A look inside a Juiced 52V 13Ah battery.

[Explorer-1]

There have been a few photos in the past of the Juiced battery as people had to open them to fix the connector, this look might go a bit farther. I bought a defective battery just for the case, but turned out the case is too small to fit my replacement pack once all nicely protected. While I deal with a very slow tire leak and think about what I might want to do with all these batteries around here, I thought I'd start with a look inside the Juiced battery.

The battery charges up, but not to the correct voltage, something like 1-2V less I can't remember right now. It says 100% on the bike, and it works fine for maybe 5 mins, then it basically cuts out every 30-60sec after that if you reset the battery by turning it on and off. It might be a BMS Temp or Power issue, but since it does not charge to the correct voltage I'm guessing a bad cell or 2 in a group. I thought I'd take a look at what they put in these packs.

I've manage to to get the balance connector removed so I'll try to measure each cell group from there and see if anything stands out. We can see from the BMS photo that it has a relatively low 25A rating, but is adequate for the bike.

 

[Explorer-1]

OK so I checked each bank and it turns out the problem is with the cells. The first 13 banks range from 4.069V to 4,074V, but the last bank is only 3.217V.

I could try to bring the last bank up to 4.070V, but I'm guessing it has a bad cell and won't get there happily. That probably ends the story here, I doubt I will try top repair the pack, and my new pack is too large for the case so... I guess I have a batch of 18560 cells I don't really need or want to add to my collection.

Although since Juiced bikes will run on 48V and could turn the 52V pack into a 48V pack very safely. However Juiced controller on the RCS likes 52V as I think they under change their packs in the first place. I'm not sure how well the RCS works on a 48V Nominal pack. Does anyone have any experience using older 48V Juiced packs with the RCS?

 

[Explorer-1]

So it turns out the [ potentially ] bad cell is one of the last 5 cells [ last group ], and they are located at the bottom of the pack. I thought maybe someone dropped it, but then i noticed this very strange hole that looks man made with lots of scratches around it; someone made all those scratches, but why. Did someone try to investigate, did they know that had a bad pack and shipped it anyway? Of course just speculation but this is a pretty weird coincidence. Now I'm a little more interested in finding out just which cell in the last group is bad, if it turns out to be the one marked by the hole this would be quite interesting. Although I don't see how they could have determined which cell was bad after the pack was assembled without some very special analysis that they would not have taken the time for, and if they had found the cell before assembly surly that would not have tacked the final strip in place or even used the cell in the first place, and that would not explain the hole. Did someone accidentally make the hole and damage the battery. You can tell I love a good mystery.

 

[harryS]

Doesn't look low quality to me. They used a form to hold the cells, and the photos may not show the air space between them.

The hole could be burned into the electrodes from someone setting the cells down on something conductive during assembly. I did that with a battery I took apart. I let it slip into my desk drawer where it found a pile of paperclips. The electrodes vanished quietly.

Might be worth getting a little DC-DC stepdown converter and adjusting it to 4.0 volts and try charging the last group thru the balance connector. I had a 36V pack last July that started dying around 40V after a about 5 miles. Same problem as yours. One cell group down about a volt. I ordered a new battery.

Still, curious about that first pack, I checked it a week later, and the low cell group was now down 1.5V, So I recharged it separately to 4V and it stayed charged with the BMS disconnected. I've replaced the BMS, put it back together, and will test it to see if that was the cause,

 

[Explorer-1]

The hole could be burned into the electrodes from someone setting the cells down on something conductive during assembly.

Seems unlikely; look at the closeup, and would not explain all the scratches. Nothing else near as a second contact point is visible. I'm quite familar with such things from when i was young i don't see the signs.

…try charging the last group….

Yes i mentioned i could try that, but was skeptical that would hold, but i may try it.

Well you can upgrade your 13ah pack to 15.6ah for $50

Did you watch the video?

 

[Explorer-1]

A small update.

First just in case not everyone was following the cryptic messages, the video posted above on upgrading a Juiced 13Ah battery to 15.6Ah does not apply in this case, which is very clear from the photos. This is important information because some of you probably have seen that video and contemplated doing that mod. Maybe even buying a second battery with the intention of doing that mod, but as can be seen here not all Juiced 13Ah batteries use the same cells and if you get the pack shown in this thread then you cannot do the update. In theory if one had the weight of the two packs one could know without opening the pack if it used 5P configuration or a 4P configuration with higher capacity cells. The important thing here is to remember a manufacture can change the cells they use at any time, so what you are buying is not always what the original specs say.

