Please help me solder this hacky co-op battery

[potatop]

Hello everyone! I got a backup battery from the local bike co-op and it seems to have been rewired to remove the locking mechanism at some point:



The large red and black wires (black connected to the light blue) are connected to the discharge terminals on the outside. The small red and black wires conmect to the visible charging port. What I assume to be the lock bypass is at the top of the image.

When I hook up the controller to the positive and negative terminals on the outside, nothing happens, but if i connect the negative controller terminal to the white sheathed wire inside (which the small black charging ground wire is connected to), the system fires up. Does someone know what the white and blue cables are, and how the charging/discharge grounds should actually be connected?

Thank you!!

 

[amberwolf]

First, what voltage is the battery supposed to be?

Second, what voltage battery does your bike use?

Since it does power up with the charge port connected to the controller, this isn't likely, but is possible: If your bike uses a higher voltage battery than this one is, it may not be compatible as many controllers will shutdown to protect the system once battery voltage drops below their LVC, and some even shutdown to protect the system if the battery voltage is above the controller's HVC.

Do you have a voltmeter?

If so, please measure the voltages as noted, with the meter set to 200VDC, and post that voltage here for each of the tests below.

Put the red lead on the red wire junction, and the black lead on the blue/black junction. This is the discharge port voltage.

If the voltage is something close to or above what the battery's nominal voltage should be, then connect it to the bike and turn it on and retest the voltage. If it has dropped to nearly nothing, then the BMS has shut off it's output (thick blue) to protect the cells against overdischarge (or some other thing, but usually that).

If the voltage is very low without it connected to the bike, a few volts, then same thing.

If the voltage is about the same with it connected to the bike as without it, then the battery's output is probalby ok, and there's something else going on, perhaps the wiring order to the bike's controller is wrong inside the connector, or the LVC of the controller is higher than the battery voltage, or the HVC of the controller is lower than the battery voltage.


Then measure the voltage with meter black lead on the white/black wire junction, and the red lead on the red wire junction. This is the charge port voltage.



Once we see what readings you get, and what your system's voltage is supposed to be, we can work out further steps and info.

 

[potatop]

Thanks! I will borrow a voltmeter after work today and check the specifics. The battery is 48v, my motor is 36v but I had planned to only use the throttle under 75%.

The controller is actually an Astroflight 204 model airplane controller that was used by a local high school with this 36v Heinzmann motor for a solar ebike competition. The controller is labeled 60v/50a max, which makes me doubt that's the limiting factor.

 

[999zip999]

Is that a brushed motor ?

 

[potatop]

Is that a brushed motor ?

It certainly is.

The voltage at the black/blue ground is nearly nothing - 0.6V or so. using the charging lead as ground, it's 29v.

 

[999zip999]

There are complete kits for 200.00 motor controller throttle electric brake cut off pas a dash if you pay for it everything but a battery.
You need to find a multimeter or As long as you have a multimeter or voltmeter we can help you out from The rat's nest I see tell me why I would make a charge port or two wires to the charger and two wires to the controller that's it it's best to always disconnect the battery when not in use.
Plus a peice of paper>
I think that there a set of charge wires a ND out put wires. And only two wires to charge. Get out your meter red does not mean positive red does not mean negative in Chinese it means the first wire I could pick up just like the Italians and now for a male's red means nothing black means nothing the other colors are in a rainbowdl in Italy

 

[potatop]

I know I can get a brushless motor setup for under $200, I'm just trying to get started at a low cost right now and reuse some used components to learn a thing or two. The voltage tests are listed above... i see you're saying I should have tested all possible combinations of leads, though. Looking at bms diagrams, it seems like there are typically 2 grounds (charging and discharge) and one terminal? Could this mean I just need to switch the ground leads?

 

[amberwolf]

The voltage at the black/blue ground is nearly nothing - 0.6V or so. using the charging lead as ground, it's 29v.

