GoldenMotor.com Forum

General Category => General Discussions => Topic started by: KimABQ on May 16, 2019, 05:24:40 PM

Title: 48v10Ah battery problems
Post by: KimABQ on May 16, 2019, 05:24:40 PM
I have a new MP Edge with 48v10Ah LiFePO4 battery that I purchased from Gary in mid December last year. It has less than one hour total on the motor / battery due to installation taking a long time plus illness and weather. Since completing the install when I ride it only travels about 1/2 mile before it quits. It will start again randomly but only for a short distance and then it quits working again.
The throttle has all battery lights on and they stay on. I have disconnected all wiring except throttle and PAS and still the same problem. When system quits I measure battery voltage at output plug and it is typical ~53v, lowest was 52.2v. All wiring looks good.
As per Gary's instructions I have pulled the wheel and removed the controller to test it with power on. The LED gives one flash when power is turned on but there are no other flashes until power is removed. Then it gave two flashes consistently, but now only one flash when powering down.
When charging the battery it cuts off at 54.8vdc and has never been near 58.4v, which is supposed to be the output of the charger and I am guessing the proper charge voltage.
Gary had me disassemble my battery pack and check individul cells. Most cells were at 3.34+/-1. However, there was one cell at 3.66v so I put a small LED load across that cell and when it dropped to 3.62v the charger came back on and ran for a few seconds before shutting off again. During that few seconds three cells climbed above 3.66v and the charger quit when the first cell reached 3.85v. I then discharged all cells above 3.62v and when the last cell was drawn down to 3.62v the charger starts again and the cycle repeats - three cells above 3.62v, one of them reaching 3.85v and charger shutting down. The charger runs less than 5 seconds during each cycle.
The other cells gradually increase their voltage but after several hours of doing this cycling process the lowest cell was at 3.39v and the highest cells before discharging were at 3.76, 3.72, and 3.71 and two at 3.68v. The remaining cells ranged from 3.39 to 3.53v. Total battery pack voltage was 56.51v.
I am stumped at was is causing the problem. The BMS does not seem to be balancing the pack and when it is left on charge for hours without me discharging any cells. The charger light stays green and no low level cells seem to increase in voltage nor do any higher voltage cells drop. Everything seems to remain static. I do not want to disassemble the pack to charge discharge each of the cells with a walwort, but I do not know what else to do at this point. Should I hook it to the motor and see if I can get it to discharge and balance under that load?
this is a new battery and charger so I would hate to cause more damage.

Any help would be appreciated.

UPDATE: I reassembled the Edge on the trike and and put the front end on a stand so I could run the motor using the throttle. It started off at 55v, ran 12 minutes and quit. It was down to 53v but recovered to 53.2v. After 10 minutes it started up again and ran for 7 minutes. Votage fell to 53.0v and recovered to 53.1 after the motor quit. I let it rest for 20 minutes and it started again but only ran for 10 minutes and quit. It shut down reading 53.0 and recovered to 53.1v. Lights stay on for the throttle all the time. Nothing is getting warm; not controller, nor battery cells.
Three questions:
1) Should I keep doing this until iI drain the battery low enough for shutoff or will it cause damage?
2) Will draining the battery down help it to finally balance when I recharge it?
3) What is causing the shutdown? Controller? BMS?

Title: Re: 48v10Ah battery problems
Post by: Bikemad on May 17, 2019, 01:14:07 AM
Hi Kim and(https://i.imgur.com/evDSMvT.png)to the forum.

I suspect the high voltage cells (>3.65V) are causing the BMS to disconnect the charge current, and the lower cells are unable to charge up properly.

If a single cell is too low, it could trigger the Low Voltage cutoff function of the BMS under load to prevent it from discharging any further.

Your pack appears to be quite unbalanced, and I suspect it will require some manual balancing by either charging the lower cells, or discharging the higher cells until all the cells are at the same unloaded voltage.

I don't know how much current the BMS is able to bleed off from the higher cells while balancing, but if it is less than 50mA, it could take days or even weeks to properly balance with the charger:

(http://liionbms.com/graphics/gross_balance_time_graph.gif)

A 12V 60/55W car headlamp bulb (or a 12V 50W halogen downlight bulb) can be used to discharge higher voltage cells, but you will have to keep an eye on the voltage to make sure it doesn't drop too low.

It should be possible to discharge individual cells via the balance lead plug which connects to the BMS.

The balance lead wires are usually rated for ~3 Amps, but the maximum current from a 12V 50W halogen bulb should be less than 2.5 Amps when connected across a single LiFePO4 cell.

If the voltage of the high cells drops very quickly to the same voltage as the lowest cell with the lamp attached, it is probably a weak/faulty cell.

Unfortunately, until the cells are reasonably balanced, it is difficult to know whether the battery is going to work correctly.

