Android tablet - how to measure LiPo charging current?

john_s

While experimenting with few cheap Android tablets I stumbled across the inability to directly measure LiPo battery charging current at its terminals.
I inserted digital amp-meter between LiPo and the corresponding on-board socket but then my tablets didn't want to start up.

I ended up measuring a total current from the plug-in adapter instead.

So my 2 questions are:

1 - why couldn't I measure tablet's LiPo charging current directly with amp-meter in series with it?
2 - is there another method to measure it directly at the LiPo during its charging?

These are A13 tablets that use the AXP209 ic to control all things power and charging related.

Perhaps AXP209 keeps an eye on internal batt resistance and does not allow even the smallest mOhm addition of multimeter current measuring circuit in series with the battery?

I appreciate any comments .

Thanks,
John

sam_sam_sam

What setting did you use millamps or amps
The millamp setting has to much resistance that is part of the meter
Try using the amps setting it should work

erco

Yep, it should work. Try different settings and/or different meters, even an analog meter.

john_s

I used 2 different Fluke multimeters - an old 8080A and newer 787 Processmeter.
Both were set in mA range - I'll try the A range and report. Thanks.

Duane Degn

How many connections are there on the battery? A lot of electronic devices have batteries with three terminals. One of the terminals is used as some sort of feedback to the charging circuit.

When I tried making a Propeller controlled cell phone, I had to add a resistor to the circuit to trick the phone into thinking it's normal battery was installed.

Oh, wow. This is post #5000! Five stars!

erco

Duane Degn wrote: »

Oh, wow. This is post #5000! Five stars!

@Duane: That's HUGE Bro!