Long-time reader of Endless Sphere here. Decided to post a positive comment about purchasing from SuPower because they went the extra mile for me. Hopefully my experiences will also be useful for other newbies like me.
Summary: SuPower (http://www.supowerbattery.com) were helpful and went the extra mile to ensure the battery was delivered to me despite Fedex issues.
In August I purchased a 10S3P pack with Sanyo NCR18650GAs. These are new ~3.5Ah cells with more than enough punch for my modest lightweight 500W setup.
(I claim this is still my first ebike ... If you ignore the fact that since 2012 I've had fun deliberately over-volting a 350W geared motor until it gave up, and then later replaced the flammable LiPo with a 'free' GMax battery, but hey, at least the same controller and the bike frame live on 8) ).
This pack is ~10Ah, lightweight and overspec'd for my current needs... but I figure that my next motor will probably be larger so its useful to build in a safety margin and besides the cells will last longer if treated carefully so its useful to have some headroom in both capacity and continuous discharge. (I'm still in shock in how much battery technology has improved in the last 18 months - amazing how much capacity & current per $ is now possible using safe chemistries.)
SuPower does not include their cell brands on their website. However their email rep (Lillian) costed out several possible specific builds and specific batteries via email.
I kept the English sentences simple and was careful to confirm all of the details. Typical email turnaround time was 24 hours. I requested genuine XT60 connectors and asked for a the opposite connector to be included (they actually included two - both free; wish I'd also asked for some heat shrink wrap too). I went for a slow 2 Amp charger (sufficient for my needs; and again if I treat this battery gently maybe it will be usable in 3 years. I paid $321 (battery+charger+$75 shipping)via paypal and the assembled pack and charger were shipped with a Fedex tracking number. The pack looks like the following except I have charge and discharge leads -
http://www.batterysupports.com/36v-37v-42v-105ah-30a-1000w-lithium-liion-ebike-battery-pack-p-459.html
Postal problems: Unfortunately due to a family emergency I was out of the country when Fedex tried, but failed, to deliver it because they required a signature. After trying to deliver a few times, it was then held at the local Fedex office, then Fedex decided to send it back to the shipper. At this point I returned and was able to trackdown the package however the Fedex would not release the package back to me. My many many daily phone calls to Fedex were unproductive. Fortunately, after emailing Lilian, SuPower was able to release the package and get it pulled from the Memphis storage area to be redelivered to my house (this time without requiring a signature). Fedex charged ~$110 for a package to be released from its International holding area. I paid this fee using Paypal to SuPower and they immediately paid Fedex. They did not charge me for their additional time required etc. And... hurrah... yesterday it arrived.
The battery arrived well packaged (bubble wrap, box-within-a box, extra paper padding) and has already been tested on the bike
I don't have a testing rig (just a multimeter; yeah yeah ..will probably at least buy a cheapo wattmeter sometime for the bike someday) and sorry ... I'm not going to teardown the battery to check the construction. At 50% capacity the main battery voltage gave a 0.3v rise compared to open circuit when charging at ~2Amps. The charger was very warm - I wouldn't want to leave it un-ventilated - it hit 126F / 52C after an hour.
I've been very pleased with SuPower's level of service and would recommend them. They went the extra mile to help select an appropriate pack and customize it, and ensure the battery was re-delivered when external factors conspired against me. They also emailed me to check the delivery when the tracking number finally showed that it had been delivered. I'm just very very glad I went with a supplier that was already recognized on E.S., rather than a too-good-to-be-true ebay seller. The possibility that my new battery pack might have been sent back to China and to disappear forever seemed a remote but very real possibility earlier this week - which is probably what would have happened if the original seller had not intervened.
So I encourage you to 1) stick to sellers that have a good track record on E.S.
2) Be prepared to go explore custom builds beyond a seller's web listing - Use email etc to find out what they can build for you and at what cost.
3) Handle the logistics of package delivery better than I did if you're not going to be around to accept the package.
