If you are building packs today, which cells to choose?

Batteries, Chargers, and Battery Management Systems.
nukezero
10 kW
10 kW
Posts: 556
Joined: Jul 02, 2013 5:00 pm
Location: Los Angeles, CA

If you are building packs today, which cells to choose?

Post by nukezero » May 06, 2017 9:54 pm

Assuming you have a 8T MAC motor and BBS 48v, and you want to build a new battery pack, what cells would you use? Assume that you require 30A constant. Right now, both my battery packs are a meager 10Ah and after 2.5 years, they lost capacity. I'm down to 6-7Ah at best. Having learnt my lesson, I think it's best to build with more Ah now so when it loses 30% after 2-3 years, it still has at least 10-12Ah.

I am currently using 18650-25R the blue ones.

Based on my 2 hour research and update, it seems that today, the most popular cells are:

Sanyo/Pano 18650 GA
Sanyo 20700B 4000mAh !! whopping capcity0
Samsung 21700-30T gray cells
LG MJ1 (not as good as sanyo)
Samsung 35E

But here's my problem. If I were to go with 20700/21700 sized cells, I found that they do not have cell-spacer/holders like they do with the 18650. Also, it would appear that 20700/21700 seem to have better voltage drop than 18650, and some companies claim they have longer cycle life/life span. If that is the case, is there any more reason to continue buying 18650 for ebikes? Considering how eBikes, we can easily use 20700/21700 in a triangle pouch bag.

flat tire
10 kW
10 kW
Posts: 780
Joined: Feb 26, 2014 12:20 am

Re: If you are building packs today, which cells to choose?

Post by flat tire » May 06, 2017 10:13 pm

Orange DH w/ Cyclone mid on 6kw
Gary Fisher w/ Leaf hub on 6kw
RC Lipo and domino throttles only!

User avatar
Ykick
100 GW
100 GW
Posts: 5945
Joined: Nov 26, 2009 6:10 pm
Location: San Diego, California

Re: If you are building packs today, which cells to choose?

Post by Ykick » May 06, 2017 10:25 pm

I think the GA is an all around great choice for 18650 format. The new 20-21 stuff is way too new for my tastes and will undoubtedly inflict some growing pains.

RC Lipo is where I learned lithium packs but it can be difficult wrapping your head around true 13S 48V and/or 14S 52V configurations. 12S is common, nice, easy combo but unfortunately not really 48V.

I currently use “some” RC Lipo but I do install a small BMS wired for charge only. Discharge taken directly off the battery terminals.
Talent must not be wasted.... Those who have talent must hug it, embrace it, nurture it and share it lest it be taken away from you as fast as it was loaned to you.

- Frank Sinatra

User avatar
jonescg
1 GW
1 GW
Posts: 3390
Joined: Aug 07, 2009 9:22 pm
Location: Perth, Western Australia

Re: If you are building packs today, which cells to choose?

Post by jonescg » May 06, 2017 11:12 pm

Ykick wrote:I think the GA is an all around great choice for 18650 format. The new 20-21 stuff is way too new for my tastes and will undoubtedly inflict some growing pains.

RC Lipo is where I learned lithium packs but it can be difficult wrapping your head around true 13S 48V and/or 14S 52V configurations. 12S is common, nice, easy combo but unfortunately not really 48V.

I currently use “some” RC Lipo but I do install a small BMS wired for charge only. Discharge taken directly off the battery terminals.
I have always found 14s LiPo to be a good number for representing "48 volts". Vmax for 14s LiPo is 58.8 V, which is roughly the same as 16s LiFePO4 58.4, which is roughly the same as four lead acid cells in series (58 V). IN all cases the voltage drops as soon as you load it up, typically around 50-54 volts. The frustrating thing is that many non-plug and play BMS modules use LTC chips or the like and these only have 12 channels, so you need two of them.

flat tire
10 kW
10 kW
Posts: 780
Joined: Feb 26, 2014 12:20 am

Re: If you are building packs today, which cells to choose?

Post by flat tire » May 06, 2017 11:19 pm

One of the best things about RC lipo is bulk charge without a BMS. If you've vetted your cells and inspect them frequently, AND are very conservative with depth of discharge you can bulk charge them at like 4C and keep all your cells in just as good balance as any 18650 pack.
Orange DH w/ Cyclone mid on 6kw
Gary Fisher w/ Leaf hub on 6kw
RC Lipo and domino throttles only!

nukezero
10 kW
10 kW
Posts: 556
Joined: Jul 02, 2013 5:00 pm
Location: Los Angeles, CA

Re: If you are building packs today, which cells to choose?

