Will these batteries work? (4 20AH 12V Lithium Cells)

[ultralight001]

I've been considering building my own battery, and I've done a lot of research and understand the basics of balance charging, 18650 packs, and so on. I'm still trying to figure out though, if four of these cells connected in series would provide an easier-to-make battery compared to say an 18650 cell pack.
http://pages.ebay.com/link/?nav=item.view&alt=web&id=172540807844&globalID=EBAY-US

Some problems. One, the batteries are rated at 1-2 amps of discharge rate. Two, how would one go about balance charging only four cells, and drawing over 20 amps to power a hub kit?

 

[Hwy89]

Where did you see that the packs are rated at 1 to 2 amps discharge. I could not find that on the listing, but if it is true they would be a poor choice for powering an ebike. It would take 40 of them to get 48v @ 20 amps. I find it hard to believe that the discharge rating is that low. Are you sure that what you saw wasn't 1 to 2 C rating? If so they would provide 10 to 20 amps each.
It is risky to be the first to try a new product, especially when it comes to Chinese lipo batteries so you might be better off choosing the RC lipo that many here have had good luck with.

 

[flat tire]

If it's as you say the discharge rating will make those ebay cells unsuitable for an ebike power source.

A 4s pack is easy to balance charge. You can either solder on a standard balance connector and charge it with a hobby charger, or even balance each cell individually since they are only 4 of them.

If you want to build an ebike battery out of premade packs that come with balance leads go to hobbyking.com and check out the lipos. In most cases it is true that this is easier than building an 18650 pack.

 

[ultralight001]

http://www.ebay.com/itm/Portable-DC-12V-20000mAh-Li-ion-Super-Rechargeable-Battery-Pack-with-EU-Plug/141728974752?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D888007%26algo%3DDISC.MBE%26ao%3D1%26asc%3D40130%26meid%3D15a30cf4c0c448e8ad405e9bf1a2c035%26pid%3D100009%26rk%3D1%26rkt%3D2%26sd%3D122349874758

That listing says 1-2A in the description, but I honestly don't believe that. And if it's true, if it has an integrated BMS I can rip that out and wire them to my own 4s 20a bms.

 

[flat tire]

I would say buy it and give a try but the price is too good for the energy capacity and they look suspiciously small so who knows what you're really getting.

 

[Matador]

I've been considering building my own battery, and I've done a lot of research and understand the basics of balance charging, 18650 packs, and so on. I'm still trying to figure out though, if four of these cells connected in series would provide an easier-to-make battery compared to say an 18650 cell pack.
http://pages.ebay.com/link/?nav=item.view&alt=web&id=172540807844&globalID=EBAY-US

Some problems. One, the batteries are rated at 1-2 amps of discharge rate. Two, how would one go about balance charging only four cells, and drawing over 20 amps to power a hub kit?

I know if I was a complete newbie into eBikes and that I would have bought four of these batteries to wire in series, there would probably be > 95% chance that I would NOT be happy with them. Good thing I'm not a gambler.

 

[MadRhino]

My guess is: 2000 mah instead of 20000. :wink:
That would explain the 1-2 A discharge, and the small size.

 

[Matador]

My guess is: 2000 mah instead of 20000. :wink:
That would explain the 1-2 A discharge, and the small size.

The pack is just so small.... You could not even fit 16 x 18650 cells in it... (153 x 74 x 36 mm)

 

[Sunder]

You guys are way too cynical. You could easily make 20,000mah pack using these 9900mah 18650s

How can they get 9900mah in there, when the likes of Tesla and Panasonic can't even break 3400mah? The secret ingredients is elbow grease and ground up hens' teeth (rooster teeth don't work). They are also assembled with left handed hammers and reverse threaded screw drivers. The trade off of course is that the power density is sacrificed, which is why they only do 1-2a despite their size.

Seriously though, I bought a couple of those packs ages ago, not even for eBike use. it was to keep a 12v 3G modem running in my car, when the ignition was off(I was so much of a geek, even when we went camping I wanted internet, and needed a high gain antenna in the car to get reception). The one I got was meant to be 12000mah, which, replacing a 500ma wall charger, it should have lasted at least a full day. Didn't even get 4 hours out of it.

