Having Problems! help me please!

[nomad85]

I have been losing power after 8Ah of my battery have been used up. My controller's light dims, and the cycle analyst shows 27-30ish volts( I have a 48v 15Ah battery) I have to unplug and plug the power back in and I can turn the controller back on, but it happens again in a few minutes. If I go slowly it wont cut out. I have talked to Ping and the battery does not seem to be the issue, after the power is cut, it still reads 53v resting. I have a 20Amp immediate start controller from crystalyte, and the 407 motor. Sometimes I think it seems a bit slower than normal, and uses more power to go as far, but it has been rather windy as of late, and today it seemed as fast as usual, and got normal range, but it still cut out around 8AH.

Thanks for any help.
Kyle

 

[Kurt]

So you are saying as soon as a load is put on the battery the voltage drops to around 30v but when there is no load on the battery its fine.

How about before this, like just of the charger for the first couple of ah usage is the battery strong and dose the voltage sag to 30v then?
If the voltage drops only after 8ah it must be the battery.If the voltage is saging from the start it could be l bad connections or something like that.
How many ah did you get from the battery when it was new the full 16ah?
How old is the battery?
What about the charging of the battery have you been charging it to full capacity and letting it balance?

Wind and hills that kind of thing shouldn't make any huge difference in how many AH you get from your battery just how fast You use it .

Kurt.

 

[nomad85]

So you are saying as soon as a load is put on the battery the voltage drops to around 30v but when there is no load on the battery its fine.

Well sort of, but its not immediately when load is applied. I can go full throttle but after a few 100 feet it cuts out again, I reconnect the battery to the controller, and it might go a mile and cut out again. There is no more voltage sag than normal, but then bam its down to 27-30v and the throttle wont respond again.

How about before this, like just of the charger for the first couple of ah usage is the battery strong and dose the voltage sag to 30v then?

its fine for the first 7.5 or so AH, then like clockwork it starts acting up.

How many ah did you get from the battery when it was new the full 16ah?

about 14 but I usually only use 6-8 AH per cycle

How old is the battery?

I got it in june? it was about 900 miles on it.

What about the charging of the battery have you been charging it to full capacity and letting it balance?

Thats what ping asked me, so I have been leaving it on charge longer, but it seems to balance fine, up to 60v or so.

thanks Kurt,
Kyle

 

[Ypedal]

Do you still cover the same distance with 8ah as you used to ?

Is it an integrated CA meter or one with a shunt ?

One sure way to find out.. but it involves peeling duct tape !!

 

[nomad85]

Yeah, everything seems normal, except the power cutting out at 8ah. I still get about 2 miles per Ah at top speed.
How do I check the CA? It plugs right into the controller.

 

[swbluto]

I vote a battery autopsy is in order!

(I recently had a strange "It's now 7 ah from its nominal 10 ah? WTH." episode and found that one of the cell groups died or was permanently enervated. So I'm getting that replaced and that should boost my available AH back up to 9-10ish AH. It was a ping 10AH pack)

What we know at this point is that the voltage sags after a certain amount of discharge. This would likely indicate that either a cell(s) was/(are) dying, the BMS is faulty, or something in the CA is triggering at a certain discharge or, more likely, reached voltage. Was the BMS ever exposed to moisture?

Anyways, the first step for me would be to visually check everything on the bike and then do a discharge test on the battery. Record the voltage curve as it discharges and you'll be able to *entirely* rule out the battery.

 

[fechter]

The BMS may have failed to do its job or one cell could have been defective.

It should be possible to measure the voltages and figure out which cell is bad.

 

[nomad85]

If it was the battery wouldn't the resting voltage be lower than 53v after 8Ah? Ping said thats about where it ought to be. I was thinking it might be the BMS, but I cant figure why it would only act up after 7.5-8 Ah... How can I measure the voltage of each cell group. Id rather not untape the pack...

 

[fechter]

Resting voltage may not tell the whole story. It would be better to measure under load if possible, even a light load.

If you can access the BMS, you could measure the cell voltages on the wires going to it.

 

[nomad85]

After a power cut, I reconnect the battery and the voltage it about 47-48v at 15-20Amps load, and then after a while it cuts out again. is there a certain way to measure the voltage from the BMS?, it is easily accessible.

 

[swbluto]

After a power cut, I reconnect the battery and the voltage it about 47-48v at 15-20Amps load, and then after a while it cuts out again. is there a certain way to measure the voltage from the BMS?, it is easily accessible.

Well, here's the (almost) whole story. The BMS has a ~2.0 volt LVC for each parallel group in the battery(each parallel group in your pack would contain about 4 cells in your 16ah ping 2.0 pack. If this was ping 1.0, then it probably only has 3 cells). Above a certain amount of discharge, a "weak"/dying cell can drag down the whole parallel group prematurely and cutout the battery but this has no effect on the other parallelized-cells in series. So, in essence, if a cell were dying in your battery pack, there'd only be a ~1 volt difference between that and a perfectly healthy pack: In other words, the battery's total voltage won't point out much, even under load.