Now the update; with a tropical storm in the vicinity the rain had me indoors on Sunday so I had time to babysit a battery, given that the low voltage cell group was still well above safe levels at 3.2xx V I decided I would try to charge the one bank while keeping a close eye on it. It charged up just fine not even a hint of heating and everything was very smooth, the charging lasted into today where I could not watch it as closely and the group got up to 4.153V before I stopped the charger. This is 0.083V above the average 4.07V for the other cell groups.

So the next part of the plan is to confirm the operation of the BMS. At this time the conditions of the battery don't really point to a BMS problem, but instead some issue with an out of balance cell group being included by accident in the pack assembly.

Next step is to just connect the BMS back up and confirm that it is not discharging cell group due to a circuit fault.

If the voltage stays stable, then the following step will be to connect the charger to the entire pack and see if the pack will change and balance the now high cell group with the rest of the pack.

Off to connect the BMS as soon as I have time to watch it closely for a while. I'm mildly hopeful this pack will be working before the weekend for the first time since it was shipped from Juiced to its original customer.

 

[tomjasz]

Doesn't look low quality to me. They used a form to hold the cells, and the photos may not show the air space between them.

When I’m wrong I’m REALLY WRONG!
Mea culpa!
My apologies.

 

[Explorer-1]

Good news! I reconnected the BMS and didn't have any issues, do to some messing around I charged the cell group over the others to full charge, so then I discharged the cell group again and it worked fine. Then I balanced it all out again at 4.183V and then plugged in the charger again. It charged the pack until 58.81V and the charger light turned green. I left it on the charger to see what it was going to do and over the an hour or so the pack voltage raised to 58.84V (I'll update if it goes any higher, I've not disconnected the charger just yet, I have a feeling it may stop at 4.205V for each group, but I forgot to check the exact charger voltage before I plugged it in).

I'll be reassembling the pack in the next couple of days if I can find a suitable sealant and tape. Looks to me like the pack could be back in action soon, so maybe I'll have to break my distance record for a single trip this weekend, I have a good location scouting trip i could do.

 

[Explorer-1]

I got some time to reassemble the battery. Since I didn't have large heatshrink to encase the battery I had to bandage it up instead. Probably give it a test run a bit later today.

 

[MikeL]

My bike was shipped with 48v 14Ah battery that had a couple of discharged cell groups. Two groups measured about 3.2-3.5V while the rest were at about 4.2V.
I charged them manually with RC charger and so far the battery works OK. I did 3 full charge/ discharge cycles. Those weak cells behave a bit differently, but seem to be OK. About 0.05V difference between them and the rest of the groups when battery is fully charged.
If it was an RC battery (no BMS), those cells would be already dead. BMS saved them by disabling battery output when voltage dropped below minimal for those cells.
BMS balancing current is only 0.05A and it could not fix such disbalance. Well, maybe it could, but it would require a 100 of charge/discharge cycles.

 

[Explorer-1]

MikeL, that's amazing. They must have some people not awake during battery assembly, but also no QC because this type of problem could easily be caught.

You are right the BMS saved this battery as well, it was shutting down the output as the one cell group dipped too low.

I don't think my hobby charger goes down to 4.2, but I have several single cell chargers. This time I lucked out as I have magnetic contacts so dirt simple to charge any group in this pack. I even did a discharge of the group brought it back up to balance with the other cells and then plugged in the charger for the pack, to bring the entire battery upto full charge. it all worked great, then I reassembled it.

I just got back from my first 45km test ride with the repaired pack and it is working great. I'll charge it tomorrow when I can watch it but I don't expect any issues. I will check the final pack voltage though.

Update: The back charged back up after it's first discharge to ~49V (3 bars) to the exact output voltage of the charger to everything is good. Well unfortunately you can't see if it overcharged a group slightly to make up for an undercharged group, but it looks to me like the BBS as a pretty small differential between groups. My next discharge is likely to be deeper to 1 or 2 bars.

 

[Cormode]

Explorer-1, Do you have any more wide angle photos of the BMS? I have not taken apart my Juiced battery since it is still under warranty, but I am curious about the BMS.

It is hard to say for sure in the closeups you provided, looks to me that the BMS is maybe it is an "ANNPower" or "Super Power" model.

In either case, that news is a bit of a disappointment. I don't think either company sells a BMS with anything other than passive/fixed top-balancing.

