LVC Problem? with BBS02

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LazyTriathlete   10 µW

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LVC Problem? with BBS02

Post by LazyTriathlete » Nov 06 2017 12:34pm

I ordered a BBS02 kit with 13.5ah 48V battery as part of Lunacycle's anniversary sale and installed it on a cheap front suspension 700C bike. It was a dream for a few weeks but now the system is cutting off much sooner than I would expect. I was easily completing my 12 mile commute every day with the battery going down to 46-48V from 52.5V (85% charge). Now as soon as I get to 49V everything shuts off instantly. The screen turns off and there's no power until I disconnect and reset the battery in the cradle. If I do that, everything comes back but only temporarily until it cuts off again.

This happens every day at pretty much same same place on my return commute. It's a flat paved shared use path so it has nothing to do with loose connections. I end up pedaling back home without any assist and when i check the voltage on the battery it is always between 49.0V and 49.3V. It's too consistent and predictable for me to think that it's due to a loose connection. The controller and motor come back to life as soon as I charge back to 85% so I can't see this being an issue with a blown controller.

I checked the programming on my controller to check the Low Battery Protect and it's set to 39.5V, the lowest setting allowed. Limited Current is set to 18A and Designated Assist is set to 8 in the throttle settings.

After a week of runaround from Luna and no luck fixing it on my own I feel like I'm SOL and the only way forward is to buy another battery and motor to eliminate possibilities but that feels like throwing good money after bad. I'm really disappointed with the QC and customer service from Luna right now. Does anyone have any ideas what could be causing this? Ways to diagnose the cause?

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Re: LVC Problem? with BBS02

Post by DAND214 » Nov 06 2017 1:16pm

What I see is a balance problem with the cells in the battery. By not charging to the full charge the cells will not balance. When you reconnect the battery it runs again till the low cell hits LVC and the BMS shuts down the battery. You need to let the battery charge full and let it continue to be charged. It might take a few days to balance the cells or longer. It is also possible you have a bad cell in the battery that will not balance due to a weak cell. Let the charger on and do not disconnect when the light turns green or says it's full. This happens a lot to many batteries that are partial charged to save life cycles. If it continues you need to contact LUNA and tell them about it till they respond. I know they are busy but are an OK dealer.

dan

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Re: LVC Problem? with BBS02

Post by tommie » Nov 06 2017 2:02pm

I have the same set-up as yourself, but as Dan suggests you should leave the charger on to balance the cells. My 13aH 48v battery comes off the charger reading 54v. After 12 miles it will sag down to approx 46v on the display at times but your`s shouldn`t cut out.
Could well be some of the cells aren`t getting balanced or a dud cell in there.

Luna are on this forum here dealing with BBSxx issues https://electricbike.com/forum/

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Re: LVC Problem? with BBS02

Post by Raisedeyebrows » Nov 06 2017 2:44pm

Be sure to check your battery's voltage after you think it's charged with a multi-tester and check your charger's output voltage as well. You probably already have done this but wanted to mention that seeing as the display's on those units are notorious for not being accurate, mine was way off and my battery was fully charged when the display told me it wasn't. Just wanted to say don't rely on the display to tell you what's going on with your battery, hope you get it figured out, I wouldn't purchase another unit until you get this figured out.
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Re: LVC Problem? with BBS02

Post by Lurkin » Nov 06 2017 3:28pm

If you have the ability to, after running the battery to 'shut off point' check the voltage of each parallel group via the balance leads before charging. This will tell you which group is on the blink.

Then charge in full, check the groups again. If it continues to be out, leave it on the charger and it should continue to balance. Leave it on there until you get a measurement that reads equal with the other groups. Then you will know its in balance. Charge and discharge cycle a couple of times and I'd be keep a close eye on it and be charging somewhere where it doesn't really matter if it catches fire. It will be interesting to see if it was outish out of the box and has become worse over time or whether there is permanent damage there which balancing cannot fix.

