Lipos a good option for high performance small pack?

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Lipos a good option for high performance small pack?

Post by flat tire » Mar 11 2017 7:44pm

OK, looking to make a 20S / 74V nominal pack. Maybe 30S / 111V nominal. Small pack, capacity around 1.5WK. Max draw I will use from this pack will be 10KW.

So I'm thinking about using these:
https://hobbyking.com/en_us/zippy-compa ... -pack.html

The idea is to balance charge them in parallel as 10S using a second charging harness. I intend to use my 3010B for charging with no BMS so the ability to easily split into 10SxP will be very convenient.

Is this a bad idea? Would I be better suited by another brand / cell count per package? The main reason I want to use LiPos for this pack is other chemistries have too much voltage sag at high power draws from a small pack. They will also be easy to wire up.

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Re: Lipos a good option for high performance small pack?

Post by MadRhino » Mar 11 2017 8:49pm

RC lipo is a good choice when you need lightweight, compact, high power and fast charging. All those advantages have a cost: They need careful management and disciplin to be safe, and they don't last very long.

They can supply more power than your requirement. You could do with round cells. If you go for RC lipo, you would be better bulk charging them at full voltage, and even better charging fast. The only safe way to charge RC lipo is to be present, supervising the whole charging cycle. This is much easier to do when charging in 15 minutes than an hour. Another important safety is to monitor every cell, and for this reason you should not parallel them within a series. If you need 2p, you assemble 2 series in parallel, and not one series of 2p.
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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 11 2017 9:21pm

Which round cells do you suggest for my requirements? It sounds like the advantages of lipo in my case are negated by lack of reliability and no real ease-of-charging advantage.

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Re: Lipos a good option for high performance small pack?

Post by motomech » Mar 11 2017 11:22pm

flat tire wrote:OK, looking to make a 20S / 74V nominal pack. Maybe 30S / 111V nominal. Small pack, capacity around 1.5WK. Max draw I will use from this pack will be 10KW.

So I'm thinking about using these:
https://hobbyking.com/en_us/zippy-compa ... -pack.html

The idea is to balance charge them in parallel as 10S using a second charging harness. I intend to use my 3010B for charging with no BMS so the ability to easily split into 10SxP will be very convenient.

Is this a bad idea? Would I be better suited by another brand / cell count per package? The main reason I want to use LiPos for this pack is other chemistries have too much voltage sag at high power draws from a small pack. They will also be easy to wire up.
I think you would be better off using a second 10S balance charger. Building balance harrnesses is a PITA.
4000mAh's is not much capacity. When they get a little tired, you will start to get 1 or 2 Volts sag when they are discharged below half.
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'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/10Ah Multistar Lipo rear 4Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, Crazy Bobs run ghetto tubeless. 25 mph. Mean Well HLG-320H-54A
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Re: Lipos a good option for high performance small pack?

Post by ScooterMan101 » Mar 12 2017 12:13am

Lipo's have labor intensive charging requirements, go to your local RC Flyers airpark and ask . I have gotten even more information on Hobby Lipo Charging / Discharging / Storage / etc by asking several local RC Flyers ,
than from reading all the threads here on E.S. about them.

You are better off with 18650's , For the voltages and total watt hours that you want, you will need to have a custom made pack, PM anyone here for info on where to get a pack made, Hint , Do NOT get E-Bay packs, or other packs that have only 2c discharge rates.

Posting a question about batteries, without stating :

1) What motor are you using and what max amps and watts do you want to run through that motor ?
2) Are you going up any hills ? If so what is the Degree of Incline ? and for how long ?
3) How far do you want to go ?
4) Diy Road Bike ? or Mountain Bike ? or Super MTB like what MadRhino and other have ?

is incomplete , different riding parameters have different battery requirements.


RC LIpo's are good for pulling allot amps, if you get the right ones, but as motomech said 4000mAh is low you want at least 5000-5800 mAh per pack minimum , that is where getting a custom made pack , made with 3200 mAh per cell 18650's would be easier for you .



flat tire wrote:Which round cells do you suggest for my requirements? It sounds like the advantages of lipo in my case are negated by lack of reliability and no real ease-of-charging advantage.
My first conversion ... Sold

viewtopic.php?f=3&t=71378&p=1077497&hil ... 1#p1077497

It's 2018 already, lets get some real , improved e-bike / e-velomobile / e-motorcycle designs .