This means' Juice's advice for extending the life of a battery pack has a hole in it. If you never charge above 80%, you won't balance. As the cells start to drift with usage you will end up one group very high or very low and then that group takes damage faster since it is living close to full or empty. https://support.juicedbikes.com/en_us/how-do-i-get-1500-charge-cycles-out-of-a-52v-pack-B1Qyl9vzY

I wish the Juiced batteries had a BMS that would actively balance.

 

[harryS]

Doesn't Juice tell you to do a full charge every other month or so? That would resolve that issue. I doubt any ebike batteries have active balance BMS. That's for cars and powerwalls for your house.

 

[Cormode]

Doesn't Juice tell you to do a full charge every other month or so? That would resolve that issue. I doubt any ebike batteries have active balance BMS. That's for cars and powerwalls for your house.

There is some information gaps in the periodic full charge approach. In the daily instructions Juice says to fully charge the battery and leave it connected for 30 minutes after it gets to full. I guess this 30 minutes is for balancing to occur. Since balancing happens at fixed ~50mA, I would assume this means the accumulated imbalance is expected to be 25mAh or less for the day. It stands to reason that if you have gone 30 days without balancing that there may be more accumulated imbalance and so you need to leave it plugged in completely full for 15 hours to bring it back to balance. Or maybe more, or maybe less. You mostly can't tell.

If you have current and voltage monitoring on the charger you can watch to see how close battery voltage gets to 58.8 when the BMS cuts off flow.

As near as I can tell the Explorer-1 just balanced his pack to return it to functionality. The charger and built-in BMS could have done that. The trouble is they would have needed to leave it on the charger for something between 2 weeks and 3 months to bring it back into balance, and during that time they wouldn't have been hard pressed to know if it was done or needed more time.

I guess the frustration revolves around the cost. An passive balance BMS has a wholesale cost of about $10 and active balance BMS has a wholesale cost of about $50 and entire battery has a sticker price well over $1000. Active balancing would add years to the life of a battery pack at a marginal cost which would barely move the needle on the overall price.

 

[Explorer-1]

There is some information gaps in the periodic full charge approach. In the daily instructions Juice says to fully charge the battery and leave it connected for 30 minutes after it gets to full. I guess this 30 minutes is for balancing to occur. Since balancing happens at fixed ~50mA, I would assume this means the accumulated imbalance is expected to be 25mAh or less for the day. It stands to reason that if you have gone 30 days without balancing that there may be more accumulated imbalance and so you need to leave it plugged in completely full for 15 hours to bring it back to balance. Or maybe more, or maybe less. You mostly can't tell.

If you have current and voltage monitoring on the charger you can watch to see how close battery voltage gets to 58.8 when the BMS cuts off flow.

As near as I can tell the Explorer-1 just balanced his pack to return it to functionality. The charger and built-in BMS could have done that. The trouble is they would have needed to leave it on the charger for something between 2 weeks and 3 months to bring it back into balance, and during that time they wouldn't have been hard pressed to know if it was done or needed more time.

I guess the frustration revolves around the cost. An passive balance BMS has a wholesale cost of about $10 and active balance BMS has a wholesale cost of about $50 and entire battery has a sticker price well over $1000. Active balancing would add years to the life of a battery pack at a marginal cost which would barely move the needle on the overall price.

I'm not sure if I have more pics, but I can confirm it is a passive top balancing BMS like almost all BMS in battery packs these days that are aimed at consumers that are less than 5kW.

Ignore all the BS on the internet about how to extend the live of the Lithium batteries even from the 'experts'. You basically have to learn about them yourself and then sift through the information. Ignore all the information about charging to 80% many people have ruined their batteries that way as you have noted on how the balancing works on 99.9% of all the packs. People have taken the Full-Charge issue out of context, deleted all the details and now just state "don't charge to 100%" which is just BS. The fact that most packs are poorly designed such that they have high parasitic drain, the 80% stuff is a nice way to kill many batteries (not just talking bikes here). It frustrates me to no end, but you can't fight the internet so...

 

[Explorer-1]

I looked and I don't have any pics of the BMS that show anything more really. In one of the pics above the model number though is visible on the sticker. I was trying to do as little disassembly as possible.
I've attached one that shows it end-to end, but still only from the heatsink side, so it does not show much additional detail. You can see that it is a B- common mode BMS.

 

[Explorer-1]

Small update: This pack is still working great, but I now have what looks like a very similar problem with another one of my own 13Ah batteries. Just need time to disassemble and fix. However; since Juiced now has G2 batteries I'm not going to get to fixing my battery for a while.