Where is a great place to find quality 18650 cells cheap?

[CarlRich]

Ok, I shouldn't say cheap. I want good cells with 3c or better rating that I can charge at least at 1c if not faster. I've purchased four battery powered Razor dirt bikes for my sons for christmas (all used) and want to increase the ride time and reduce a 12hr lead acid battery charge time to 1 hour lithium charge time.

I've just ordered a 36v 15Ah pack from Aliexpress.
https://www.aliexpress.com/item/US-EU-No-Tax-DIY-lithium-18650-battery-pack-15AH-36V-Electric-Bike-battery-for-36V/32757165516.html

What I don't understand is how it can use the name brand cells stated yet it only has about a 1C discharge rating and can only be charged up to 5A which is 1/3 of 1C?

So I'm thinking of building my own pack for 36v 15Ah. This would be 10s 5p (50cells)with 3000mah cells or 10s4p (40cells)with 3500mah cells. I'd love to do this for $150 or less but am finding 18650 cells with 3c discharge rating or better that are $4 plus. Where can I access cells of this quality for $2 each? I noticed a seller here on endless sphere selling cells with tabs removed in bulk for cheap. Good deal or likely used cells?

https://endless-sphere.com/forums/viewtopic.php?f=31&t=61608

ANY recommendation would be helpful. I'm new to E biking but have long used li-po packs for high powered (12s lipo 5,000+watt) electric ducted fan rc jets so somewhat familiar with batteries and chemistry.
thanks in advance,
Carl

 

[Punx0r]

The discharge and charge rates specified for the aliexpress pack are most probably a result of the BMS ratings, not the cells.

That said, there are a LOT of fake/re-wrapped 18650 cells in China. If a price looks too good to be true, it probably is...

I can't comment on the cells in the ES for sale thread, hopefully someone familiar with them will.

 

[phild]

I noticed a seller here on endless sphere selling cells with tabs removed in bulk for cheap. Good deal or likely used cells?

viewtopic.php?f=31&t=61608

No, brand new unused cells direct from the Polish factory ... they make for Samsung and Panasonic and Sanyo the brands he is able to get from this factory vary.
Tumich has sold a lot to Endless Sphere friends - the freight from Poland takes a while but air-freight of batteries is becoming more difficult anyway. I've purchased from him twice with very satisfactory results.

 

[Hillhater]

^^^+++ as above . Cells from Tumich are genuine and good quality.
He is an good guy to deal with also.

 

[CarlRich]

Awesome, he's my guy then. Thank you. Now to figure out which cell is right for me....
Need 36v pack with max discharge of 20A and want around 15Ah capacity. Researched all he has listed. Much to consider but most appeared only truly good at 1C for 300 or so cycles. Would like to charge at 1C. Trying not to go over 50 cells, 10s5p.

Tumich, could you make a suggestion or say which cells you have available? I would order 50 to 100 to make up to 2 packs.

 

[redilast]

Charging at 1C is really bad for cycle life, especially if you charge to the full 4.20v. With some cells you might see 1/3 as many cycles with a 1C charge rate vs like a 0.2C.

 

[CarlRich]

Wow, bummer. Guess I'm used to using LiFePo4 packs as a receiver pack in RC planes. We can charge those with 2C charge rate no problem at all. Sounds like if I want my kids to ride these electric dirt bikes all day with 1 hour down time for charging I need LiFePo4 packs or really high capacity with li-ion so they ride a couple hours then done for charging the next 5 hours?

 

[Hillhater]

Just do the same as you would for RC gear....use swapable packs. One on charge whilst the other is in use.

 

[redilast]

Wow, bummer. Guess I'm used to using LiFePo4 packs as a receiver pack in RC planes. We can charge those with 2C charge rate no problem at all. Sounds like if I want my kids to ride these electric dirt bikes all day with 1 hour down time for charging I need LiFePo4 packs or really high capacity with li-ion so they ride a couple hours then done for charging the next 5 hours?

One option is to just charge to like 4v per cell at 1C. Then you can get like 80% capacity without sacrificing cycle life.

 

[CarlRich]

I believe LifePO4 packs are heavier and more expensive but wouldn't they allow much faster charging? The tinkerer in me wants to build my own pack but I don't think there are inexpensive life cells. The batteries get placed inside the Razor Mx650 dirt bike and get inclosed with 5 or 6 bolts. Major pain to have 2 packs and recharge. THanks for the continued great feedback.

 

[Ykick]

I charge RC Lipo 2-3C, sometimes 4C rate with no detectable degradation over several years. In fact, I think it’s kinda better for good, healthy RC Lipo cells to bulk charge quickly rather than dragging it out over a long period of time.

Experience has taught me the practical thing about all of this “charging voodoo” is to merely refrain from cells sitting full SOC for any length of time.

Do these ramblings relate to 18650 cells? Maybe some chemistries but probably not all. However, since the OP mentioned being an RC guy I though it would be helpful to relay my 7-8 years daily using large quantities RC Lipo for both eBike battery packs and RC aircraft.

One interesting test with an IR temp gun - take a warm just used RC Lipo and note the temperature. Then hit it with a very high charge rate and check the temperature every minute a few times. Next do the same test beginning with similar temperature pack but now charge at a much lower rate. Check temperature at similar intervals and I think you may see something rather surprising....

 

[Punx0r]

There are 18650 cells, like the Samsung 30Q and similar, that will tolerate 1C charging, but at reduced cycle life. You have to ask through: do you really need a long cycle life for a child's toy? How many times are they really going to use it? If only a modest cycle life is required then RC "lipo" would allow charge rate you require.

 

[Hillhater]

Batteries , like most things in life, are a compromise.
Power , capacity, weight, cost, safety, etc are all variables you have to choose from.
Unfortunately, you cannot have them all in one package, and if you insist on keeping the cost low, then you seriously limit the other factors.

 

[CarlRich]

Have decided on LiFe cells. Looking for suggestions for life cells you've found to be a great value. Good price for the cells performance. 3000mah or larger would allow for a pack of 60 cells for 15Ah. Cheap doesn't always = value.

 

[Hillhater]

Maybe these ?
http://www.evassemble.com/index.php?main_page=index&cPath=2&zenid=d05mb3e2tgsqmmrcbhtt3dc9c4

 

[Punx0r]

Be careful: Aside from A123 (which you've already identified) most LiFePO4 on the market is either low C-rate cells of OK quality or low C-rate junk...

 

[BikePilot]

My son's Oset runs on a 6s4p pack of 18650 cells and it does great. I charge at 0.5c but rarely ever takes more than an hour because it lasts longer than he does. That pack gives massively more range than the 2x 12v 10ah yuasa agms that were standard and dropped 11lbs from the bike!