Max1555 and Max756 questions

Discussion in 'General Electronics Chat' started by bisctboy, May 27, 2009.

  1. bisctboy

    Thread Starter Member

    Nov 3, 2008
    If I use a dc/dc step up boost converter to bump up a solar panel's voltage output from 1.5v (3 X .5v cells) up to 5v, can I use this output to charge a 3.7 Li Ion battery? I know I need at least 3.7v or more to charge the battery, but I didn't know if there was something about using a boost converter that wouldn't allow me to use the increased voltage to charge a battery that is rated a higher voltage than my voltage before the boost converter. I am using a Max756 chip for this.

    I will also be using the Max1555 chip in my Li Ion charging circuit which protects the battery. According to the spec sheet, the charging circuit is set at 280mA. If I am wiring solar cells in parallel to gain more current, am I just wasting current if my solar panel exceeds 280mA? What happens to the wasted current....heat?

    Finally, is there any issue with using a boost converter to boost the voltage output on the solar panel, then later in the circuit using another boost converter to boost the output of the 3.7v battery to 5v so I can charge my ipod and blackberry?

    My circuit will look like:
    Solar panel --> Max756 booster --> Max1555 Li Ion charger --> 3.7v Li Ion --> Max756 booster --> blackberry/ipod

    I've included the spec sheets on both chips...

  2. b1hiker

    New Member

    Jun 28, 2009