Nicad Charging, Cuttoff Circuit for Large Pack

Hello, I haven't posted for a while, but could really use some help. I am in the process of building an ebike battery pack from Nicad cells that were donated to me by a friend. I received 250 of these (please click to view spec sheet) 1.7ah sanyo cells, and am assembling them into 30s1p blocks that I plan to parallel together for discharge, and separate with diodes for charging.

Basically the only thing I don't have planned out is how I'm going to cut off the current coming into the separate strings from a single source. My plan is to use thermistor/thermal switch cutoffs as a safety, but NOT as the primary charging cutoff. It's because they switch back on after the batteries cool enough. My estimate is that they would heat up and cool down, and repeat that cycle until I came along and realized they were done charging. So what I would like to do is use a delta V cutoff that detects when the voltage sags at the end of the charge and cuts off the current until I reset it some how...by either unplugging or pushing a button or something along those lines. Perhaps when the voltage on the pack dips below a certain voltage per cell I could use that as a reset point.

The whole point here is I either need a small and compact design already out there (for 36v) or I need help designing one. I want to build a separate cutoff circuit for each individual string. I've had physics, and taken 1 term of circuit analysis...but the teacher was ineffective for me. So I know the basics surrounding caps, inductors, resistors as well as current/voltage controlled current/voltage sources...and a few REALLY basic things about op-amps (still didn't ever really fully understand that). But obviously I'm not an EE so designing a whole new circuit (new to me) is a bit above my head...especially being a ME major ;)

So some basic design questions for this project are:-What component could I use for cutoff that would be able to double as a discharge path and handle discharge currents (absolute MAX of 15 amps pulse, 5 A continuous from a 1.7Ah 36v string of nicad)?-What component would be able to track delta V, detect when it turns negative and signal the above device?-How could I go about setting up some sort of reset circuit to try to make it idiot-resistant?I can't really think of any more at the moment, but in the mean time here is my plan so far:

(Click here for a larger, more better picture :)

There will be 8 of these strings, not just 4.

Please let me know if you have a better source for a circuit database than I do...which basically amounts to this: electronics-diy.com