Taking a chance on Alibaba (K Power battery)

[riba2233]

Buying loose cells and building an electric bike battery pack is not something that most people are going to want to do, or be safe doing, or should attempt.

Sharing experiences of commercially available packs, learning what to look for, that's useful.

Thanks to Dan for sharing his experience.

It's not nearly as hard and inconvenient as you think it is, lot of people here has done it with great results. I'm only saying this because it's the best option today, when assembled packs are too expensive and not customized. Cells are cheap, safe, and it's not that hard to do.

 

[Alan B]

Buying loose cells and building an electric bike battery pack is not something that most people are going to want to do, or be safe doing, or should attempt.

Sharing experiences of commercially available packs, learning what to look for, that's useful.

Thanks to Dan for sharing his experience.

It's not nearly as hard and inconvenient as you think it is, lot of people here has done it with great results. I'm only saying this because it's the best option today, when assembled packs are too expensive and not customized. Cells are cheap, safe, and it's not that hard to do.

I think you are not very understanding of the abilities of the population. I sell kits in a technical market, and they are way above the general population technically, and some of the amazing problems we encounter are just jaw dropping. If you think general folks are going to make a safe pack with lithium cells, you are playing with fire. It only takes one person following your suggestion that has a major problem to cause tragic loss and major problems for everyone.

I would consider building a pack from cylindrical cells only with a proper welder (which I would build first). Use the correct tools and techniques or buy something well made, for your safety and the safety of others. Each and every one of these cells is capable of burning down your bike and anything else nearby. Even the big guys - Sony, A123, etc have fires with these cells from time to time. Have respect for the components and the skill, and earn a few bucks on the side doing what you know how to do rather than trying to learn to be a battery builder.

 

[dogman dan]

Definitely, one of the things I wanted was to NOT have to assemble it. It's not January, I'm out racking up the miles right now as much time as I have. So price comparisons were made between assembled packs. 48v 20 ah from Luna Cycle, with surely better cells, is almost $800.

Definitely, the biggest fear was that I wouldn't get anything, or that it would fail immediately.

Review now in the review section, where I do make it clear that I do not endorse the vendor, mostly because of the illegal shipping.

But it was cheap, it was delivered promptly, and I did not have to assemble the thing. If you want to assemble your battery, great! Very good loose cells are out there, and you will get more for your money,,,, minus the time you spend, cost of the spot welder, etc.

 

[brooklynboy]

I'm considering ordering one for a family member, but I have a quick question. When I check the link, it shows ( what I assume to be you) d*******n listed as a buyer of the samsung version. I don't want to make the same error and order the non-samsung version. Could you clarify what went wrong in the ordering process? Thanks.

BTW I understand you do not endorse this seller and will not be held liable for any mistakes, weather conditions for next week, us economic policies or burnt toast.....

Cheers to different people with different abilities, ambitions & attitudes!

 

[999zip999]

Remember he's running a 22amp controller with a 20ah battery.

 

[dogman dan]

That's the key thing for sure. I never planned on much more than a 1c rate of discharge.

I screwed up when I actually bought, and did not buy the one they are calling a Samsung pack. Had a brain fart, and bought the other pack that is the same price.

 

[emotate]

I was looking at this company around the same time dogman bought his. I ordered one after he posted his initial results. I of course took full responsibility for any risks involved which turned out to be fewer than I thought. I wanted the same size 48v 20ah battery with Samsung cells and Seiko BMS but I wanted it in the rear rack aluminum package with a locking key. Here is the link:

http://www.aliexpress.com/store/product/48V-20AH-Electric-Bicycle-Lithium-Battery-with-BMS-Charger-Rear-rack-Aluminum-battery-48V-1000W-Samsung/1714144_32309134019.html

I wanted it in black instead of silver so I indicated that on the order. It arrived 6 days after ordering it. and was exactly as ordered. I topped it off to 54.6v and like dogman saw a .2v drop overnight. I rode it 20 miles and 10.5ah (on my CA V3) and then recharged it with the 5 amp charger I bought from lunacycles. It took 2 hours to charge which is right on the money. I then rode it 41 miles with almost no pedaling and a lot of 6% grades and the motor cut off at about 17ah. The CA was still reading about 42v so I don't know what cut it off as the low voltage cutoff on the CA V3 was set to 36 volts. I pedaled home mostly flat and a few small hills and it rode like a normal mountain bike thanks to my zero drag gear hub from e-bikekit. Sweet.