UPDATE: I reassembled the Edge on the trike and and put the front end on a stand so I could run the motor using the throttle. It started off at 55v, ran 12 minutes and quit. It was down to 53v but recovered to 53.2v. After 10 minutes it started up again and ran for 7 minutes. Votage fell to 53.0v and recovered to 53.1 after the motor quit. I let it rest for 20 minutes and it started again but only ran for 10 minutes and quit. It shut down reading 53.0 and recovered to 53.1v. Lights stay on for the throttle all the time. Nothing is getting warm; not controller, nor battery cells.
Three questions:
1) Should I keep doing this until I drain the battery low enough for shutoff or will it cause damage?
2) Will draining the battery down help it to finally balance when I recharge it?
3) What is causing the shutdown? Controller? BMS?

1) It should not cause damage as the BMS will not allow any cell to be discharged too far, but I'm not sure if it will help either.

2) All cells are being discharged and charge at the same rate, the only balancing that can take place is when the highest cell reaches 3.65V. As I mentioned previously, if the bleed current is very low, it will take a very long time for the cells to balance correctly when they are their voltages are so different.

3) Unless you have the Low voltage setting in the controller set to 53V (I'm not even sure if it would even accept that value) then it is probably the lowest cell in the pack that is causing the BMS to cut the power. But I don't understand why the motor won't run if you still have 53V showing and all 3 lights lit on the throttle. :-\

Alan
 

Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 17, 2019, 02:45:55 AM
Alan,
Thank you for the thoughtful response. I think you are on to some important points. Let me offer a theory and let me know if it makes sense, or not!  :o
If the BMS is cutting off power when one cell hits the minimum voltage, that might explain why it quits for a while. I had thought the shutdown had to be thermally induced, but if the BMS can control output then a low cell cutoff of the power could explain the mystery shutdown while I still have 53v for the pack.
Then, would the low cells try to adjust themselves by siphoning power from the higher voltage cells? If they do, or the BMS does, that would explain why being shut down for a period of time allows the low cell to gain some voltage and it's good to go until it gets pulled down to minimum again. This is intriguing.
As I mentioned in my first post, I have been draining the high voltage cells with a small LED circuit which pulls down from ~ 3.75 to 3.62 in 10 minutes or so. The more high voltage cells there are, the longer it takes to get the pack ready to receive another charge. I do this simply measuring across the terminals in the fully assembled pack, then clip the LED load to those terminals until the cell drops. I do this to avoid taking the pack apart (see attached picture) but maybe this is not the best approach? If nothing else it does take a long time, especially as more cells get above 3.62 and also have to be discharged.
I currently do not have any ability to reset the controller. I was considering the Android / Bluetooth option but I don't know if it offers those capabilities. It sounds like it would not be able to diagnose this problem or even capture error codes from the controller.
I will get a headlamp bulb to start draining cells with. as long as my wife is not watching her car too closely!  ::) Can I continue to use my method for draining individual cells with the bulb approach?
Thank again!
Kim
Title: Re: 48v10Ah battery problems
Post by: Bikemad on May 18, 2019, 11:09:30 PM
Would the low cells try to adjust themselves by siphoning power from the higher voltage cells?

When a cell is placed under load, its voltage will sag in relation to the current being drawn, but if the load is removed, the cell's voltage will usually rise back up again.

The following graph shows just how much a weak cell can drop under heavy load:

(https://i.imgur.com/YNUy9Of.png)

The above graph plots the voltages of 2 individual cells in a 5 cell 5Ah 20C LiPo pack being used on my electric strimmer.
You can clearly see that the cell voltages gradually increase at 41m 40s when strimming is paused, and again when the strimmer finally stops completely at 49m 10s.


When your battery is put under load, as soon as the lowest cell drops below the BMS minimum cell voltage setting, the BMS will automatically cut the power going to the controller and the load on the cell is then removed.

The voltage of the low cell will then gradually rise above the BMS minimum cell voltage setting, allowing the BMS to reset the power output.

The MP Edge can be programmed via the Bluetooth dongle and suitable Android phone, but it would not be much use for diagnostics as the Bluetooth connection would also be lost as soon as the BMS cuts the power to the controller.  ::)

Can I continue to use my method for draining individual cells with the bulb approach?

Yes, but make sure that you monitor the cell voltage while the bulb is clipped on, and also check how much the voltage rises again when the bulb is removed.  ;)

You will probably need to discharge them further until the resting voltage is about the same as the lowest cell.

I was also surprised at the layout of the cells in your battery, I thought that they would all be in a single row like the ones in the 48V 10Ah LiFePO4 battery pack that Gary dismantled (https://goldenmotor.com/SMF/index.php?topic=4260.msg24829#msg24829).

