18650 VS Lipo

[Joecool]

Maybe its me since I come from a long lineage in RC. Ive been using lipos for a long long time. The biggest I have are 6s 13A 35C(supposedly) and 6s 10A 10C. These batteries are dirt cheap thru Hobbyking. I paid $50 per 6s 10A 10C lipo a few months ago and bought 6. For 300.00 bucks I cant build a decent high C rating 18650 cell 75V 20A pack. Not to mention the labor and time it would take me to build it. Im using 6 6S 10A 10C batteries wired in series and parallel for a total of 75.6V 20A 10C pack. Is it the risk associated with lipos that cause others not to use them? I also use a 1000W 8S 40A Rc lipo Balance charger coupled with 2 HP 12V server power supplies that I modified to get 24V DC to the charger. I use a 6 battery balance board or paraboard to balance charge them as well. Charges all 6 6s lipos in under 2 hours. Ive been using that to balance charge all lipos, SLAS, etc for 5 or so years. Am I missing something from not using 18650, Teslas 2720, or EV leaf battery packs?

 

[Hillhater]

Many pro's and con's either way...
Like you , I have a "foundation" from RC, dating back to NiCad, through all the various cell types up to Lipo and 18650 chemistry.
I still run both HK Lipo, Multistar, and 18650 packs on various bikes.. (i even still have a NiMh pack !).. Together with various charger systems.
So this is my experience.
Lipo (HKpouch packs) are unbeatable value and ease of assembly for multiple voltages. They also have a "flatter" discharge voltage curve, and usually a better C rate than most 18650s..meaning less volt drop across the capacity range. (4v- 3.5v).
BUT, as you say, the risk factor is higher if inexperienced users are involved.
18650s, (good ones) can provide a lighter more compact pack of equal voltage &Ah rating, but unless you pay for the very best, its unlikely you will get more than a 5C pack rating.
And you cannot avoid that steeper drop in voltage from 18650s over the capacity range (4v-2.8v)
They are a pain to assemble and cannot be reconfigured for more/less voltage etc in the way that HK packs can.
Pack building requires experience , equipment , skill , and patience, and unless its done with great thought and care can still result in a high risk pack. Most pack fires are from human error either in construction or use.
Really they are a choice for OEM pack suppliers, or extreme enthusiasts.
So, ultimately it depends on your use,
If you are a ebike commuter who nees simple fuss free light duty with easy safe recharging, then a OEM 18650 pack and charge would be the choice....
But if you are a high power , 'techie" rider who wants a pack to power a 1-2kW drive, and understands the risks, then RC pouch packs have a lot of appeal.

 

[MadRhino]

They are the same li-co chemistry. Hard shell cells need to be exceptional quality to deliver high C-rate, and they are deliberately slowed down, because the failure would be more dramatic in a hard shell.

Polymere pouch cells are giving flexibility, in both meanings of the term. They give up (swell) instead of busting, and they can be manufactured any size, with material variations if desired, very quick and easy.

For me, RC lipo is the only way I can build the power that I need in a reasonable size and weight. The lower C-rate of round cells would require too big a battery. Also, I almost never balance charge. I bulk charge, fast, never more than half an hour, most of the time 10 minutes, according to battery temp. I need low resistance for those requirements, that can’t be achieved with round cells.

The way I am using them, and the price I pay for them quality cells most of the time, is not making me save anything. Especially that I stop using them when they start losing capacity, usually replacing them every springtime.

 

[lionman]

I think once 21700 cells become more mainstream, the cylinder cell form factor will become much more useful for high power demands as current cells in this size can deliver up to 40A which is over 10c. You only need a 4P pack to deliver decent current.

As stated there are pros and cons for both and it really comes down to your use case as to which one is right for you. It also depends on where you live as cheap Lipo are not always available.

 

[amberwolf]

There's a few discussions on the topic in this list, for more existing info:

https://endless-sphere.com/forums/search.php?keywords=18650+Lipo&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

 

[Alan B]

Maybe its me since I come from a long lineage in RC. Ive been using lipos for a long long time. The biggest I have are 6s 13A 35C(supposedly) and 6s 10A 10C. These batteries are dirt cheap thru Hobbyking. I paid $50 per 6s 10A 10C lipo a few months ago and bought 6. For 300.00 bucks I cant build a decent high C rating 18650 cell 75V 20A pack. Not to mention the labor and time it would take me to build it. Im using 6 6S 10A 10C batteries wired in series and parallel for a total of 75.6V 20A 10C pack. Is it the risk associated with lipos that cause others not to use them? I also use a 1000W 8S 40A Rc lipo Balance charger coupled with 2 HP 12V server power supplies that I modified to get 24V DC to the charger. I use a 6 battery balance board or paraboard to balance charge them as well. Charges all 6 6s lipos in under 2 hours. Ive been using that to balance charge all lipos, SLAS, etc for 5 or so years. Am I missing something from not using 18650, Teslas 2720, or EV leaf battery packs?