Post by nukezero » May 06, 2017 11:24 pm

Wow, can't believe many of you guys are recommending RC lipos. Sure they are totally cheap. But my experience with them back in the days (10 years ago) with RC helicopters were not so good. Particularly, I could only get 15-25 cycles out of many of the 4400mah lipos, even with a quality balance charger. Have lipos improved significantly lately?

flat tire
10 kW
10 kW
Posts: 780
Joined: Feb 26, 2014 12:20 am

Re: If you are building packs today, which cells to choose?

Post by flat tire » May 06, 2017 11:29 pm

RC lipos have more or less always been awesome. And I don't know where any of you get the idea they're cheap..they're not.

If you care for the batteries you can get cycle count in the hundreds. Lots of RC people ruined them before the conservative LVC ESC days by running them too low. And don't charge to 4.2, less will give you more cycles.
Orange DH w/ Cyclone mid on 6kw
Gary Fisher w/ Leaf hub on 6kw
RC Lipo and domino throttles only!

User avatar
jonescg
1 GW
1 GW
Posts: 3390
Joined: Aug 07, 2009 9:22 pm
Location: Perth, Western Australia

Re: If you are building packs today, which cells to choose?

Post by jonescg » May 06, 2017 11:43 pm

Here at ES we often recommend the old half-and-half rule for lithium cobalt pouch cells. Whatever the maximum C-rate is, halve it for peaks, and halve that again for continuous. Keep them in the happy range of 3.5 V to 4.2 V and they will last hundreds of cycles, if not a thousand.

-And yes, the manufacture and quality control have gotten markedly better in recent years.

nukezero
10 kW
10 kW
Posts: 556
Joined: Jul 02, 2013 5:00 pm
Location: Los Angeles, CA

Re: If you are building packs today, which cells to choose?

Post by nukezero » May 07, 2017 12:11 am

So how would I go about building a 15Ah 13 or 14s?

Do I just buy one of the 6s 4000mah in two pieces and one 2s and series them? Then buy pairs of them to double up the capacity?

999zip999
100 GW
100 GW
Posts: 8233
Joined: Jan 10, 2010 1:40 pm
Location: Dana Point So. Cal

Re: If you are building packs today, which cells to choose?

Post by 999zip999 » May 07, 2017 12:12 am

One problem with rc lipo is poor quality control. Making them more then iffy in a multi pack ebike size battery. Making it hard to monitor unless you take apart.

User avatar
jonescg
1 GW
1 GW
Posts: 3390
Joined: Aug 07, 2009 9:22 pm
Location: Perth, Western Australia

Re: If you are building packs today, which cells to choose?

Post by jonescg » May 07, 2017 12:22 am

Yes unfortunately the cheapest way to go with LiPo is pre-built 4s to 6s packs. The QC on these packs can vary widely. Also, 5s or 7s are not a common sizes, so you would probably be stuck with 12s. For 15 Ah, you would buy 6 pieces of 6s 5000 mAh packs. Parallel three of them, then put two of these paralleled units in series. Then just order a bulk charger capable of putting out 50.4 volts from Kelly or whoever and keep a close eye on the cell voltages.

However, my advice is always to go with individual 5000 mAh cells and parallel them first (3p for 15 Ah for example) and then put 10 to 14 in series to achieve the voltage you want. This way you can make a judgement call on each cell as you assemble the pack.

User avatar
Ykick
100 GW
100 GW
Posts: 5945
Joined: Nov 26, 2009 6:10 pm
Location: San Diego, California

Re: If you are building packs today, which cells to choose?

Post by Ykick » May 07, 2017 11:14 am

jonescg wrote:I have always found 14s LiPo to be a good number for representing "48 volts". Vmax for 14s LiPo is 58.8 V, which is roughly the same as 16s LiFePO4 58.4, which is roughly the same as four lead acid cells in series (58 V). IN all cases the voltage drops as soon as you load it up, typically around 50-54 volts. The frustrating thing is that many non-plug and play BMS modules use LTC chips or the like and these only have 12 channels, so you need two of them.
14S is best compared to 52V eBike packs where 58.8V is the top full charge.

13S is actually 48V commonly sold with many China kits. That top charge 54.6V.

I assemble 14S RC Lipo (52V) using 2qty 4S packs and 1qty 6S pack all wired in series. If I need a larger pack I normally parallel cell groups but if I do it's often through the balance wires. Fairly easy to do with JST parallel balance plugs and then connect those sense wires to whatever small BMS is being used for bulk charging.

