Battery at 50% yet power is switching off

[jodypress]

So I 've a Gtech hybrid bike. the battery died on me early this year and was uneconomical to repair. I went down the route of a KT controller, PAS, ebrakes and a bottle battery. All setup and working fine.

48V 36V 15A KT Controller For 250W 350W Electric Bicycle
KT LCD4 Display
This is the battery from ebay: R-team 36V 10Ah 350W Ebike Battery Bottle Li-oin Battery Pack:

Battery Parameters：
Battery Type:BOTTLE Lithium-ion
Rated Voltage / capacity:36V / 10Ah
Battery N.W/G.W: 3.22KG/3.62KG
Battery Size（mm)90*H340mm
Case Material:ABS+Aluminium alloy
Battery Color: Black
Batteries combinations:10-S,5-P
Component: Li(NiCoMn)O2
Cell quality: 18650-2000mAh
Impedance: ≤150mΩ
Recommend to use:200W-360W

Discharge Standard current:10A-13A
Discharge Max current:28A-30A
Discharge Cut-off voltage:30V
Discharge cycle life:800 times
Discharge method :Bottom discharge

Fuse Installation position:Inside on the PCB
Fuse Diameter(mm):5
Fuse Length(mm):30
Fuse Current: 30A

Certification:
CE,RoHS,MSDS

Working temperature:
Charging:0°C~45°C
Discharging:-20°C~60°C
Storage:0°C~30°C

Safety:
PCB board and BMS Protection:
PCB board Protection:Over charge,over discharge,over load and short circuit.
BMS board Protection:BMS is used to supervise battery by measure its voltage, temperature, current and SOC (State Of Charge), give out alarm under wrong circumstance, cut off electric power link in severe situation in order to protect battery and make its life longer. BMS can balance energy among batteries to make them more identical and expand its discharge cycle.

I've checked voltage when fully charged and it's at 43v, I've just checked it on my ride home from kids school having done a total of 10 miles since last full charge and it's switched off again at about the 50% mark on the display. I've checked the voltage of the battery and it's at 38v (also showing 50% on led dots on the battery)
I normally only run PAS at 3, sometimes 4.

So firstly I'm surprised I've only been getting about 10 miles or so of average riding on a full charge. The battery being 10Ah over the Gtech's 6 or 7Ah I'd expect it to last a bit longer.

Anyway, why is it switching off at 50%, any ideas would be much appreciated.

 

[Nealh]

Might just be poor quality cells used and once at 50% the voltage sags badly or there may be a bad cell. Try riding with kt4 showing volts ( two quick press's of the on /off button) and see if the voltage sags badly in use. Even pas 3 at 33% current draw may be to much for the battery.
Try experimenting using pas 1 & 2 to see if at 50% the system switches off.
If one finds pas 1 & 2 fairs better then one needs a better quality celled battery.

Ultimately the battery is only as good as the poorest performing cell, so one bad cell is enough to undermine all the others as it becomes the lowest denominator no matter how good the others are.

 

[jodypress]

Might just be poor quality cells used and once at 50% the voltage sags badly or there may be a bad cell. Try riding with kt4 showing volts ( two quick press's of the on /off button) and see if the voltage sags badly in use. Even pas 3 at 33% current draw may be to much for the battery.
Try experimenting using pas 1 & 2 to see if at 50% the system switches off.
If one finds pas 1 & 2 fairs better then one needs a better quality celled battery.

Ultimately the battery is only as good as the poorest performing cell, so one bad cell is enough to undermine all the others as it becomes the lowest denominator no matter how good the others are.

Thank you very much for this. I'll give it a go. The battery is on charge atm, so will have to wait until it's at 50% again.
This is the link to the battery: https://www.ebay.co.uk/itm/313742766090

I might try checking the battery cells if I get a chance to see if there is a bad cell. other than that what would you recommend as a good quality battery?

would there be any other settings on the KT4 that could get around this?

 

[Nealh]

One can use C5 setting to reduce battery current esp if it is on value 10 , 10 = max permiissibe current drawn at each pas level.

