Summary

This is a 4 bay 18650 charging station that allows the user to check the voltage of each battery cell when power to the charging unit is off.

Parts Needed

• (4x) 4v1a Single cell lipo chargers https://www.amazon.com/gp/product/B071RG4YWM/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
• (4x) Batter case (to obtain -spring and +terminal with wires) https://www.amazon.com/gp/product/B013DUOJV4/ref=oh_aui_detailpage_o05_s01?ie=UTF8&psc=1
• (4x) Momentary Switch Buttons https://www.amazon.com/WGCD-Momentary-Button-Switch-Thread/dp/B06XFWVFR9/ref=sr_1_38?ie=UTF8&qid=1520473695&sr=8-38&keywords=momentary+push+button+switch
• (1x) Voltmeter https://www.amazon.com/gp/product/B00YALV0NG/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
• (10x) M2x6mm Screws
• (8x) M2 Nut
• Double sided foam tape
• 26guage silicon wire
• Power terminal (I used an XT60)

Possible Parts

• Voltage Step-down https://www.amazon.com/gp/product/B071CWMRYD/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
• Toggle Switch https://www.amazon.com/Gikfun-MTS102-Position-Toggle-Arduino/dp/B01BWL7Z44/ref=sr_1_40?ie=UTF8&qid=1520475369&sr=8-40&keywords=toggle+switch

Instructions

• Remove the -spring and + terminal from the batter cases
• Attatch the -spring and + terminal to the 18650 battery bays
• Run the wires into the charging module bay
• Run two (2) sets of -&+ wires from the buttons bay into each charging bay
• Solder the -spring and + terminal AND one set of -&+ wires from the buttons bay to the BATT -&+ respectively
• Solder the remaining pair of -&+ wires to the 5v source on the charging modules
• Solder all - wires from the BATT -, AND solder the - from the voltmeter, AND the 5v source - together
• Solder the source + to the + source for the charging modules
• Solder each BATT + to one side of the push button
• Solder the other side of the push buttons AND the + and White cables from voltmeter together
• Solder toggle switch to - 5v source to break the circuit via toggle switch if desired
• Use double-sided foam tape to affix the charging modules to the printed standoffs

Notes:

Make sure to have a PS that is able to supply 4 amps at 5v. I opted to use a step down with a 24vPS to get to 5v. The part is listed above and is working well with a powered onboard fan. This is thing XXXX.
The user can obtain voltages from each cell by powering off the unit and pressing the buttons one at a time. Pressing more than one button gives you the voltage of both batteries. Pressing the button while the until is powered gives you a powered voltage from the charger.

Hope you enjoy! This was a fun project for me.