The above process will identify a weak group of cells and will allow you to use the battery but if they have been damaged or were poorly manufactured, the above process wont actually 'fix' them permanently. They will continue to charge and discharge at different rates to the other groups and if the damaging event is still happening (i.e. BMS issue? internal shorts?) then it will continue to get worse - and this is why I'm saying to try and charge somewhere where fire isn't an issue.

Either way, I'd be:
- checking whether there is a warranty on the battery and the cost to return in case the balancing isn't sufficient.
- checking freight costs to send it back.
- considering opening it up (in the absence of voiding a warranty) to see what the story is.
- considering replacing a cell group if it proves to be damaged.

The thing that bothers me is - quality 18650 cells (which I assume this battery should be) are typically really good at staying in balance.. its weird that its done this. Hopefully a decent balance is all that is required, otherwise I suspect there is more to the story. Unfortunately, the balancing ability of BMS are usually pretty weak and this will probably take quite a while.

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Re: LVC Problem? with BBS02

Post by amberwolf » Nov 06 2017 7:33pm

For now, leave it on the charger whenever it is not in use; it could take days or longer (weeks sometimes) to rebalance a severely imbalanced pack.

You can open it and measure the individual cell groups at the balance wires at the BMS, and post those up here, and we can help you figure out which groups aren't healthy, but I'd say it's a bad battery and should be replaced, if it has a warranty.

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Rassy   10 MW

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Re: LVC Problem? with BBS02

Post by Rassy » Nov 06 2017 8:21pm

I've recently had very good follow on customer service from Luna. What I don't understand is why some are so quick to call for warranty service on a battery that is only being charged to 85% and hence not allowed to balance. Perhaps once the battery is known to be in balance (by checking cell group voltages), and then doesn't stay in balance there may be a legitimate complaint.

I think when lazytriathlete says:
I feel like I'm SOL and the only way forward is to buy another battery and motor to eliminate possibilities
shows that he/she has an attitude problem since the motor apparently runs great and determining if the battery is in balance and either does or doesn't perform properly after balancing is pretty easy to do.
-Rassy-
One Tadpole Trike equipped with a Bafang BBS02
https://endless-sphere.com/forums/viewt ... 28&t=69419
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Re: LVC Problem? with BBS02

Post by amberwolf » Nov 06 2017 8:44pm

Rassy wrote: What I don't understand is why some are so quick to call for warranty service on a battery that is only being charged to 85% and hence not allowed to balance.
I must have misunderstood his first post, as I thought that he was only using 85% of the battery, not that he was only charging it to 85%.

If he is not charging to 100% then yeah, it won't balance, and the problem will get worse and worse.

However, a pack that's made of good cells and not run down too far (which the BMS should prevent) or run too hard for the cells' specs shouldn't get out of balance in the first place, this early in it's life.

Any pack that does get out of balance like this is either too small for the usage it's seeing (too high a current for the cells, especially at a low state of charge), or has a problem with the out of balance groups (defective cells or construction problems), or has cells that just aren't made for the loads they're seeing.

Lurkin   100 kW

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Re: LVC Problem? with BBS02

Post by Lurkin » Nov 07 2017 4:35am

Rassy wrote:... What I don't understand is why some are so quick to call for warranty service on a battery ...
To be clear, I never said to rush off and claim on the batteries warranty.

I said to be aware of what the warranty entails and whether the battery is still under warranty, in case opening it will void the warranty. Further, I described a methodology to identify whether it is indeed more than an unbalanced battery...

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Rassy   10 MW

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Re: LVC Problem? with BBS02

Post by Rassy » Nov 07 2017 11:37am

Sorry if anyone feels I was picking on their advice, but I knew I had seen the warranty word a couple of times in this thread and my intent was to get him to listen to all the other good advice being given before going down that route. He had already been working with Luna and felt they were not "fixing" his problem, but it appeared to me that he doesn't understand how to properly care for or test a battery which is probably what caused his problem in the first place. As a new first time poster he seemed as intent on dissing Luna as asking for advice. We don't even know if he shared his charging method with Luna or just got frustrated because they first asked him to check for a loose connection, etc.

