"Luna Cycles"? 13s 4p Samsung 26f "48V 10Ah" pack

[amberwolf]

Reported to have charging problems, this pack hasn't yet been opened up, but first I thought I'd just test the charging. It doesn't have any brand or manufacturer or vendor markings on it, but it is supposed to be one of these Luna Cycles packs:

http://web.archive.org/web/20150822034024/http://lunacycle.com/batteries/48v-samsung-18650-battery-pack-10ah/



Took pics first, including this label that might be a double typo, but somehow seems more likely to have been meant to deceive shippers into allowing this on shipments it wouldn't otherwise qualify for due to it's capacity:


The label (mis)reads:
"18650 LI-ION BATTERY"
"4.8V 10AH"
"48 WHR 26F"
when in fact it is a 48V 10Ah 480Whr pack. :/
(either that or it is dangerously overcharged and could explode at any moment. :lol: )



It arrived here at 49.3V with no load, tested with multimeter on both charge and discharge ports, just measured with voltmeter on existing wires/connectors. Assuming it's balanced (which I can't check till it's opened up) that would be a hair less than 3.8v/cell.



Had no connector on discharge port, so I then added the Anderson SB50 I use on everything here, so I can plug it into the trike (or bike) and do test rides with it for monitoring/etc.

The automotive plug on the charge port I replaced with Anderson PP45 that I use for charging (it's what is on the Satiator which I'll be using to test charge with).

Assuming that 4.2V/cell is max charge voltage, I set the Satiator up for 4.2v x 13s = 54.6v full charge voltage, based on one of the preloaded "48v lithium" charge profiles, for a 4A charge rate, which would be 0.4C.

It charged for a while as I made dinner, but I managed to mostly-unplug the Satiator from the wall as I was moving an appliance cord from that outlet panel to a different one, as the voltage got to around 53v, and didn't notice until the Satiator had powered off and cleared the screen, so I have no idea how many Ah it put into it at that point.

I restarted the charger, and got about 1.4Ah into it before the Satiator reported a "power fault", and had to be restarted, but it only took anohter 30 seconds or so to get another fault, somewhere around 56V I think it said before the fault.

I'm presuming based on the voltage that the BMS was cutting off charge, and somehow that caused a problem the Satiator couldn't deal with on it's own, but I don't know yet.

I then hooked up the pack to the SB Cruiser, and rode around the backyard a bit, low and bursts of high throttle, one and both motors, etc., to put a little laod on there and drain it some, to retry cahrging again.

After this I retried charging, and no more power faults but it still stopped somwhere around 56V (couldn't see exactly) within a few seconds of plugging in and start of charge with "charge complete", and then the voltage on the Satiator flickered so fast between 50-something and 60-something volts that I couldn't read what it said.

I changed the profile to reduce current to 1A (0.1C) with no change in behavior.


For now I am just leaving a Turnigy Wattmeter on the charge port, where it says it's 53.17V (as a Watts Up similarly says about the discharge port), until I finish typing this up. Then I'll take them off and go store the pack in one of CrazyBike2's metal cargo pods outside overnight (in case anything dramatic happens to it, as unlikely as that is).


Presumably if it is a cell-balance issue the BMS will do some balancing overnight, then I can retry charging tomorrow.

But first I'm going to test it on a "real" ride with the SB Cruiser on my work commute, to see how it performs, and to drain it some. (should take around 4Ah or less).


Assuming this *is* a Luna Cycles pack, then the specs from the archived page above are:

 

[amberwolf]

I dozed off above, woke up and just submited so I wouldn't lose it then went back to sleep.

Anyway, these are the still-relevant specs copied from the archived page linked above:

48 volt 10ah = 480 watt hours
13s4p = 52 Genuine Samsung 26f 18650 cells
50amp continous 80amp burst BMS
Light Weight: 6 pounds
Battery Dimensions: 250 x 90 x 80 mm

"It is a high power BMS which will allow the pack to put out 50amps continous (2500 watts) and 80 amp bursts (4000 watts) alhtough running this much power will drastically reduce packs life expectancy so we recommend to not run your battery to hard if you expect it to last over a couple hundred charges."

 

[amberwolf]

Ride to/from work today, using this pack to test it a bit, went about as expected. Battery isn't meant to be high performance, and if it started out that way it definitely isn't now. :/

Acceleration (vs my EIG 20Ah 14s pack, or the A123 20Ah 16s pack) was drastically reduced, felt as if I were pulling about half a ton of stuff in the trike, even though it was basically unloaded (other than the trunk/crate weight).

