I'll start by saying, I love my Bionx equipped mt. bike. I ride to work almost every day and about 6 months ago I had ~4k miles on my first PL-350.
That's about 400 charge cycles but my typical ride uses only 60-70% of the pack according the controller SOC indicator. So 6 months ago the Bionx up and quit. Turns out it was the battery but the dealer said the controller may also be bad. Recommends replacing the whole kit.
Kinda surprised since my charge cycles weren't that deep. Figured it would last longer. I really wasn't excited about $1000 to replace just the pack with the risk that something else could still be wrong.
Plus my system is the old I2C not the newer CAN-bus. I found a dealer who would sell me the whole PL-350 kit for $1k. The caveat was that it was a demo unit, no warranty with about 40 miles on it. Bought it, installed it and it lasts me maybe 20 rides before it starts showing serious degradation (won't fully charge, voltage sags). I talk to Bionx and they say any Pl-350 pack unit that's been on the shelf since 2008-9 is probably degraded. That sucks.
I decide to hack a battery pack into my old pack. I want something safer than LiPo though. No need to burn down the garage. So I find A123 cells online through some Hong Kong dealer (I know.. very risky purchase). Plus they do tabs and will weld any config of serial/parallel I want. I like A123 since they're a pretty safe chemistry and have great power if not so great energy density. Bought 60 cells welded as 12 serial to yield 39.6 V nominal. I then soldered the old Bionx batt wires from the controller to the 5 packs in parallel. The LiMn pack in Bionx PL-350 is 60 cells connected as 10S6P. 10 LiMn is roughly equal to the 12 A123 cells in voltage. In fact with the Bionx charger I verified I never get close to the 3.7 V/cell max for A123.
Did some crude cell balancing before putting the pack together. Discharging each string and checking individual cell voltages and then charging with the Bionx. All looked kosher. The pack has been working great for my ride.
Only 20 trips so far. I measured the total Ah and it comes in about 3 Ah round trip. So the Bionx pack wasn't giving me close to 9Ah since it always ended with less than half SOC. Kind of a mystery.
So any estimates on whether this hack is going to die a premature death?
If I can get 400 cycles again I'll be a happy camper. It's only 5Ah but should be fine for my daily ride.
This pack cost me $165, including welding and shipping.