There’s no way to get a Tag History Binding into an EasyChart. You have to let the EasyChart do its own history query. The tagPens dataset doesn’t contain the actual history data, it contains the information the EasyChart needs to construct its own query. The date range info is in separate properties on the EasyChart that you would also have to bind to template properties if you wish to pass them through.
Consider using a temporary window to use to configure a chart with the desired tags, then cut and paste its dataset(s) to your template instance. Similar to what is described in this topic.