Alan

 
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 19, 2019, 05:05:43 AM
Thanks again Alan. Very useful info for troubleshooting this problem.
I have been continuing my experiment with discharging the battery by running the motor while the wheel is suspended. Basically I just clamp the throttle wide open and let it run until it quits. I monitor runtime, start voltage, shutdown voltage, and what voltage it returns to within 30 seconds. I wait for one hour between runs (except overnight) and it starts every time. I have more than 15 runs so far that started with 9-11 minutes before shutdown and start voltages were around 53.2. Now my runs are lasting 20-30 minutes with start voltages now around 52.6. with these accumulated runs I now have a total of almost 4 hours of run time and it is gaining run time with each cycle. It is like the cells are getting closer to being balanced.
However, I may be violating a basic rule because I have not charged the pack at all between runs because that seemed to reset everything when I did it before. Should I recharge or can I continue this way for a while longer?
I too was surprised by the cell arrangement. Maybe this assembly eliminates case shorts? It does make it awkward to test individual cells.
Good point about the BT / Android not functioning with BMS shutdown. Is there any display that does track these issues?
I found that 220mm heat shrink is a great size for this pack, but 250mm works well too.
Thanks again!
Kim
Title: Re: 48v10Ah battery problems
Post by: Bikemad on May 19, 2019, 03:45:58 PM
Hi Kim,

I would be tempted to charge the pack until the green light comes on and then measure/record the cell voltages. Then I would leave it connected to the charger overnight and measure/record the cell voltages again to see if there is any difference.

It might be worth leaving the battery connected to the controller and charger while both are turned on. The residual current draw from the controller and Throttle LEDs etc. should cause the high cell voltage to drop slightly and allow the charger to cut in again. Each time it cuts in, it should begin to very slowly balance the cells until the charger cuts off again.

(https://i.imgur.com/FnmD5lE.png)

I am not aware of any display that could be used to diagnose this particular problem, but it will be interesting to see if fully balancing the cells completely cures the fault.

Alan
 
Title: Re: 48v10Ah battery problems
Post by: Adamsavage79 on May 21, 2019, 04:18:10 PM
If your pack is unbalanced, then I would suggest putting it on the charger and leaving it on after the green light comes on. It would be good to do this overnight. The more you discharge the pack, the longer it will take to balance the pack.
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 23, 2019, 02:28:34 PM
While I do not understand why discharging keeps the pack unbalanced, I did as you suggested and let the pack stay on the charger overnight without any load. It did not seem to change the pack since it can still only get up to about 55.v.  :-\
Title: Re: 48v10Ah battery problems
Post by: Bikemad on May 23, 2019, 04:11:54 PM
I would be tempted to charge the pack until the green light comes on and then measure/record the cell voltages. Then I would leave it connected to the charger overnight and measure/record the cell voltages again to see if there is any difference.

Did you also measure the cell voltages before and after the overnight charge? If so, was there any noticeable difference between the highest and lowest cells on both checks?

The more you discharge the pack, the longer it will take to balance the pack.
I do not understand why discharging keeps the pack unbalanced

Passive balancing will only commence when the highest voltage cell in the pack reaches its maximum charge voltage (typically ~3.65V), therefore it will obviously take longer to reach this balancing point if the battery is more deeply discharged prior to charging.

For a reasonably well balanced battery, an overnight charge might be sufficient to balance the cells, but as your cells are so far out of balance, it would only make a very slight difference to the balancing of the cells.

Also, if you have the "UL" version of the charger, leaving it on overnight is not likely to be beneficial as the charger would not cut in again to continue charging:

The main thing is the charger Alan is showing is the CE version of the chargers. I did have those in the past but switched to the UL versions as that is what is required in North America. The UL version does not have a switch for 240. It also does not cycle back on as the voltage drops when the cells are balancing. So with the CE version it will keep coming back on topping up the cells and the UL version it does not.

Manual balancing using a light bulb to discharge the high cells is probably the easiest (and quickest) way to balance your battery.
The professional way (but a lot more involved) would entail dismantling the pack and connecting all of the cells in parallel for a few hours until their voltages were all stabilised at exactly the same level.

Running the battery down with no load is basically draining some of the available capacity from all of the cells (both high and Low) by a similar amount, and this is unlikely to have any significant effect upon the balancing of the cells.

At this stage, we are still basically guessing as to what is causing the cutting out, if you were able to confirm that one (or more) of the cells was unusually low prior to the motor cutting out, then it might confirm a weak or imbalanced cell.

If it still cuts out with no obvious sign of a very low voltage cell, it might even be a controller problem.  :-\

If the BMS is cutting the power, I would expect the LEDs on the throttle to go off at the same time, like they do on Nathan's video demonstrating his BMS problem (https://www.youtube.com/watch?v=qzgpSYgV-gw&feature=youtu.be).