I don't yet know if they were caused by the battery or the controller, but I got cutouts several times on the trip home, starting way before the halfway mark, after only about 3 and a quarter miles total ride distance. The motor would lose power then recover immediately, as the voltage dipped to 39.9v and then rose anywhere from 3 to 5V once load was removed by motor cutting out.


Performance stats from the CA, first for trip to work then total trip (I forgot to reset it after noting the info for the trip there):

50.9Vrest
40.4Vmin
-11Amin
50.81Amax
2.073Ah
94.79wh
45wh/mile
2.144miles
20.1MPH max
14.7MPH avg
8m43s triptime

48.9Vrest
39.9Vmin
3.934Ah
176.62Wh
-11Amin
50.81Amax
40.2Wh/mile
4.445miles
20.1MPH max
14.3MPH avg
18m38s


I didn't check the battery temperature when I got to work (forgot) but when I got home, with the battery starting at 77F (sitting unused for 9 hours indoors), it was 101F a couple minutes after I stopped, readings taken inside the shrinkwrap with the probe of a candy thermometer that has proven to be accurate to a degree or less, when referenced to other thermometers I have here.

I didn't measure in the core of the pack because I dont' know the detailed construction inside, and didn't want to risk shorting something out by inserting a steel probe between cells thru shrinkwrap I can't see thru. So it's probably a bit warmer inside the pack. (air temperature outside the insulated samsonite case I kept it in during the ride was 98F, just getting ready to rain (which it did about 20 minutes later)).


Will do some further load testing on the bench, stationary, to see if it was the BMS cutting out or not, tomorrow if possible.

If I can make up some extension cables for the Sorenson, I will also test the trike using the Sorenson lab PSU at progressively lower voltages, to see where it's cutout is. (I can't bring the trike into the room with the Sorenson, as the Sorenson can only be used in the utility room as it's the only outlet that can run it, and the trike won't go thru the doorways to get there. So have to make extensions for the Sorenson either on AC or DC side, and run that out the window almost a couple dozen feet away, then another 8+ feet to the closest place I can get the trike to it. )


After I find out if the BMS is cutting out or not, then I'll open up hte pack to check individual cells/groups.

 

[amberwolf]

Load testing today, using a Watts UP on the discharge port, and a stove element stuck into the SB50 on the other end of the WU, which at this voltage provides almost a 2A load. Not a lot, not as much as a bike, but better than any other simple-to-hook-up load I had at hand.

The pack is still at the SOC from the previous on-trike test; though it's resting voltage has risen to 50.4V. (3.9Ah was used in that test)

Start of testing, as soon as I hooked up the load:
49.6V
1.82A
78F (load element temperature; room temperature was 77F)

2 minutes into test:
48.54v
1.79A
148F
7.1Wh
0.149Ah

5 min:
48.46v
1.77A
167f
10.6wh
0.22ah

10 min:
48.27v
1.88a
179f
26wh
0.328ah

30min:
47.98v
1.78a
180f
53.9wh
1.12ah

60min:
47.62v
1.75a
177f
90.7wh
1.867ah

Then I had to go do some stuff, so I disconnected the meters and load, and came back 2.5 hours later to finish up:

start
48.08v
1.76a
79f

20min:
47.19v
1.73a
183f
0.56Ah
27wh

45min:
46.36v
1.69a
178f
1.379ah
64.9wh

90min:
44.81v
1.64a
172f
2.536ah
117wh

105min:
44.0v
1.61a
172f
2.987ah
137wh

110min:
43.45v
1.58a
166f
3.111ah
143wh

115min:
42.43v
1.55a
166f
3.23ah
146.3wh


120min:
41.22v
1.48a
156f
3.31ah
150.1wh

and just a moment later it cut off, as I watched it drop rapidly down to 40v and then blanked both meters as the BMS shut off both charge and discharge ports. (which itself is strange behavior, making me think that both charge and discharge wires are actually wired to the same points on the BMS, rather than separate points).

As soon as I removed the load, nothing changed. I removed both wattmeters, one at a time, then plugged the WU back in, and it then started up showing 41.1V output.


So no need to test the trike for it's LVC; it's pretty certain that it's the BMS shutting off. That means right at 3.0V per cell for LVC, assuming they're all balanced (which is far from certain).

