Ebike battery 36V 10 Ah HW-RH05 with HW-YJ-12 BMS & 38120LE (Tear down)

[Kiriakos GR]

The modification of my regular bicycle to ebike is one of my active projects.

HW-RH05 is the only one rear rack battery case capable to host those Headway Lifepo4 38120LE and 38120S.
The specific battery  now belong to me after an single combat over eBay.
The battery was listed as damaged by a young man. 
By it arrival from Germany, I had to open it for cells inspection, BMS Inspection, cells balancing inspection.

I did not liked the fact that MOSFET was with out heat-sink,  with lots of work and patience I did manage to convert an regular heat-sink at the necessary shape and dimensions.
Even added some very high quality thermal paste and the result speaks by it self. 
The first properly cooled HW-YJ-12 BMS is a fact and Greek patent. 


HW-YJ-12 BMS basic specifications:
12S Lifepo4
Charge:10A Max
Max continuous discharging current :16A
Charging voltage DC:43.8V
   
Headway Lifepo4 38120LE is a special new type LiFepo4, it dimensions is huge compared to 18650 standard Li-po. 

After 24 hours of tests, measurements, charging, balancing, improvements, I am finally ready to close it top cover and start using it.
Current status twelve cells in great condition and undamaged, BMS in great shape too.

What seemed as problematic was the charger that came with it, but this is another story, which will be hosted in another topic.   

Enjoy the pictures.

[Kiriakos GR]

 

[Tomjasz]

I really like that Headway battery case and rear rack. Both appear to be very strong and well made! You have made me look closer at Headway batteries. For now I have good NMC batteries from EM3ev, but I have another project in mind.

[Kiriakos GR]

I did fall in love by the first sight with this specific rear rack.
But it availability in Europe is almost zero.
One thieve in Germany are selling it for 570EUR as new.

I got very lucky, very - very - lucky, by getting it as used from a young man who was very disappointed from the arise troubles coming by his KIT ( a small 250W hub with planetary gears).
 

[Kiriakos GR]

This topic gets a second life at October 2021. 

One of the twelve LiFePO4 cells, this suddenly died, no voltage output at all (before six months).
Today I did take apart the battery pack for inspection.

And right now I am running a test of high significance.
The one million euros question, this is of what is the remaining capacity of stored energy at these LiFePO4 cells, after these be used (gently) for eight years?

In theory an 250W motor KIT at 36V this is expected to require 7A as max current from the battery.

I am now running battery capacity tests (with my finest tools  ) and as soon I will finish of data and clues collection, I am going to post the results of this new project.

[Kiriakos GR]

They are two test results that blown away my mind. 

Everything comes down to how much faith consumers can demonstrate to LiFePO4 chemistry  ? (when its cell this is an 10 Ampere / hours container of energy).

1) The first of the two remarkable findings, this has to do of how an discharged LiFePO4 behaves regarding voltage recovery ( by it shelf) after this be totally discharged down to 2.22 Volts .
a) The battery did it most ... fastest ... voltage recovery within the first 60 minutes.
b) The battery kept going by an ... Slower ... voltage recovery rate for another 17 hours, and I did disrupt the logging after 18H mostly because I did run out of patience. 

2) The second of the two remarkable findings,  original battery capacity on paper 10 Ampere / hours, new measured  battery capacity 8.6 Ampere / hours after eight years.


LiFePO4 Battery 38120 specifications, these mention approximate life cycle of 10 Years and or a number of recharge cycles.


After of me processing the new data, I think that it worth the risk, of me to get an replacement of the single damaged cell, instead rebuilding the entire pack.
In the world of electric bicycles, them powered due regular Lithium Ion, these packs never survive to last for over two years under regular use.
Today I feel some partial joy, because I have rock solid proofs that LiFePO4 chemistry, if this used by appropriate way, it can help consumers wallets significantly.

Just imagine that within a period of eight years,  four regular Lithium Ion battery packs they would have be turn to e-waste instead.


Pictures bellow....
First pair = LiFePO4 voltage recovery   (18 Hours graph,  2 first hours graph) 
Second pair = LiFePO4 discharge cycle. (53 minutes, regular graph, full screen graph) 
 
(Here it worth to be noted, that when LiFePO4 this is discharged at 10A rate, then my second attempt to continue discharge with 5A load instead, this did not deliver more than 0.275 Ampere / hours as add-on gain.
The new sum of  Ampere / hours this is now 8.87 Ampere / hours but this is unusable, because a BMS controller this will activate it LiFePO4  Low-voltage protection at  8.6 Ampere / hours and then the pack will stop working until the next charging cycle.
   

 

[Kiriakos GR]

Naturally this test it would not be complete with out of me to record facts of the last parameter, that is voltage settle time after a full charge.
This test gives good hints of battery internal resistance degradation too.

At my latest session of 24 Hours logging, as it appears at the graph, the specific LiFePO4 seems healthy enough so to be trusted as usable one battery cell.


LiFePO4 Battery 38120 specification this mention up to 30A as discharge rate,  my testing today just proves good longevity of this battery cell at the specific application of 250W / 7A ~ 10A.
According my personal statistics, I was had to charge the battery pack once a week, that is four times its month = 48 times per year (Cycle life ≥ 2000 times).

In summary ..
This HEADWAY LiFePO4 38120 cell under test,  it did demonstrate good performance and longevity.

The one permanent damaged HEADWAY LiFePO4 38120, this is the reason which I got the entire battery pack cheaply several years ago.
I did succeed to recover this cell at usable state, and because I did frequently use of my ebike, this was able to operate even at lower capacity than all the other eleven cells.   

The problem with HEADWAY brand this is international product availability.
They did not do much so them to expand the number of sales partners.
HEADWAY website this now indicates that manufacturing of LiFePO4 has stopped.  Even so it appears to be a single person in China, this be related to HEADWAY along with a Facebook account.
The problem is that they there is no any within EU warehouse with stock, and shipping cost this is extreme from China.

HEADWAY LiFePO4 38120 pricing today this is 15 Euro a piece.
But the few own stock of it at eBay, they sell at double to triple price per cell, and this issue is not related with Covid-19.

I will personally wait as long it takes, so to find a single cell at reasonable pricing.