Electrical – Trickle charging a Li battery from motorcycle battery


Sorry if this doesn't belong in the forum, however I'm unsure of where to start and am rather clueless with electronics, but keen to learn more.

Essentially I would like to charge this GPS device from a Motorcycle battery such as this, without it draining flat between rides, or draining the bike battery. It can be wired in so it charges only while the engine is running or all the time.

Charging while bike is running:

How long would it last off the internal battery?
Would it be possible to include an additional mobile battery to increase capacity?

Wired into the motorcycle battery:

How long would it roughly take to drain the motorcycle battery?
Would it be possible to trickle charge? If so how?

Device Details

All the details I can find for the GPS device are:

  • Internal Battery: 3.7V 500mAh Polymer Li-Battery
  • Charging Consumption: 100 mA
  • General Consumption: 50 mA

Motorcycle battery capacity

  • 3Ah

All and any advice is very much appreciated!

Best Answer

Simple answer - NO!

Longer answer can be found at various sites, such as this one

Li-ion cannot absorb overcharge. When fully charged, the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium and compromise safety.