All good points. This is not a fool-proof solution, and has a lot of "manual safety" for now.
The Segway seems satisfied with the battery. (I still have the original 12.0 no-lipo-support software.) I can't see how it would even know. A 11.1v 3S pack has replaced each of the 10S NiMH packs that was there, so the operating voltage is within acceptable range. I kept all of the original NiMH circuitry and temperature sensors. I'll keep an eye on it, but my suspicion is that it will actually be a little bit pessimistic. If it allows NiMH to get down to 1.0 volts per cell (10v a string), then the LiPo is safely within limits, and limiting might kick in a bit early. If it allows 0.8volts per cell (safe for NiMH), then manual intervention is required.
For now, I have a self-contained LiPo monitor (pictured) installed on one or two packs. It will sound an alarm if any cell goes below 3.1v.
Charging is a bit of a hassle, since all 9 cells on each side need to be balanced. I have a Junsi iCharger 3010B with 1000W output, and can charge half the pack (9 cells) in 30 minutes or so (2C), twice per battery pack, four times total.
I have not yet measured range, but I don't expect it to be impressive. The packs are 2200mAh, and I will be limiting discharge to 70% or so. (The NiMH cells were SAFT 4.5Ah) That's still much further than the dead packs got me!
It's all experimental at this point. It would not be expensive ($20 or so) to add pack-monitor/alarms to each battery, so that's likely the next approach, just to make sure no one cell drops below limits.
External taps for charging would be nice, so I don't have to keep taking the screws out.
I also have to tape the 110v AC charging port shut, so nobody carelessly plugs in a power cord and blows up the cells with overvoltage.
Wet weather use is right out, since it's fully open on top.
R/C LiPo batteries have plummeted in recent years. I paid $8.00 each for those 3S packs at HobbyKing.com. 5000mAh packs are available for $22.00 or so, complete with hardcase. If you're willing to hog out most of the battery shell, there is a LOT of room in there. Range might also improve just because the batteries are so much lighter than NiMH. The whole Segway feels lighter. I'll have to measure it.
If anyone knows the pinout/protocol of the battery pins, I sure would like to understand this link better.
|