Lipos a good option for high performance small pack?

Another downside I dunno if anyone has mentioned is weight. These super-high discharge packs look significantly heavier per Ah than good high capacity 18650. They trade off electrolyte for more anode and cathode, which makes them heavier and more volatile per Ah. Good for short RC plane flights, where you must have that high discharge and can carry/charge extra batteries on the ground and "refuel" every 10-15 minutes. But if you have several in parallel on your bike to get 16Ah, and are pulling a small fraction of the 400A they are rated for, they are just adding unnecessary weight. 1S4P=400A*30+V=12+kW, 3.6kg. 2S4P=400A*60+V=24+kW, 7.2kg. 3S4P=36+kW, 10.8kg! (all of these only 16Ah, which is pitiful for 30+mph).

If you have a really monster bike, maybe they are worth considering (I'm still skeptical). The extra mass adds up real quick. If you want a bike that isn't super heavy, best to stay away from these.

You got it wrong. My battery pack that is 24s 1p 10000 mah and delivers 250A cont (400A burst), would be heavier built with round cells.

Most of all, it would be much longer to charge.

The 18650s out now are higher energy density than any lipo I'm aware of but only if you have low power requirements on a small pack or a very big pack to fulfill heavy power requirements. For a 18650 pack w/ 20 amp continuous discharge rating to deliver the requirements for a pack like MadRhino mentions you would need 13p which with a 2500mah battery gives 32.5Ah...a much bigger pack even if the 18650 chemistry weighs less per KWh.

Yep. And those counting the weight of round cells, always forget to count the assembly weight of those numerous cells. I am the first to say round cells are better for most, but they just don't make it for me and many of us who are building performance bikes.

As an off the wall noob idea, why not 2WD dual 24v ~hub motors, running on a 22v lipo hobby pack each.

e.g. 20ah:
https://hobbyking.com/en_us/multistar-high-capacity-6s-20000mah-multi-rotor-lipo-pack.html

(2.5kg (light enuff for a front luggage rack), 10C)

No balancing.

Swapping in fresh charged spare paks is easy.

a 20a controller on each motor, yields ~440w per motor at 2C battery rate. 880w total is not bad power.

~880wh total for both paks isnt bad for if u throw in fast charging and pak swapping.

It adds much flexibility since either pak can be used selectively, to achieve seamless long range. Favour using the almost empty one, and only recharge/swap when optimally low, yet never be completely without power.

cycleops612 said:

off the wall

Click to expand...

I agree that sounds like a fun build for a low power ebike. I was already running 5KW on my old Leafmotor and now I need 10KW to punish the QS205 that'll replace it. More power is always good. I think the next step up from there is a motorcycle.

Notice the difference between ...

Maximum amps for chassis wiring
and
Maximum amps for power transmission.

Maybe 7 amps max for charging through a 22 awg wire
But
When drawing amps from the battery - through controller - to motor
a 12 awg wire is rated for only 9.3 amps per wire, so 18.6 amps to the controller

Not quite sure of that since the lipo's have 10 awg Red/Black wire and they are suposed to be able to put out over 100 continious ( for us that stick to the only pull 25% - 33% of rated amps from Lipo packs then even 10 awg is a little small ? )


I had used 12 awg wires for my series/parallel harness from battery pack to the controller to Mac motor of 26 amps ( 13 amps per wire)
for the few times that I have used lipo packs on it now, looks like time to make a 10 awg series/parallel harness ?

