52V / 24Ah triangle battery from Lunacycle is only charging to ~55V | it isn't the charger, already tried to jumpstart

Hi,

I wondered why the capacitiy of my battery was so bad and then saw the charger shutting off at only 55.4V instead of 58.8.

• I'm sure it's a 52v battery

• I tried to charge with a 2A backup charger instead of the advanced luna charger, so it can't be the switch at the charger

• Also I tried jumpstarting the battery through the charging wire, didn't help

• I tried letting it charge 24h, didn't do balancing..
  I already contacted the support, they said I should follow the troubleshooting instructions on the forum not really helpful :?

Sending it back isn't an option for me since I live in switzerland and the afford would be too high.

I only see one option: Open the battery and see whats wrong and do a hard reset on the bms.

Or what are you guys thinking?

Thanks for helping me out

I think you will have to open the battery pack and measure the voltage of each group of cells. It is likely that you will find one or more of the groups are out of balance. Write down the voltage values for each group and post the numbers here. It is possible to manually balance the battery through the sense wires. You can find out how to do that here. Work slowly and carefully and pay attention to what you are doing with conductive tools. Batteries are very unforgiving.

Hmm ok,

I will work carefully and let you know when I have measured the voltages.

Thanks very much!

A nominal 52V pack is 14 cell-groups in series. The specific voltage you mention suggests that one cell is bad, and it drained the rest of the cells in that group.

One of the safety features of the charger is that it monitors the 14 cell-group voltages, so the charger does not try to bulk charge the remaining 13 cell groups to 58.8V

If it was a cheap "dumb" charger, and did that, the result would be 4.5V per cell, which would be very bad. You need a digital multi meter (DMM), and even a simple $20 model would be helpful. If I am correct, 13 cell groups will be at 4.2V, and one cell group will be around 0.02V.

As this is a LunaCycle pack, it's more than safe to assume that it has a BMS rather than relying on the charger to detect and protect the cell groups. And indeed, both of the chargers mentioned in the original post are 'dumb' chargers.

If one cell group were drained completely, the BMS would have shut down the pack entirely. It would not be possible to utilize the pack, even at degraded capacity, via the discharge port (though it may still offer power via the charge port, depending on what kind of BMS they're using). My guess is that multiple cell groups are out of balance to a lesser degree.

This is really interesting. Looking forward to seeing more. Can a single bad cell bring down an entire group?

“This is really interesting. Looking forward to seeing more. Can a single bad cell bring down an entire group?”

Yes. Even if it has only lost a fraction if its capacity the total capacity for that group will be lower than the other groups. When the pack is charged the lower capacity group will hit full charge first and the BMS will stop the charging. If left on the charger long enough the BMS will attempt to balance by discharging the high and charging the low but it is very slow and there is no indication that anything is happening. Most users disconnect the charger when it signals full and not give the BMS time to work.
On discharge the lower capacity group will run low first and the BMS will cut off the load while all the other groups still have some charge left.
This cycle happens over and over and each time the unbalance gets a little worse. When it gets bad enough to be really noticeable the first option is to leave the battery connected to the charger for a substantial amount of time while the BMS slowly corrects the problem. The second option is to open the battery, disconnect the BMS and hook a single cell charger to each of the low groups or put a resistive load on the high groups to bring them all to the same level.

So thanks for all replies!

I just opened the pack and measured the individual banks at the bms connector. They are all at 3.79V but the last 2 groups (assuming 13 and 14) are out of balance, the first is at 2.83V and the other at 3.53V. So I need to balance the pack right? I heard of charging an individual group only so it gets in balance with the others, is it possible and how doea it work?

I have to add that I made a stupid mistake while measuring, I worked very carefully but it sparked to times, I mabye have shorted out the bms connections.. I hope I didn't destroy the bms with that ._.

The chargers are crap I heard (one of them is the charger that came with the pack, and the other one is a luna advanced charger (52v, 300w)

Thank you all very much! C:

https://ibb.co/M9Q3khX
https://ibb.co/sFPfKPm

This is how a luna triangle pack looks at the inside

This post explains it quite well. How to rebalance the pack:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=107665

Matador

Thanks!

I know tried charging after disconnecting amd recpnnecting the balance connectors. Know, when I plug in the charger, it jumps to 58.8V instantly and isn't charging.. (the battery voltage is at ~54v) Before it was charging to 54v amd then turned off, not showing 58.8v volts.

Did I damage the bms, with shorting the balance wires?

If it's a 52V battery (14S). Then full charge at 4.20V per cell (14 x 4.20V) is exactly 58.8V.

Some charger by Luna offer a swith to charge at a lesser voltage than full (for example charge at 90% instead of 100%) to prolong the lifespan of the battery.

Is it possible you have such a charger and accidentaly flipped the switch ?

Matador

jnlk6 said:

So thanks for all replies!

I just opened the pack and measured the individual banks at the bms connector. They are all at 3.79V but the last 2 groups (assuming 13 and 14) are out of balance, the first is at 2.83V and the other at 3.53V. So I need to balance the pack right? I heard of charging an individual group only so it gets in balance with the others, is it possible and how doea it work?

I have to add that I made a stupid mistake while measuring, I worked very carefully but it sparked to times, I mabye have shorted out the bms connections.. I hope I didn't destroy the bms with that ._.

The chargers are crap I heard (one of them is the charger that came with the pack, and the other one is a luna advanced charger (52v, 300w)

Thank you all very much! C:

Click to expand...

OK I get it now. This is why it does not charge to 58.8V.

