I have tried couple time reload, the maximum amount you can reload with a single transaction is CAD 500. I tried 600 and got declined on paypower end, after which I had to do refund and tried 500 again.
However, most cashier doesn't know it is reloadable and usually call for store manger to assistant. Some store manager would still refuses to reload for me.
With the single transaction capped to 500, I would just buy more new cards. It is not worth it dealing with cashier and store manager. Everytime it costs me 10 mins and I might not get the card reloaded.