Anyway, I wish him the best in sorting his problem out and hope he comes back with a positive result and good attitude.
-Rassy-
One Tadpole Trike equipped with a Bafang BBS02
https://endless-sphere.com/forums/viewt ... 28&t=69419
One Delta Trike equipped with a Bafang BBS02
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LazyTriathlete   10 µW

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Re: LVC Problem? with BBS02

Post by LazyTriathlete » Nov 08 2017 11:41am

Thanks all. I'm hesitant that there is some kind of warranty seal on the battery that's going to burn me if I crack it open to test the groups from the BMS. Luna keeps telling me that it's just a loose connection but it works perfectly up until 49-50v which is where it cuts off and the pins are all popped out and in good position to make contact.

As for the 85% charging, I was careful to only charge to 85% 4-5 times in a row before doing a 100% charge to avoid such a scenario.

Also, I am using a Grin Satiator to charge the battery and I am using a standalone multimeter to measure the before and after charges to confirm what the Satiator display shows.

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Re: LVC Problem? with BBS02

Post by DAND214 » Nov 08 2017 12:00pm

So you are saying that the battery still shuts down at 49v. Does Grin's Satiator go into trickle mode or shut down completely? Being not familiar with charger, I am not sure if it will fully charge the battery. It will charge till the BMS shuts off but does it charge again if the BMS calls for more? I know it's a great charger but do you have another charger?

Dan

LazyTriathlete   10 µW

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Re: LVC Problem? with BBS02

Post by LazyTriathlete » Nov 08 2017 12:08pm

DAND214 wrote:So you are saying that the battery still shuts down at 49v. Does Grin's Satiator go into trickle mode or shut down completely? Being not familiar with charger, I am not sure if it will fully charge the battery. It will charge till the BMS shuts off but does it charge again if the BMS calls for more? I know it's a great charger but do you have another charger?

Dan

I have the cheapo charger that came with the kit from Luna but I was having trouble getting it to charge the battery at all which is why I gave in to buying a premium tier charger. I'm not as smart about the Satiator as I should be after dropping all that money into it but from what I understand it goes into trickle charge once it reaches the required voltage to maintain the set voltage so it should end up with a balanced 100% charge after some time if the BMS keeps calling for more.

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Re: LVC Problem? with BBS02

Post by DAND214 » Nov 08 2017 12:49pm

So I would contact LUNA again and explain that there are no loose connections. A loose connection will shut down at any voltage, not at 49v every time. It being a 13.5ah pack I sure would expect more like 30 miles with assist since I get at least 2miles per AH with a heavy bike and a MAC 7turn. I would guess that the battery was bad from the start if you were only getting just over 12 miles out of it.
As I had said before, They are not a bad dealer, have been good to me.

Dan

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Rassy   10 MW

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Re: LVC Problem? with BBS02

Post by Rassy » Nov 08 2017 1:07pm

Does your battery cut out at that same spot from home after a 100% charge or only after an 85% charge? In your initial post you only mentioned the 85% charge.

At this point I would recommend going to the full charge and balance (I know, it's hard to tell if it's balanced if you can't get access to the BMS for testing the cell groups, but just leave the charger on for a while) after every ride since it is probably harder on the battery to be going to the lower voltages then to the higher voltages. Maybe Luna will allow and give directions for testing the cell group voltages.

If you don't have a watt meter between your battery and controller, that would be a good addition. I like the WattsUp, but there are some much cheaper ones available:
https://www.amazon.com/RC-Electronics-I ... tsup+meter
As a first step the watt meter will let you determine how hard the battery is really working and how much of the batteries capacity is required for your round trip.