So for a 15a controller C5/10 is:
pas 1 is 13% or 1.95a.
pas 2 is 20% or 3a.
pas 3 is 33% or 4.95a
pas 4 is 50% or 7.5a.
pas 5 is 100% or 15a.

Rather then use the bike as normal on pas 3 or 4, start from a fully charged battery and use pas 2 constantly to see if range and cutoff % are better, one should see better usage unless the battery is not performing well.

The cells being 2000mah are likely very poor - mediocre cells used and china unbranded ones, the performance seen may be a reflection of this. Use the kt4 voltage readout to see what the voltage does under loading.
Let us know how much the volatge sags in the normal pas 3 or 4 use, then compare it with pas 1 or 2 use.

 

[jodypress]

One can use C5 setting to reduce battery current esp if it is on value 10 , 10 = max permiissibe current drawn at each pas level.

So for a 15a controller C5/10 is:
pas 1 is 13% or 1.95a.
pas 2 is 20% or 3a.
pas 3 is 33% or 4.95a
pas 4 is 50% or 7.5a.
pas 5 is 100% or 15a.

Rather then use the bike as normal on pas 3 or 4, start from a fully charged battery and use pas 2 constantly to see if range and cutoff % are better, one should see better usage unless the battery is not performing well.

The cells being 2000mah are likely very poor - mediocre cells used and china unbranded ones, the performance seen may be a reflection of this. Use the kt4 voltage readout to see what the voltage does under loading.
Let us know how much the voltage sags in the normal pas 3 or 4 use, then compare it with pas 1 or 2 use.

Hi Nealh,

So I've been running the bike since last full charge at PAS of 2. Today the bike got down to 50% after 16 miles and then cut out. Voltage was at 37.5 on the KT4 display and when I checked with a multimeter, also 37.5

So I've got a lot more distance (which makes sense as using the motor less) and to be fair was more equivalent to Max power on original Gtech battery.

I get the feeling that the battery is just cheap and cheerful and that I'll just have to charge it more often than I expected.

Do you have any links to bottle batteries with decent cells?

 

[Nealh]

One can only assume that at 50% one or more of the cells in a parallel group collapses and triggers the cutting out , there is an outside chance the BMS may be the issue.
But my guess is that the 2000mah cells are poor.

First of all the battery should have 12 months warranty, I would contact the vendor as the battery is far from satisfactory, if no joy from the vendor one can open a dispute with ebay. Explain what has happened to the battery and they should side with you as having a faulty item.

The battey is 360wh so should manage 30 - 40 miles in pas 1.

Your controller max rating is halve that of the batteriies max continuous rating so poses no excess stress to the battery.

 

[Nealh]

A lot of cheap batteries use china cells, that said some are pretty good so not all should discounted. The proof will be to see if yor seller helps you out.

Yosepower have a good rep on here and cs seem to be very good.
Finding a battery with quality cells is hard esp bottle type.

 

[saneagle]

I've checked voltage when fully charged and it's at 43v, I've just checked it on my ride home from kids school having done a total of 10 miles since last full charge and it's switched off again at about the 50% mark on the display. I've checked the voltage of the battery and it's at 38v (also showing 50% on led dots on the battery)

Your controller is set to 48v instead of 36v! 48v controllers switch off at 38v.

 

[jodypress]

Your controller is set to 48v instead of 36v! 48v controllers switch off at 38v.

I did wonder about that but how do I set my controller to 36v?

 

[jodypress]

One can only assume that at 50% one or more of the cells in a parallel group collapses and triggers the cutting out , there is an outside chance the BMS may be the issue.
But my guess is that the 2000mah cells are poor.

First of all the battery should have 12 months warranty, I would contact the vendor as the battery is far from satisfactory, if no joy from the vendor one can open a dispute with ebay. Explain what has happened to the battery and they should side with you as having a faulty item.

The battey is 360wh so should manage 30 - 40 miles in pas 1.

Your controller max rating is halve that of the batteriies max continuous rating so poses no excess stress to the battery.

I'll contact ebay seller and see what they say

 

[RogerA]

Try changing P5 to 12. That should force it to recognise the battery as 36V. The default value of 0 means it tries to automatically identify it, and if your battery is 43V charged as you said, then it may think it's a 48V battery.