AWG gauge Conductor
Diameter Inches Conductor
Diameter mm Ohms per 1000 ft. Ohms per km Maximum amps for chassis wiring Maximum amps for
power transmission Maximum frequency for
100% skin depth for solid conductor copper Breaking force Soft Annealed Cu 37000 PSI
0000 0.46 11.684 0.049 0.16072 380 302 125 Hz 6120 lbs
000 0.4096 10.40384 0.0618 0.202704 328 239 160 Hz 4860 lbs
00 0.3648 9.26592 0.0779 0.255512 283 190 200 Hz 3860 lbs
0 0.3249 8.25246 0.0983 0.322424 245 150 250 Hz 3060 lbs
1 0.2893 7.34822 0.1239 0.406392 211 119 325 Hz 2430 lbs
2 0.2576 6.54304 0.1563 0.512664 181 94 410 Hz 1930 lbs
3 0.2294 5.82676 0.197 0.64616 158 75 500 Hz 1530 lbs
4 0.2043 5.18922 0.2485 0.81508 135 60 650 Hz 1210 lbs
5 0.1819 4.62026 0.3133 1.027624 118 47 810 Hz 960 lbs
6 0.162 4.1148 0.3951 1.295928 101 37 1100 Hz 760 lbs
7 0.1443 3.66522 0.4982 1.634096 89 30 1300 Hz 605 lbs
8 0.1285 3.2639 0.6282 2.060496 73 24 1650 Hz 480 lbs
9 0.1144 2.90576 0.7921 2.598088 64 19 2050 Hz 380 lbs
10 0.1019 2.58826 0.9989 3.276392 55 15 2600 Hz 314 lbs
11 0.0907 2.30378 1.26 4.1328 47 12 3200 Hz 249 lbs
12 0.0808 2.05232 1.588 5.20864 41 9.3 4150 Hz 197 lbs
13 0.072 1.8288 2.003 6.56984 35 7.4 5300 Hz 150 lbs
14 0.0641 1.62814 2.525 8.282 32 5.9 6700 Hz 119 lbs
15 0.0571 1.45034 3.184 10.44352 28 4.7 8250 Hz 94 lbs
16 0.0508 1.29032 4.016 13.17248 22 3.7 11 k Hz 75 lbs
17 0.0453 1.15062 5.064 16.60992 19 2.9 13 k Hz 59 lbs
18 0.0403 1.02362 6.385 20.9428 16 2.3 17 kHz 47 lbs
19 0.0359 0.91186 8.051 26.40728 14 1.8 21 kHz 37 lbs
20 0.032 0.8128 10.15 33.292 11 1.5 27 kHz 29 lbs
21 0.0285 0.7239 12.8 41.984 9 1.2 33 kHz 23 lbs
22 0.0253 0.64516 16.14 52.9392 7 0.92 42 kHz 18 lbs

wesnewell said:

ScooterMan101 said:

Charge , only through the Balance Leads ?
Balance leads are .. 22 awg .
How much current can you pass through a 22 awg wire ?

Click to expand...

About 7A per cell.
http://www.powerstream.com/Wire_Size.htm

Click to expand...

ScooterMan101 said:

...
a 12 awg wire is rated for only 9.3 amps per wire...

Click to expand...

That's for 100 feet of 12 awg. Are your runs 100 ft?

That said I use two pairs of 12 awg (equivalent to 8-9 awg) between the battery and controller because the connectors I use have 4 contacts, each rated @ 30A DC.
By doubling the contact area I get no issues (heat) with contact resistance.

as u were. i deleted my post - waffle.

flat tire said:

The 18650s out now are higher energy density than any lipo I'm aware of but only if you have low power requirements on a small pack or a very big pack to fulfill heavy power requirements. For a 18650 pack w/ 20 amp continuous discharge rating to deliver the requirements for a pack like MadRhino mentions you would need 13p which with a 2500mah battery gives 32.5Ah...a much bigger pack even if the 18650 chemistry weighs less per KWh.

Click to expand...

Well, I've ordered LG HG2, which are rated 3Ah, 6.6C (20A). I'm running 15S4P (60 cells), which is 12Ah, 80A. I've only got a 1000W motor, this should be more than enough (low 3V*15S*80A=3.6kW). 2.9kg for the cells (granted, packing will add a tiny bit).

I might upgrade to 15S6P for 18Ah (50% more range), 120A (90 cells, and 3V*15S*120A=5.4kW, way more than I will use atm). That would be 4.3kg.

Hobby packs might be a little bit cheaper, but definitely heavier (but so are lower capacity 18650, which I think is what the cheapest hobby packs are made from). I probably should have looked a little more at the hobby packs. I had a hunch 18650 would be highest volume and so have the best economy of scale advantage, over pouches, which (seem to) lack standard sizing. I got my 60 cells for US$320 shipped, a little over US$5 per cell.

