Sunthings charger has a less than stellar reputation for quality. So the starting point would be to get a much better 36v lifepo4 charger as soon as it's affordable to you. Or if nothing else, a second cheapie. Chargers often conk out, and a spare is crucial if you are relying on the bike for basic transportation.
Look for a deal on a metal case 5 amp charger, they seem to be pretty good and keep themselves cool enough to last longer. I really love mine. You can charge completely in less than 3 hours.
Did you perhaps get a cheap 48v sla charger with your kit? If so, you can use it if you must, once it has the same connector you need on it. It will just stop slightly undercharged, but not harm the battery.
For a good charging setup for lipo, the choices are endless. The ones that have their own power supply are usually the cheap slow 50w ones. You need better than that, your battery empty needs about 700wh to charge, so 14 hours with a 50w charger? yuk.
One better charger that gets recomended a lot is the 14s hyperion, which would need a large power supply to run it. The RC lipo chargers will also do lead, nimh, nicad, and lifepo4. So having one, even a 50w cheapie, can be handy for other battery powered stuff than bikes. Good for say, a small A123 setup for your headlights or a drill battery that lost it's charger.
