Battery only charging partially

[Chris Maluszynski]

Hi

The battery of my Wisper 705 is only charging to 2 LEDs after the bike has been in storage. (It was connected to charger set at 39v, but I’m now realizing this was probably wrong - it should probablyhave been disconnected and then charged occasionally instead?)

I suspects some cells are critically low and that’s why it can’t be balanced by the charger?

Or would it not charge at all if this was the case? It clearly does charge to a level. I’ve charged it now maybe 5 times and it seems not to improve.

 

[Nealh]

Have you physically checked your charger output is 42v ?

 

[Chris Maluszynski]

Nope. But how could it not be if it’s charging? I’ll check in a bit. Can this be done by just measuring without it actually charging anything?

 

[StuartsProjects]

But how could it not be if it’s charging?

Could be faulty, hence the need to check.

 

[Nealh]

Yes.
Plug the charger in the wall socket and switch it on, then simply check the out put voltage .

 

[Nealh]

Do Wisper batteries have a sleep mode ?
David @Wisper can give you the answer on that one.

 

[Nealh]

Hi

The battery of my Wisper 705 is only charging to 2 LEDs after the bike has been in storage. (It was connected to charger set at 39v, but I’m now realizing this was probably wrong - it should probablyhave been disconnected and then charged occasionally instead?)

Can you elaborate on the above, was the battery left on the charger at 39v or was it charged to 39v then disconnected and the bike stored ?

 

[Chris Maluszynski]

I checked and it’s showing 43v. However right now when I connected the battery it immediately switches off the charging even though the battery should be a bit discharged (I used the bike briefly after previous charge)

 

[Chris Maluszynski]

Battery is showing 34.7v

 

[Chris Maluszynski]

After a while it’s going slowly up. Now it’s showing 36.6

 

[Woosh]

Charge the battery again, write down the output voltage every 15 minutes. When the LED on the charger goes green, leave the charger on for another hour. Let us know the result.

 

[Chris Maluszynski]

Thanks. Will attempt. But how do I measure the output voltage while it’s charging? Where do o connect the probes?

 

[Woosh]

Connect the probes to the battery output port like you normally do when not charging.

 

[Chris Maluszynski]

Start charging at 34.0
15min 36.0
30 min 37.0
38 min Orange turns to green and charging stops. Voltage drops to 36.0 instantly.
I’m now waiting another hour and will report.

 

[Nealh]

There obviously isn't a very low cell group otherwise it woudn't try and charge at all, the possibility is that there is a dead cell or two in one of the parallel groups or the BMS is faulty. An outside chnace is a broken sense wire.
What ever the fault the battery needs opening and some checks carried out.

 

[Nealh]

How old is the battery ?

 

[Chris Maluszynski]

the battery is old. Not sure how old. I got the bike used two years ago but it was probably something like 4+ years old by then.
if you guide me I’m happy to get to work on the battery, but I lack experience so will need to be held by the hand by smart people here

 

[Chris Maluszynski]

I should probably also mention that the 5A fuse of the battery blew recently.

 

[Nealh]

Likely needs recycling then, but we can guide you in to taking ten cell group readings.
First though you need to open the case to get to the cell pack.
Once opened one needs to find the BMS and the multi pin sense wire connector and take a pic of it for us.

 

[Chris Maluszynski]

I’ll get started on this tomorrow. How do I open the case without breaking anything?