Have to open it up and measure them.



Anyway, so with 3.9Ah used on-road test, plus 1.9Ah in the first half of this test, plus 3.31Ah used in the second half, that gives 9.15Ah total capacity.

That's not too bad, but most of that is under unrealistic loading of only 1.5-1.8A.

 

[amberwolf]

Opened up the pack a bit, just the top where I guessed the BMS would be (the side the wires enter up to), and got these voltages with no load at the discharged state from above. Lowest cells are marked with an *

Most positive cell at top of list, working down to the most negative cell:
13 -- 3.40
12 -- 3.31*
11 -- 3.34
10 -- 3.24*
09 -- 3.28*
08 -- 3.36
07 -- 3.36
06 -- 3.34
05 -- 3.36
04 -- 3.37
03 -- 3.39
02 -- 3.36
01 -- 3.38

I also tried to measure the cells during discharge, with that stove element load, but they dropped too fast for my really slow hands to get any meaningful data other than that it's cell 10 that drops to 3.0v first and shuts off the BMS outputs. Cell 9 is only 0.02V behind it at that point, I think, based on repeated tries to catch it.



Then I setup the Satiator to charge it at 5A (0.5c), and started charge, measuring the cells again. I was too slow to really catch their first moments for most, but repeated measurements shows me that all the cells are charging at the same rate, in that all their voltages are within flickering 0.01V of each other by the time they reach 3.65V, only about 3-4 minutes into charging.

So most likely none of htem have significantly different internal resistances, at least not when averaged as 4P groups.

So the low cells may simply be that--low cells, possibly with lower capacity and possibly not.

I'll just have to leave it on the charger for balancing, assuming it doesn't get the power fault message again. If for some reason it won't balance using the Satiator, I can try one of my regular chargers, adjusted down to 54.6v (4.2v per cell x 13 cells).


Some technical stuff; I'm not a battery expert so perhaps I've misinterpreted specs, but:

As a side note, the only way to get 10Ah out of this pack would be to draw at most 0.2C from it, or 2A. Since that's unlikely to happen on an ebike pack (IIRC it was more like 5-8A continuous even on my old "normal" ebike DayGlo Avenger with the little Fusin geared hubmotor).

Because the cells are rated anywhere from 2550-2600mAh, when drained at 0.2C (0.5A per cell), down to 2.75V, then since the BMS cuts off at 3.0V (AFAICT without a spec sheet for it), it can't get that last tiny bit of energy out (not sure how much it is, and it is probably not more than a few percent at most).

4 x 2.6Ah for each parallel group is 10.4Ah. 4 x 2.55Ah is 10.2Ah. So as long as the "lost" energy below the BMS cutoff is only between 0.2 and 0.4Ah, it will still provide 10Ah....as long as it's discharged at 2A or less.

I don't know what the derating is for discharge currents above that, though--it may not be significant. It might be, though, because of the heating of the cells at higher discharge rates.

Just some thoughts and speculations.

 

[wesnewell]

The 26F batteries are 2C max discharge rated batteries. So anything over 20A from a 10ah pack is exceeding max discharge specs. It's a very poor choice for an ebike battery. At 20A a 13s pack will sag about 5V
http://lygte-info.dk/review/batteries2012/Samsung ICR18650-26F 2600mAh (Pink) UK.html
If I had to use a 10ah 18650 pack, and I don't, I wouldn't use anything less than 8C rated cells in it, like the 25r cells. I can't understand why people keep buying this crap. It's not even cheap.

 

[999zip999]

I thought number one was the negative one and you went from negative 2 positive when you count the cell numbers

 

[amberwolf]

That's exactly what I did if you read the post.



@Wesnewell: I mostly agree, although if you have a low-power bike that's mostly pedal-assist, or just not used for high-current stuff, this pack would work fine.

For stuff like my cargo-haulers, it wouldnt' last long at the high-current demands of two 30-40A controller/motors at the same time, with frequent hard starts from a stop.

Luna doesnt' sell this one anymore (or at least, not on the same page it had been on, archived at the link in a previous post), but I haven't looked to see if they still sell anything similar in performance / price /etc.




Back to the testing: this pack has been balancing since end of charge exactly 2.00 hours (per satiator screen) after beginning charge. It's taken in 9.56Ah total, all of it during the charge, so far no measurable amount in the balancing, which has been running since about 1am (14 hours so far).