As it turns out I learned Alibaba is the largest ecommerce site in the world. Bigger than Amazon. They are waiting for a thumbs up from me before paying the vendor. They give you about 2 weeks during which time you can test out your purchase and make sure it is all good or you can open a dispute in which Alibaba will negotiate a compromise discount or refund with you and vendor. In my book that takes a lot of the risk out of it. On the down side, if you do return it you are on the hook for the return shipping charges which to China is not cheap.

Comments welcome. I am a noobie. Built my first ebike this last week with lots of wisdom garnered from these pages and picking brains at e-bikekit and the folks at Grin. What a blast.

 

[amberwolf]

I then rode it 41 miles with almost no pedaling and a lot of 6% grades and the motor cut off at about 17ah. The CA was still reading about 42v so I don't know what cut it off as the low voltage cutoff on the CA V3 was set to 36 volts.

BMS of the battery, most likely from a low cell (group), pack is probably either not balanced, or BMS is setup to not allow use of the full capacity.

Could also be problematic cell(s) that don't fully charge or have lower capacity than other cell(s).

You'd have to measure each cell (group) at the BMS balance connector with it in the discharged state to see whcih cell(s) are low.

 

[dogman dan]

Could be a controller cut off at 42v, as well. Pack LVC is supposed to be lower than 42v on the one I bought.

I got 17.9 ah from mine when I rode it for a capacity test. I got stopped at 42v, but neither the kit display or my CA went dark. I got stopped by the controller. Like me, if your CA was still reading, no way the bms tripped your battery off.

A side effect of controllers set for a chemistry with a higher stop point, than 13s NMC. Or whatever this is.

 

[OldTimer]

I was looking at this company around the same time dogman bought his. I ordered one after he posted his initial results. I of course took full responsibility for any risks involved which turned out to be fewer than I thought. I wanted the same size 48v 20ah battery with Samsung cells and Seiko BMS but I wanted it in the rear rack aluminum package with a locking key. Here is the link:

http://www.aliexpress.com/store/product/48V-20AH-Electric-Bicycle-Lithium-Battery-with-BMS-Charger-Rear-rack-Aluminum-battery-48V-1000W-Samsung/1714144_32309134019.html

I ordered the exact same battery as you did. Even asked for the black aluminum case like you did. Did you notice that the price dropped from $425 to $403.75? Looks like the Seller is running a 5% sale on all of his batteries. Have you opened up the case yet to see if it contains Samsung cells and a Seiko BMS? How did you mount the battery on your bike? Post some photos when you have time. Thanks.

 

[emotate]

The CA turned off so I suspected the BMS but the leads from the battery were still hot at 42v when I put a multimeter on it so it does look like the controller. It is the Grin 25 amp controller so I wouldn't think it would be set that high.

As requested by OldTimer. I will post some pictures of my battery installation. Hopefully later today. I did not confirm the cell or BMS brands. I believe Dogman opened his BMS case and it looked like the one in the ad on Aliexpress. I took the plastic cover off the keylock, charger, output connector end and the whole battery assembly with BMS was tightly shrink wrapped and tucked into the aluminum case. It was pretty tight and I did not want to try and push it out or try to cut back the shrink wrap while still in the case. I will take off the handle end and try again when I have the time.

 

[dnmun]

no pictures so no way to diagnose but sounds like a bad connection if the battery still has voltage at the output.

 

[999zip999]

Or controller lvc. The price is good for a 20ah battery. Hell my 20ah A123 cells get only 17.5ah. Plus you must be happy with 40 miles. I don't like running new packs too lvc. Maybe some extra time on the charger for balancing. Glad you're having fun. You can't go around with that new grin all the time. Just look in the mirror at yourself.

 

[amberwolf]

The CA turned off so I suspected the BMS but the leads from the battery were still hot at 42v when I put a multimeter on it so it does look like the controller. It is the Grin 25 amp controller so I wouldn't think it would be set that high.

