
I'm making a bluetooth capable, battery powered portable speaker - I have some 12V lead acid batteries lying round and I want to use those since the amp accepts 12V power. Its important to me that I can use a 5V micro-usb cable as a power supply because they're so common/universal. Everything in my setup works fine except for charging the battery. I've tried two different step up converters. One overheats massively when power in is connected to the 5V supply, and the other is a slightly fancier buck-boost converter which comes with a small LCD which displays voltage and current out - however this one, once connected to the battery, shows a tiny jump in current and then goes down to zero. I'm fairly certain the converters aren't inherently faulty since I've tried running the converter output straight to the amp rather than the battery and then everything seems to work fine.
How am I meant to charge this battery? Is there some component I should be adding in somewhere?