Another not very old Luna Wof V2 with problems?

[73Eldo]

Short version:

Luna Wolf V2 pack I bought new back in September and have follow everything in the care and feeding booklet that came with it. I have 3 packs so not sure how many cycles this has on it, my guess would be no more than about 30. No signs of issues or concern till 3 rides ago. All seemed normal on a typical ride on a cool but much warmer than some rides day except when I was getting close to home which the last mile is up hill I noticed the sag seemed worse than usual and it took longer to recover. Was around 48 volts midway the plateau before the last climb. Just as I started the final climb it went dead. Got home and inside and with a volt meter 90 port is dead and 60 is 24v. I thought was strange but it was cool out and I pushed a little harder than I usually do on the home stretch. Let it sit for a couple hours and checked it again before charging and it was reading 48v.

Morning charged it 2a 100%. All seemed fine on ride #2. Range seemed great and sag didn't seem unusual and seemed to recover fine. Similar ride and ambient temps to ride #1.

Ride 3. Charged 2a 90%. Similar route and ambient temps again. All seemed fine except near the end sag seemed to be a little worse than normal but it seemed to come back quick so I didn't put too much thought into it other than to be sure to take it real easy which I did. Same as ride #1 just as I started the final climb dead. This time I know I looked at the meter just a second before it went dead and it said 48. Same as before got it in and 24v and 0. Same as before let it sit for a couple hours and saw the 24 slowly creep up to 24.9 and then next I checked it was at 48 again. Hooked up a 60w 120v heating element I had laying around thinking I would do a nice slow discharge and another 100%. Over 10 mins it went from 48.2 to 47.1 then I walked away for a minute and it was back to its 24v thing.

I'm going to keep trying to discharge it then do a full charge but I'm thinking I may need to open a ticket with Luna on Monday because it sure seems like I have a bad cell in there. I have a V1 Wolf I got used that was my only pack for most of the summer and its been great so getting another one seemed like a good idea.



Long version with lots of details:

With the weather getting better I have been getting out closer to daily vs weekly that I was doing in the cold. I got my V2 Wolf pack in Aug or Sept so its not very old. I did everything the booklet suggested as far as the break in and storage. I have the advanced charger and almost always charge at 2 amps and 80 or 90 depending on if I think I will need the range. I do 100% charges every few weeks when I am riding fairly often. I have 3 packs and I'm usually the only one riding so I was trying to rotate through the packs so none sit too long.

When freezing temps came and I started keeping the packs inside I switched to using the new V2 pack because I think its built in connectors are better for a lot of plugging and unplugging. Its the pack I used most of the winter. I have ridden in temps below freezing. Keep it inside except when I am actually riding. I usually keep the packs between 48-52 volts when they are not being used and charge them before a ride so they don't spend any time fully charged or dead. I rarely run them below about 46v. Most rides end around 48. If I do run them down I give them time to cool or warm up in the case of winter before charging.

A couple rides ago it was above freezing for a change and all seemed normal. Near the end of the ride which is about a mile of hill I did notice voltage was getting low and the sag was taking a long time to recover but forgot to turn the assist down on the one flat area and it just went dead. Had to pedal the last uphill bit home. When I got inside I put a volt meter on it and got nothing on the 90 and around 24 on the 60. Figured it was on the cool side out and I did push it a little harder than I normally do so didn't really think much about it. Came back to it a couple hours later just to make sure it was room temp and before hooking the charger up and hooked the volt meter up again. This time about 48v on both ports. Left it overnight.

In the morning still same readings so I put the charger on 2a 100%. Normally when I go to 100% on a battery I have not done 100% on for a while it seems to take at least twice as long as normal before the charger shuts down. Went for a ride and all seemed well. Seemed to have plenty left over when I got home which I figured was just that 100% vs my usual 80 or 90.

Today hooked up the charger 2a 90% and it started out at 47.5. Seemed to take about the normal amount of time. Did about the same 20 miles on similar routes as before with similar temps about 45*F. All seemed well and normal till just like last time on the final climb it seemed like the sag was more than usual but it seemed to come back quicker than the first time so I thought all was well. Was careful not to push too hard and I noted that the meter said 48 just before I started the final climb home and just as before I think in the same exact spot it went totally dead. Same as before I got inside and 24v. Let it sit with the meter on the charge port and over about 2 hours saw it creep from 24.1 to 24.9. Went back maybe 15 mins later and back to 48.

Pack was room temp except for the 2 hours I was out riding and this trip I didn't stop for more than maybe 5 mins about an hour into the trip. Pack didn't feel cold when I got it inside. After sitting for about 4 hours since it went dead I hooked up a couple 60w 120v heating elements I had for another project thinking I would slowly fully discharge it then do another 100% charge. I stood by it and watched the meter for about 10 mins. It started out at 48.2 and over the 10 minutes went down to 47.1 before I walked away for a minute. When I came back things were back to 24v on the charge port only.

