Hybrid NiHM cells as battery source with tons of Amps

[rsimpsonbusa]

Hi Everybody.

My Toyota Highlander hybrid battery had to be replaced( $4000) so I kept the batteries. I tried to use one cell(voltage 10.6DC read with multimeter) as a source for a ESP8266, before killing my ESP32s, via an LDO, (AMS117) but they get fried after 10 secs or so.

I was daring enough to connect it directly to the VIN-GND directly before a cap blew off. (I do have spare parts )

What a I doing wrong? Obviously the cell has a ton of Amps, buts amps are requested by the load, not pushed by the source, correct?

RSN

[fly135]

Amps are pushed by the source. That's what voltage does. Looking at the data sheet you use up to 15V on the regulator. So that doesn't seem to be the problem

I think your confusion about amps is that they are computed by ohms law, which requires both the output voltage and the input resistance of the circuit being fed. It has nothing to do with how many amps the source can deliver unless it's too little. Then the amps will be reduced because you need to add the source output impedance to the load input impedance. Otherwise the source impedance is ignored.

John

[fly135]

What is the voltage rating on the cap? And what voltage do you measure on the cap. Electrolyte/Tantalum caps will blow if you install them with reversed polarity. The first thing I would do is check the output voltage of the LDO and make sure you are using the right part and delivering the correct regulated voltage.

[G6EJD-ESP32]

Your problem is due to regulator power dissipatation. An ESP8266 requires let’s say 3.3v and 100mA it uses less but the maths is easier, that’s 3.3 x 0.1 = 0.33Watts.
With a 10.6v input to the regulator, let’s say 11, it can accept up to 15v, the power being dissipated by the regulator is (11-3.3) x 0.1 = 0.7Watts, this results in the ams1117 getting very hot and it shuts down, when cooled it should recover until it over heats again. Try putting your finger on the regulator! It will be hot.

The solution is to regulate down to say 7v using a regulator with a heat sink or use a switch mode psu that does not over heat.

[rsimpsonbusa]

@ G6EJD-ESP32 thanks. I used an LM2576 and it works fine.

Regards.