Aventon Pace 500 electrical failure - SOLVED

[MikeEllis]

About 3 weeks ago, my Aventon Pace 500 went dead after less than 5 minutes of riding. Motor stopped and display went completely blank. Battery had just been charged.

The bike is 2 years old. I've got 1900 miles on it and no prior problems (or accidents). It's garaged when not in use.

Aventon's customer support has been polite and friendly but slow and, to be honest, nearly useless. They won't supply technical manuals, schematics, or even pinouts. The nearest Aventon dealer is almost 200 miles away, so that's not an option.

In the interim, I asked my local bike shop to take a look. They're a good outfit specializing in higher end e-bikes with Bosch mid-drives, but lacking tech info the best their electronics guy could say is that the battery seems fine.

I ordered and received a replacement display from Aventon. Same behavior. Doesn't even come on. The handlebar switch comes with the display unit, so that's also now eliminated as a point of failure.

I see no indication of physical damage to any of the cables. The battery connector pins and receptacles are all clean and shiny.

The motor controller is tucked tightly into the frame along with a bundle of cables and connectors. I've been reluctant to pull it out as it looks tricky to do without stressing the attached wiring.

At this point, it seems pretty clear that power is not being delivered to the display. Guess I need to figure out whether that is meant to be supplied from the controller or from a separate group of cells in the battery enclosure.

Further diagnostic suggestions appreciated!

 

[MikeEllis]

Update:

I just took the battery pack off the bike to check the open circuit voltages on the connector. The battery pack has an ON button and a row of 4 LED's to indicate state of charge. After turning it on and observing all 4 LED's lit, I measured the voltages between various pin sockets (5 total) on the connector. Everything was 0.0V with the battery on.

So I guess that either:

1. An internal fuse is blown, or

2. There's an interlock in the battery pack that withholds power from the connector when it's not plugged to the bike, or

3. There's an interlock that's detected some unhappy condition within the battery.

I'm flying blind here since Aventon won't provide circuit info. Any help much appreciated!

 

[AHicks]

If you have no voltage showing anywhere, I would carefully open the battery case for further troubleshooting.

 

[MikeEllis]

If you have no voltage showing anywhere, I would carefully open the battery case for further troubleshooting.

Thanks, that makes sense.

FWIW, I sent the measurement info to Aventon. They just responded "If you see that you battery connections are not between 50-54v then the issue is your battery. You would need to purchase a new battery."

My strong sense (based on more indications than just the above) is that Aventon is prepping itself for sale and has instructed its customer support to avoid anything that risks liability.

 

[MikeEllis]

The battery pack has two molded hard plastic end caps. The top has the ON button and LEDs. the bottom has the charging port plug.

I removed both and inspected. To the eye, everything is shipshape. No loose wires or evidence of overheating. No soot, no burnt electronics smell, no evidence of water incursion.

If there's an interlock or fuse it must be in the middle of the battery pack. I didn't try to pull that out. It's potted into place with silicone and besides I'd already had my first beer of the evening. :wink:

 

[MikeEllis]

It occurred to me last night that I could also check the voltage at the charging port (slaps forehead). I measured 53.9 V (as opposed to 0.00 V at the output connector). I take that to mean that the cells (or at the very least one string of cells) is near full charge. Right?

 

[litespeed]

The way I see it is they are ready to sell you a new battery which is worse case scenario. So……I’d take the pack apart carefully, prior to the first beer of the day/night. Sounds like it could either be a easy fix of some sort or worst case may be some form of BMS failure. If the battery doesn’t work and they won’t repair……I don’t see where you have anything to loose but much to gain if your able to repair.

Pay attention, take your time, have proper PPE (wear safety glasses/thick rubber gloves & remove jewelry) and try to not poke/stab with metal/conductive objects ie; screwdrivers, chisels, fingers or any other appendages! :wink: carefully dismantle until you can figure out what the issue is. Maybe search the web for others doing the same CSI on either your battery pack or one that looks similar. You tube is a great resource, sometimes!

