Electrical – swap a USB power sources for a 3-AAA battery source

ledliponimhusb

I'm putting some battery-powered lights into a boat, and I have the following question:

I bought a bunch of cheapo LED lights, as pictured:

lights

They run on 3 AAA batteries. They work fine using 1.2V NiMH rechargeable batteries, and I've wired them up just to share one set of batteries, rather than each containing their own (still works fine). Rather than recharging batteries all the time, I figured it would be more convenient to get one of those USB LiPo power-packs for phones, and charge that when needed.

My question: Is anything bad going to happen if I hook up 5V USB power-pack in place of the (3.6V total) batteries? If I need a resister in series, how do I tell what resistance I need?

Best Answer

My question: Is anything bad going to happen if I hook up 5V USB power-pack in place of the (3.6V total) batteries?

The LEDs will likely fail

If I need a resister in series, how do I tell what resistance I need?

Measure the voltage when operating on new batteries and note it down. Swap to the 5V supply but put 1 kohm in series and gradually lower that 1 kohm until you see the same voltage as measured previously. Use that modified value of resistor for each LED lamp you have i.e. they will all require their own individual dropper resistor.

Related Topic