Lipo battery charger
Q1 on state can be varied by PWM from Uno to control battery current. If Rcur is in B+ lead V across Icur = V_ADC2 - V_ADC1.
If Rcur is from B- to ground then V Rcur = V ADC2. Vbattery is monitored with an ADC channel (ADC1 or ADC_V)Ĭurrent is measured by measuring voltage across Rcur with an ADC (ADC2 or ADC_I). Worst case here = (5V - 3V) x 1A = 2 watts.Ī buck converter could be used (UNO controlled) if desired.īattery current is monitored by a small resistor Rcur from B- to ground (or in B+ lead) Power dissipation = (Vin - Vbattery) x Icharge
#Lipo battery charger full#
Max power dissipation for a A max charge rate would be 2 Watts when the battery was at 3V and full charge was wanted from 5V in. The main point of note s that in its simplest form the charger uses a linear charging mode so a modest amount of heat needs to be dissipated in the control transistor. I will only outline the basic system here. Terminate and stay active until recharge needed. Low current "trickle up" for very low voltage cellsĬonstant current charge until Vmax is reachedĬonstant voltage charge until I_cutoff is reached. This can achieve all the usual basic capabilities
#Lipo battery charger plus#
If you really want to meet your specification you can achieve a few ten's of mA charge using with a UNO and a few resistors (possibly just one.)īut, a good compromise can be achieved using a UNO (or similar) + one transistor plus a few resistors and capacitors. If using a UNO with no external active parts the current drive rating of the UNO pins limits the maximum current able to be provided. UNO + one resistor very low current charger: These ICs and all related components can cost as little as a few dollars. The use of any of the available LiIon charger ICs is an easy and low cost way of adding a charger. This is a capable charger but the UNO would not be the major part of it. If you only want to use a UNO + passive components then the hardware intensive method of application note AVR146: Lithium-Ion Battery Charging via USB with ATmega16/32U4 which Ignacio suggests does not meet your need. I'll assume that you are trying to charge from a 5V "USB" source.