Yes, people successfully run naked with vetted RC Lipo but I don't. At least not for charging. Discharge isn't so much an issue IMO since that takes place outdoors and the controller LVC will most likely catch something bad before it goes terribly wrong. And if not, at least you're probably outdoors.

I tend to still use RC Lipo for very small yet powerful eBike packs. But for a longer range commuting eBike, the Panasonic GA 18650 packs often sold in 13.5Ah configuration is my favorite choice. 2qty of those swapped out can provide 27Ah total capacity for an insane amount of range. 1qty pack is often perfect for around 20 miles no BS range.
Talent must not be wasted.... Those who have talent must hug it, embrace it, nurture it and share it lest it be taken away from you as fast as it was loaned to you.

- Frank Sinatra

999zip999
100 GW
100 GW
Posts: 8233
Joined: Jan 10, 2010 1:40 pm
Location: Dana Point So. Cal

Re: If you are building packs today, which cells to choose?

Post by 999zip999 » May 07, 2017 12:57 pm

For a daily commuter I would use 18650Ga or better. Are you spot welding a pack. How abot this kithttps://endless-sphere.com/forums/viewtopic.php?f=31&t=87434&sid=f152d209b0eeca11ff06a25a104e2986 I don't know it's amp rating. Should be good for 40amp as 6p maybe itcan handle more current with tests. A little bigger a heavier then spot welding. How are your 25r holding up ? I reread the thread 2.5yrs how many cycles ?

nukezero
10 kW
10 kW
Posts: 556
Joined: Jul 02, 2013 5:00 pm
Location: Los Angeles, CA

Re: If you are building packs today, which cells to choose?

Post by nukezero » May 07, 2017 1:22 pm

999zip999 wrote:For a daily commuter I would use 18650Ga or better. Are you spot welding a pack. How abot this kithttps://endless-sphere.com/forums/viewtopic.php?f=31&t=87434&sid=f152d209b0eeca11ff06a25a104e2986 I don't know it's amp rating. Should be good for 40amp as 6p maybe itcan handle more current with tests. A little bigger a heavier then spot welding. How are your 25r holding up ?
My 25R's are nearly 3 years old. Been thru at least 300+ cycles. It lost 30-35% capacity for sure, but still charges up nice to 54.1V still. But now, when I put a 25A load on it with the Mac 8T, there is a big voltage drop because I have those LED twist throttles and before, it never drops from a top-off charged battery. Now, when doing full throttle hot off the charger battery, the LED light drops 1 dot, which tells me the cells are aging and can't hold current anymore. =(

titusmc
100 W
100 W
Posts: 112
Joined: Sep 30, 2015 1:42 pm
Location: Troy, New York

Re: If you are building packs today, which cells to choose?

Post by titusmc » May 07, 2017 5:08 pm

14S5P (or more in parallel) of Samsung 30Q or LG HG2.

Ohbse
10 kW
10 kW
Posts: 758
Joined: Dec 26, 2013 5:15 pm
Location: Auckland, New Zealand

Re: If you are building packs today, which cells to choose?

Post by Ohbse » May 07, 2017 6:21 pm

Samsung 30Q 18650's still ideal cell from an energy/power/safety/longevity perspective for your use. 14s/6p (or really as much as you can package) would deliver the goods for quite some time.

The larger format cells appear to have more capacity and less sag, however that's proportional with the increase in volume/mass - they're not really any better, just a slightly different form factor. With current pricing you can purchase a lot more 18650's for the same cost, more cells will give less sag/more energy etc anyway - so unless you've got some very specific packaging constraints where the larger diameter cans will fit perfectly I would give them a miss for now.

User avatar
spinningmagnets
100 GW
100 GW
Posts: 10752
Joined: Dec 21, 2007 10:27 pm
Location: Ft Riley, NE Kansas

Re: If you are building packs today, which cells to choose?

Post by spinningmagnets » May 07, 2017 6:47 pm

I would wait on the 20700 cells for a few months, and stick with all the components available for building 18650 packs. If you do choose the 20700's, please post pics...

It depends on how many amps you want from the pack, and how small/large the pack must be. The factory ratings for the cells are not necessarily how I would rate them, but here it is: 25R 20A, 30Q 15A, PF 10A, GA 8A? (these cells used only as an example)

If you need a tiny 2P pack to fit your frame, 25R @ 2P would be 40A, and 30Q @ 2P would be 30A (5-Ah and 6-Ah respectively, for the same size of pack)

If you can fit a 3P size of pack, I wouldn't even consider the 25R...the 30Q @ 3P would be 45A at 9-Ah, and the PF would be 30A at 8.7-Ah (2900-mAh per cell?), but...it is cheaper than the 30Q.

