While I'm no expert on this, the first thing I see is that without an output 
diode in series, the battery voltage would upset the feedback voltage to the 
chip. That changes everything. Perhaps it caused it to drive the fet on 100% 
and it fried. An output diode, past any feedback point, is always good for 
switchers as chargers IMHO.



> --- On Thu, 8/14/08, Matthew Miller <namiller2@naxs.net> wrote:
> 
>> From: Matthew Miller <namiller2@naxs.net>
>> Subject: [EE] Need advice on a boost converter for charging batteries.
>> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
>> Date: Thursday, August 14, 2008, 9:28 AM
>> Hello,
>>
>> 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. I built the typical application circuit that is
>> in the device's
>> datasheet and under workbench tests it operated fine, with
>> the exception of
>> a bit of audible noise. The web page for the LT1680 is
>> here:
>> http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1031,C1115,P1597
>>
>> My trouble is that I connected the converter ground to the
>> battery pack and
>> then when I touched the positive wire to the battery
>> terminal there was a
>> big blue spark and now the converter is no longer working.
>> :( I haven't
>> repaired the converter yet, but I'm wondering if the
>> converter design I used
>> is appropriate for this application?
>>
>> I would appreciate any suggestions, insight, or questions.
>>
>> -- 
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