diff --git a/freqtrade/data/converter.py b/freqtrade/data/converter.py
index 63a6c98df..1ef224978 100644
--- a/freqtrade/data/converter.py
+++ b/freqtrade/data/converter.py
@@ -116,21 +116,23 @@ def order_book_to_dataframe(bids: list, asks: list) -> DataFrame:
     return frame
 
 
-def trades_to_ohlcv(trades, timeframe):
+def trades_to_ohlcv(trades: list, timeframe: str) -> list:
     """
     Converts trades list to ohlcv list
+    :param trades: List of trades, as returned by ccxt.fetch_trades.
+    :param timeframe: Ticker timeframe to resample data to
+    :return: ohlcv timeframe as list (as returned by ccxt.fetch_ohlcv)
     """
     from freqtrade.exchange import timeframe_to_minutes
     ticker_minutes = timeframe_to_minutes(timeframe)
     df = pd.DataFrame(trades)
     df['datetime'] = pd.to_datetime(df['datetime'])
-
     df = df.set_index('datetime')
-    df_new = df['price'].resample(f'{ticker_minutes}min').ohlc()
 
+    df_new = df['price'].resample(f'{ticker_minutes}min').ohlc()
     df_new['volume'] = df['amount'].resample(f'{ticker_minutes}min').sum()
     df_new['date'] = df_new.index.astype("int64") // 10 ** 6
-    # Drop 0 volume columns
+    # Drop 0 volume rows
     df_new = df_new.dropna()
     columns = ["date", "open", "high", "low", "close", "volume"]
     return list(zip(*[df_new[x].values.tolist() for x in columns]))
diff --git a/freqtrade/data/history.py b/freqtrade/data/history.py
index e594af430..fd3aee2a9 100644
--- a/freqtrade/data/history.py
+++ b/freqtrade/data/history.py
@@ -93,7 +93,6 @@ def load_trades_file(datadir: Path, pair: str,
     if not tradesdata:
         return []
 
-    # TODO: trim trades based on timerange... ?
     return tradesdata
 
 
diff --git a/freqtrade/exchange/exchange.py b/freqtrade/exchange/exchange.py
index fed903a4a..86078ae05 100644
--- a/freqtrade/exchange/exchange.py
+++ b/freqtrade/exchange/exchange.py
@@ -988,22 +988,6 @@ class Exchange:
         except ccxt.BaseError as e:
             raise OperationalException(e) from e
 
-    def build_ohlcv(self, trades: List[Dict], timeframe: str, since: int = None,
-                    limit: int = None) -> List:
-        """
-        Build ohlcv data from trade list.
-        trade-list has to be in the ccxt format, which is a list of dicts containing at least:
-            * timestamp
-            * price
-            * amount
-        :param trades: List of Dicts
-        :param timeframe: timeframe to convert to (e.g. "5m")
-        :param since: start at a specific data, as oposed to the trades-list start date
-        :param limit: Limit amount of candles
-        :return: ohlcv data (as returned by ccxt.fetch_ohlcv)
-        """
-        return self._api.build_ohlcv(trades, timeframe, since, limit)
-
 
 def is_exchange_bad(exchange_name: str) -> bool:
     return exchange_name in BAD_EXCHANGES
diff --git a/freqtrade/utils.py b/freqtrade/utils.py
index 48734883c..e77b76208 100644
--- a/freqtrade/utils.py
+++ b/freqtrade/utils.py
@@ -97,7 +97,7 @@ def start_download_data(args: Dict[str, Any]) -> None:
 
             # Convert downloaded trade data to different timeframes
             convert_trades_to_ohlcv(
-                exchange, pairs=config["pairs"], timeframes=config["timeframes"],
+                pairs=config["pairs"], timeframes=config["timeframes"],
                 datadir=Path(config['datadir']), timerange=timerange, erase=config.get("erase"))
         else:
             pairs_not_available = refresh_backtest_ohlcv_data(