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Re: Lipos a good option for high performance small pack?

Post by MadRhino » Mar 12 2017 12:21am

flat tire wrote:Which round cells do you suggest for my requirements? It sounds like the advantages of lipo in my case are negated by lack of reliability and no real ease-of-charging advantage.
A battery made with 18650 round cells wouldn't be very much bigger and heavier. It would be more expansive and more work to build, but long lasting and much safer for someone who is not willing to accept the downsides of RC lipo. Then, many are making good high density 18650 cells now. If you are going to build a battery with them, select the one that has the specs for your need.
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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 12 2017 4:01am

The issue with adding a second charger is they are not isolated and so they can't run from the same power source. Otherwise, I would do exactly that. Yes, bulk charging is an option.

I will build the pack myself. I stated the specs as 1.5KWh pack with 10KW max draw with reduced voltage drop being a priority. Do we really have that many choices for good, competitively priced batteries now that more information is required? Like, when I made my last pack, the options for 18650 basically were Samsung 25R or maybe 30Q for high discharge small 18650 pack unless you wanted to spend double per battery or more for some really exotic cells with for a marginal advantage (I don't want to do this I want greatest bang for dollar once the cell basically meets my requirements). I would not dream of buying an ebay pack or non high end cells, unless they're lipo, since expensive lipos have the same issues as "value" lipos and are not remotely cost effective.
ScooterMan101 wrote:RC LIpo's are good for pulling allot amps, if you get the right ones, but as motomech said 4000mAh is low you want at least 5000-5800 mAh per pack minimum , that is where getting a custom made pack , made with 3200 mAh per cell 18650's would be easier for you .
OK, I'm not using lipo, but if I were, this makes no sense because the 4Ah cells not only have greater capacity than 18650 but also can supply more current with less voltage drop even for a cheap cell like the hobbyking brand and even if capacity were not greater. Plus, it's clear I would have several packs in parallel to meet my capacity requirement.

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Re: Lipos a good option for high performance small pack?

Post by Eskimo » Mar 12 2017 5:54am

Lipos are for fanatics :wink: If you are really into your hobby like a stamp collector. They don"t like if you try to make their use as easy as possible, they bite back at some point.
I have used them 12 years now. Only them, nothing else. Mainly because A. i have strong RC-background, so they felt like natural choice and B. they are cheap and light.
No major problems in 12 years, they deliver and behave. Propably because i am pretty religious with them, they are like a separate hobby on their own aside of riding. Connecting 20-40Ah pack every time again after charging. You need to be fully wake, well slept, balanced. Three of my packs are five years old, and they still deliver their capacity.
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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 12 2017 6:11am

Damn! That's good advice, thanks. I should add I've been using RC lipos for years and haven't had any fires or dangerous issues even with all kinds of helicopter crash damage...charging has never been a problem, ever.

Anyway, I'm committed to using 18650 now...my local battery shop offers 30Q and LG HG2 for around the same price. Which one is recommended, or is there another cell I should consider?

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Re: Lipos a good option for high performance small pack?

Post by MadRhino » Mar 12 2017 9:39am

Yep. You need to be some sort of fanatic to use RC lipo to power a bike. It is not like RC models that are using a single brick. Big packs are much more likely to become dangerous if you don't babysit them. True that they can last pretty long, when you are not hard on them. I am pulling all the Amps they can deliver, always close to the limit, and I bulk charge them at their max C rate spec everytime. I do ride a lot of mileage but still, they last only one riding season. They are not destroyed, but they lost 20% of their capacity and can't safely deliver anymore the power that I need. So, I am starting every new season with fresh Lipos. Performance has a cost.

Round cells are the best solution for most. The investment in time and money is rewarded with a battery pack that is much safer and does last very long without much care. That is true with all genuine high density round cells, while some Chinese cheap cells can be a very bad investment.
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Re: Lipos a good option for high performance small pack?

Post by wesnewell » Mar 12 2017 10:03am

I've been using rc lipo exclusively for 6 years now and have never regretted it. I run 10ah 24s packs with up to 60A draw. I would never use 18650's for anything other than flashlights. For $180, I replaced my first pack after over 4 years and and about 16K miles. I bulk charge using external balancers most of the time. Still waiting for something better. It's coming, but it isn't here yet. At least not in production yet.
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Re: Lipos a good option for high performance small pack?