And it's easily accessible in the sense you can cut apart the BMS's shrinkwrap after removing the duct-tape. The ribbon cable contains the wires that lead from each parallel group and you can record the voltage by measuring the wires directly(disconnecting the ribbon cable would make measuring each consecutive two wires, with a voltmeter, easier.). It's likely you'll only notice something suspicious from a discharged pack(even 8 ah), so take the measurements after discharging. Once done, is there any noticeable deviations? Most will have a voltage near 3.22-3.3 volts at that amount of discharge but there's likely one that's hanging at around 3.0-3.15 volts: That's your suspect.

After doing that, charge up the battery pack again, and measure the voltages in the same manner. Is the one that was vastly different before still vastly different?(Let the battery sit for a few minutes) If so, you probably just have an unbalanced pack and that can be resolved with an adjustable power supply, but it's sounding like the damage might be permanent with a premature cutout at the half mark: mine occurred at the 70% mark. Fixing the battery pack will be a pain if you have no experience soldering and desoldering. I'm still in the process of getting replacement cells and I'm waiting for shipping from China to become affordable before doing so(Getting 2 cells shipped would cost $50 right now! That's just shipping.).

 

[nomad85]

And it's easily accessible in the sense you can cut apart the BMS's shrinkwrap after removing the duct-tape. The ribbon cable contains the wires that lead from each parallel group and you can record the voltage by measuring the wires directly(disconnecting the ribbon cable would make measuring each consecutive two wires, with a voltmeter, easier.). It's likely you'll only notice something suspicious from a discharged pack(even 8 ah), so take the measurements after discharging. Once done, is there any noticeable deviations? Most will have a voltage near 3.22-3.3 volts at that amount of discharge but there's likely one that's hanging at around 3.0-3.15 volts: That's your suspect.

So I just measure each pair of wires?

After doing that, charge up the battery pack again, and measure the voltages in the same manner. Is the one that was vastly different before still vastly different?(Let the battery sit for a few minutes) If so, you probably just have an unbalanced pack and that can be resolved with an adjustable power supply, but it's sounding like the damage might be permanent with a premature cutout at the half mark: mine occurred at the 70% mark.

Can you explain what you mean here? If the suspect cell is still low, its probably just unbalanced? Or if it is normal after charging its just unbalanced?

 

[nomad85]

Well, I measured each pair of wires and they were all at 3.3 volts. I did notice that Some of the duct tape was slightly melted near the negative wires on the BMS. Might it be a BMS issue? My charger has been putting out 68v for some reason, could that have messed up the BMS? I just fixed the charger, and locked the adjustable resistor in place hopefully...

 

[swbluto]

Well, I measured each pair of wires and they were all at 3.3 volts. I did notice that Some of the duct tape was slightly melted near the negative wires on the BMS. Might it be a BMS issue? My charger has been putting out 68v for some reason, could that have messed up the BMS? I just fixed the charger, and locked the adjustable resistor in place hopefully...

Was that with the battery discharged to a problematic 8ah state of discharge? You're going to want to measure it when it's discharged.

And I don't know if 68V would mess up the BMS, but it could mess up a few cells by overcharging if the BMS let it. The BMS should have a over-voltage cutout so it shouldn't be too much of a problem, but I don't know enough about the BMS to know what would happen to it if the BMS itself was over-volted.

 

[nomad85]

Yeah, each group was at 3.3v after the cutout at 8Ah.

 

[swbluto]

Hmmmm. It doesn't sound like LVC might be a problem, but I'd still do a discharge test on the battery to at least test the BMS under higher-current loads. If it starts to cutout prematurely, and the cell voltages are fine, then it's likely some element on the BMS is damaged. With the burning/darkened mark you noticed, I suspect that particular area was overheated at one time and that may have damaged at least one of the surrounding components. I'd test the entire operating current range that your ebike draws. Also, measure cell voltages during discharge. It also sounds like the abnormally high charge voltage might have damaged the BMS somehow.

If that shows no abnormalities, then we can rule out the battery and bms entirely, and move onto the controller and hub motor.

 

[nomad85]

I checked the voltages again, after a few power cuts and a mile more of top speed riding and another power cut; most cells were at 3.29, one was at 3.27 and one was at 3.28. I have not noticed any unusual voltage sag before a power cut, and it works fine after I reconnect the battery, that is until the power decides to cut out again. I don't think its the motor or controller as it only happens after 7-8Ah, if it were the motor or controller I would expect it to happen all the time. But maybe I am overlooking something. The only changes seem to be the BMS, it melted some of the duct tape, and I noticed it doesn't get as warm during the balancing phase of the charge. It used to get very hot when left on the charger with the green light on, now it feels cool. The pack seems to balance fine though.

