title: Excel error may be caused by pandas writing or big data? advise needed
body: <p>I am reading multiple xml files extracting some data then forming a pandas Dataframe with my data. These are the main steps that I do:</p>
  <ol>
  <li>open an xml file</li>
  <li>extract some elements</li>
  <li>create a pandas dataframe with the extracted elements</li>
  <li>append the results in the excel file named &quot;output.xlsx&quot;(using the code below in python)</li>
  </ol>
  <p>My steps are repeated for all xml files that i have (15gb of initial data that usually have 100MB of valuable text data)</p>
  <p>This is my python code for appending data frames in the output excel file:</p>
  <pre><code>book = load_workbook('output.xlsx')
  writer = pd.ExcelWriter('output.xlsx', engine='openpyxl')
  writer.book = book
  writer.sheets = {ws.title: ws for ws in book.worksheets}
  startrow = writer.sheets['Sheet1'].max_row
  output.to_excel(writer, startrow=startrow,index = False, header = False)
  writer.save()
  </code></pre>
  <p>When I open the &quot;output.xlsx&quot; in Excel, I receive a prompt message saying &quot;We found a problem with some content in &quot;output.xlsx&quot;. Do you want us to try to recover as much as we can?&quot; with a yes or no answer</p>
  <p>This is the log file that excel generates:</p>
  <pre><code>&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot; standalone=&quot;yes&quot;?&gt;
  &lt;recoveryLog xmlns=&quot;http://schemas.openxmlformats.org/spreadsheetml/2006/main&quot;&gt; 
  &lt;logFileName&gt;error001280_01.xml&lt;/logFileName&gt;&lt;summary&gt;Errors were detected in 
   file 'D:\JUPYWORKDIR\2009Results\output.xlsx'&lt;/summary&gt;&lt;repairedRecords&gt; 
  &lt;repairedRecord&gt;Repaired Records: String properties from /xl/worksheets/sheet1.xml part
  &lt;/repairedRecord&gt;&lt;/repairedRecords&gt;&lt;/recoveryLog&gt;
  </code></pre>
  <p>I am worried that saving my results to excel format is corrupting my data, i will read &quot;output.xlsx&quot; with pandas in future in order to do some data analysis, does this problem effect my future analysis? I wanted to know why this problem is generated and should I save my data in CSV? any suggestions?</p>
  <p>Ps. Checking the last row of &quot;output.xlsx&quot; using python code it is the same number of rows when i import the excel file in a pandas Dataframe, lastly checking the last row of the &quot;recovered file&quot; of Microsoft excel i still find the same number of rows so i think its a generic error of Microsoft excel because of large data but i am not sure</p>