Help! BMS Board dead, 1.4v low battery output?

[Matt Badboy6]

Hey all,

I have a 48v / 11.6ah Hailong battery running a 1000w rear hub motor on a Cannondale conversion. On my last couple of excursions my power cut off as soon as the battery dropped to around 48v (sits on 54.4v after a full charge). This happened on 2 occasions. This morning I powered the bike up, the LCD lit up and then immediately died

I took the battery off the bike cradle (charger says fully charged) and tested the voltage from the power out points of the battery and my circuit tester says it is only pushing out 1.4v..? So I took the casing off and hooked up a test from the actual inner battery and zoom, voltage full off the scales.

Does this mean the BMS is dead, or is 1.4v just needed to run the LCD??

Yours,

Matt.

 

[Andy Bluenoes]

Does the battery have an on/off switch? It might read different voltage if it does, when its powered on. One of my previous batteries did that.

 

[Matt Badboy6]

No, no on/off switch mate.

 

[Nealh]

Look for and check the fuse. if that is ok you will need to measure the 12 cell groups via the bms white jst connector which will have 12 or 13 small wires. Disconnect the jst lead and use your DVM pins on each one moving the pins along the connector as a pair. Write down the 12 voltage readings then we might be able to figure out where the fault may lie.

 

[Nealh]

Post your results here so that we can see them.

 

[Matt Badboy6]

Hey Nealh,

Did as you said and found a dead pin! I followed that wire back and it had come away from the battery. Thanks for the heads up .. now, where's my soldering iron??

Thx again,

Matt.

Edit; yep, will do. I'll take some pics as I go and up them too.

 

[Nealh]

Depending on the voltage of that cell group you may need to manually charge/discharge that one group to the level of the others for the bms to balance charge properly, other wise the bms will shut off to soon if one or the other hits hvc first.

 

[Nealh]

If it is a bad solder joint then resoldering is fine, If that sense wire is tight then might be worth extending it with a bit of heat shrink covering the joint and double checking the other sense solder /wire joins.

It makes life so much easier when you find a definite reason/cause .

 

[Matt Badboy6]

Just done a quick fix and glued the wire on. I'm not riding until the weekend so I'll solder it on then.

Good news! LCD fires up straight away and the voltage is sitting at 54.3v so that group that was disconnected seems fine.

Pics at the weekend guys and thanks again Nealh.

Matt.

 

[Nealh]

We love a good ending on here.
Don't forget a cheque or payment fee via Paypal for 0.00p for services rendered .

 

[Matt Badboy6]

Some pics of what I did guys ..

 

[Matt Badboy6]

Would anybody say this is cell leakage..??

 

[Deleted member 4366]

Cells leak from the top. AFAICS, that mark lines up with a cell bottom.

 

[Nealh]

To me it looks like a scorch mark also the end of the sense wire shows scorching , the tab also looks slightly blackened unless its just the light making it look bad. The next two sense wires in view to the left also show staining on the wire ends. I wonder if the sense wire came a drift from heat as it has broken off through weakness ? I noticed two or three bad spot welds on the cell ends and a burn mark on the very end weld, a bit too much power applied during welding or not a good initial contact between cell and nickel strip causing sparking and burning.
What is the amp rating of the charger you are using ?

 

[Matt Badboy6]

The blurb on their website says Standard charge at 2A and fast charge at 5A although there is no physical switch on the charger to switch between the two. It takes about 5hrs to charge from flat.

I'll give the battery a good look over at the weekend and look for more charing on the other side. I'll up more pics for you guys too

 

[Matt Badboy6]

Cells leak from the top. AFAICS, that mark lines up with a cell bottom.

Is cell leaks a common thing on ebike batteries d8veh?

 

[Deleted member 4366]

It used to be very common with the cheap Chinese cells, but I hardly see it now that most e-bike brands have switched to branded cells. I have batteries with as many as 10 leakers out of 60 or 70 cells. it makes me wonder what to do with the remaining good cells, because I don't know whether they're going to leak in the future. I did repair some of these batteries for some people, but I never heard what happened after that.
here's an example:

 

[Matt Badboy6]

Thanks for the image. I'll know what to look for when I give my battery pack a good going over at the weekend