Leaf battery modules are pouch cells designed for automotive service with cans around them to provide protection. Their size is not a great fit for ebikes.

Hobbyking Lipos are great and I use a lot of them, but to compare with automotive modules or 18650s a physical protection system must be built around them, they are not rugged.

The C rating of RC Lipos is too high by about a factor of 3, so they are not as high current as they appear.

A number of people in the RC and in the ebike community have lost houses to lipo fires. Some people are very risk averse. Of course 18650's also burn, but commercial packs with quality BMS's inside are theoretically less likely to, and some people prefer that perception of safety.

One advantage of 18650's is the packaging flexibility. Ebikes don't have a lot of battery space, making a custom pack that fits well is easier with small pieces rather than big bricks.

To be clear it is best to use AH when you mean amp hours, not A which means amps.

 

[MadRhino]

...The C rating of RC Lipos is too high by about a factor of 3, so they are not as high current as they appear.

Specs for any Chinese products are very irregular. The only good measures of battery quality and safety are IR and Temp. Internal resistance telling how much abuse they can survive, temperature telling their ‘comfort zone’ during both charge and discharge.

Round cells assembly with BMS are making people feel safe, and they don’t monitor charge. That is not safe practice with lico chemistry. Do BMS have a thermometer and a gas sniffer?

That said, batteries are not more dangerous than gazoline. But people are more confident with batteries than gas, and battery fires are drawing media attention.

 

[wturber]

That said, batteries are not more dangerous than gazoline. But people are more confident with batteries than gas, and battery fires are drawing media attention.

Potential problems with gasoline tend to warn users because gas leaks can generally be smelled. Also, fueling is relatively quick and usually done with someone monitoring the fill. The other thing gasoline has going for it is simply that people are more used to dealing with it. People are less familiar with lithium batteries and/or high amperage DC current.

 

[ScooterMan101]

Yes it is the perceived risk that keeps more people from using them. I have made a battery bunker for my Lipo's. and charge outside and charge at about 1 c rate to about 1.2 c rate .

Are you using the 750 watt or the 1,000 watt HP Server Power Supplies ?

Can you post some pictures of how you modified them ? Close up of your solder areas that you soldered on the Board .

No you are not missing anything from not using 18650's, I have stopped using them except for inside my little scooter, and even thinking about using lipo's on that when the 36 volt 18650 pack in it now no longer gives me much range .

Although when I do finally get a mid-drive so that I can go on the trails/up hills and mountains, I Will be building a box for those lipo's .

When I do finally go back to using round cells I will be looking at 21700 cells. ( the same as the newer Tesla's ) but bought from somewhere else as Tesla does not sell just batteries. Waiting for them or another size to be larger mAh per cell than what is available now .

I am still trying to figure out how to balance charge a round cell battery pack, should I decide to make one in the future , since with them there is usually 4 or 5 in Parallel, where as the lipo's have the advantage of being 5000 mAh each cell/pouch or even more, so there is only 1 balance wire per cell in the pack, in other words they are 1 P packs.
Now that I use Hobby Chargers that have the balance feature, I prefer to charge that way . I can see the state of charge for each cell,
whereas with a retail bought 18650 cell pack , I do not see the state of each cell and have to put all trust in a BMS. That sometimes fail and burns houses down . One ES member said that when he built 18650 packs 2 out of 5 had BMS's that did not function properly.
With a good Hobby Lipo charger that problem does not exist.

And if someone is not good at looking at the display to see how much your Hobby Lipo pouches are draining down to during your ride ... just plug a small lipo checker into your balance wire connector and set the alarm to sound when any cell goes down to the voltage you set it at , like 3.65 or 3.75 , etc .

Is it the risk associated with lipos that cause others not to use them?

I also use a 1000W 8S 40A Rc lipo Balance charger coupled with 2 HP 12V server power supplies that I modified to get 24V DC to the charger.

Ive been using that to balance charge all lipos, SLAS, etc for 5 or so years. Am I missing something from not using 18650, Teslas 2720, or EV leaf battery packs?

 

[Mikebike]

There must be something in the water out here in the mid-atlantic (I'm in va) cause I was just at the local hobby store and bought a balance charger, cell checker, and parallel charging splitter.
Almost bought the lipo cells from them also to support my local hobby store but just wasn't quite ready yet.
Used the search function here to see if I was crazy to be thinking about using lipo instead of lithium ion and saw this post.
I think I am going to go lipo. The ease of making a battery myself (have several e-bikes now with old batteries) with the connections/balance leads already built in appeals to me. Also, the brick configuration actually works for me (since I am a cargo bike style kinda guy and have room on the racks for rectangular shaped batteries).
Also, I like to pedal and get a workout. I really only use the electric assist to get going with my heavy style bikes and on hills when necessary. I don't use torque assist, just throttle when I am feeling like it/need it.
Only concern I really have now is if the lipo can handle heat OK. My plan is to put them in my rear bags and just connect 2 sides of 6s to make a 12s total (one 6s in each rear side bag). Any concerns with LIPO in a rear bag getting any hotter in 98 degree weather vs a 18650 type battery in the same bag?