I'm really thinking I got a bad cell in there. If this was one of my other packs that I bought used and know are at least 3 years old I would not be as worried but this is the pack I bought new and have tried to be extra careful with to keep it happy. Anyone got any ideas or spot anything am doing wrong? If not I'm thinking I may have to open a ticket with Luna on Monday. Till then I am going to keep trying to slowly discharge it which could take a while with it only going for 10 mins at a time then taking a couple hours to turn on again.

[73Eldo]

I just went up to check and see if it reset itself and it hasn't. Wondered what would happen if I hooked up the charger. Charger display briefly says 24 then jumps to 48. Discharge port stays dead. Disconnected charger and checked voltage 24. Hooked up charger for a minute and same thing but after a minute the discharge port went to 48. Shut off the charger and left the volt meter on the discharge port and after about 30 seconds it seemed to go nuts turning on and off before settling on off.

I'm guessing it will charge up again but I really think something isn't right. This one has never acted like this before and my V1 which has a lot more use and abuse has never done anything like this even when I have killed it to the point BMS shut it down.

[73Eldo]

Left it just sitting inside for 11 hours not connected to anything and its still only at 24.6v. I wish I new more about how the BMS was supposed to work in this. The pack can't be a 24v. The 24 must be some sort of safe mode that the BMS goes into when it decides to do a low volt shutdown.

I'm thinking that because I was able to discharge a little from when it self reset that the bad cell group is now low enough that it can't recharge a little from the others. Or maybe there is an issue with the BMS circuit to that group so its not properly charging? This was one of the fears I had with the Wolf packs is that they are so well sealed up you can't even trouble shoot them. Maybe if I had the liquid one I would at least know where things were and it would be safer cutting into it because you could kinda see stuff but not so with the black one. Besides black cover the internal potting material is also black. My v1 has the black cover but the potting is clear.

[AZguy]

FWIW I know zero about the specific workings of these particular packs, however the voltage you are seeing with a DVM may just be due to the BMS in an "off" state and even in an "off" state there will be leakage so into a very high impedance load like a DVM you may see voltage, sometimes significant (most of my packs only show a volt or two on a DVM in the "off" state). If you can put a very small load on this, ideally just a few milliamps, and see if that voltage drops it would help confirm or dispel that notion. If you have some resistors, say in the 1KΩ-10KΩ and put them across the DVM while you are measuring, that would likely do it. If it drops a few volts I might go so far as to add more resistors [in parallel] to see how much it keeps dropping and compute any potential leakage current.

What to do with that information? Hard to say but at least it's something. If it drops down to a volt or so with some light load then it's likely leakage and the BMS output is "off". If it doesn't then it suggests something really is "more wrong" with things.

A potted battery like this is pretty much a throwaway if it really is bad... there's not really any practical way to repair them... frankly, it can be argued that *any* electric bike battery isn't terribly practical (or at least economical) to repair and if potting lowers the overall failure rate then potting puts things ahead of the game although that's small consolation if the battery turns out to be dead.

Hopefully it's not really bad and can come back to life... me I'd still do some light load tests just for the data if nothing else...

[73Eldo]

I will try a little load on the meter to see if that changes anything. I think I know where my resistor stash is. My old Simpson meter may be there too.

I let it charge at 1a for about 30 mins then re connected my heating element. My 120v 60w element seems to be pulling around 1 amp so that is a nice slow easy load. It had charged up to about 50v and after about 20 mins was already down to 48.2 which seems like a lot of drop for only 1 amp. 200w @ 48 volts (and easy cruise on a BBSHD) would be 4 amps ish so my 1 amp is really a lower draw than its gonna see in use.

[73Eldo]

I was watching it this time when it shut off. With that 1a load it was dropping about 1/10th of a volt per minute. It dropped at 47.2 and that is room temp with a 1 amp load so temps should not be a factor or surge sag. I'm going to let it go to 100% again since I doesn't seem like it wants to go any lower then set up my load test again and see what it does.

Now I just have to remember where I put my old mini charger so I can charge another pack while this process is going on and I can go for a ride.

[Dshue]

I wonder if it has always had a low voltage cut off in the BMS at that point and you're only reaching it faster now due to cells failing. Whether the same holds true with lithium batteries as lead acid I don't know but with parallel lead acid batteries the rate of equalization isn't linear from a high state of charge to a low state of charge. The lower the state of charge the faster you'll see discharge from equalization.
I would charge the pack to a known state of charge then leave it sit disconnected and monitor the discharge. If you have weak cells you'll see obvious levels of discharge.

[73Eldo]

Its on its way to 100% now. When its finished do you think I should let it sit and check the voltage? I'm assuming we are talking days? Or do my low load test again and see if there are any signs of a change good or bad? Over the last couple months I have not noticed it seeming to discharge but I'm not carefully monitoring it either. It hasn't sat for more than about a week without a charge and a ride.

