Hi Karen,
Are these Magic Pies fitted to three separate bikes, or is it a single cargo trike or velomobile fitted with three Magic Pies?
Multiple motors will draw too much current for a single standard eBike battery pack
(unless a very low maximum current setting is used on each of the motors) and they would really require two
(or more) identical batteries connected in parallel to provide sufficient power for all motors.
If it's just a single motor that runs OK at part throttle, but cuts out under full throttle, it sounds like the motor is trying to draw more power than the battery
(or possibly its BMS) can supply.
If this is the case, you will need to reduce the maximum current setting until the motor stops cutting out at full throttle.
If the 24V battery has been left uncharged for a long time
(6-12 months or longer) then the battery may no longer be useable. You can try leaving it on charge for at least 24 hours to see if it will return to a useable state, but it is very unlikely to make a full recovery if it has been left for long periods without regular recharging.
Alan
