Battery on Wisper 905se only charges to 50 percent

KevinMull

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Mar 25, 2016
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I've had my Wisper 905se about 5 years and only use it occasionally during spring/summer. This year the battery (Samsung 575) only charges to about 50%, according to the LCD controller anyway ( 2 bars) although all LEDs are lit on the battery itself.

I get a reading of 36v on the battery with my multimeter.


I have contacted Wisper who recommend that I send the battery to them for testing.
Before I send it off does anyone have any advice on what the problem could be?
Could it be the controller at fault showing an incorrect reading?
 
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wheeliepete

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Feb 28, 2016
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I've had my Wisper 905se about 5 years and only use it occasionally during spring/summer. This year the battery (Samsung 575) only charges to about 50%, according to the LCD controller anyway ( 2 bars) although all LEDs are lit on the battery itself.

I get a reading of 36v on the battery with my multimeter.


I have contacted Wisper who recommend that I send the battery to them for testing.
Before I send it off does anyone have any advice on what the problem could be?
Could it be the controller at fault showing an incorrect reading?
If the battery only reads 36v after charging, then the probem is with the battery, not the controller. Poss. the cells are very out of ballance or a dead string of cells.Have you tried riding your bike?
 

vfr400

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Jun 12, 2011
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You should measure the battery voltage with a meter immediately after you take it off the charger. 36v sounds very vague. What's its exact voltage?
 

KevinMull

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Mar 25, 2016
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You should measure the battery voltage with a meter immediately after you take it off the charger. 36v sounds very vague. What's its exact voltage?
I took a reading immediately after charging, it read 36v exactly, which is normal as it is a 36v battery (?)
 

KevinMull

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Mar 25, 2016
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If the battery only reads 36v after charging, then the probem is with the battery, not the controller. Poss. the cells are very out of ballance or a dead string of cells.Have you tried riding your bike?
36v is the 'nomianl voltage' of the battery. It rides ok, just shows 2 bars on the controller and then goes down to none after around 20 miles
 

wheeliepete

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Feb 28, 2016
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36v is the 'nomianl voltage' of the battery. It rides ok, just shows 2 bars on the controller and then goes down to none after around 20 miles
41.5-42v is the normal fully charged voltage for a healthy 36v battery. Does the light on your charger turn green on full charge?
 

Nealh

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Aug 7, 2014
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I took a reading immediately after charging, it read 36v exactly, which is normal as it is a 36v battery (?)
Something quite not right then, it should be north of 41.5v.
What voltage reading does the charger give on it's own ?
 
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vfr400

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Jun 12, 2011
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The charger switches off when the whole battery reaches 41.6v or when the first of 10 cells reaches 4.2v. Using logic ant taking what you've said as true facts, your battery is way out of balance for whatever reason. The only thing you can now do to move forward is to open the case and measure the individual cell voltages on the multiple connector attached to the BMS, then you'll know what to do.
 
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artspeck

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Nov 21, 2016
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I've had my Wisper 905se about 5 years and only use it occasionally during spring/summer. This year the battery (Samsung 575) only charges to about 50%, according to the LCD controller anyway ( 2 bars) although all LEDs are lit on the battery itself.

I get a reading of 36v on the battery with my multimeter.


I have contacted Wisper who recommend that I send the battery to them for testing.
Before I send it off does anyone have any advice on what the problem could be?
Could it be the controller at fault showing an incorrect reading?
 

artspeck

Pedelecer
Nov 21, 2016
63
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83
Sunderland
#7
I may have the answer to your question, finally. I’ve got the 806SE with 700 battery.
Meter readout on battery shows fully charged yet the lcd screen shows only one bar.
After 3 weeks watching every video known to man on this subject, I’ve fixed it.
Press all 3 buttons on the lcd screen all at once and hold for a few seconds.
Eventually the screen will show either the number 45, 36 or 24. These readings should match the voltage of the battery. Mine was showing 45 when in fact it needed to read 36 to match the 36 volt battery. Just press up or down to show 36, release all buttons together and as long as it’s still reading 36, switch off at the battery, wait a few seconds, switch back on and it will now show full charge at the display. I’m absolutely euphoric to have this sorted, something no professional could tell me, not even Wisper tech dept could tell me. Good luck, and please let me know if this helped. Art
 
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KevinMull

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Mar 25, 2016
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#7
I may have the answer to your question, finally. I’ve got the 806SE with 700 battery.
Meter readout on battery shows fully charged yet the lcd screen shows only one bar.
After 3 weeks watching every video known to man on this subject, I’ve fixed it.
Press all 3 buttons on the lcd screen all at once and hold for a few seconds.
Eventually the screen will show either the number 45, 36 or 24. These readings should match the voltage of the battery. Mine was showing 45 when in fact it needed to read 36 to match the 36 volt battery. Just press up or down to show 36, release all buttons together and as long as it’s still reading 36, switch off at the battery, wait a few seconds, switch back on and it will now show full charge at the display. I’m absolutely euphoric to have this sorted, something no professional could tell me, not even Wisper tech dept could tell me. Good luck, and please let me know if this helped. Art
My LCD (XT-LCD W108) doesn't have buttons on it, they are separate and tethered to the LCD. I have tried hold all three together but nothing happens
42867
 
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artspeck

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Nov 21, 2016
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That’s a bummer for you, sorry. What I did was to go through every single YouTube video I could find on lcd till I came across just one that matched.
 
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KevinMull

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Mar 25, 2016
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Wisper have quoted £125 to repair and return (plus my delivery cost to them) or return FOC if no fault found. . Is this reasonable?
I'm not confident in going under the hood myself to even test and not sure of any local e-bike battery repair services (Manchester)
 

wheeliepete

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Feb 28, 2016
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Wisper have quoted £125 to repair and return (plus my delivery cost to them) or return FOC if no fault found. . Is this reasonable?
I'm not confident in going under the hood myself to even test and not sure of any local e-bike battery repair services (Manchester)
It's difficult to say if that price is reasonable without knowing what's up with the battery and what work they have to carry out. If the issue is unballanced cells, then it can be quite time comsuming to carry this out, dependant on how many are out. They may also fit a new BMS as a precautionary measure. You may find someone cheaper to test the pack, but you could be charged £30 or £40 to be told it's knackered. You can at least trust Wisper for an honest appraisal and if it's beyond repair they will tell you and prob. charge you nothing.
 

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