At the end of charge all cells were at 4.15V except the three that were significantly lower at LVC, which were 4.14V for #9 and 12, and 4.13v for #10. The balancing section of the BMS was warmish, but cooled quickly to ambient and hasnt' warmed up since, at least not during any of my checks.


So the HVC for cells on the BMS is apparently 4.15V, so they can never fully charge to the 4.2V required to get the full capacity from each cell.

That makes it even less likely that you'd be able to get the full 10Ah into or out of the pack, though I guess it's still possible depending on how much capacity is in that 0.25V at the lower end of the curve, and the 0.05V at the top end, and how much each cell starts out with.

But presently this pack doesn't hold the full capacity (maybe it will be better once it's balanced).


As a side note, the original charger for this (that I don't have here for the testing/etc) outputs 54.8V. But this pack actually only needs (with the 4.15v/cell LVC) 13 x 4.15v = 53.95v (or 54v to round it up).

I'm going to go setup the big Sorenson for 54.6V (4.2V/cell) and hook up this pack to it to let it balance at a constant voltage (since the Satiator keeps turning it's relay off and on every few seconds, rather than just leaving it's voltage out there). Then we'll see if it balances better/faster.

 

[amberwolf]

BTW, per the link from Wesnewell's post there's a chart for capacity vs voltage during charge at just under 0.5c; I've added a purple set of lines and text to this chart from that link.

It appears to show that you'd only get about 2200mAh out of each cell if you only charge it to 4.15v per cell (presuming discharge down to 2.8v, which is what it shows as 0Ah capacity).

But since the BMS on this pack only allows discharge down to 3.0V, AFAICT, that doesnt' quite let you get all the capacity at the lower end out--but it appears to be insignificant amount, based on that chart, so we'll just ignore it.




So while we can discount possible loss of capacity at the lower end of the curve, that chart makes it appear a significant amount of capacity is never stored at all, because of the 4.15V HVC in the BMS. (up to ~400mAh per cell).

Per the math, this pack is perhaps an 8.8Ah pack, not a 10Ah pack.

Since it did take in about 9.5Ah during charge, and output 9.15Ah during discharge, the math / chart may not be completely applicable due to the different rates it was charged/discharged at in my tests vs the chart.

So perhaps split the difference between the chart/math and the pack's advertised rating....

 

[amberwolf]

So the sorenson didn't start charging it either. I re-measured the cells at the wires into the BMS from the balance connector, and got the same as before.

I got out the Fluke 77 DMM (as opposed to the other one that is pretty reliable but possibly not perfectly accurate), and it measures 4.11-4.14V, (again, most cells at the latter, lowest 3 at the former and 0.01v above). Doesn't really matter much, but it makes me guess that the BMS isn't actually shutting off because of cell HVC...if it was, it should be some even voltage like 4.15V, normally, and once it drops below that it ought to turn back on.


So...I disconnected the sorenson from the charge input, and applied the stove element load to the discharge output, just for a few seconds, enough for it to start to get kinda warm.

Then I hooked the sorenson back to the charge input, and the wattmeter immediately showed current flow into the battery pack again, at the 5A I had set the current limit to.

It dropped over the next couple of minutes to half that, then a quarter, and then slowly dropped from 1.2A down over the next couple hours to just a few mA, and voltage rose to 54.7V, which is a hair over 4.2V/cell. It was 1.458Ah in at that point.

All cells were at 4.22V/cell, except the lowest one that was at 4.21V. All bleed resistors were active (warm to touch, definitely above ambient).

But BMS did not shut off charge current at this point.


I tested whether it would or not by turning the sorenson voltage up by two volts, slowly, which also re-increased the current flow...but the BMS did not stop this input. I increased it a bit more, for a total of 60V, and still the BMS did not stop it--at this point it was back to 5A (current limit). Then I disconnected the sorenson from the pack input and watched as the voltage dropped almost instantly back to 54.8V, and over the next few minutes back to 54.7V.

If it had been a charger fault, unattended, it would have overcharged the pack and possibly damaged it or worse.



I'll have to retest the charging and BMS HVC again later, using just the Sorenson rather than the Satiator, to see if it is something in how the Satiator was setup in the profile I used, or if it's actually the BMS.


If I just need to change the profile setup, or use a different charger, that's ok.