Alan
 
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 24, 2019, 05:22:35 AM
Here is a synopsis of the progress so far:

I will let the charger work on the pack overnight and recheck cell voltages in the morning. I may have found a solution but I will have ot run it on the trike a few times to be sure.
Definitely looks like progress!  ;D
Title: Re: 48v10Ah battery problems
Post by: Adamsavage79 on May 24, 2019, 05:53:32 AM
It sounds like you found a way to balance the pack. Work in progress. Keep up updated!
Title: Re: 48v10Ah battery problems
Post by: GM Canada on May 24, 2019, 01:09:33 PM
I have been watching this thread from the sidelines as I like hearing other opinions on topics without injecting my own sometimes.

You likely have a CE charger. We only carried the UL ones for a short period of time. They are more expencive, lower quality and don't work well at cell balanging.

If the pack is up to 58.2 and the chargers does keep cycling it sounds promising the pack is balancing. Once you are on the road again with this pack charge it fully after each ride and leave it on the charger to continue to cell balance. I generally leave my packs on the charger unless its been a week since my last ride. Then I charge them once a month minimum and top them off before a ride if the pack was off the charger.

Gary

Title: Re: 48v10Ah battery problems
Post by: Adamsavage79 on May 24, 2019, 03:34:57 PM
I don't use my bike to go to work or  anything, so I always leave it on the charger overnight. So about 8-9 hours and then I let the pack sit for several hours before using it. I'm determined to get the max life out of this pack, this time. Anyway, hopefully you are on the road to getting this fixed.
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 24, 2019, 04:32:08 PM
UPDATE: I left it on the charger last night and this morning the pack measured 57.2 for a loss of one volt from last night.


I finally got time to measure the cells and the pack voltage had dropped ome more to 56.8. Here are the cell voltages:

Cell #   V      Cell #   V
1   3.47      9   3.51
2   3.57      10   3.52
3   3.63      11   3.49
4   3.50      12   3.55
5   3.72      13   3.44
6   3.52      14   3.68
7   3.61      15   3.52
8   3.64      16   3.45
   
TOTAL 28.66      28.16
            
      Pack Tot   56.82

Considering the wide variations I do not think the pack is balancing.  ???

Thoughts?
Title: Re: 48v10Ah battery problems
Post by: Bikemad on May 25, 2019, 10:50:52 AM
Hi Kim,

Now that all the cell voltages are at a more even level, have you tested the battery on the trike to see if the motor still cuts out?

As the cells are still out of balance, it might be worth leaving it on the charger overnight again and remeasuring the cells to see exactly what changes.

I have entered your last results into a spreadsheet to see how they compare and here is the outcome:

(https://i.imgur.com/LEFDXOg.png)

Most of the cells are below the typical 3.65V ±0.025V maximum cell voltage, but there is no obvious sign of a rogue cell that stands out from all the others. Although, placing a load on the pack and measuring the cell voltages while under load might produce a different result.

If the BMS is not balancing the cells, it is either faulty, or it simply needs a lot longer to reduce the 0.28V difference between the highest and the lowest cell voltages.

Another overnight charge is not going to fully balance the cells, but if the BMS is working correctly, it should at least show a slight improvement in the current 0.28V difference between the highest and lowest cells.

Balancing cells does take time, My LiPo balance charger can drain up to 300mA per cell while passive balancing, and I have it set to balance throughout the charge process rather than just at the end, but it still takes a long time to balance a fully charged 4 cell pack with a 0.15V difference:

(https://i.imgur.com/8IbD7Zn.png)

If your BMS is only able to drain ~30mA, it will obviously take a lot longer, especially when you consider that the low cells can only increase in voltage while the charger is actually charging, in other words, not while the green light is on.

Alan
 
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 26, 2019, 12:07:20 AM
Thanks again Alan. I appreciate your wisdom and insights.
I did not test the pack on the battery because I would have to put new heat shrink on before assembly and I was not ready to trust it yet.
I went back over all the tests I logged and put them all in the same type of table that you used. I was able to see that the cell voltage differences have been getting smaller....slowly!
I spent today manually balancing the cells and this is what I ended up with:

5/25 Post Balance Measurement-------:            
Cell #   V      Cell #   V
1   3.63      7   3.61
2   3.62      2   3.62
3   3.65      4   3.62
4   3.62      5   3.62
5   3.62      6   3.62
6   3.62      10   3.62
7   3.61      11   3.62
8   3.64      12   3.62
9   3.64      13   3.62
10   3.62      14   3.62
11   3.62      1   3.63
12   3.62      8   3.64
13   3.62      9   3.64
14   3.62      16   3.64
15   3.64      15   3.64
16   3.64      3   3.65
            
Pack Tot   58.03      Pack Tot   58.03
            
Max   3.65      Max   3.65
Min   3.61      Min   3.61
Diff   0.04      Diff   0.04