Post by Matador » Mar 12 2017 10:43am

flat tire wrote:Which round cells do you suggest for my requirements? It sounds like the advantages of lipo in my case are negated by lack of reliability and no real ease-of-charging advantage.
Find some spec lists for 18650s ont the net (ex : http://www.best18650battery.com/) and than use some maths logic...

As an example :
https://endless-sphere.com/forums/viewt ... 9#p1252830

Also study the discharge graphs.... How many mAh can you REALLY expect at your amp load and at the LVC you chose :

Check this : https://endless-sphere.com/forums/viewt ... 14&t=85770
And this tool is cool : http://lygte-info.dk/review/batteries20 ... arator.php

Dont forget NOT TO leave your pack fully charged for long periods of storage in order to preserve the capacity of your cells : https://endless-sphere.com/forums/viewt ... 14&t=86777 (calendar aging of lithium cells).
At the same time, BEWARE of Battery Murderer Systems (BMS, that can drain your cells to 0.00V - unrecoverable....) if you leave it connected and the cells were already close to 0% (3.00V).
Aslo

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Re: Lipos a good option for high performance small pack?

Post by ScooterMan101 » Mar 12 2017 12:31pm

If you were at a RC Field flying a Helicopter you might not think it makes sense , because you are only using one battery at at time.

The minute you start using Hobby LIpo's for a E-Bike or E-Motorcycle you are now series and paralleling 4 , or perhaps several battery's together to make one big pack, the higher the amp hour for each pack that you can get/buy ... the less you have to string together. doing many Series / Parallel connections have its drawbacks.

Should have said before my first reply , that you have used RC Lipo's before . in that case you could use them , 4 packs on a bike is enough for me ( 2 together in series , then another 2 together in series, then a custom made by me , harness to put those packs in parallel.

Using 2 lipo packs is convenient,
However connecting and disconnecting 4 each ride is not that much fun, and for 6 packs or 8 packs , etc. doing all that each time after each ride and before each ride is just too annoying.








flat tire wrote:
ScooterMan101 wrote:RC LIpo's are good for pulling allot amps, if you get the right ones, but as motomech said 4000mAh is low you want at least 5000-5800 mAh per pack minimum , that is where getting a custom made pack , made with 3200 mAh per cell 18650's would be easier for you .
OK, I'm not using lipo, but if I were, this makes no sense because the 4Ah cells not only have greater capacity than 18650 but also can supply more current with less voltage drop even for a cheap cell like the hobbyking brand and even if capacity were not greater. Plus, it's clear I would have several packs in parallel to meet my capacity requirement.
My first conversion ... Sold

viewtopic.php?f=3&t=71378&p=1077497&hil ... 1#p1077497

It's 2018 already, lets get some real , improved e-bike / e-velomobile / e-motorcycle designs .

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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 12 2017 3:30pm

Thanks for posting the 18650 comparison site. It looks like not many batteries have been released lately. Is that due to the site not being updated or is there some other format than 18650 to be considering?

From the data I'm leaning toward the HG2. Does this battery have any drawbacks relative to the 30Q?

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Re: Lipos a good option for high performance small pack?

Post by Matador » Mar 12 2017 4:35pm

flat tire wrote:Thanks for posting the 18650 comparison site. It looks like not many batteries have been released lately. Is that due to the site not being updated or is there some other format than 18650 to be considering?
From the data I'm leaning toward the HG2. Does this battery have any drawbacks relative to the 30Q?
Yes, possibly the website has not been updated yet.

I read a lot on the HG2 and 30Q. Both seems awsome. From what I read they seem to be equivalent (30Q actually quite capable at 20A, while HG2 could actually heat up a little at 20A continous).... Some people seem to lean forward the 30Q a bit more. Heak I'd even choose the 25R if I could afford.

But here in Canada, shipping gets expensive with HazMat fees, customs, taxes.... It seem even buying from Luna, which sells bare cells (30Q, 25R, HG2) at good price would end up quite expensive in Canada. For me there are not a lot of options for. There is alwas Grin... but man their pack (as good as they are i'm sure) are soo expensive....

