Why would you stuff a document in a jar full of acidic liquid? Wouldn't that have the oppose of the intended effect? Aren't the jars way too small for this anyway? The article you attached seems pretty convincing - why don't you like this theory?
No acidic liquid was found - Keyser merely states that the presence of asphalt indicates that liquid was involved, and that most liquids known to the Parthians were acidic, ergo whatever liquid that was contained within the jar must have been acidic.
The jar is certainly not too small for most scrolls - if you take a look at the DSS, many of them are actually 10 cm wide or narrower.
Basically my main objection is the following:
Since the "Baghdad Battery" was discovered (by whomever) in the context of magic bowls (which are a late Sasanian/early Islamic phenomenon), is composed of a Sasanian vessel (per Simpson), and is best grouped with other artifacts that were discovered in Sasanian contexts, it makes absolutely no sense to consider it "Parthian," yet all descriptions of the device consistently date it to Parthian times, often even before the Christian era. I suppose people figure that pushing it back to the time of Christ will make it all the more impressive - trust me, nobody cares about Late Antiquity, as far as most scholars are concerned it's a black hole.
Similar vessels were discovered containing scrolls, therefore we're obliged to consider whether the "Baghdad Battery" might not have been intended for electroshock therapy or electroplating jewelry.
I'm not saying that Keyser's theory is absolute bunk; I actually agree that it
could have been used to do what he says it did. I'm just not sure that it did. This may simply be an example of a happy coincidence, a scroll jar that just happens to be a battery if used under the right conditions (perhaps the first example of Iraqi "dual use technology"?).
The one fly in the ointment, so to speak, in my objection is the presence of asphalt at the bottom of the copper tube. Then again, it could have melted down from the lid, who knows. He himself agrees that it would have been useless except for very particular circumstances (the iron rod slips down and touches the bottom of the copper tube). I don't agree with him that the presence of asphalt necessarily means that liquids were involved; or rather, they could have been involved, in the sense that asphalt can keep liquids out as well as trap them within.
One final thing. If it was discovered in the context of magic bowls (and boy, would I love to get a look at those particular bowls - they're probably on the streets of Dubai or Jerusalem right now, though), then the device probably wasn't built by "Parthians" or even "Sasanians" but rather by Jews or Mandaeans.