Hi Roo and
to the forum.
Gary
(GM Canada) is usually very good at sending out stock items, especially when you consider that he works full time during the week and has to organise the running of GM Canada during his time off (and he also has to fit in family duties as well).
Shipping and processing times.
When you place an order and the item is instock we do our best to ship it within 24 to 48 hours. In most cases all the orders from any particular day are packaged and labeled in the evening. Then they are dropped off at the post office the next business day. We do our best to get them ther by the 4:30 pm cut off time but that is not always possible. This is why we say 24 to 48 hours processing time to ship. Also at peak times it can take an extra day or two to get the shipment out but we do our best to avoid these delays. Honestly we do our best, but we can't perform miracles.
Most of the above is completely understandable, with the exception of the last part, because I don't believe it's physically possible to do everything that Gary manages to achieve without the occasional miracle.
You also need to realise that items being shipped within 1-4 days does not mean they will be delivered within those 1-4 days.
Regarding the battery question, it will be difficult and awkward to charge and properly balance the cells unless you intend to do this separately using a suitable additional charger
(and power supply) with the required balancing capabilities.
You would also need to add some sort of cell monitor to the new cells to ensure your new cells are protected against being overdischarged or imbalanced etc. as any
BMS incorporated into your existing battery will not be able to monitor or protect the additional cells.
Alan