Hi All, Wondering if I could get any advice for an 8fun battery problem?

[Bezzer]

Hi All, Wondering if I could get any advice for an 8fun battery problem?
Hi All, I am new to this forum but it looks great! I have been using an 8fun kit for around 18 months with very few problems (other than when it is wet it cuts out). Recently the battery died and I was unable to charge it (36v 9AH). I took the battery apart and found quite a bit of moisture inside so dried the components with a hairdryer and eventually the battery began to charge again. However, it was only delivering around half the power and would only charge to max 3 out of 4 lights on the meter. Then the battery failed completely. I have done the following tests:

Voltage direct from the cells is 37v exactly. Voltage out of BMS is virtually zero. However if I touch the transistors on top while I am earthed the output voltage goes up to about 36v?? Can I assume that the battery cells are ok and the BMS has a fault? The BMS looks like this and has the model number BMS 18-20 KLH15S01



I contacted 8fun and they said they do not sell the parts - only batteries! But they will ask the battery factory in Hong Kong??

Would anyone know where I could obtain one of these or have it repaired?

Thanks

 

[Deleted member 4366]

The BMS is a logic device. I measures the cell voltages and overall current. When it detects something isn't right, it switches off to protect the cells from further damage.

37v is too low. It should be about 41.7v hot off the charger.

I suspect that the water has drained some cells to below the minimum. If they went as far as 0V, they'll be scrap. You have to pull out the multi-pin connector and measure the individual cell voltages by starting at one end of the connector and working your way down in adjacent pairs until you have 10 results. Unfortunately, you posted a thumbnail rather than a photo, so I can't see what you've got to advise more detail.

Use this method to post a photo:
http://www.pedelecs.co.uk/forum/announcements-feedback-support/15268-does-forum-picture-upload-work.html

Have a look at this thread:
http://www.pedelecs.co.uk/forum/electric-bicycles/15289-bottle-battery-repair.html

 

[Bezzer]

Thanks for your answer. Sorry about the thumbnail - this should be better

 

[Deleted member 4366]

I need a proper high resolution picture. Why do people never do what I asK? Please use the method I suggested. Sorry to be so blunt.

 

[Bezzer]

These are pics I grabbed off a German website. I will take a hires pic tonight - thanks

 

[Deleted member 4366]

OK then, but you can still have a go at measuring the cell voltages, which should show the cause of your problem.

 

[Bezzer]

So I have taken a hires pic
https://www.dropbox.com/s/zqv9k22oo04ifr2/2013-11-19%2018.25.51.jpg

If we say the pins run from 1-9 left to right then I have ok voltage between earth-1, 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, but 8-9 is showing zero volts an 9-batt+ only 1 volt. Could this be the problem?

 

[Deleted member 4366]

Just to be sure, there's 10 bleed resistors at the top of the photo. They're the flat black things. Measure between the battery negative and the top of each of those resistors. You should get 10 cumulative results. Please post them here. Be careful to make sure you get a good contact with your probe. The pads sometimes have varnish on them, which you need to penetrate.

 

[Bezzer]

Thanks for that. I checked the voltages as you said and got the following results going left to right 1-10.

0v, 5.9v, 11.8.v, 15.5v, 21.4v, 24.3v, 28v, 32.7v, 35.4v, 35.5v

The direct output from all cells (batt- and batt+) is 36.8v

 

[Bezzer]

I have now realised that pin 1 and 10 are really showing no incremental voltage difference. Could these cells be both next to each other and water damaged?