Question on front hub battery from eBay

[Ambrose Liao]

I got a question on my listing in eBay. I thought I'd share my reply with the group.

Question:

Dear ambroseliao,

Hello! Do you have the wavecrest front wheel? Even with dead batteries, it is the heart of the bike! No other bms comes close to the performance, of the electronics in this front wheel.!! Do you have it?? Thank you!

My Answer:

"The Wavecrest Labs front wheel battery was a very beautifully designed piece of engineering, however, the Saft D sized NiMH cells used in the front hub are notoriously saggy and were the weak link in that design. Battery chemistries have improved significantly since the original WCL hub design. Both Li-Po and Li-Fe batteries are vastly superior to NiMH. They are dramatically lighter and have very little internal resistance when compared to NiMH cells. If you have used a Tidalforce bike with a meter such as the Cycle Analyst to monitor voltages while riding, you would know how bad the NiMH cells were. The console LEDs did not reflect real-time voltages of the pack so it isn't very useful for pack monitoring. Under medium loads, you would experience significant voltage drop and under heavy load, the system would drop below low-voltage cutoff of the cells! The BMS in the front wheel would cut back power fed to the motor in order to stop harmful low voltage and motor cut-out. This reduced the power of the motor when it is needed the most. Not optimum. Newer Li-Po and Li-Fe batteries have vastly superior internal resistance and power output capabilities and are significantly lighter in an external pack configuration without the heavy front wheel. 

Besides the weak Saft NiMH D cells, the front hub was notoriously heavy. Each hub/wheel/tire combination weighs over 30 lbs! The M-750X without the heavy front hub feels like a totally different and much more powerful bike with the ultra-light and very powerful 37V 10Ah Li-Po pack included with my kit. The 25 lb weight reduction is highly significant. With the battery mounted on the water bottle mount, the balance of the bike is superb. The battery monitoring function of the included Cycle Analyst is also vastly superior to the LED console. The console is still useful for the Turbo mode and Cruise functions.

I hope this better answers your question.

Ambrose"

I then ran out of space since I hit the maximum word length of the reply! :)

[OptOut]

Hi Ambrose,

It's been many years since I used 2 x 10 ah lipo packs in parallel with my dying front hub pack. The main reasons I chose then to go with LEVT's OEM hub rebuild was longevity and cost. The lipos only lasted about a year before age killed them, not use. This is the first year that my LEVT refurb hub is unusable since the rebuild many years ago. When originally done and for a few years after it did not have any of the problems you mention. The LED state of charge which measures based on current flow not voltage of the hub was an accurate indication of how much current was used, and I never had premature low voltage cutoffs. This does become a problem when the battery is old and no longer has full capacity, but by that time you only have a year or 2 of useful life left. 

The specs at the time said lipos would last several years but I felt I got burned by how expensive and short lived mine were. 

I did get to taste what the low resistance and high power of lipo feels like and it was great!

How long do the batteries really last now? 

Thank you,

Joe (mobile)

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[Ambrose Liao]

I don't have a long history with Li-Po cells, however, reading about them, they seem to last for about 2-3 years of average use. They don't like to be kept at full charge though. Half voltage seems to be the recommended way to store them.

In my observations with the TF front hub which are probably not accurate since I've not used a new front hub battery before is that the voltage sag is dramatic! Probably because of the age of the cells. Glad to hear your got many years of good use from your LEVT refurb battery.

The cost of Li-Po is dramatically lower recently. It seems that the nascent drone market has driven the price of high powered cells down significantly.

The Multistar brand in particular is very inexpensive. You can order a 6S and a 4S cell in a 10Ah configuration (which you need to put in series to achieve the necessary 37V TF configuration will cost you less than $200.

http://hobbyking.com/hobbyking/store/__64438__Multistar_High_Capacity_4S_10000mAh_Multi_Rotor_Lipo_Pack_US_Warehouse_.html

http://hobbyking.com/hobbyking/store/__64439__Multistar_High_Capacity_6S_10000mAh_Multi_Rotor_Lipo_Pack_US_Warehouse_.html

The big gotcha is that they are not available at the moment.

[OptOut]

Thanks Ambrose,

I may try these or something similar when available. They're about a fifth of what they cost last time I tried.

Best,

Joe (mobile)