Maybe post your whereabouts so maybe someone close can help too?!?!

Good luck!

Tom

 

[MikeEllis]

Thanks, Tom!

The way I see it is they are ready to sell you a new battery which is worse case scenario. So……I’d take the pack apart carefully, prior to the first beer of the day/night. Sounds like it could either be a easy fix of some sort or worst case may be some form of BMS failure. If the battery doesn’t work and they won’t repair……I don’t see where you have anything to loose but much to gain if your able to repair.

I think you see it right. I suspect the cells are likely ok so it's worth seeing if there's something simple like a loose discharge wire connection or a replaceable fuse -- especially since the battery pack is out of stock and Aventon doesn't know when it will be back in stock. :?

Pay attention, take your time, have proper PPE (wear safety glasses/thick rubber gloves & remove jewelry) and try to not poke/stab with metal/conductive objects ie; screwdrivers, chisels, fingers or any other appendages! :wink: carefully dismantle until you can figure out what the issue is. Maybe search the web for others doing the same CSI on either your battery pack or one that looks similar.

I hear you loud and clear. Many moons ago I dropped a small wrench into an inverter enclosure and shorted a 120VDC, 2000Ah battery system (the two thousand ampere-hours is not a typo). It was, shall we say, rather memorable.

You tube is a great resource, sometimes!

I just finished watching a couple of Micah Toll's DIY battery pack videos. https://www.youtube.com/watch?v=TY7FwffZ5vc and https://www.youtube.com/watch?v=gBdA-Glj_0o . Good stuff! I've now got a much better idea what I'm likely to see inside.

Maybe post your whereabouts so maybe someone close can help too?!?!

Burlington, VT. I'll add that to my profile.

 

[miro13car]

your battery pack must have some kind of BMS which obviously failed.

 

[MikeEllis]

your battery pack must have some kind of BMS which obviously failed.

Sounds likely, thanks. Whatever failure the failure is, it's a complete open circuit on the discharge side, but not on the charge side.

 

[MikeEllis]

I've now partially disassembled the battery pack. Getting it out of the extruded aluminum enclosure was challenging. Had to carefully cut the beads of silicone sealant on each end then use body weight to carefully push the pack through with the handle of a 4lb sledge hammer. Don't know how I'll ever push it back in, since the BMS is on the far end.

They used decent cells, Samsung 18650's. The pack looks well sealed and and I see no obvious damage to cells and wires. In particular, the main discharge wires are secure when tugged. I can see the solder connection for the negative. The positive connection is concealed beneath the cardboard and kapton tape.

I'm hesitating before cutting away the wrapping. Any thoughts about the chances of finding something repairable?

 

[AHicks]

My bet is you won't have to cut any of the wrapping. Find the 2 big wires exiting the pack, and check them for voltage. If present, follow the wires to the point there is no voltage.

 

[MikeEllis]

Found the problem -- a bad solder joint on the negative pin of the discharge connector. Hard to get really good photos with my phone camera's autofocus trying to be helpful, but it's pretty clear that the negative lead was never firmly attached to the gold-plated pin socket. Looks like the heat shrink tube and a glob of silicone were all that held it in contact for the past two years.

It explains all the symptoms and measurements I've reported. Damn shame I had to compromise the compartment seals and cut away the Kapton tape that covered the BMS to be able to confirm the open circuit and locate the problem. If Aventon had been willing to share a schematic I'd have figured it out a whole lot sooner since it would have been obvious that there should be continuity between the negatives of the charging port and the discharge port.

Oh well, now I need to get decent soldering iron, some appropriate solder, Kapton tape and silicone sealant to put it all back together. Used to have most of that stuff at hand but we recently downsized and I let it all go. I'm hoping the bad solder joint is the only problem and that none of the other wires are also badly soldered.

 

[MikeEllis]

I found a local electronics repair shop to do the repair (solder the negative discharge lead, heat shrink, glue, repackage) at a very reasonable cost.

Took the bike for a ride this morning. Seems to be working perfectly.

Thanks to all for the helpful comments and encouragement!