More power (literally) for the HP-41, follow-up.

[Diego Diaz]

Hi all,

@Chr Yoko, It seems to me that the easiest solution will be to find a suitable small box and "insert" the battery pack before shipping. Hopefully, cheap enough to not affect the final cost.

@Massimo, Just in time, I'll be back in Spain on August 4. ;-)

@Sylvain, Nice point to get a safe bag to charge the pack when out of the calculator. Regarding the battery charger you've chosen, I'm afraid it is not suitable for this application.

This charger is intended for use mostly on heavy duty battery packs (up to 6S) with high current rate both in charge and discharge in the range of tens of Amps. and fast charging.

These batteries are common in the RC field: Drones and radio controlled vehicles. And since they're built using several unprotected cells (in series and/or parallel configurations) an active method of controlling (balancing) the charge of every cell is required; hence the complex type of charger.

The application for the HP-41 uses one single (protected) cell designed for low current operation (1Amp max).

The charger circuit (4057) takes care of the whole process and needs just a simple smartphone charger and a UCB-C cable. I've used my Samsung's charger along these days.

Due to the current limitation the charging process takes several hours but this ensures a minimal temperature rise. Slightly warmer around the USB-C connector is all it gets.

In the attached picture are detailed every IC and the protections applied.

Hope this clarifies the point.

All the best.

Diego.