I suggest a different approach...
Presuming that you are using a properly maintained battery, specified for that aircraft, thay battery is sufficent to start that engine, in appropriate conditions, using the proper technique.
If the battery is not holding or taking the necessary charge, maintenance activity is appropriate. If the engine is hard to start, perhaps it needs a maintnenance look. If the pilot technique is not adequate, well...
If the aircraft is too cold for a normal start (cold soaked at freezing or cooler), it should be safely and effectively preheated (takes an hour minimum to do properly).
If the battery has been run flat with repeated attempts to start, you are very near to damaging the stater motor by overheating it, and a wait of at least 30 minutes (time to preheat!) will be required to allow it to cool. If you have a good battery, you can ruin a starter before you discharge the battery, by not allowing it to cool. One published start cycle for a GA engine is: 30 seconds cranking, 30 seconds cooling, 30 seconds cranking, 5 minutes cooling, 30 seconds cranking, 30 minutes cooling.
Certainly, a small start cart is nice to have around (though you'll have to source that funny Piper plug for the cable if you're making it), but you really should not need the start cart, other than for protracted operation of the aircraft electrical system on the ground.
I am guilty, in my ealier days, of wanting to fly so badly, I boosted a dead aircraft battery to get it started. Knowing what I know now, I would not do it without allowing time to cool things down. During this time, a normal battery charger would get you going. If no plug in is available, then yes, a start cart boost will be required.
Pilot DAR