E3 ZUMA Restoration

Hi E-bikers, I recently purchased a second-hand Currie 2015 IZip Zuma E3 (48V). The previous owner let it sit for several years. I knew it had a few issues (including a flat-lined battery) but it was a beautiful bike and wanted to resurrect it to its former glory and save it from the dumpster it was headed to. Unfortunately, it looks like the specific bike from this series was discontinued and this has only complicated my endeavor.

Upon getting the bike I was able to quickly disassemble the battery pack and replace/spot-weld in 2500mah LG 18650s. Luckily the BMS still worked bringing the bike back to electrically running condition. Now I can I-zip around electrically but the chain drive is still giving me trouble. The smaller battery in this bike really needs the pedal assist to make it really useful with such a small battery.

The pedals on the bike slip when peddling and after some disassembly I have concluded the freehub body has a problem preventing the teeth from engaging (or worse the teeth on receiver are gone). I tried cleaning it and reassembling it to no avail. Is it possible to get a part number of this freehub body? I had a hunch that the motor is a Bafang 500W CST but I couldn't be sure (see pics). Even knowing this, I couldn't seem to find replacement parts for the freehub. I attached several pictures to help the effort. Any help would be much appreciated. I sent an email to Currie and received no response, but as a secondary customer, I don't blame them.

https://photos.app.goo.gl/fdnGaFPP2YZjFMw53

After the battery was rebuilt the bike could get around 8 miles on totally flat Florida ground with just twist throttle before the display would shut off. I assumed was a low voltage shut off. Is this in line with what is expected stock? Does this approximate range make sense?

Again to recap my questions are:
Is it possible to replace the freehub body on the motor entirely? What about the teeth on the motor side?
Is the normal operation of the controller display to shut-down upon low voltage cutoff (LVC) on Currie bikes?
Is the motor on this bike a Bafang CST 500W? (See pics)... If so, I may be able to get some parts somewhere.

I dig how the battery is the seat tube. Paint it black and it would blend in nicely.

I may be misinterpreting your question, but that looks like a screw-on freewheel, and the entire unit can be replaced.

Sort of hard to tell from the pictures, but if it is a screwed on freewheel, the whole thing can be replaced but you need a special tool that grabs the inside of the gear cluster.

I don't know about that model specifically, but if the BMS in the battery pack cuts off due to a low cell, for sure the display will go off.
The controller may have its own LVC that would stop the motor but the display would stay on.

You should be able to get way more than 8 miles range. More like 20 miles.

What can happen sometimes is one cell group in the battery is lower than the others and will cause the BMS to cut off early. This may be due to a damaged cell group or may be simply out of balance. A good test is to run it until it cuts off or almost there, then measure the voltage on each individual cell group. By comparing the voltages, you can see if there is one that is low. Alternately you can charge the pack, then measure the voltages on the cells and compare.

If the pack is out of balance, it can be challenging to get it balanced again. Ideally you would use a single cell charger to top off each cell group to get them all up to 4.2v. The BMS will try to balance the cells, but most of them do this very slowly and only at the end of the charge cycle.

Monsterscooterparts has a lot of izip parts and assorted Currie stuff if for some reason your freehub is not repairable wouldn't hurt to try them and see if they have the hub used in that model.

Thanks for the feedback everyone. I do think the pack is hitting LVC. Just for some information on the battery I have rebuilt it with 13 series chains of 3 18650s in parallel. So about 8Ah at 48v, so this should send it 20 miles with no pedaling?? The range is my biggest indicator that there may be something else wrong..... but my old 48v ebike was getting about 1mile per Ah and that seems close but was an entirely different setup (1000w gear-less motor). thoughts?

If the pack is only 3p cells, then 8 miles is pretty good. Most bike batteries are bigger. It's likely the cells are sagging under load and may be tripping LVC prematurely. Cells rated for high C rate will work better.