19003 Battery Input limit

WisBlock
1

I’m using a 19003 Baseboard with a solar battery charger providing power to the VBat input.

The spec sheet states a max input of 4.3V for VBat… per the schematic, the VBat input supplies a voltage divider to allow measurement of VBat, and to 2 chips that both have 6.5V max inputs.

Can anyone tell me what is driving the 4.3V absolute limit per the data sheet.

Thanks in advance.

2

The Battery input is for batteries, not for external solar battery chargers.
Once you connected the external solar battery charger to the Base Board, you had two chargers working against each other. There is a risk that something gets destroyed.

If you want to use an external solar battery charger, it needs to have a 5V output and you can connect it to the other connector on the Base Board, called “Solar”.

3

Thanks for the reply.

for more context, The charger I’m using provides a “load” output that mimics a battery and as far as the base board is concerned it looks like a battery. I have this configuration running and the only issue is that the battery “output” can go to 4.5v on the VBat versus the spec’d 4.3v.

On the 19003 schematic, D2 and D3 “switch” between the solar and usb inputs and provides voltage to VBUS_D. D3 clamps the voltage on VBUS_D to 5.6V,

VBUS_D feeds the TP4054 VCC input. if neither the solar or usb connection is there, the charger chip is not activated as there is no VCC to pin 4. The charger will not turn on. The data sheet for the TP4054 states it will draw 2uA from the battery in that state.

My question is, the VBat connection goes to ICs that allow 6.5-7V max inputs and the 1.0M/1.5M voltage divider that is driving the ADC for battery measurement ( it will be about 2.7v @ 4.5v VBat)… why is max spec for VBat 4.3v?

4

VBat goes to

  • to the charger chips output, that’s why I recommend to contact only a battery
  • to the 3.3V regulator that generates the supply for the WisBlock modules
  • a voltage divider to be able to read the battery voltage

If you destroy the WisBlock Base Boards power supply implementation by connecting something else than a Li-Ion battery, your warranty is void and we cannot help in any way.

5

Wow…

I seem to have hit a nerve here… I understand that this configuration is non-standard and will commit not to do a warranty claim for 15$ worth of components. lol.

Thanks for confirming that I read the schematic correctly.

I was more curious if the 4.3v spec limit had an engineering basis or was a leftover from “generic” or earlier boards.

I will do some testing with my configuration for the benefit of possible future engineers… if it melts the board I will change the circuit and give RAK some more business.

Stay tuned.