 

[Nealh]

The Kt dual voltage controllers usually detect battery voltage type automatically,thye don't have a option to switch between 36 or 48v. They can have issues with inbetween voltages like 12s if used.
I have never seen a default p5/0 value,all the displays I have used are always preset to 10 though if it is set to 0 then worth a try. Asfaik the P5 is just a damping effect used for the battery bar indication.

 

[jodypress]

The Kt dual voltage controllers usually detect battery voltage type automatically,thye don't have a option to switch between 36 or 48v. They can have issues with inbetween voltages like 12s if used.
I have never seen a default p5/0 value,all the displays I have used are always preset to 10 though if it is set to 0 then worth a try. Asfaik the P5 is just a damping effect used for the battery bar indication.

Thanks. I've contacted the ebay seller so will see if they respond.
I've also checked and P5 was set to 15, so I've changed that to 12. Will see how it performs.
My gut feeling is that there is a setting in the KT4 that is cutting out at below 37.5v. Even when on PAS1 and it gets to about 37.5 it will still cut out.
Surely if the battery is reading 37.5v then that should still provide enough power to run a 250w rear hub motor on PAS 1 or 2 ? I'm not an electrical expert so my reasoning isn't necessarily sound

 

[egroover]

Parameter C12 min voltage setting, could it be the controller is set to 48v and where the default cutoff is 40v but with a setting of -2v taking it to 38v?

C12 Controller Minimal Voltage Setting - Dillenger KT-LCD3 User Manual [Page 28]

Dillenger KT-LCD3 Manual Online: C12 Controller Minimal Voltage Setting. The C12 parameter setting will display on the meter after C11 settings. The KT-LCD3 will display as follows: C12 parameters are settings for the controller's minimum operating voltage (voltage shortage value).

www.manualslib.com

 

[jodypress]

Parameter C12 min voltage setting, could it be the controller is set to 48v and where the default cutoff is 40v but with a setting of -2v taking it to 38v?

C12 Controller Minimal Voltage Setting - Dillenger KT-LCD3 User Manual [Page 28]

Dillenger KT-LCD3 Manual Online: C12 Controller Minimal Voltage Setting. The C12 parameter setting will display on the meter after C11 settings. The KT-LCD3 will display as follows: C12 parameters are settings for the controller's minimum operating voltage (voltage shortage value).

www.manualslib.com

I've checked and C12 is set to 4 which is default setting.

 

[matthewslack]

I've checked and C12 is set to 4 which is default setting.

From the manual page rather from direct experience, what happens if you set C12 to zero?

I would expect the cut out to happen 2V lower, which in the absence of any other solution might be good enough?

 

[jodypress]

From the manual page rather from direct experience, what happens if you set C12 to zero?

I would expect the cut out to happen 2V lower, which in the absence of any other solution might be good enough?

I'll give it a go and see what happens. I guess if it cuts out at 35.5v and not 37.5v this could indicate the controller is viewing this as a 48v battery not a 36v battery.

 

[Nealh]

As I mentioned the kt displays don't have a switchable solution for 36 or 48v, the system simply registers the voltage and automatically knows what is being used.
I use 12s with my KT's and have no such cutting out isssue, all I can say is swap out the lcd4 for a lcd3 or even an lcd2 and see if the issue is solved.

The kt allows battery use down to lvc whch is 30 - 33v, the battery spec says bms is 30v and the lcd4 is the same.
One can try the P12/0 route to see if it helps.

 

[egroover]

maybe a moot point but you say when fully charged your battery reads 43v ? I thought the maximum is 42v from a 36v battery...? Mine from new have never read more than 41.something when charged

 

[Nealh]

Depends if the volatage reading is via a DVM or the lcd 4 ?
My lcd4 isn't vary steady, the static reading can vary by 0.5v.
My current 12s reads 44.9v on my DVM, 44.8v with a lcd3 and then the lcd4 dances up and down it will read anything from 44.4 - 44.8v and this fluctuates continually.

Though I like the lcd4 for it's size, I am seriously considering reinstalling the lcd3 permanently.