 

[nomad85]

I checked the voltages after charging, most were at 3.7, but one was at 3.35... Strange that they are all about equal after the power cut, but one is so far off after a charge, could the BMS not be balancing correctly, or is the cell likely weak and that's my problem?
So much for being optimistic.

 

[swbluto]

That does seem strange.

Do you ... not have the equipment and/or knowledge to do a discharge test? That'd probably be effective in pinpointing the problem.

 

[nomad85]

Do you ... not have the equipment and/or knowledge to do a discharge test? That'd probably be effective in pinpointing the problem.

What would I need to do?

 

[swbluto]

Do you ... not have the equipment and/or knowledge to do a discharge test? That'd probably be effective in pinpointing the problem.

What would I need to do?

In its barest form, connect wires up from the battery to a "load" and adjust the load over the bike's operating current range. It likely works upto 30 amps or so, so I'd just test in whatever increments would seem easiest to do. Basically, take battery after you've discharged to that problematic ~8 ah mark, and hook it up to something electric. Like light-bulbs or heating filament wire. To increase the current, just hook more light-bulbs in parallel(the higher-wattage the lightbulbs, the faster this would be and the less lightbulbs needed). Measuring the current, though, would be the harder part and it's likely you'll need a shunt to measure the higher current. But, you can measure the amount of current each lightbulb demands when you add in each additional amount through your regular multimeter(It probably has a limit upto 10 amps or so) for a low number of lightbulbs, and just calculate how much current your circuit is demanding depending on the amount of lightbulbs in parallel: For example, if each lightbulb seems to draw 1 amp, then 10 lightbulbs in parallel would roughly draw 10 amps. At each amount of current, measure the voltage across each cell group to see how each one dips. BE CAREFUL! You want to make sure you measure the cell voltages with the probe in the voltage hole and the voltage setting is on or you may damage the multimeter.

IF it cuts out:

If there's one group of cells that appears particularly low(like 2.1 volts) at higher currents, than that may be your problem
. There might be a weak cell or it may be unbalanced(It would need to be charged back up).

If all remain relatively even in the voltage department, then it sounds like something is wrong with your BMS and it's likely you'll need to replace it. If you're experienced and knowledgeable enough, you may be able to fix whatever part needs to be repaired on the BMS, but you'd already know that if that was the case.

IF it doesn't cut out(assuming you test the higher currents "long enough"):

Then it's probably not the battery.

 

[nomad85]

In the meantime I think I will use some SLA batteries. Can I use my chargers I got from ping to charge them? I would probably do a 5s2p setup for 60v and 18Ah. My current charger puts out 60.5 volts, but its adjustable. I also have 2 36v sla chargers, but I would rather keep the performance closer where it is now (48v lifepo4).

 

[nomad85]

Well I changed my BMS. Now the pack cut out immediately when I try to use it.
I checked the voltages after a charge and most were 3.77 but one was at 3.9 and one was at 3.3 Seems like the old BMS didnt do its job and let the pack discharge with bad cells?

I am so frustrated. The other day my main bike stopped working... it was raining and I hit a big bump, and it just stopped working... the controller still turns on, the CA shows up and the battery I am using looks right on the CA but the throttle doesn't work, I am guessing the halls sensors might have gotten messed up... but I have ridden in the rain before without issue, and this was a light rain. And it happened right when I hit a bump... strange.. now I have to use my slow backup bike with heavy SLA batteries because my expensive shit isn't working. I was really excited about e-biking, but now its starting to seriously suck.

 

[Ypedal]

See... this is where you get pissed off.. tear the whole thing down to the nuts and bolt and put it all back together one piece at a time.. spending hours on waterproofing and sealing and thinking the setup thru a to z.. then .. once you get done you wait for a rainy day and test your work !!!..

2 possible outcomes to this.

First one is you succeed and get the bragging rights on claiming to have a submersible ebike.. or 2nd it gets wet in the wrong place again and it's back to the drawing board ! :lol:

 

[nomad85]

See... this is where you get pissed off.. tear the whole thing down to the nuts and bolt and put it all back together one piece at a time.. spending hours on waterproofing and sealing and thinking the setup thru a to z.. then .. once you get done you wait for a rainy day and test your work !!!..

I was worried that it just didnt seem to do anything when I applied throttle. I thought maybe the halls were shot and I would need to get a sensorless controller... thankfully I unplugged all the connections today to let them air out, and plugged them back in.. still nothing, tried again, then I pedaled around and I got a mph reading on the CA then the throttle worked. I am going to waterproof the crap out of it now.. So I am pretty happy, except for the battery situation, but Ping is being really helpful and has assured me that we will figure it out.

In the mean time does anyone have and old SLA chargers they don't use/need, I only have a 36v charger, and I use a 48v configuration, makes charging quite interesting.