24V 18650 LiIon Battery System

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24V Modular 18650 LiIon Battery System

Release status: beta [box doku]

24v liion battery system.jpg
Description Modular 24V litium ion battery system based on 18650 cells
Author(s)  Uli (Uli)
Last Version  0.2.1 (28.02.2020)

Introduction

This battery system consists of one or several battery cell holder modules, a battery management system module to charge the cells with surplus energy and protect the cells from over- and under- voltage. Optionally a state of charge display module shows the voltage of each parallel cell string.

Battery Cell Holder Module

Designed as a 24V battery, 7 batteries are wired in series (7s) and each of these consists of 2 cells which makes 14 cells per module. As the nominal voltage of a typical 18650 lithium ion cell is around 3.6V, 7 of them in parallel results in a nominal voltage of 25,2V. A typical end-of-discharge voltage is 2.8-3.0V making 19.6-21.0V in a 7s system. A fully charged cell usually has a voltage of no more than 4.2V, resulting in a maximum voltage of 29.4V for the whole battery system.

Battery Management System Module

yet to come...

State of Charge Display Module

yet to come...

Parts

A complete bill of materials will be listed here shortly.

Housing

There is no design for a mobile housing or case yet, but it will be updated here, when there is one.

Assembly

1. Order PCBs, electronics parts, 18650 cells, cables, and screws
2. Assemble 7s battery cell holder module
3. Assemble battery management system module
4. Assemble current state of charge display module
5. Assemble and connect cables and wires
6. Test basic setup
7. Test battery under load
First batch of the Panasonic NCR18650B cells arrived.
Desk full of tools, electronics and cells while putting together all the parts for the 18650 battery system.
First working version of the 18650 battery system ready for testing.

Debugging

yet to come

Open Issues

t.b.d.