I bought 25 Makita BL1840 battery packs which contains 10 Sony VTC4 cells (2000mAh@10amps, 30A max continous).... He sells them to me 15 Canadian dollars each, but it's local pick-up in my case (so no shipping, customs or taxe fees). Bear in mind, each pack is used, but with less than 100 cycles.... So I bough 250 VTC4 cells for 360 CAD (around 270 USD)....
Of course, I had to dissasemble packs, which is labor intesive and requires tools (Torx 10H screwdriver, dremel, etc...), then I had to test each sell which is time consuming and requires special chargers (I use Foxnovo 4S digital chargers), and there is no garantees that all cells will be good.... But from now on I tested 130 cells... 128 had as new capacity (i tested 103 to 107% of the 2000 mAh rating) and 2 cells I had to ditch because they were at 0.3V.... Looking good for now. But, I still have to yield out any potentially bad cells by doing Internal resitance testing. But still, I have a good feeling about this.... Not the same feeling I had testing 250 OLD laptop cells in the past.
Last edited by Matador on Aug 22 2018 8:49pm, edited 1 time in total.

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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 12 2017 4:45pm

I can get VTC4 for less than the LG or Samsung cells. The thing is, is it worth taking such a big hit in capacity (2Ah vs 3Ah) if I'm planning for at least 200 cells now...that's a lot to give up when I should have enough cells in parallel at 20S to handle my power requirements.

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Re: Lipos a good option for high performance small pack?

Post by Matador » Mar 12 2017 5:27pm

flat tire wrote:I can get VTC4 for less than the LG or Samsung cells. The thing is, is it worth taking such a big hit in capacity (2Ah vs 3Ah) if I'm planning for at least 200 cells now...that's a lot to give up when I should have enough cells in parallel at 20S to handle my power requirements.
BEWARE of VTC4 cells unless you have a VERY RELIABLE SOURCE (like Doctorbass for instance)
They are THE MOST CONTERFEITED CELLS in the world (lot's of people want them for their vaping habit.... lots of amps means lot of smoke)...
So much rewraps of fakes...

Yes, big hit in capacity with VTC4 as you say... You probably don't need 30A/cell unless you use a monster of a controller for your ebike motor...
Telsa cells are really intersting too ! They're not NMC chemistry bur rather LCA... LCA typically deliver mid-amp load range (like 8A max), but they pack monstrous energy density (3000 mAh ballpack around 240 Wh/kilo). They are rather expensiver though.

I choose VTC4 because they are hard to damage and I have them for 1.50$ CAD per cell at my door (1.12 USD/cell)....

The thing is you cannot have both... 18650 are either designed for really high drain but with mid- to low- range capacity or high capacity but that's at low amp-load. Plus if you push a high capacity cell at high amp, it will NOT deliver it's promised mAh (tested at 0.2C LOL), will heat up a lot and end up damaged...

Of course you can get an "all-around" cell, with mid-amp load potential and mid-range capacity, like the GA or PF cells.... 8 to 10A max.... and 3000 or 2600 mAh.... But dont go for the NCRB cells (4.8A max; 3400 mAh at 0.2C) unless you'll have a very low power setup (less thant 10Amp controller for 4P battery).

Personally, I prefer a heavy battery that will give me some "willy joy"- kind of power and last a loooong life, rather than a light battery that heats up a lot and deteriorates quickly (good range at 1st cycle, but notice sag, and then.... battery giving less and less range and I'm always hitting LVC under load even though there is still 1 third of the Whrs left in the battery).

The bottom line is, there is a sweet spot between HIGH CAPACITY and HIGH AMPERAGE to find, so that you can have a battery that is not too big, not too heavy, but still lives a long life and give you lot's of enjoyable time.
I would ask people that have similar setup as your what battery they use and what their experience is with that battery (how does your battery hold up so far ? Do you ride a lot in a week ? Is there a lot of steep hills ? Do you like to lean on the throttle a lot or you go for slow econo-range style driving ?).

Experience beats theory in that matter.

- But it's hard to go wrong with high en cells like 30Q, HG2, VTC4, VTC6, 25R. They are great.

- Using more all-around cells (Like the GA, Tesla cell, PF cell, etc) might give you more range (more mAh), but you have less error margin (you must watch your amp consumption a bit more in order not to overstress the cells, unless of course you make a massive battery with lots and lots of cells in parallel to conterbalance the slightly lower amp-rating)

- To me, cells like the NCRB that offer sky-high capacities (that is 3400 mAh) are like a fake promesses .... Yes they will deliver that much mAh, but in a lab and at a 0,68A(0.2C) load per cell.... So a 4P pack will give you 3400 mAh per cell, yes, but that is if your ebikle is using just 2.72 Amps load... Is that even possible ???? Not really. Pull out 20A from that pack and they will sag a lot and probably give you a lot less mAh that a PF cell at the same load... In the end, your were better with a lower capacity cell that had more power... At least they dont heat up like crazy and go tits-up on you after 50 cycles.

