Oxygen S-Cross Intermittent power loss

[DBye]

Following a ride to work in the drizzle last Friday morning my Oxygen S-Cross CB has developed an intermittent power fault.
The symptoms are:
Assistance will fade or cut out altogether when riding
Turning the system on/off sometimes rectifies the fault, or it will cut back in of its own accord
Sometimes when turning back on the screen displays that the battery is flat (the battery is fully charged, and the power indicator built into the battery indicated full charge -see attached photo for screen)
If i continue pedalling when the screen is as shown in the photo, often the battery display will "recharge" hit around 35v, and the assistance will kick in again.
I've tried disconnecting the brake switches and throttle, but none of those seem to be the culprit.

Anyone have any ideas for what else to try? I guess I should take it back to Oxygen, but if it is something simple like a loose connection it seems daft to do so. Particularly as I'd have to wait until I'm off work as they only open Monday - Friday 9-5pm.

 

[Nealh]

Your screen shot shows 24.8v which is very bad for a 36v system, a working bms should not let voltage drop much below 32 or 33v. You can check the battery first, charging it and then voltage test it with a DVM don't rely on the screen as it may give a faulty reading if moisture has got in and check all of the wiring. If necessary disconnect and reconnect everything checking for damp and esp check the battery docking area/ connection point. . After that If the bike is under warranty then let Oxygen sort it out first. Don't just assume the battery is ok you must do simple checks first to eliminate any doubt then fault finding can begin.
Moisture ingress may cause a fault almost anywhere in the system from wiring connectors, lcd , controller and battery. If it has got in to the controller or battery then it may have caused shorting or a intermittent fault, in which case they may need opening to inspect. The lcd may be tricky though and sealed, another option is to place items in sealed bag with rice to draw out moisture.
If it was just a pas issue then the sensor or magnet on the bottom bracket may have been knocked/moved but yours is likely to be battery/lcd related.

 

[Deleted member 4366]

Check that the connector near the motor is pressed in all the way to the guide line.

 

[DBye]

Thank you both for the advice. I have:
1. Charged the battery and checked it with a multimeter, it is producing ~40V. I should note that the display doesn't read low 20V's for long, and after powering on and off or peddling a bit it reverts to high 30V's.
2. I've checked the rear motor connector, it seems pushed in as far as it will go.

More worryingly, when checking the rear motor connector I noticed that the rear gear cable and motor cable have caught the front chain ring when going to lowest gear. Will be zip tying those two out of the way asap.

Water damage does seem most likely, although disappointing as it was a shower at best. I'll take the display and control pad off the bike tonight for a good dry out. The front controller pad doesn't seem well sealed at all.

I'm enjoying the bike and after a lot of spoke issues (had the wheel trued and it seems to have settled down) things were going well. Oh well.

 

[Deleted member 4366]

40v is still too low for a fully charged battery. It should be close to 42v.

Take the battery out and check that the connections in the battery and in the receiver are dry. Next, fully charge the battery again, then measure the voltage on the battery terminals immediately after you disconnect the charger. When you have the reading, measure the voltage on the charger's jack.

 

[Nealh]

Yep as d8veh has said 40 is to low and if that is the best it will charge then some cells are past their best, only opening and checking the cell via the BMS JST connector will tell you the state of play. I have 2 15ah dolphins not in their prime but are well balanced charging to 41.4/5v andl give 25-30 miles range without issue, both are used regularly come rain or shine.

 

[DBye]

I took it back to syebc. After they had it a couple of days have now got it back all fixed. Problem they think was that the battery was loose on its terminals and everytime I hit a big bump (so often on Sheffield "roads") the connection was disturbed or cut completely.

Have bought a pair of these to try and see if they dampen the vibration a bit:
http://www.schwalbe.com/en/tour-reader/big-apple-plus.html

£8 each at planet x at the moment.

The low voltmeter reading was a result of using an analogue volt meter and rounding (minimum reading on the scale was +/-5v).

I'm glad it was something simple and not the rain!