Roger, I always fully charge a new battery before it's put into service. The BTs can take up to a couple of days to bring a battery to full charge due to their low charge rate, the BT Plus charges at 1.25A, the BT Junior at .75A. If the battery needs to be put in service sooner, I'll use a regular automotive type charger set at 2A for the initial charging, then attach the BT to maintain the battery while the vehicle is parked. I've found that using a BT on our Harleys has increased battery life from a couple of years to 4-5-6 years. Hope this helps.

Mike