Pride legend suddenly stops and emits 7 beeps

Do you get any flashes from the controller lights? This is usually the way you diagnose errors. A high number of flashes/beeps often means there is an issue with the controller or joystick.
Batteries are only fitted if they are needed so a 'spare' battery isn't very likely. Most wheel chairs and scooters need a powerful battery to spin the electric motor so a pair of batteries are used. The two batteries also act as a counter weight to keep the chair upright.
They are normally fitted in a 'serial' or 'in-line' set up. Basically into one battery, across to the second battery then out through the second battery.

Try a local auto transmission rebuild company.

Or, here for your parts

https://www.google.com/search?q=pride+DRVASMB1627

Motor transaxle and brake is here
https://www.monsterscooterparts.com/brands/pride/models/legend-xl/motor-assembly-motor-transaxle-and-brake-for-the-pride-legend-xl-sc3450.html

More here

https://www.google.com/search?q=pride+DRVASMB1610

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You manual merely says this on Page 26

Make sure the seat is locked in position.
Lift the seat off.

https://manualzz.com/doc/8931129/pride-legend-owner-s-manual

There are some videos for Pride Scooters here

https://www.google.com/search?q=Pride+Legend+remove+seat

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Look for a loose connection on the throttle pot. really sounds like a a connection that is loose. Scooter Doctor App

I’m happy to assist further over the phone at https://www.6ya.com/expert/bill_bcbb89783b08c489

mechanical error.. did u buy it new?

mechanic is the solution

This is not good news. Sorry See the following link. Pride Mobility INFMANU1773 Operation Instructions Manual Page 16 Fault...

hi i hsave a pride legend classic mobility scooter it will run ok for a few yards then suddenly stop but if u wait for a bit it will go again whats the problem thanks

check the wiring from the batteries as a wire could have come loose.

Regards
GeWiz

lets look at that model number and seriel number. I can look up it's history. Take the batteries to Advance or Auto zoon, Get them "Load Tested" it's free. Are there any flash codes or beep codes. the light on the console will flass or a beeping noise after you turn it on ? these are codes which we can tell what can be a problem. mike