The batteries are not interchangeable - they have different voltages so the small one won't power the Plus and the large one will fry the electronics in the Original drive.
SwiftPaws Home Original
LiPo battery: 11.1V 1500mAh 3-cell 25c that has an xt60 connector that plugs into the main drive unit; and a four pin connector that plugs into the charger for charging. A fully charged Home Original battery is good for about 10 minutes of motor run time - that's about five 90 second play sessions.
Your SwiftPaws Home Plus
LiPo battery: 14.8v 5000mAh 4-cell 25c that has an xt60 connector that plugs into the main drive unit; and a five pin connector that attaches to the charger for charging. A fully charged battery is good for about 30 minutes of motor run time.
Disclaimer
The advice given above is general in nature and you are responsible for the safety of your batteries. SwiftPaws is not responsible for any direct, indirect, special, or consequential damages and personal injuries, including that to life, and health, resulting from the customer’s application and use of batteries sold by SwiftPaws.com.