All of the 4 Pismo batteries I have examined use the Benchmarq, now TI, bq2040 Gas Gauge IC. In addition there is a Seiko S-8233A Battery Protection IC and a series switch, an NEC uPA1712 MOSFET. And I think possibly a chemical fuse that gets blown if the voltages or currents sensed get too extreme.
Often the older batteries die during discharge by the S-8233A undervolt detecting the weakest cell section before the whole pack voltage drops enough to trigger a valid gauge AH capacity downwards recalibration. To the user this looks like the onscreen battery time indicates some normal amount of run time remaining and then suddenly things just go dark, no warning to the user about getting close to battery power down. So if you can skillfully swap in a set of matched used lithiums in just the weakest section you might be surprised to get a significant step up in run time without tweaking the bq2040 internal bits (but not back to brand new, just back to whatever the last valid AH recalibration happened to be just before the battery started undervolting in one section). I have done this several times successfully but is is a pain getting inside the pack non-destructively.
The skill comes in the order of disconnection and reconnection of the battery string from the Seiko and bq2040. The battery power at the very top of the string needs to be disconnected first to disable protection, and reconnected last, only after all the lesser battery string voltages being watched by the Seiko are wired in and stabilized. Reminds me of watching those old movies about defusing bombs, no, no, don't cut the blue wire, cut the red wire...kaboom!
When rewiring the battery string connect the ground first, then the 3.7V section, then the next at 7.4, continuing upwards until the top of the string at about 12V which if I remember correctly is the short red wire...no wait, it's been some years, I think...kaboom!
Every time I have gotten the urge to play with the bq serial bus bits I have found yet another flea market Pismo pack that one way or another I have got up to about 1 hour run time by luck of the pick or by just by cell voltage, capacity and esr matching and then cell section swapping so I have never messed with the bq2040 reprogramming. Some of you Arduino experts can have some fun with this one, just go read the data sheets. I do not know if reprogramming capacity has been locked out in some way. The pack can be bench tested by a 470K pull down to ground, between -enable pin 2 and pin 6 which is the - or ground pin. Please don't burn down you house. Fire has happened to laptops with unmolested lithium batteries, it is not just a recent thing with hoverboards.
Wally