Of course, I must say... I'm no battery expert. I just enjoy reading on that subject a lot.... Think I should have been an engeneer in another life, as I enjoy playing with batteries a lot.... building/thinkering with electric stuff... I enjoy it almost more than my work actually.... I have a strong scientific background.

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Re: Lipos a good option for high performance small pack?

Post by Matador » Mar 12 2017 5:29pm

From what I see you want to be in the 10kW ballpark... with 200 cells....
So I would ask doctorbass for more precise advice If I were you... He is playing in similar kW ranges than you plan to do for you build...

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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 12 2017 6:04pm

OK, thanks for the reference on doctorbass. I will send him a PM. I may do up to 300 cells total, in two 10s packs, for a total around 3KWh with 30Q or HG2 cells. That would give me a really sick real world range.

I enjoy messing with the batteries too, my last pack was 19s5p samsung 25R all soldered with thick copper braid. That was pretty reliable but I had a few loose connections after two years of service and lots of off road riding. Now I have a spot welder and nickel strips coming...hopefully that will be more reliable although it will require multiple runs of nickel to get the current capacity I need.

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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 23 2017 5:27pm

So to update this thread I just got 10 of the 10s hobbyking packs linked in the OP. I will use at least 8, maybe all 10 if everyone's healthy. I'll be using Anderson PP45 connectors to put the packs in series and Anderson PP50 w/ 75 amp connectors for everything else like series connection, controller connection, and for bulk charging.

I expect absolutely nothing from this pack except relatively high discharge current for the stated capacity, compared to 18650.

As far as balance charging goes, that is to be done with individual packs. I can put in a balance harness to parallel balance each 10s assembly, but that may not be necessary or desirable as it doesn't allow for individual cell monitoring.

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Re: Lipos a good option for high performance small pack?

Post by MadRhino » Mar 23 2017 5:57pm

P45 not enough. They come with 5.5mm gold bullits, use them as is and tape the connections. 75A Andersons are OK, the minimum you should use on RC lipo. No power wires on the bike smaller than 10ga silicon, ideally 8ga.
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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 23 2017 7:08pm

You're crazy if you think those crappy stock bullets can flow more current than a 45 amp Anderson. Or maybe I'm crazy for thinking that without testing it, but I don't have much faith in RC hobby connectors...they're all so crappy. Anyway, the 45 amp connectors are just from each individual pack to the power harness, so the rating is actually quite fine. The 75 amp PP50 connectors will be more of a restriction, but my bursts above the rated power level will be pretty brief so I'm not concerned.

I'm running some 10ga teflon wire I have on hand for the power harness.

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Re: Lipos a good option for high performance small pack?

Post by MadRhino » Mar 23 2017 8:07pm

flat tire wrote:You're crazy if you think those crappy stock bullets can flow more current than a 45 amp Anderson. Or maybe I'm crazy for thinking that without testing it...
Yes you are... invited to test them before cutting them off and replace with 45A Andersons that have very poor contact surface and make a connection that has twice the impedance. Andersons less than 75A rating, are not safe for lipo.

I have used the stock 5.5mm bullets to assemble my lipo bricks for years, pulling +100A everyday. 2 years ago I started cutting the bullets off, because I now splice and solder my lipo bricks together. The bullets were not 100% reliable from 150A. :wink:
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Re: Lipos a good option for high performance small pack?

Post by flat tire » Mar 23 2017 8:27pm

OK, I will test before converting to the Andersons. The maximum burst current draw thru each PP45 from each pack with 5P if they're shared equally will only be 36 amps. Are you saying the Andersons are over rated? The full parallel current will just go thru 2 PP50 75 amp connectors, one for each parallel assembly to bridge to series and one to hook the series connection to the controller.

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Re: Lipos a good option for high performance small pack?

Post by MadRhino » Mar 23 2017 8:38pm

The 75A Andersons are good. They really can stand 75A continuous, 200A bursts. That is when they are properly crimped AND soldered.
The 45A Andersons are not secure. They are making a weak connection that has poor contact surface.
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