Yosepower kit - battery

[Sebastien]

Hello to everyone,

I'm new on this forum and happy to join Pedelecs community.
I've converted my "old" bike to e-bike with a Yosepower kit ( 36V/350W rear motor 26") 2 years ago yet.
My battery was a Yosepower 36V/12,5 Ah. At the beginning in 2020, I can ride for around 55 km with normal power.
The Yosepower kit isn't perfect because level 1 or 2 are useless. I have to ride with level 3 or 4. My first litshui controller has stopped to work suddently. I replaced it with a new one but now it becomes noisy...
This summer in 2022, I can ride only for 45 Km. The battery has lost capacity.
I have discussed a lot with the seller, and finally they has exchanged the battery with a new one in the mid-september.
But the problem is worst, the new battery (36V 13 Ah) seems to have less power and less capacity because I can ride only 42 km and voltage falls to around 35V. The previous falls around 36V in the same conditions. I have also seen to display that voltage falls from 39V to 35V during few seconds and grow to 39V after, very strange behaviour...
I'm very disappointed with that. The seller asks me to open the battery and test all cells voltage. All is good (cell are egal).
As I said to him, the voltage coudl be good, but the capacity not.
I would like to discharge the battery with resistors or bulb lamp to see how much amp it can deliver.
I have found this resistor : https://www.amazon.fr/Robinet-aluminium-Résistances-boîtier-wirewound/dp/B008MKZMIU/ref=sr_1_2?__mk_fr_FR=ÅMÅŽÕÑ&crid=2ZWEDEI31KJFV&keywords=resistance+100w&qid=1664974123&qu=eyJxc2MiOiIxLjcwIiwicXNhIjoiMS4wMCIsInFzcCI6IjAuMDAifQ==&sprefix=resistance+100w,aps,109&sr=8-2

Do you think is a good way to test it (2,6 Amp) ?
The seller has asked me to send the battery again to after sale service if I think isn't good...
Thanks for help.

 

[Sebastien]

I have tested my battery with power resistor at a current rate of 2,2 A.
It has delivered 12,5 Ah.
It isn't good for a battery of 13Ah rated for 10A of CDR and peak of 20A.

 

[Nealh]

12.5ah at 2.2a for a 13ah rated battery sounds about spot on.
One will only see the full 13ah if one discharges it fully down to 2.5 - 2.8v per cell at a meagre 0.2a per cell.

 

[Sebastien]

12.5ah at 2.2a for a 13ah rated battery sounds about spot on.
One will only see the full 13ah if one discharges it fully down to 2.5 - 2.8v per cell at a meagre 0.2a per cell.

Ok but how much will deliver this battery at 5A or 10A ? My 26" bike has only around 45 km of autonomy at normal power. My first battery of 12.5 Ah has 59 km and more power in same conditions.

 

[matthewslack]

45km = 28 miles and 12.5Ah at 36V nominal = 450Wh, so 16 Wh per mile for a hub drive in level 3 PAS.

Doesn't sound too bad. I think the cells in your replacement battery are perhaps not as good as those in the original, and sag more, so triggering the low voltage cutoff sooner.

 

[Sebastien]

Yes but I lost in this replacement because my previous was much better at the beginning : more power and more autonomy. Now with the new one, I have less autonomy and less power. The voltage falls very quickly from 42v to 40v even with 2A, and then continously falls during discharge. I'm very worry how long will last this battery...

 

[Nealh]

You don't know if the replacement batterywas another returned one or not, if the cells are no name china cells then their consistancy will be variable.

Typically a 2.5ah cell going by other china brand cells is approx/
At 5a discharge or 1a per cell one might see 11ah down to 3.3v perc cell or 33v.
At 10a or 2a per cell one might see 10.5ah to 3.3v/33v.

Cheap or mediocre cells will cetainly loose capacity within 2 years .

 

[Sebastien]

The battery is an april 2022 product but not the same cells as previous. Yes it is China brand High Power with 2600 mhA cells. For my test the battery was at very low voltage 30.9 V at the end. So if I stop it to 33V, I would get less capacity (maybe 11.5 Ah).

 

[Sturmey]

I have tested my battery with power resistor at a current rate of 2,2 A.
It has delivered 12,5 Ah.
It isn't good for a battery of 13Ah rated for 10A of CDR and peak of 20A.

Actually, that a very good result. Even brand new good quality Samsung cell often test about 5% under there nominal capacity, as shown in link below.

Test of Samsung INR18650-35E 3500mAh (Pink)

 

[Sebastien]

Do you really think it is good, not for me.
Because I have used lithuim battery for 15 years in model aircraft and at low rate, I will get more than the nominal capacity, for example 13.3 Ah for a 13 Ah.
Normally with a 13 Ah battery witha CDR of 10A, I should get 13 Ah at 10A. But if I want to test this current, I should buy more power resistor so I need to know if I should invest or not.

 

[Nealh]

Your never giong to get 13ah from a 13ah battery at a CDR of 10a, your thinking is pie in the sky. The only time one is going to get the max capacity is at 0.2a discharge with a voltage range of 4.2v - 2.8v.

Any no name china 18650 with a 10a CDR is likely to be quite poor compared to a good branded cell, even the good branded cells with a 10a CDR will have shortened life cycle and reduced capacity if often used to 10a. It recommended at most for good life cycle to use a 10a CDR cell at max 60/70% current draw.

 

[Sebastien]

Your never giong to get 13ah from a 13ah battery at a CDR of 10a, your thinking is pie in the sky. The only time one is going to get the max capacity is at 0.2a discharge with a voltage range of 4.2v - 2.8v.

Ok but 0.2a is very low for a 10S 36V battery pack. So I should get 10 Ah ? But my previous battery was really better and given for 12.5Ah. It's a pity, I'd have to keep it. Newer is not better today unfortunetaly.

 

[Nealh]

Ok but 0.2a is very low for a 10S 36V battery pack. So I should get 10 Ah ? But my previous battery was really better and given for 12.5Ah. It's a pity, I'd have to keep it. Newer is not better today unfortunetaly.

The 0.2a rate is a standard test used by all battery producers to rate their cells and to get the mah rating.

The sam 25r is one of the best if not the best 2500mah cell in it's class.
One can see that for 2500mah the CDR is 0.2a , at CDR 10a the mah is only approx. 2300mah.
Now look at the discharge to 3.3v which is a fairly minimum discharge voltage if one wants reasonable life cycle.
At CDR 0.2a one see's 2250mah and only approx. 1200mah at 10a.
this is for single cell and no 5 in parallel.
Test of Samsung INR18650-25R 2500mAh (Green) (lygte-info.dk)

 

[Sebastien]

Ok so for my battery with 5x2600 mhA cells, the std rate is 1.0A. Ib my test, I fall to 31v, so I get less than 12.5Ah. Maybe I need to test it at 8A. If I get only 1300 mhA per cell, it's not good at all...

 

[Sebastien]

I have tested my Yosepower battery again with an average current of 7.5A. (8.33 Ah at beginning and 6,8 A at end).
The voltage goes down from 41,9V to :

• 39,9V in less than 1 minute
• 38V in 16 minutes
• 35.7 V in 45 minutes (only 6Ah restored )

I have get a capacity of :

• 11 Ah at 34V
• 12,25 Ah at 33 V
• Then it drop in few minutes to 30v

It was mesured with a wattmeter, there are some error in precision with it around 0.2 A and 0.2V.
So my battery is maybe good ? but it has a lower voltage during discharge than my previous, so less power.
I think I can only use in my ebike 10 Ah in normal condition, maybe less...

 

[Sebastien]

What do you think about my results ?