That indicates that the discharge output (black/blue, where the controller black goes) is disabled by the BMS in the battery, because it is too discharged to allow operation.

29V at the charging input indicates the battery needs to be charged, and is completley empty for a 36v battery, at only 2.9v per cell.

If it's really supposed to be a 48v battery, and it's really 29v, then it's dead dead, damaged dead, way overdischarged at only 2.2v/cell, assumign a 13s 48v battery (rather than a 14s 52v battery).

In theory you could hook up a 36v charger to it and let it charge to full for that charger, then hook up a 48v charger and let it charge to full for that, and it would "work". But the cells could be damaged, and possibly have unpredictable failures later on (potentially including a fire, which while unlikely and very rare, and low-risk, is a high-consequence failure to be avoided wherever possible. ).

I would open it up to measure the actual cells before doing ANYTHING else. This will let you see how many cells in series it actually has, so you know what voltage it should actually be charged to, before doing anything that could be a problem later.

 

[999zip999]

Sometimes used are broken beyond repair people don't know about batteries and they're willing to sell you a used battery not knowing one thing about it .What is the voltage of your charger.?
Is there printing on the battery that says voltage ampere hours is there printing on the charger that says voltage and amps ?

 

[potatop]

Yeah, this was just donated to the co-op with no explanation so who knows what its past life involved.

The battery says 48V 8AH. The charger says 54.6V 1.5A.

The battery had been sitting for a while so I charged it again. Here are some new figures from the different ground leads, all with the positive on the red junction (I also tried different combos in case the red isn't actually positive, but nothing):

black/blue - still almost nothing
"charging" ground - 54.87V
"lock bypass" - 39.58V

I was reading about jumpstarting the BMS by charging through the discharge leads for just a minute. Is this something I should try?

 

[999zip999]

I guess you have one or more low cells below cutoff for one reason or more. So lvc in BMS is triggered to shuts down the battery. Did you pay money for this battery ?
Is best to know the state of charge as each parelle group of 13 cells starting at neg end as one.

1. 3.95v
2. 4.10v
3. 2.85v


13. XXX
Charger voltage. Xxx volt
Battery starting voltage
End voltage.
Please fill in the blanks.

 

[Balmorhea]

Like amberwolf says, a lithium ion battery that has dropped from 48V nominal to 29V actual is dangerous, and can’t be returned to an undamaged state.

I urge you to open up the battery enough to probe each cell group for voltage. If any of them is much under 3.0V, it should be considered suspect. If any is significantly under 2.7V, it’s hazardous garbage.

If you want to keep messing with that battery out of curiosity, you should only keep it where it can burst into intense flame without catching other things on fire. A barbecue grill is good for that.

 

[potatop]

Thanks everyone! I didn't pay for it yet, I volunteer at the co-op and wanted to take the opportunity to test it before I or someone else pays money for junk or gets hurt. I may pry it out but I am a little freaked out by tearing batteries apart and if it already has shit cells I don't know if it's worth my time.

 

[999zip999]

Check with meter the main battery out puts before BMS just the battery.

 

[999zip999]

Buying a used battery it's like buying used underwear if you have to get you got to do it. Otherwise leave it in the barbecue and not in your bedroom. Don't leave it under the bed because she will find it. Damm used underwear.

 

[amberwolf]

The battery had been sitting for a while so I charged it again.

Well, now you have no way of finding out the extent of the problem, or if it did actually have overdischarged cells, so I would recommend considering the pack hazardous, and never to be stored indoors.

It might be perfectly fine...but since you've removed the possibility of verifying that, it's much safer to consider it a fire hazard.

The problem with this issue is that you can never know if there is fire-potential-damage until a fire actually starts, and its' too late do do anything about it then. The fire can be so hot so fast that you cannot remove the battery from the environment, and the surrounding area and structure can be lost, along with any living beings present inside.

It's a very low risk...doesnt' happen very often.

But when it does happen, it's disastrous consequences.