" engine chatters, but won't start" can be taken a number of ways. Does it spit and sputter while cranking but will not run? Or, as I suspect, and would be more common, is the noise coming from the starter, and it's not spinning the engine? That is an indication of a weak battery. A jump start or putting a battery charger on it for 15 minutes will prove it.
Since you were working on the van, I'm hoping you just had the doors open and the dome lights ran the battery down. You can also measure the battery voltage to check for a shorted cell. Even a weak battery will read around 12.0 volts between the two terminals as long as it's not trying to supply high current. If it reads less than 11 volts, the battery probably just decided it didn't want to be a battery any more.
If you put a charger on it, leave it on low charge, not high. Battery chargers don't put out a nice steady DC current like batteries store. Their output goes from 0 volts up to around 18 volts and back to 0 volts. The average current is sufficient to recharge the battery, but the pulsing causes the plates in the battery to vibrate. That will not cause a problem on new batteries, but the lead on the plates of older batteries will flake off and collect in the bottom of the case where it builds up high enough to short out the cell. Alternators put out three phase current so the voltage and current never drops to anywhere near zero. There is much less stress on the plates.