This is as close as I could get because the cells would change as others were being charged or discharged so I quit chasing the rabbits.
I will let it on the charger overnight because I want to see if it gets better or worse before I put it back in the heat shrink and case for a road test.
Also, the total pack voltage is less than the 58.4v charger rating. Is that okay?
I hope this is progress.  :-\
Have a great Memorial Day weekend!
Kim



Title: Re: 48v10Ah battery problems
Post by: Adamsavage79 on May 26, 2019, 01:12:03 AM
Thanks again Alan. I appreciate your wisdom and insights.
I did not test the pack on the battery because I would have to put new heat shrink on before assembly and I was not ready to trust it yet.
I went back over all the tests I logged and put them all in the same type of table that you used. I was able to see that the cell voltage differences have been getting smaller....slowly!
I spent today manually balancing the cells and this is what I ended up with:

http://5/25 Post Balance Measurement-------:   
         
Cell #   V      Cell #   V
1   3.63      7   3.61
2   3.62      2   3.62
3   3.65      4   3.62
4   3.62      5   3.62
5   3.62      6   3.62
6   3.62      10   3.62
7   3.61      11   3.62
8   3.64      12   3.62
9   3.64      13   3.62
10   3.62      14   3.62
11   3.62      1   3.63
12   3.62      8   3.64
13   3.62      9   3.64
14   3.62      16   3.64
15   3.64      15   3.64
16   3.64      3   3.65
            
Pack Tot   58.03      Pack Tot   58.03
            
Max   3.65      Max   3.65
Min   3.61      Min   3.61
Diff   0.04      Diff   0.04


This is as close as I could get because the cells would change as others were being charged or discharged so I quit chasing the rabbits.
I will let it on the charger overnight because I want to see if it gets better or worse before I put it back in the heat shrink and case for a road test.
Also, the total pack voltage is less than the 58.4v charger rating. Is that okay?
I hope this is progress.  :-\
Have a great Memorial Day weekend!
Kim

That looks much better. Less of a difference. You have a couple higher voltage cells, but overall the pack looks to be much more balanced. It's normal have a one cell @ 3.62 vs 3.61v. I believe as long as they are all with in .01-0.02 of each other, than that would be a fully balanced pack. Alan can correct me if I'm wrong.
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 26, 2019, 03:41:40 PM
Good news and bad news.  ::)
Good news is that I left the pack on the charger overnight and it rose to 58.2v, the highest I have ever seen.
the bad news is in the cell voltage chart below:
5/26 Post Balance Measurement-------:            
Cell #   V      Cell #   V
1   3.59      16   3.54
2   3.66      13   3.56
3   3.71      1   3.59
4   3.60      11   3.59
5   3.75      4   3.60
6   3.62      10   3.61
7   3.68      6   3.62
8   3.72      9   3.62
9   3.62      15   3.62
10   3.61      12   3.64
11   3.59      2   3.66
12   3.64      7   3.68
13   3.56      3   3.71
14   3.72      8   3.72
15   3.62      14   3.72
16   3.54      5   3.75
            
Pack Tot   58.23      Pack Tot   58.23
            
Max   3.75      Max   3.75
Min   3.54      Min   3.54
Diff   0.21      Diff   0.21


It got out of balance again with a difference of 0.21v between high and low.
Any thoughts?
Kim

Title: Re: 48v10Ah battery problems
Post by: Adamsavage79 on May 26, 2019, 04:14:06 PM
Is the charger itself throwing the pack out of balance ? The reason I'm suggesting this, is because you had it nearly balanced and then you charged it. Never heard of a charger doing that, but I've heard of stranger things...
Title: Re: 48v10Ah battery problems
Post by: Bikemad on May 27, 2019, 12:18:20 AM
Hi Kim,

I think you are worrying unnecessarily, because I definitely don't see those results as "bad news".
If you ignore the values obtained while manually balancing the pack, compared to your original results (Pre manual balancing) the pack has definitely improved significantly:

(https://i.imgur.com/TnZwtQS.png)

The difference between the highest and lowest cell (was 280mV but now 210mV) has actually been reduced by 70mV, which is an overall improvement of 25%.

I suspect that another night on the charger (without manual balancing) will improve them even more (although it might only improve by a small amount) but I'm hopeful that the balance of the cells will continue to improve with regular charging.  ;)

The biggest problem with the manual balancing is the time it takes for each cell voltage to completely stabilise after you have manually topped it up, and the lower cells that have been topped up more, will typically drop more than the higher cells, even though you may have topped them all up to the exact same ~3.65V.

Even though the cell voltages will have dropped after they have fully stabilised, the resting cell voltages should still be nearer to the ~3.65V than they were before they were topped up.