Strangely enough, the 12000mah pack is about the same size as as the 20000mah packs. So either they've been able grind the hens teeth even finer for better contact surface and hence capacity, or their lies are getting even bigger. Who know?

 

[Matador]

LOL ROFLMAO !

 

[ultralight001]

People have increased capacity a ton by decreasing discharge rate, so it's probably close to true. But if it's 1-2 amps I can't use them.

How many cells would I need for a 20AH pack? I'd like to go with generic cells so that the price to build is around $250 max. I'd prefer less, like 150.

 

[Matador]

People have increased capacity a ton by decreasing discharge rate, so it's probably close to true. But if it's 1-2 amps I can't use them.

How many cells would I need for a 20AH pack? I'd like to go with generic cells so that the price to build is around $250 max. I'd prefer less, like 150.

250$ US is hard to reach for 960 Wh of capacity (20 Ah x 48 Volts = 960 Wh, right ?), especially if you want new cells... Depending on the capacity of each 18650 cell (about 2000 - 3000 mAh per cell @ 3.7V), your probably going to need between 130 to 91 cells (13S10P with 2000 mAh cells to 13S7P with 3000 mAh cells)...

You'd be lucky to get 2000 mAh with generic cells....

I my case, I bought used cells : Doctorbass sell Makita powertool packs for cheap and the packs always have less than 100 cycles on thems (they datalog each pack to check cycle number... If more than 100cycles, Doctorbass doesn't even take them)... They contain quality cells, but of course there are always a few bad apples in some packs (in my case, found 4 bad apples and 246 were good!)

He sells 3 kinds of Makita paks. Each pack contain 10 cells :
Makita BL1830 (18.5V; 3Ah) : contains 10 Sony US18650V cells (1600 mAh ; max 7.5A continous - 15A burst)
Makita BL1840 (18.5V; 4Ah) : contains 10 Sony US1860 VTC4 (2000mAh ; max 30A continous)
Makita BL1850 (18.5V; 5Ah) : contains 10 Samsung INR-18650-25R cells (2500mAh ; max 20A/cell)

In my case, I live in the same city as Doctorbass so I could easy pick them up myself. I bought 25 BL1840 (250 VTC4 cells) for 375 CAD (roughly 290 USD). Tested them, in my case 246 cells where as good as new, but 4 were dead (because a faulty Makita BMS drained them)... He also sells the BL1830 for a third of the price of the BL1840 packs. If you're interested, you can PM him and maybe arrange shipping ? I don't know if he would send them by mail or not. Here he shows how to open the pack to get the cells :
https://endless-sphere.com/forums/viewtopic.php?f=14&t=27707#p400378

So from Doctorbass, the deals I could get were : Sony V (0.50$/cell) ; Sony VTC4 (1.50$/cell) ; Samsung 25R (not sure, but I think 2.50$/cell)...

Otherwise, some people sell Tesla cells here :
- DoctorBass : https://endless-sphere.com/forums/viewtopic.php?f=9&t=86882
- Okashira : https://endless-sphere.com/forums/viewtopic.php?f=9&t=67661&hilit=tesla+cells+okashira

So that's one other option.

Otherwise, Tumich also has a great reputation of selling cells : https://endless-sphere.com/forums/viewtopic.php?f=31&t=61608&hilit=tumich%26amp%3Blt%3B

Otherwise, look for used pack for sell in the FOR SALE Threads of this forum... Maybe you'll find a good deal. In doubt, ask questions to people here... Some pack could have been abused, but it's my impression that most people here are honest about what they are selling and know their stuff.

There's always the option of going RC LiPo pack, but that require more care/maintenance, and awareness of the potential hazards/dangers associated with them.

 

[ultralight001]

^ Thank you for all of the great info.
I'll probably go with building an 18650 pack. I'll need a little help to understand wiring up the BMS and getting the credit charger, but I'll ask about that when I need too.

 

[LewTwo]

So either they've been able grind the hens teeth even finer for better contact surface and hence capacity, or their lies are getting even bigger. Who know?

The "new improved" version is using snake oil for the electrolyte.