Matthew Miller wrote:
> I posted about this a while back and this is a bit of an update. I
> have an
> electric golf cart that has solar panels mounted on top the canopy.
> The
> solar panels produce about 15V under load and the lead acid battery
> pack has
> a voltage of 48V. My problem is to raise the panel voltage in order to
> charge the batteries.
>
> My first attempt was to build a boost converter using the LT1680
> controller.

My first attempt would be a dsPIC controlled boost converter that separately
calculated the parameters for each boost pulse.  It sounds like there is no
way the solar panel can put out enough power to hurt the battery, even when
it is fully charged.  If so, the only choice is when to start a boost pulse
based on what is available from the solar panel.  I would "fill" the
inductor each pulse, meaning its current is always brought to a little under
saturation.

You need to measure the solar panel voltage and the battery voltage.  The
rest is math knowing the capacitance accross the panel and the boost
switcher inductance.  The capacitance and inductance will vary, but will be
easy to calibrate out at manufacturing time.  You can measure the panel
power output by watching how it charges up the cap.  The rest is firmware,
although beware of some patents in the area of solar panel maximum point
tracking.


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