Uses for a Bionx battery pack with a dead BMS

[bikezen]

Hi all,

I was given a Bionx battery by a bike mechanic who said the BMS card is dead. Bionx had remotely diagnosed this, disabled the battery and said it could not be repaired. The cells seem to be okay.

I cracked the case and took a look. I'm reading 35, 35, 24 and 35V on a termination block.

Here's the full set of images:
https://www.evernote.com/shard/s14/sh/785f7c5d-1f59-470e-a54b-e13f1bd336ee/26e445278a03f382
They seem to be getting truncated on this page.

I'm not really sure what to do with this battery. It potentially has a useful life span yet my skills with batteries are pretty limited. I've purchased a Ping battery in the past and even replaced the burnt BMS on it, mounted it in a case and used it for years.

Right now, with the Bionx, I could see removing the card, probably could get that done without zapping something or myself or ruining a cell. At that point, what to do? I see these cheap BMS cards on eBay. To get from this battery in its current state to a working, safely rechargeable battery is a bit of a leap.

Just curious what you would do with this? Perhaps the best bet is to recycle it, though it is in a nice form factor and I would love to have a hefty power pack on my cargo bike.

 

[docw009]

As you're not using the Bionx motor or controller with all of the proprietary doo dads and lock outs, would it be relatively straight forward to scrap all of the Bionx electronics and connect an appropriate third part BMS board? You have to identify all the wires to the cells and then it's like fixing your Ping?

 

[icerider]

Throw the Bionx card away and buy an appropriate BMS for the configuration of the pack (probably 13s3p).

If the balance connector has 14 leads, the pack is 13s. The "extra" wire (there may be 2) coming out of the battery are for temperature monitoring during charge.

Then use it like any other 48V battery.

In the short term, measure the voltages along the balance connector. If the pack is currently pretty well balanced, you can use it while you are waiting for the BMS. Just bulk charge the entire battery brick and monitor the balance manually.

Bionx used HIGH END cells so the battery brick alone is worth some money.

 

[bikezen]

Okay, thanks for the info.

I've pulled out the pack, removed the card, installed some Powerpoles, and getting 36V on the pack. I tried measuring the balance connectors by re-inserting the terminal block into the card and reading from the solder points on the + side to the negative ground but didn't get anything useful out of that.

I'm counting 20 wires in the terminal block total, so 19 cells?

 

[tl01]

I acquired one in a similar manner. The extra wires are for temperature sensors, according to Bionx. I wasn't savvy enough to repair it, so I completely disassembled it and rebuilt it with a regular BMS. I've been using it daily for six months now and it's been a great battery. The cells in mine were Panasonic NCR18650PF 2900mah...so definitely worth saving if they're in good shape.

 

[icerider]

I'm counting 20 wires in the terminal block total, so 19 cells?

The highest voltage Bionx I know of is 48V. 48V/3.7V nominal = 12.97 (13 cells). 14 balance leads.

I don't know what the extra 6 leads are, perhaps there are 3 thermal sensors each with two wires ??? On my older packs, the thermal sensors (2) were still separate wires running fro the battery brick to the board.

So go to the middle of the balance connector and measure the voltage between adjacent pins -- this will be the voltage on that set of cells in the series. If the pack is anywhere near balanced, you should be seeing around 2.7V between adjacent pins. Work outward in each direction to find all 14 balance leads. If the card is conformally coated, you may have trouble making electrical contact to the solder pads on the board. If you can safely probe the connector coming from the battery brick, you may get better results.

Until you are pretty sure that all the cells are functional, you don't want to try charging the pack for fear of having a shorted parallel set (3p). If that is the case, the battery will have become 12s and charging it to 48V will overcharge all the remaining good cells. In my experience, the high quality cells in the Bionx batteries are VERY robust. I have lighting packs made from cells recovered from ancient dead Bionx batteries where only half the cells were recoverable.

Keep working with the balance connector until you figure out which ones are balance leads.

 

[bikezen]

Thanks for the tips, icerider. I'll give it a shot. The terminal block is fairly small to contain so many leads. The holes for the female socket side are tiny. I think I'll try using pegboard jumpers, that should do it.

 

[bikezen]

Okay, got 'er done.

I've got 14 voltages ranging from 2.92 to 2.98, with 6 leads measuring 0 volts.

Looking good that I've got a solid pack and now need to figure out how to connect it up to a BMS and then to a charger. That's a bit but looking doable.

Any tips appreciated. Thanks.

 

[999zip999]

Start at neg . End and start building voltage per wire.
1 2.98 volt
2. 5.96 v
3. 8.94 v

14. Xxx order . Must have order.

Label wires 1- 13 or is it 14 s ?

 

[icerider]

I've got 14 voltages ranging from 2.92 to 2.98, with 6 leads measuring 0 volts.

Below 3 volts is pretty low for LiMn batteries.

They would be happier if you bulk-charged (no BMS) to (13x3.7)= 48V.

Then monitor voltages weekly and recharge if the average gets below 3.2V.

This will keep the battery safe while you look for a BMS.

 

[bikezen]

Is this a scenario where I could use a charger to apply a one time charge to get the battery up to charge? I guess there's some downsides to that in that some cells will end up overcharged or undercharged.

Any caveats to this like not leaving the battery alone while this happens, for example, staying away from wood structures, things of that nature.

 

[icerider]

Trying a bulk charge to move the batteries to nominal V/cell is probably OK.

Keep your input current low (no more than say 1 amp (which is about 1/6 C) and watch the cell voltages. Keep the highest cell below 3.8V or so.

I would be surprised if the LiMn cells developed much of in imbalance while being charged to 3.7 volts per cell. If they do, it is an indication that one or more cells may be damaged.