This is not a good idea.
The repetitive shallow cycling of the IMA battery when charged daily for a fixed time period will build a memory effect in the battery cells that can reduce overall battery capacity. Further, if the timer is left on too long the battery will be overcharged, or rebalanced, on a daily basis. This is very hard on the battery and can significantly shorten battery life. If on the other hand the timer is not left on long enough, the battery will not only shallow cycle each day but will still self-discharge down to zero such that a full charge & balance will still be required when the vehicle is placed back in service. All of the above scenarios are bad for the battery. Hybrid Automotive and quality focused battery builders agree that daily shallow cycle charging is not a good idea for IMA battery health.
The proper way to treat your IMA battery when storing it for long periods of time is to allow the battery to self discharge. The self-discharge does not harm the battery in any way. When it is time to place the vehicle back into service, simple charge and balance the cells once for 20-24 hours at the end of the storage cycle. The practice is much better for the long-term health of the battery.
If you still want to use a timer with your Hybrid Automotive Prolong Grid Charger, we are happy to provide an external timer for $10 that will allow full programmable control of your Charger.