Bionx 48V SL 350 XL battery charging issue

max_m

1 mW
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May 20, 2018
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Burnaby, BC
Apologies, I'm sure this is covered in another thread - but not an easy topic to search for.

I recently bought a used Bionx SL 350 HT XL system, it's been working ok but with moderate range (I was considering getting new cells).

A few days ago I noticed the display showed low battery (one bar) even if it had been plugged in overnight. It still seemed to have enough power for my ride (about 15miles with some big hills).

Now when I plug in to charge, the ring turns red for a few seconds then go off, and the battery does a little alarm chirp. Same thing when I touch the charge port.

I measured charger voltage to 25.8V. It draws almost no current when plugged into the battery (measured with a Kill a Watt).

I'm not sure how to measure battery voltage without opening.

The system still turns on, but showing battery as empty. Diagnostics mode on the bike display shows 00441 in the lower corner when not pedalling.
 
I went for a ride with regen on and got it up to 46V (pic is before ride). At least it's not chirping anymore, but charger still doesn't come on.

Bad news?

Screen Shot 2018-06-16 at 4.24.10 PM.png
 
Those voltages are pretty low and might suggest that you have one cell shorted (and it would have drained its little buddies wired in parallel). That would worry the BMS which might refuse to attempt to charge but still allow regen to feed the battery.

Is there any change in current or wattage on the charger plugged into the battery and not plugged in ?
 
There was no current when I plugged it in when battery was 43V. I'll ride and regenerate a bit more to get it to 48V and see how it behaves.

Right now it's at 46V and one battery bar on the display - does that seem about right?

Is there a trick to opening up the case? I've removed the bolts, and separated along the seam but something is still holding it together.
 
46 volts and 1 bar -- that sounds about right. At that voltage it should charge happily if charger and battery are healthy.

Getting in -- after you take out all the bolts (and unlock it and raise the locking handle IIRC) You need to pry all around VERY gently. If it is like the older ones I have opened, the last thing Bionx did before screwing the battery housing together was to squirt what looked like clear RTV silicone sealant all over both sides of the battery. This results in the battery being firmly held in the case and no rattle at all. But... when you go to pull it apart you need to break that bond. Mine have always pulled loose nicely and left the adhesive/sealant attached to the shrink wrapped battery block.

Once you are in you should find a multi-wire connector from the battery to the BMS -- at that connector you should be able to check the voltage of each of the serial sections of the battery (IIRC the battery is 13S4P). 13S gives you 14 identical thin wires at that connector. If there are more wires, then they probably go to thermocouples to sense battery temp for the BMS. I don't remember ever seeing a wiring diagram for the connector but be careful checking voltages. If you short between two of those voltage sense wires they will probably just evaporate in a blue flash.
 
I had the same happen. Fortunately no damage besides a smoked charge port connector. You can replace it or solder the cable on directly.

I'm not sure what BionX is doing to these connectors, but they have a tendency to get roasty.
 
Good to know it's likely the connector. I soldered the cables to the connector legs, going to charge it to full before putting it back together. The board gets quite warm, I assume that's normal?
 
Yes, that's normal. It's got a DC/DC converter onboard that boosts the 26V from the charger to 48V+ for the pack. It gets a bit cozy after a while.
 
Any idea why they're doing the 26V charger with boost circuit instead of just having a proper charger output? Is there some limit at 50V that they can't exceed for end user equipment?

And the 48V BMS boards are just crap anyway. If they're not frying one thing, they're frying another.
 
It's so they can use the same charger and plug for their 24V, 36V and 48V systems.
 
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