Your battery is :
------------NOT CHARGED: ----------------------------------------> CHARGED:
B1 (-) -------- 2.83V -------------[ Add + 0.41V]-------------------> 3.24V
B2 ------------ 3.53V -------------[ Add + 0.41V]-------------------> 3.93V
B3 ------------ 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B4 ------------ 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B5 ------------ 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B6 ------------ 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B7 ------------ 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B8 ------------ 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B9 ------------ 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B10 ----------- 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B11 ----------- 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B12 ----------- 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B13 ----------- 3.79V -------------[ Add + 0.41V]-------------------> 4.20V
B14 (+) ------- 3.79V -------------[ Add + 0.41V]-------------------> 4.20V

TOTAL: ------- 51.84V --------[Add (14x0.41V) = 5.74V]---------> 57.57V

Seems like your charge should stop at 57.6V if all your cells were at 3.79V except two groups are at 2.83 and 3.53. Are you sure none of the other cell groups are at 4.20V (all at 3.79V). ONCE ONE CELL HITS 4.20V, the whole Battery charging is shut off by the BMS to prevent some cells from overcharging. Therefore the other lower cells don't have a chance of climbing to 4.20V too.

Matador.

Butif you have a charger that has a switch to charge at only 90% or so instead of 100% (luna advanced charger), then maybe the end charging voltage is more around 54.1V or so...

If so then your charge profile will be more like so:
------------NOT CHARGED: ----------------------------------------> CHARGED:
B1 (-) -------- 2.83V -------------[ Add + 0.16V]-------------------> 2.99V
B2 ------------ 3.53V -------------[ Add + 0.16V]-------------------> 3.69V
B3 ------------ 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B4 ------------ 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B5 ------------ 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B6 ------------ 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B7 ------------ 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B8 ------------ 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B9 ------------ 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B10 ----------- 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B11 ----------- 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B12 ----------- 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B13 ----------- 3.79V -------------[ Add + 0.16V]-------------------> 3.95V
B14 (+) ------- 3.79V -------------[ Add + 0.16V]-------------------> 3.95V

TOTAL: ------- 51.84V --------[Add (14x0.16V) = 2.24V]---------> 54.08V

Maybe you also need to troubleshoot your advanced luna charger voltage:
[youtube]H9ENLcYFn54[/youtube]

Matador

It can't be the charger sonce I have a backup one that also doesnt charge the battery fully. It cant be the switch of the charger.

I'm pretty sure there isn't a cell at 4.2v, I can test it again tomorrow. Could it be that theres a loose connection between the cells?

Thanks for your help.

Then it's going to be the battery. I suspect you "BMS" does not balance. It's probably just a PCB.
You need to manually balance each cell group back to 4.20V using a Hobby Charger.

I thinked of that too.

So how you recommend to do this? I don't really have a clue

Disconnect the JST connector off the BMS and tap in the balance leads through that connector and charge through them at 4.20V. Do that for each row of cells. Sorta like this:
https://www.youtube.com/watch?v=qf4W3F2Lqhc
or like this
https://www.youtube.com/watch?v=DP1-VBNJmsg
or like this:
https://www.youtube.com/watch?v=jx8fq16VT2k

Matador

Now I understand, thanks! I looked for a charger and found this:

https://www.ebay.de/itm/5V-1A-Li-io...-4-2V-Charging-Protection-Board-/272969439726

This should work right?

Thank you so much!

jnlk6 said:

Now I understand, thanks! I looked for a charger and found this:

https://www.ebay.de/itm/5V-1A-Li-io...-4-2V-Charging-Protection-Board-/272969439726

This should work right?

Thank you so much!

Click to expand...

It will work. It will be slow... charging at 1.0A, but it will work.
In any case, when charging through the thin wires that are the balance leads, you don't really want to charge too high amperage (or the wires will melt). One amp should be perfect. Just be carefull with polarity so to not burn any electronics.

Just first, bulk charge the whole battery with your normal ebike charger. So all the higher voltage groups are at 4.20V. Once done, unplug your ebike bulk charger. Then go with the tiny charger to bring the lower voltage groups individually back to 4.20V. When all cell groups are at 4.20V (check with a voltmeter), then replug your BMS and use your battery normally. You will have to carefully remove the white putty paste on the BMS JST connector to unplug it an tap into it (the putty is just there to make sure it doesn't unplug with vibrations while you ride your ebike). Do not use a metal knife to remove the putty as this will cause a short circuit.

Matador

Ok! Yeah I will be careful.

So thank you and I will write here soon and let you know if it worked out.

Have a nice day!

You're welcome. And remember, be super carefull with polarity. Don't wear any metal ring or anything that could cause a short circuit. And if possible keep an extinguisher at close proximity just in case.

Matador

I have respect of these batteries I know they can catch fire or even explode. So I have one last question: The picture of the charger (ebay link in my last post) says that there is output + and - wires and battery + and -
which one I should I use, to charge the cells? I understand that you can use a micro usb cable OR a input with 5V + and - cable, but for what is the battery plus and minus?

jnlk6 said:

I have respect of these batteries I know they can catch fire or even explode. So I have one last question: The picture of the charger (ebay link in my last post) says that there is output + and - wires and battery + and -
which one I should I use, to charge the cells? I understand that you can use a micro usb cable OR a input with 5V + and - cable, but for what is the battery plus and minus?

Click to expand...

For that TP4056 charge board, I'm thinking you need to plug the battery on the "battery+" and battery-".
The "output+" and "output-" are there only if you plan to permanently mount the battery to that PCB and then you would use these "output+" and "output-" connections to discharge your battery through the circuit boad, so that the board can offer the "3A discharge over-current" and "2.5V low voltage cutoff" protection features of the PCB circuit.

In your case, you want to use this TP4056 circuit only to charge the cells, so you want to use the "battery+" and battery-" connections to charge the lithium cells (NOT the "output+" and "output-" connection which are diseigned for discharge purpose).