The controller LVC only disables the controller, so if the CA turned off it can't be the controller LVC.

Only the BMS cutoff would do that, unless you simply have a bad connection.

(or the CA's Shutdown Voltage is set really really high--normally it's about 15V)

 

[emotate]

I wondered why my cheek muscles were so sore. 999zip999 nailed it. If having too much fun is a sin I am guilty with no hope of repentance. Today I rode 13 miles up a canyon and then coasted home. I pedaled enough to keep it around 250 watts on a light uphill grade and under 750w when it got steeper. I was at about 1.5 miles per ah when I turned around and then back to 2.5 miles/ah by the time I got home. Turns out I could have gone another 6 or 8 miles further up the canyon and will next time as I only used 10ah total on the trip. Still having a blast. Can't lose the grin quite yet.

Amberwolf, did you mean "the controller LVC only disables the motor"? If so, I think you are right. Maybe it was the BMS and it kicked back in when I tested the battery output because the CA fired back up right after that as well. Hope I don't have some bad cells that the BMS is favoring by cutting out. What are others seeing for LVC on a 48v setup?

 

[DAND214]

Got a couple batteries this week and the omly thing on the box was my address and theirs. What does this certificate look like?

Dan

 

[amberwolf]

Amberwolf, did you mean "the controller LVC only disables the motor"?

No, I meant exactly what I said.

It does disable the motor as a side effect of disabling the controller, but the only thing the controller LVC does is tell the controller's own MPU to not respond to external commands (throttle, brake, etc), to protect both the battery and the controller's own circuitry (FETs, gate drive).

 

[dogman dan]

Properly shipped, there would be labels on the outside saying, hazmat, lithium battery, etc. Packing would be fire resistant, like vermiculite instead of easily ignited foam.

Guess I misunderstood, I thought you meant your CA stayed lit, when the motor cut off. That's what mine did. Both the CA and the display still lit, but the motor started cutting out. I reduced the speed, continued another 1/4 mile, then it began to cut out too much to continue. 42v.

For sure, your bms cut you off. It might get better, with a better balancing. Or not. I never expected more than about 18 ah myself. cheap cells. Some will be underperformers for capacity.

 

[dnmun]

no, just not balanced and one cell is still undercharged. you lose 10% between full charge and 4.10

 

[999zip999]

More time on charger and please don't run down to lvc on battery. More time on charger to balance and fill up low cells. Time on charger, charging and balancing. Running to lvc will unbalance the pack.

 

[rsilvers]

I just ordered http://www.aliexpress.com/item/48V-20AH-Electric-Bicycle-Lithium-Battery-with-BMS-Charger-Rear-rack-Aluminum-battery-48V-1000W-Samsung/32309134019.html

We will see how it goes.

 

[dnmun]

Running to lvc will unbalance the pack.

this is commonly assumed but never proven. one would expect that the cell that hits the LVC will remain the low cell when the pack recharges and without sufficient time and balancing current that can fill the low cell it will remain so.

usually a cell that develops higher internal resistance from being discharged to low voltage under load will resist the charging current so the voltage expressed at the terminal is higher than the SOC would suggest and often is the first cell to fill up and hit the HVC. but not always. in my experience anyway.

 

[999zip999]

Dnmum the reason I say this is a lot of people here want the cheapest Chinese pack. With this comes generic cells. Higher quality matched cells do a lot better and can last a lot longer. But quality cost.

 

[emotate]

Thanks for the feed back. The battery is back on the charger to hopefully balance those cells. Any guidelines as to how long to leave it? Interestingly, when I top it off with the 2A charger that came with the battery, when it gets to 54.6v the charger cycles on and off every 2-3 seconds for about 2 minutes then stays off. Is that the BMS balancing doing that? The 5A charger from Lunacycle shuts off and stays off.

Also, thanks for the warning on avoiding LVC. I did not know that.

 

[riba2233]

If it's shutting off it's not just balancing, it's reaching HVC, which is voltage higher than balancing voltage. That implies some kind of larger imbalance. But I could be wrong,maybe the bms is just set up that way, with lower difference between balancing and HVC voltage. Usually it's 4.2 for balancing and 4.25 for HVC.