41 Series Battery & Charger?

[BarryT]

Hi all,
. I have a question regarding the 41c Battery Pack. I've noticed some of the batteries have 2 prongs and some have 3. Does anyone know why there was a difference? Was one version more stable than the other? Do they both use the same charger? I would 'assume' they use different chargers, but perhaps the gap in the split plug of the 2 prong charger is large enough to straddle\bypass the middle prong?

. The connector on the 3 prong one resembles that of the Classic series, but on those, one of the outer prongs is power to the calculator, whereas the other is the charging circuit for the battery, and the center pin is the ground. Is this also true of the 41c's 3 prong battery pack, or is that middle prong just "there", and of no real use? Again I "assume" that it's there for a reason and not just for the moral support of the other two pins , but, I could be mistaken.

. Anyway... if I were to look for a battery pack to refurbish, should I look for a 2 or 3 prong? Is either more rare\valuable than the other? Not that I'm looking to pick one up to sell, I want it for my 41cv ... but it's always fun to have something that's rare when you can.

Thanks in advance.
. -=Barry