Fortunately, the BMS is able to add capacity (using the same amount of current) to all of the low cells simultaneously at the end of the charge (but only when the charger cuts in again) therefore it should gradually increase the voltage of all the lower voltage cells if the battery is left charging for a long enough period of time.

The BMS does not have to "chase rabbits" one at a time, it simply slows all the fast rabbits down, which allows the slower ones to gradually catch up.  :)

Is the charger itself throwing the pack out of balance ?

It is definitely not the charger, as there is no way the charger could reduce the voltage of individual cells, only the BMS has the ability to do that.

As previously stated, the "post manual balancing" figures have definitely improved over the "pre manual balancing" figures, which is a positive and reassuring result.

Alan
 

Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 27, 2019, 02:54:45 AM
Thanks Alan and Adamsavage799 for your willingness to continue helping. I really appreciate it.

Alan is correct that there has been improvement. My question was whether or not it was caused by the manual balancing effort. I am willing to give that another try if it speeds up the process.
But for now I will leave it on the charger for tonight. It has been there since yesterday so we'll see if there are any changes by tomorrow.

Should I try it on the trike or should I wait until it is in better shape? I don't want to make things worse.

And Alan, how do you post the spreadsheet table? I have not been able to figure that out even when I tried to post it as a graphic. So I end up with clunky, misaligned text instead of nice, color coded tables.

Thanks again,

Kim
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 27, 2019, 08:04:26 PM
Here are today's measurements:
5/27 Post Balance Measurement-------:            
Cell #   V      Cell #   V
1   3.56      16   3.51
2   3.65      13   3.55
3   3.73      1   3.56
4   3.58      4   3.58
5   3.82      10   3.59
6   3.60      11   3.59
7   3.70      6   3.60
8   3.74      9   3.62
9   3.62      12   3.63
10   3.59      15   3.63
11   3.59      2   3.65
12   3.63      7   3.70
13   3.55      3   3.73
14   3.74      8   3.74
15   3.63      14   3.74
16   3.51      5   3.82
            
Pack Tot   58.24      Pack Tot   58.24
            
Max   3.82      Max   3.82
Min   3.51      Min   3.51
Diff   0.31      Diff   0.31

The pack stayed on the charger all night. It is a MEBO GY200-48AL rated at 58.4v and 3A. I have not seen it kick on to charge state since yesterday, but it may have when I was not watching.

The pack voltage rose by 0.01 but 10 cells fell in voltage, while only 5 cells rose. Number 5 is at 3.82v. That seems awfully high. The difference from high to low also rose to 0.31v.

I believe something is malfunctioning. Since some cells increased the power could have come from the charger or from other cells. Since cell #5 is at 3.82v that is well above the desired charge voltage for a balanced pack. And none of the cells changed in a way that bettered the pack balance, so I have to wonder if the BMS is the source of the problems. Is there a way to test the BMS?

The saga continues.
Kim

Title: Re: 48v10Ah battery problems
Post by: Bikemad on May 27, 2019, 10:32:30 PM
Hi Kim,

I have found some information for a typical 16s LiFePO4 BMS:

(https://i.imgur.com/JrlF0gx.png)

The typical overcharge protection voltage is 3.85V per cell. As your highest cell is at 3.82V, it would appear that the cell overvoltage protection function of the BMS is working correctly, but the balance function does not seem to be bleeding the excess voltage from the high cells as it should.

(https://i.imgur.com/c0rmPkv.png)(https://i.imgur.com/cgbzSqM.png)

For the charger to cut back in again and begin topping up the lower cells, the highest cells would need to be below ~3.65V, but as you still have 5 cells that are 3.65v or over, this is unlikely to happen.

You currently have 7 cells below 3.61V (the typical balance voltage shown above) and 9 cells above it.
If the BMS was working correctly, I would expect the 9 high cells to gradually reduce to ~3.61V, but they obviously are not doing this.

As things have not improved as I had hoped after another overnight charge, it is beginning to look like the BMS will need to be replaced.  :(

I suggest that you contact Gary to see what needs to be done now, as the battery is presumably still under warranty.

Alan
 
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 28, 2019, 12:09:50 AM
Alan,
I agree. I think the BMS is not bleeding the higher cells like it should so balancing cannot be achieved.
Thanks for the info - very useful. It might be worth creating a sticky thread explaining cell parameters, how they get out of balance, and how to diagnose and rebalance them This sure has been a learning opportunity for me. I hope a new BMS solves it!
I will contact Gary tomorrow.
Thanks again.
Kim
Title: Re: 48v10Ah battery problems
Post by: KimABQ on May 28, 2019, 06:30:43 PM
On the charger all night. Here are today's measurements:
5/28 Post Balance Measurement-------:            
Cell #   V      Cell #   V
1   3.55      16   3.50
2   3.65      1   3.55
3   3.73      13   3.55
4   3.57      4   3.57
5   3.82      11   3.58
6   3.60      10   3.59
7   3.71      6   3.60
8   3.74      9   3.62
9   3.62      12   3.63
10   3.59      15   3.63
11   3.58      2   3.65
12   3.63      7   3.71
13   3.55      3   3.73
14   3.75      8   3.74
15   3.63      14   3.75
16   3.50      5   3.82
            
