Battery/BMS Peculiarity

[Bikes4two]

I have a 250w 36v TSDZ2 with a VLCD6 display and a 10Ah bottle battery and the battery has dveloped a peculiar 'feature' in that:

• - the bottle battery has an in-built on/off switch:
  - if I mount the battery into the bottle cage and then switch the ON/OFF switch on, the motor will not power up from the handlebar display and the battery level LEDs do not light
  - if however I switch the battery ON and then mount it in the bottle cage, the motor will power up, the battery level LEDs illuminate and all works fine
  - switching on and off from the display responds as normal
• I double checked it was the battery by swapping batteries with a friend’s identical system and the issue went with the battery (rather than staying with the wiring/motor on my bike).
• I removed the top and bottom parts of the bottle battery to check for any obvious water ingress, chaffed/loose wires and measured the resistance across the battery ON/OFF switch and all was fine.

From the guage wires on the battery ON/OFF switch, I have deduced that the switch signals the BMS to power up, thus pointing to the BMS as being at fault.

Has anyone experienced this sort of battery/BMS behavious before and/or can suggest a way forward?

The battery came with a 2A charger but I switched to a 4A charger a couple of weeks back - is it possible that the BMS doesn't like 4A?

The silver lining to this particular cloud is that when parked up I know that if I switch off at the battery, a wouldbe thief wouldn't know how to power up the motor and pedal off into the sunset without some effort .

 

[Bikes4two]

Bump - anyone any ideas please?

If required, where would I start looking for a replacement BMS.

Thanks in anticipation.

 

[wheeliepete]

Not come across this issue before, I would advise you live with it if the battery is otherwise working/charging OK. BMB Battery sell a replacement BMS to fit the bottle case, but may not be a plug and play replacement.

Lithium BMS System for Bottle Battery with 5V USB Cells in series 10

Lithium Ion BMS System for E-Bike Bottle Battery. It has a +5V USD output for charging portable device, cell phone, ipad etc. Please kindly note that:If your battery before September 2016 in our company to buy,then change the BMS you need to re-soldering all the original balance cables.

bmsbattery.com

 

[Bikes4two]

Thanks @wheeliepete - that link is now safely book-marked in the event that the BMS in my battery subsequently causes me problems.

I will indeed be living with the issue - it's a strange one. What brought my comment about using a 4 amp charger rather than the supplied 2 amp one, was a comment by @Nealh in a post here where there was a suggestion that a 4 amp charge might not suit all cells and I was wondering if the same might apply to BMS although I note that the BMS you linked to, gives a max continuous charge of 5A.

As for the spec of my own bottle battery cells, no info was supplied - maybe the supplier might tell me (the truth)?

 

[Bikes4two]

Probelm Solved (Apparently)

• I took the top and bottom sections off the bottle battery and established that the the 2 thin wires on the power on/off switch in the bottom section went to the BMS in the top section of the battery.
• The wires were on a plug/socket on the BMS to it was relatively simple to carry out continuity checks whilst wiggling wires around etc.
• Eventually I narrowed the problem was down to the physically position of the on/off switch in that the connections soldered to the rear of the switch were very tightly against the main terminal connection block (the block in the bottom of the battery that makes contact with the battery holder contacts).
• I took out the on/off switch (after melting the hot glue) at which point one of the soldered leads dropped off where I have to assume the tight fitting had stressed the joint.
• I then bent the rear connection points to clear the adjacent connection block and re-soldered, re-glued the switch into place and re-assembled everything.
• All in all a simple job once you know how the and what the switch actually does and of course, some simple diagnostic techniques.
• I am wondering if bending the switch rear connector blades may have weakend the switch or the switch has weakend do to its origanal assembly (switches of this sort are not generally very robust if the ones used in my camper are anything to go by), so I'll look out for a 'better' switch if I can find one!
• The one fitted looks like this:
• 

Thanks to all those who contributed to my original post.