Edit: I couldn't tell from your posts if your commute is 12 miles one way or 12 miles round trip.
-Rassy-
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https://endless-sphere.com/forums/viewt ... 28&t=69419
One Delta Trike equipped with a Bafang BBS02
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LazyTriathlete   10 µW

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Re: LVC Problem? with BBS02

Post by LazyTriathlete » Nov 08 2017 1:13pm

Rassy wrote:Does your battery cut out at that same spot from home after a 100% charge or only after an 85% charge? In your initial post you only mentioned the 85% charge.
It cuts out at the same voltage regardless of where it starts from. I just get a little further before i get cut off when I charge to 54V instead of 52.5V.

Also, my commute is 12 miles round trip. I typically get cut off at mile 9-10, just before the big hill. :x

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Re: LVC Problem? with BBS02

Post by LazyTriathlete » Nov 15 2017 10:09pm

Day 15 and still no resolution from Luna. I finally got someone to agree to send me a battery due to the cut off happening at 49V day after day. The next email I received was a completely new person telling me that my motor core was overheating and they would replace that instead.

I understand that batteries are expensive in every way but pretending that it's an overheating issue at this point seems a bit ridiculous. I even turned down the assist in the programming to the point where I can only get ~350watts of power out of the motor at any given moment and it still cuts off at 49V. I'm getting really tired of the runaround at this point and am considering a chargeback as my last hope to get some movement on a remedy.

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Re: LVC Problem? with BBS02

Post by fechter » Nov 15 2017 10:24pm

To me it sounds like a bad cell group in the pack or the charger just doesn't go high enough to balance the pack. Even if the charger voltage was low, I would expect a new pack to be well balanced and stay that way for a long time.

Have you checked the motor temp just to eliminate that as a possibility? Doesn't seem likely.

I guess the other thing to ask is when it cuts off, does the display go blank? If the BMS is tripping, all power coming out of the pack will be cut off. If the thermal thing in the motor trips, I think it shows an error on the display.
"One test is worth a thousand opinions"

LazyTriathlete   10 µW

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Re: LVC Problem? with BBS02

Post by LazyTriathlete » Nov 15 2017 10:27pm

fechter wrote:I guess the other thing to ask is when it cuts off, does the display go blank?
Yes. It is a complete cut off. No screen, no power, no response from the power button. If it was a bad cell group wouldn't my max voltage measure low?

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Re: LVC Problem? with BBS02

Post by DAND214 » Nov 16 2017 1:04am

Run it down to maybe 51v Or only charge to 51v and ride it till it and see if it shuts down a 49v. We know it will but that will eliminate the motor. After it shuts down with not run time then they will understand. Or they can send you the motor and then the battery later. It's their choice. They can pay you once or two times, it's their option.

Dan

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fechter   100 GW

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Re: LVC Problem? with BBS02

Post by fechter » Nov 16 2017 10:46am

LazyTriathlete wrote:
fechter wrote:I guess the other thing to ask is when it cuts off, does the display go blank?
Yes. It is a complete cut off. No screen, no power, no response from the power button. If it was a bad cell group wouldn't my max voltage measure low?
I've had a pack that behaved like yours before. One cell group was bad. It would charge up to a normal voltage so looked OK on the charge cycle, but apparently had way less than the rated capacity, so the one group would hit cutoff way before the others. It's hard to detect a single bad cell in a 14s string by looking at the overall pack voltage.

The only way to really know would be to rip apart the pack to get access to the BMS connector to make individual cell voltage measurements. Even then, it might look OK when there is no load, but sag down when loaded.

One more question: Do you know how many Ahr you are getting out of it before is shuts down? If you have a CA, it would display this. If not, I think the Satiator has an Ahr measurement of how much it took to charge it back up, which would be pretty close.
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Re: LVC Problem? with BBS02

Post by tomjasz » Nov 18 2017 5:48pm

30 day warranties!
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

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