Pack Tot   58.22      Pack Tot   58.22
            
Max   3.82      Max   3.82
Min   3.50      Min   3.50
Diff   0.32      Diff   0.32

They are almost identical to yesterday. The BMS has not changed anything so I think it's safe to say that it has ben the problem.
Kim
Title: Re: 48v10Ah battery problems
Post by: KimABQ on June 01, 2019, 03:23:39 PM
Hi all,

I contacted Gary on 5/28 and he said he would send a BMS to replace the one on my pack. So I hope to be back in operation again soon. The problem started the end of March and I have been down since then!  :'(

As for the BMS replacement, does anyone have any advice concerning does or don'ts when performing the removal of the old unit and installation of the new one? I want to be sure I do the repair properly since I will be working with enough current to cause damage to cells and/or BMS.

also, I am guessing it would be good to manually balance all cells before connecting the new BMS just to make its work easier to start with. Is this correct?

Thanks thanks again for your help, especially Alan. I would not have gotten this far without your feedback and insight.  ;)
Kim
Title: Re: 48v10Ah battery problems
Post by: KimABQ on June 08, 2019, 07:00:45 PM
I installed the new BMS and let it charge overnight. The pack came up to 58.2v this morning so that is a first.  ;D But the individual cells still varied by 0.26v so I manually balanced each cell and here are the current readings:

6/8 With New BMS -------:            
Cell #   V      Cell #   V
1   3.64      1   3.64
2   3.64      2   3.64
3   3.65      14   3.64
4   3.66      15   3.64
5   3.65      3   3.65
6   3.65      5   3.65
7   3.65      6   3.65
8   3.65      7   3.65
9   3.66      8   3.65
10   3.65      10   3.65
11   3.66      4   3.66
12   3.66      9   3.66
13   3.66      11   3.66
14   3.64      12   3.66
15   3.64      13   3.66
16   3.66      16   3.66
            
Pack Tot   58.42      Pack Tot   58.42
            
Max   3.66      Max   3.66
Min   3.64      Min   3.64
Diff   0.02      Diff   0.02

It looks pretty good so I will test it now on my bike with the wheel suspended. If it runs for an hour then I will heat shrink it and put it back in the aluminum case for a road test.

Thanks Gary for the replacement BMS and great customer service!

And thanks to Alan for his expert help on this mystery. In hindsight, I think the BMS was bad from the start but I never noticed it until the cells went way out of balance and began to shut the pack down. It has been a learning experience. I'll let you all know if it is finally fixed.

Kim

Title: Re: 48v10Ah battery problems
Post by: KimABQ on June 09, 2019, 02:22:55 AM
Well, battery and BMS are working great. That's the good news.

Unfortunately the motor still only ran for about 10 minutes before stopping again. While nothing felt hot (other than the throttle which was much warmer than I remember), after a rest the motor would start again. I applied some freeze spray to different parts to see if I could find the thermal issue and as soon as I sprayed the controller the motor started again. I repeated this several times and the controller definitely did not like getting warm and started as soon as I sprayed it. The ambient temp was 90F, but I don't think that would keep the controller on the edge of shutdown.

I noticed that the front disk brake was slightly engaged and adding drag/ load to the motor because its cable was being pulled by part of the stand this time. I would think this would trip safety thermal or load sensors before any damage would occur, but now I believe it may have damaged the controller. Any thoughts on this?

Do I have to replace the controller or just some of the parts?

The saga continues!  :-\
Title: Re: 48v10Ah battery problems
Post by: Adamsavage79 on June 09, 2019, 02:57:11 AM
Do you know how hot the controller was getting ?
Title: Re: 48v10Ah battery problems
Post by: Bikemad on June 09, 2019, 02:40:28 PM
I noticed that the front disk brake was slightly engaged and adding drag/ load to the motor because its cable was being pulled by part of the stand this time. I would think this would trip safety thermal or load sensors before any damage would occur, but now I believe it may have damaged the controller.

A binding brake should not be able to cause permanent damage to the controller, as the thermal protection would prevent it.

A badly binding brake can place a great deal of load on the motor and this would cause the controller to get warm.  If the brake was binding enough to significantly raise the temperature of the controller, the controller's thermal protection would cut the power going to the motor to prevent further overheating.

