Inside the Aneng BT-168 battery tester

This unit is a modern LCD version of the classic cell/battery tester. There is one notable difference though, and it is the lack of a load resistor to give an indication of the cells ability to supply current. As supplied, the current drawn by the 9V contacts is about 1mA, and the current on the sliding contact varies with the voltage of the cell as follows:- 1V = 5mA 1.5V = 3mA 4.2V = 1mA If you wanted to add a load, then suitable resistors could be 470 ohm quarter watt across the 9V battery connection point, and a 10 ohm 1W resistor across the sliding contact, noting that the dissipation will be about 1.8W with a freshly charged lithium cell, so a 1W resistor is only rated for intermittent use. The 9V connection point can actually measure up to about 13.5V. I think the most interesting thing about the circuitry is the way it uses a single regulator for both inputs, but boosts one up first. Both test points do have polarity protection - a simple diode on the 9V input and a MOSFET on the low voltage input. As with many of the things I've looked at recently, this one came from AliExpress (not a sponsor). Here's a link to the item. It's an affiliate link, but that will not affect the price you pay. https://s.click.aliexpress.com/e/_c3Qauhph The cost is typically around £2. Supporting the channel with a dollar or two on Patreon helps keep it independent of YouTube's quirks, avoids intrusive mid-video adverts, gives early access, bonus footage and regular quiet Patreon live streams. https://www.patreon.com/bigclive Alternatively, for a single coffee contribution you can use PayPal:- https://www.paypal.com/paypalme/bigclive #ElectronicsCreators