 

[Johne-bike]

There must be something in the water out here in the mid-atlantic (I'm in va) cause I was just at the local hobby store and bought a balance charger, cell checker, and parallel charging splitter.
Almost bought the lipo cells from them also to support my local hobby store but just wasn't quite ready yet.
Used the search function here to see if I was crazy to be thinking about using lipo instead of lithium ion and saw this post.
I think I am going to go lipo. The ease of making a battery myself (have several e-bikes now with old batteries) with the connections/balance leads already built in appeals to me. Also, the brick configuration actually works for me (since I am a cargo bike style kinda guy and have room on the racks for rectangular shaped batteries).
Also, I like to pedal and get a workout. I really only use the electric assist to get going with my heavy style bikes and on hills when necessary. I don't use torque assist, just throttle when I am feeling like it/need it.
Only concern I really have now is if the lipo can handle heat OK. My plan is to put them in my rear bags and just connect 2 sides of 6s to make a 12s total (one 6s in each rear side bag). Any concerns with LIPO in a rear bag getting any hotter in 98 degree weather vs a 18650 type battery in the same bag?

I live in Thailand, and ride in similar temperatures to what you experience.

My Fatbike with Mxus 3000w V2 4T Hubmotor is powered by a 13s 1p 16000mah LiPo pouch cell battery pack, I assembled myself from 13 LiPo pouch cells I purchased direct from the manufacturer in China. They are built into 3 bricks of 6s,4s and 3s to fit the limited space on my Fatbike triangle. I bulk charge them with a Cycle Satiator at 3 or 4amps to 85% capacity, and every time I do check them on my RC balance charger, they are in perfect balance. The bike is ridden on mainly flat, gravel farm trails and after 18 months of almost daily pleasure riding, they have never given a problem, or become hot in use and I can't detect any drop off in their performance but to be fair, I'm normally drawing between 5 and 10 amps, with occasional full throttle bursts of 50 amps.
I've also got another electric Fatbike of my Daughter's, and 2 electric scooters all using 18650 packs with BMS's and you really notice the voltage sag on all of them is so much greater than my Fatbike with the LiPo pouch cells. I wouldn't hesitate to purchase another set of these pouch cells and do the same again when they eventually expire.. Unless something better appears by then..!

 

[Mikebike]

Thanks for the help!
Anybody interested in this subject, I recommend the thread below which I just stumbled upon. Thread is in the items for sale section-new.
Re: Assembled Hi-Power LiPo battery packs - any interest?

Very interesting reading and definitely makes me more comfortable with lipo.

 

[John in CR]

There must be something in the water out here in the mid-atlantic (I'm in va) cause I was just at the local hobby store and bought a balance charger, cell checker, and parallel charging splitter.
Almost bought the lipo cells from them also to support my local hobby store but just wasn't quite ready yet.
Used the search function here to see if I was crazy to be thinking about using lipo instead of lithium ion and saw this post.
I think I am going to go lipo. The ease of making a battery myself (have several e-bikes now with old batteries) with the connections/balance leads already built in appeals to me. Also, the brick configuration actually works for me (since I am a cargo bike style kinda guy and have room on the racks for rectangular shaped batteries).
Also, I like to pedal and get a workout. I really only use the electric assist to get going with my heavy style bikes and on hills when necessary. I don't use torque assist, just throttle when I am feeling like it/need it.
Only concern I really have now is if the lipo can handle heat OK. My plan is to put them in my rear bags and just connect 2 sides of 6s to make a 12s total (one 6s in each rear side bag). Any concerns with LIPO in a rear bag getting any hotter in 98 degree weather vs a 18650 type battery in the same bag?

Mike,

Since you have a cargo bike and can handle rectangular batteries, it's time to graduate from the fire prone batteries for toys and use automotive grade stuff that is better in every way (ease of build, life, price, safety, checking balance, etc). These in the for sale section are right up your alley. 24cents/wh that easily bolt right together https://endless-sphere.com/forums/viewtopic.php?f=9&t=93941

 

[oxorio]

They are built into 3 bricks of 6s,4s and 3s to fit the limited space on my Fatbike triangle.

Thanks very nice design! Can you show how it looks like? if you have any recommendations for battery pack that you bought, it would be also very useful!