From the motor's point of view, it would be similar to someone riding at full throttle up a 4 mile long hill at ~25 mph for 10 minutes  without easing off and with no pedal assistance from the rider (and also without the 25mph cooling breeze flowing over it), so it is hardly surprising that the inside of the controller eventually gets too hot, causing it to cut out. ::)

Although there it is a remote possibility that a faulty thermistor could be causing the thermal protection to cut in prematurely, I suspect that the binding brake is far more likely to be the culprit. ;)

How difficult is it to turn the front wheel by hand when the brake is being partially applied by the stand?

Do I have to replace the controller or just some of the parts?

If it is just the binding brake causing the cutting out, then it will not be necessary to replace the controller.  However, if the cutting out was due to a faulty temperature sensor (thermistor) then the entire controller would need to be replaced as it is not really practical to replace just the thermistor due to the construction of the controller.

I suggest that you ensure that the brakes are not binding and then see if the cutting out still occurs, if it runs without cutting out, then give it a trial run on the road and see how it behaves.

Alan
 
Title: Re: 48v10Ah battery problems
Post by: KimABQ on June 10, 2019, 03:08:08 AM
Thanks for the responses.

Adamsavage79
The controller was barely warm to the touch.

Bikemad
Thanks for confirming that the thermal protection should normally prevent controller failure.
The test rig simply suspends the wheel so there is no load other than the wheel itself and no air flow from traveling. The room was 90F+ but Albuquerque summer temps are often in the 90s to 100s so these conditions may challenge the system. And the fact it is dry heat will not help!  ;)
My experience with digital thermistors is that they are binary - they either work properly or not at all. I will go with that idea and do an early morning test ride like Bikemad suggests to see how it performs. I think I will go gradually but continuously uphill just in case it quits. Then the return ride would be much easier!  ;D

However, the new BMS is working wonderfully!  8)

Kim
Title: Re: 48v10Ah battery problems
Post by: KimABQ on June 14, 2019, 04:40:19 AM
I took the trike out yesterday for a test ride. Air temp was low 80'sF. I rode about 1/4 mile and the motor quit. Turned around to go back and the motor started again when I was nearly home. It has to be a controller temperature issue so I just ordered another controller from Gary because I believe I damaged this one when the brake was engaged while running the motor.
We'll see if this new controller cures the current problem.
I'm thinking about converting the front brake to hydraulic to avoid a potential repeat of the cable causing the brake to engage. Does anyone have any suggestions? Can I set up an emergency brake on a hydraulic system?
Meanwhile, battery charges to 58.2v and all cells seem happy! New BMS is awesome!
Title: Re: 48v10Ah battery problems
Post by: Adamsavage79 on June 14, 2019, 04:45:21 AM
I'm Curios, is the wire harness warm to the touch if the bike is not in use, but plugged in ? Also after the motor quits, how hot does the controller or motor feel ? The motor should feel almost hot and that's normal if you ride it hard. If it's burning hot, then you would have a problem. I'm more inclined to believe the controller is the problem. I have glitchy controller myself, but it works well enough that's simply not worth the time and effort to figure out why it's glitchy.

Also, just how much was your brakes preventing your wheel from turning ?
Title: Re: 48v10Ah battery problems
Post by: KimABQ on June 14, 2019, 07:58:34 PM
I'm Curios, is the wire harness warm to the touch if the bike is not in use, but plugged in ? Also after the motor quits, how hot does the controller or motor feel ? The motor should feel almost hot and that's normal if you ride it hard. If it's burning hot, then you would have a problem. I'm more inclined to believe the controller is the problem. I have glitchy controller myself, but it works well enough that's simply not worth the time and effort to figure out why it's glitchy.

Also, just how much was your brakes preventing your wheel from turning ?

The controller and motor never got hot, just mildly warm to the touch. The wiring harness has no indication of warmth at all. I too believe it is the controller now so I ordered a new one. The out of balance battery  caused by the bad BMS kept my attention and masked the controller problem but the new BMS is perfect. Sometimes trouble shooting is just one step at a time.  ???

I have now had the controller in and out several times and am getting pretty good at it, so if I were closer to you I would be glad to help!  ;)

The brake was engaging enough to make it eventually get hot but I could still rotate the wheel. I actually smelled it which is what caught my attention.
Title: Re: 48v10Ah battery problems
Post by: Adamsavage79 on June 14, 2019, 11:38:01 PM
Does the controller cut out if the wheel is off the ground ?
Title: Re: 48v10Ah battery problems
Post by: KimABQ on June 19, 2019, 09:15:00 PM
Does the controller cut out if the wheel is off the ground ?

Yes

New BMS and controller fixed the drop out problem. Continuous journey for over an hour with no problems!
Title: Re: 48v10Ah battery problems
Post by: Bikemad on June 19, 2019, 09:51:03 PM
Kim, it's good to know that the replacement controller has finally sorted the cutting out problem.

Alan