[Dshue]

I would let it sit a few days. Over three days I wouldn't expect any change with a good pack.
My pack has sat for weeks with no change. Measuring to the tenth of a volt.

[73Eldo]

I could not just sit and wait. I let it get to 58v then put my 2 amp load on it. Took it exactly 4 hours to shut down at 46.6 volts this time. I have a ride with a friend tomorrow and will use my other 2 packs but as soon as that is over I will take my V1 pack up to 58 and see how long it takes with the same load and what voltage it drops at. Maybe its normal? I have been out on 4 hour rides before and it seems like my fat butt had to be drawing more than 100 watts per hour but maybe not? If I was not using that much power you would think I could make it the last 6 blocks with a dead battery but that distance just about killed me.

[Dshue]

It would be worth using the same test on a known good battery.

[73Eldo]

I'm not sure what spec my V1 battery is but when I was using both they seemed to get about the same range so if I do the test and they come out about the same I will know its somehow all in my head. I may still start a ticket with Luna to see if they can tell me what the cutoff voltage is supposed to be on both packs and just to get it and its SN noted in their records in case this is a trend and some duds got out. I sort of hope its in my head because that was a very expensive battery. The fairly suddenly going dead sure isn't good for the old range anxiety.

[AZguy]

I don't think I've ever hit BMS LVCO - motor controller hits long before.

I think how much the voltage will drop if just sitting can have a lot to do with the BMS. E.g. my monster battery and a shark show almost no drop in many weeks but I have some "dolphin" packs that will show steady drop over time, and different amounts - the dolphins are all from different suppliers and for sure have different BMS's (I've opened them)

I think continued charging to 100% and since you have a load discharging. Even if 1A that's enough to get a feel for capacity - e.g. it should go for at least 10hrs (I'd think more) with the 1A load... If I could see it doing at least 10hrs at 1A I'd be taking it out on the bike.

I have multiple batteries so if one is giving me any concern at all and I'm going on a long ride (I've got zero fear of pedaling a dead battery home if less than ten miles) so it's easy to bring a spare in that case... Someone "gifted" me a monster (14s8p) battery recently but he said it was 8-10yrs old and so I just wasn't so sure about it. I'm still on it's first cycle (for me) but if I go more than five-ten miles from the house I just bring a spare.


Not to thread hijack (I'll start a new one once I've got time on it LOL) but I think this was a very lucky find. He said he charged it and it took/held the charge (he did not discharge it). It took me at least a month before I got around to building an adapter for it to connect to my bikes. I still haven't run a full cycle on it, I just plugged it in without even charging it, just the charge it was given to me with (just over 58V). I've been running it hard, often at 500-750W continuously and have run about 14Ah on it and it's at about 51.2V now. After a few cycles my concerns over it will likely fade. I suspect I'll easily get more than 20Ah from the thing. I often get 30-35mi on my old 13s4p so riding the same leisurely way I'd get more range than I'd likely ever want to do... but it sure is fun to ride it super hard - it has such light sag even when hammering it and I'm impressed that my BBSHD doesn't get more than a little warm even hammering it like that although I do keep RPM's up in the 70-80's... Not bad for $10 investment to build the adapter...

[73Eldo]

After yesterday evenings test I put it back on the charger and got it above 50v before disconnecting it for the night. After about 10 mins it was at 51.6 . 6 hours later its at 51.4. I too keep thinking that with that light a load it should have gone longer. Tonight's test with my other pack will tell me a lot I think.

I have only bumped into the battery BMS cutout a couple times before in almost 10 months use and 5 of those were almost daily use. First time was just after I got the bike I was going around my block trying to make it die so I could get a feel for what the gauge looked like and how long I really had once it said it was empty. The other time was testing a new build and going further than I should have knowing that the battery didn't have a full charge and I was on a new system that even though its identical models the gauge reads a lot different. I may have shut one down on my first below freezing in the snow ride too just not realizing how much power it takes to push through snow and how the cold reduces capacity. All those were with my v1 pack. I don't think I ever shut down the V2 till a few days ago.

[73Eldo]

V1 vs V2 test has begun. Ride with the V1 was fine today but I wasn't on that bike so maybe the guy was pedaling harder than me but it came back from a 90% and 20 miles still over 50v. My bike did too but I think the pack I had is 19 or 21 ah so that was expected. While on the ride did I think an 80% charge on the V2 and it was at 56.6. Its been 6 hours and its still holding at 56.6. The V1 pack started out at 58.4 and I got 4 hours before bedtime which was how long it took my test rig to wipe the V2 down to just below 47 when it shut down. If it looks close to the to the the other one I may stay up and see if it kills like the other. If its not close I will shut down and continue tomorrow.