But if it's something in the BMS that is HVCing at the wrong point (early) and then doesn't shutoff if charging is restarted after that point once a bit of load was applied to temporarily bring below the cutoff, that could be potentially dangerous to leave for unattended charging.


All speculation at this point, until I get the chance to redo the test.



At present, the BMS is still bleeding down the cells. We'll see where it stops.

 

[amberwolf]

Various life stuff kept me away from this for a while; still not enough time to go back and redo the other tests, but needed to move this pack from it's storage area temporarily, and checked voltages with the Fluke 77-III without any load on pack while I was at it.

All cells except the three previously low ones were at 4.16v, those three were at 4.15v.

Pack overall voltage is 54.1v.

 

[amberwolf]

Problem with this pack again:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1249555#p1249555
I pulled it out of storage to use it, after a couple months or so of sitting charged up, it should have been still ready to go, but I'd guess the BMS has drained cells (dunno which ones, ahve to check), as it is several volts below full. I can't remember the exact voltage; was not the primary thing I was doing today and this was just something I was going to test iwth (but couldn't due to it's charge state).

The problem isn't the charge state, but that when I tried to recharge it, I could not--the BMS has turned the input off, and will not accept a charge--no current flows. (using hte satiator on a 13s profile I made for this pack, or on the 14s profile for my EIG pack).

The output is not turned off, however.

For now I put it back in storage and will get back to finding out what the problem is, if it's the same as before or not (where it had to be drained further in order to force a recharge).

 

[amberwolf]

I'm sure you know this but you may be better off ditching the BMS and using some simple gauges with self-monitoring/balancing if its draining the pack over time. It could be just one bad cell/group also, but if one cell is going you wouldn't want it to ruin the other cells in the group. Also if it leaks due to internal short it may harm nearby cells. I lost some tool pack cells to this in the past since I left them in storage but still connected to known corroded cells.

The main reason at present for not disconnecting the BMS was to test the pack to verify the problems the original owner had with it first, before adapting it to my own uses. Then they can make their own report about it later, for their experience with it.

The reason I will probably leave the BMS on there later is that it'll eventually be used for Raine's trike, at least until I get better / more packs for my own trike/bike, at which point I can move one of my old ones (probably the A123 EM3EV) over to it, if necessary. Raine doesn't have the experience or ability at present to do all the manual care for a BMS-less pack, and needs just a plug-in-the-wall solution. When it charges right, this pack works for that, and at the much lower loads and range it would see on that small slow trike, it'll discharge fine too. Setting up alarms and cell-level monitors so it doesnt' get overdischarged whiel riding without a BMS would be easy enough, but much harder for Raine to deal with than just knowing about how much range it should have, and having it just cut off when it's empty to protect itself.

The charging issue is the only real problem at present (besides whatever self-discharge it might have).

If it were on my trike/bike, if it could handle the loads, I could keep an eye on it with monitors/alarms easy enough, and the risk of overdischarge would be small, but it's way too small a pack for my cargo haulers (would need to be about four times this size, minimum, probably more).

The construction on your pack looks the same as a 25R pack from Luna that I disassembled. Once you remove the shrinkwrap you should find fiber-reinforced tape and contact paper. The BMS is on the top in the middle of the pack. In my case the battery had a fatal flaw in its design which blew the BMS, so I just pulled it and tested cell health with a Hyperion tapped into the 14S balance port the bms had previously occupied. From there it was used at 80% DOD for a few months along with celllogs for checking balance.

Hmm...I thought I had a post with pics of the internals, etc, from when I opened it up to check the cells, but I don't see it. I'll have to dig out the pics out of my "uploaded" folder and repost them. I guess I was just too tired and forgot to post it.

I like your wooden cargo area btw!

Thanks--it'll look a lot better once I get the new version finished, at least until I beat it up with cargo in it.

I love the look of wood stuff, I'm just not much of a woodworker (or anything else, really; just a hack), so things rarely turn out "nice". Sometimes I get lucky.

Need any more A123s?

I can always use more batteries, but I don't have the budget to buy them (I used up my discretionary funds for the year, except for what I'm saving up to buy parts for building a couple of Lebowski controllers if that works out). In theory, someone else is planning on sending me an old pack of one type or another, that's not being used anymore, but I don't know when that will happen (or if), but it is part of what I'm working on the new controllers for. Even if the pack doesn't get sent, I'll still have better controllers that do what I want, eventually.