LCD 3 issue

[Kwozzymodo]

I have a question regarding my ebike set up:

I have a home made li-ion battery 36v 6.8a with bms (10s2p). It is charging to 40.4v

I have an S-06S controller and Q100 motor.

when I turn on the system usung the thumb switch from the lcd 3, nothing happens. When I disconnect and reconnect the lcd, it turns on straight away. The system appears to work fine and the thumb controller toggles between screens, shifts assist from 0 to 5 fine.

Why won’t the lcd turn on the system via the thumb switch?

 

[Deleted member 4366]

Why is it only charging to 40.4v?

 

[Kwozzymodo]

I‘ve not left the battery to charge for an extended period. Of the 20 batteries in the pack - 18 read 4.0v and two read 4.1v.

If I measure volts across +ve and -ve I get 40.4v

 

[Deleted member 4366]

It should charge to 42v, but 40.4v won't stop the LCD from working. The working of the LCD is simple, but complicated. When you press the switch, the battery wire sends its 36v (approx) through a resistor to a 5v regulator that then powers the CPU. The CPU then latches the battery voltage on via a transistor that also sends it on to the controller, so the controller switches on. While it's latched on, the cpu keeps its 5v supply to stay active. When you press the button again or if the sleep timer activates or if the battery voltage is sensed below the LVC level, the cpu de-latches the battery voltage, so both itself and the controller switch off.

That brings us to reasons why it switches off, which could be that the software in the cpu is faulty. That can happen, though not that likely. Or, the cpu gets a second signal from the switch that tells it to switch off. That's more likely and could be due to a sticky switch or water in the switch. Finally, the sensed battery voltage: I think that the damping factor P5 can affect that, so try setting P5 to zero to eliminate it.

Maybe the software is faulty and it it needs a complete disconnect to do a reset.

 

[Kwozzymodo]

Thanks for the reply. I agree that the battery voltage should be circa 42v and will see if an extended charge sorts this issue out. The lcd thumb switch seems to work okay, once the lcd is powered up. I think the issue may have something to do with the sensed voltage, as you mention. I have some spare lcd3 units, so could try a swap out if the change to P5 doesn’t work.

I will adjust the settings and report back.

 

[Kwozzymodo]

I’ve set P5 to zero and still have the same issue - the unit works well, but can only be turned on by disconnecting and reconnecting. I’ve tried another display and that works fine. So, it looks like a faulty display unit. Is it worth taking it apart to see if I. An fix it, or should it just be sent back to the supplier for replacement?

 

[Deleted member 4366]

There isn't anything you can do to fix that fault.