If you can fit a 4P size of pack, then you can suddenly get a boost in range with the GA providing 3400-ish mAh per cell. Approximately 32A and 13.6-Ah. The PF would be 40A and 11.6-Ah

Most ebikers like having a 5P pack at a minimum (depending on how far your commute is between charges, at 14S, that would be (14 X 5 =) 70 cells. At 5P the PF would be 50A (more than needed, not necessarily a bad thing, cells wouldn't be stressed or hot at 30A), and 14.5-Ah. The GA would be 40A with 17-Ah of range.

6P? GA would be 48A and 20.4-Ah

There are other cells that I am not familiar with, and there might be a better cell for your application (amps per cell, range in Ah per cell, and cost). Without any further information available to me, I'd say...for 30A and a 4P size of pack, get the PF cell...for 5P or greater, get the GA cell and enjoy all that extra range...

[all numbers quoted here are approximate, don't trust these numbers, do your own homework]

nukezero
10 kW
10 kW
Posts: 556
Joined: Jul 02, 2013 5:00 pm
Location: Los Angeles, CA

Re: If you are building packs today, which cells to choose?

Post by nukezero » May 09, 2017 1:05 am

So where is the best place to buy Panasonic 18650-GAs today in the US?

I'm currently looking at:

which one of these are legit and which one sells fakes?

www.imrbatteries.com
www.batterybro.com
lunacycle.com
www.fasttech.com
www.orbtronic.com


Right now, I'm thinking orbtronic and fasttech might be more legit. what do you guys think, any experiences?

DVDRW
100 W
100 W
Posts: 201
Joined: Sep 10, 2012 10:57 am
Location: Tallinn, Estonia, EU
Contact:

Re: If you are building packs today, which cells to choose?

Post by DVDRW » May 09, 2017 5:22 am

My favourite cells are Panasonic 10A 2900mah NCR18650PF 2.5€ each.

999zip999
100 GW
100 GW
Posts: 8233
Joined: Jan 10, 2010 1:40 pm
Location: Dana Point So. Cal

Re: If you are building packs today, which cells to choose?

Post by 999zip999 » May 09, 2017 11:07 am

USA https://lunacycle.com/panasonic-18650-g ... wholesale/ $2.75 per cell . At lease it's in the states. Lower shipping ?

nukezero
10 kW
10 kW
Posts: 556
Joined: Jul 02, 2013 5:00 pm
Location: Los Angeles, CA

Re: If you are building packs today, which cells to choose?

Post by nukezero » May 09, 2017 5:25 pm

999zip999 wrote:USA https://lunacycle.com/panasonic-18650-g ... wholesale/ $2.75 per cell . At lease it's in the states. Lower shipping ?
edit. nevermind.
Last edited by nukezero on May 09, 2017 6:21 pm, edited 1 time in total.

User avatar
rojitor
100 kW
100 kW
Posts: 1031
Joined: Mar 23, 2011 6:39 pm
Location: vigo spain

Re: If you are building packs today, which cells to choose?

Post by rojitor » May 09, 2017 6:21 pm

Excuse me guys. If I see it correctly it's a 50 units pack. That's 5.50 + shippings

nukezero
10 kW
10 kW
Posts: 556
Joined: Jul 02, 2013 5:00 pm
Location: Los Angeles, CA

Re: If you are building packs today, which cells to choose?

Post by nukezero » May 09, 2017 6:21 pm

rojitor wrote:Excuse me guys. If I see it correctly it's a 50 units pack. That's 5.50 + shippings
That's correct, it's not $2.75 per cell. That would be outrageously cheap.

kocetoMR
1 W
1 W
Posts: 61
Joined: Jun 13, 2016 3:19 pm

Re: If you are building packs today, which cells to choose?

Post by kocetoMR » May 09, 2017 10:47 pm

DVDRW wrote:My favourite cells are Panasonic 10A 2900mah NCR18650PF 2.5€ each.
Where you get for this price? :(

hemo
1 W
1 W
Posts: 63
Joined: Mar 30, 2016 5:13 pm
Location: England, GB ( UK).

Re: If you are building packs today, which cells to choose?

Post by hemo » May 10, 2017 4:53 pm

Nkon.nl 2.50 euros a cell however you have to buy 540 ceils to get that rate.

Post Reply