Good and reliable solution. Yet, weight and size will be bigger than lipo equivalent after it's built and fitted to the bike. The assembly harware, BMS, case and mounting hardware have to be added to the cell count weight.

My 4 brick packs, 24s 10,000mah, are weighting 5.1 kg assembled. They fit in a soft padded bag with quick release that is about 225g with mounting bracket, 72mm X 172mm X 222 mm outside dimensions. The new bricks that I will be riding with this summer are the same size and weight, but 60C cont and 120C burst, 5C charge. Not that I need all that extra power, but lower resistance will make them much better in extreme weather, hot or cold. They will charge in the same ~12 minutes that I am doing now.

OK, I got the PP45 connectors and the lipos in the mail. The lipos are all in good shape and now I must make the enclosure.

The PP45 are ABSOLUTE AND COMPLETE crap. The poster who disparaged them earlier was not joking. They do have a spring to keep the contacts mating, but the contacts themselves are comically small. There is no comparison whatsoever between these and the SB50 connectors.

To make pack swapping and balancing even easier, I ordered all SB50 connectors for my Lipo harness. This means I can easily replace packs in the event one takes a shit. I'm thinking about rotating my 10 packs and only using 8. Is this a good idea or am I unlikely to have the batteries die soon with proper care and storage?

I knew you would not use the 45A Andersons. :wink: If your lipo bricks are with 5.5 mm gold bullets just series them red on black with the bullets and tape them with quality electrical tape. You have nothing to gain replacing them with 75A Andersons. Also, the big Andersons will only make bulky connections using space in your battery enclosure. I suggest making 2 short wires, one red and one black, that have Anderson at one end and a 5.5 mm bullet at the other. Use them to wire from both poles of the battery assembly, to the exit of the enclosure (those can be 4 making 2 "Y" if you are using 2 series). From there the power wires between the battery to the controller, and phase wires between motor and controller, can have 75A Andersons. Use genuine Andersons, I mean it. Copies are crap even when they look fine. Crimp them good, the crimp gets weaker after some time, especially when the connectors are often wet or abused with very high power. Adding solder does make sure water does not get in and corrode the wire in the crimp.

I got the Andersons from Powerwerx so hopefully they're legit.

Thinking now I'll use all 10 batteries and if I have cells die I can either make a new pack or go from 5p to 4p. Will I be ok or is there a decent chance I'll be 4p within a few months?

I would make 4p then, that is a big battery to put on the front already. Even then, I would have prefered using higher Ah bricks and make only 1p. The idea is that less connections are better, and series are better than parallel. One series of high Ah is better than parallel many series of smaller bricks. Lipo are now available big: 10000 mah, 12000 mah... up to 22 000 mah cells. You could have built with one series, making very few connections as compared as the harness that you are doing now. Anyway, that is your first, and you have to start somewhere. Keeping a few bricks in the fridge will be good when you have a weak cell, and let you swap a new brick to keep riding.

OK, I will rotate rotate 2 packs out each charge to keep spares. The whole assembly isn't going in front, just half the packs.

Is there somewhere in particular you recommend getting the big lipo cells from?

MadRhino said:

I would make 4p then, that is a big battery to put on the front already. Even then, I would have prefered using higher Ah bricks and make only 1p. The idea is that less connections are better, and series are better than parallel. One series of high Ah is better than parallel many series of smaller bricks. Lipo are now available big: 10000 mah, 12000 mah... up to 22 000 mah cells. You could have built with one series, making very few connections as compared as the harness that you are doing now. Anyway, that is your first, and you have to start somewhere. Keeping a few bricks in the fridge will be good when you have a weak cell, and let you swap a new brick to keep riding.

Click to expand...

Just hypothetically, what do u think of using a single hobby pak lipo on a 24v ebike - for 350-450w (15-20 amp~ controller)?

As u say, they come in 20ah size, a handy 440wh.

Would the lowish 22v voltage be too big a problem?

Are there mods that would lessen such problems if any?

An appealing app would be a super light road ebike. For a trim rider, Even 250w would fly. Drop bars for wind resistance & good top speed, sub 2kg battery & sub 1kg geared hub motor & a ~11kg 28" ~racing bike, good range, simple fast charging. Total bike weight sub 15kg.

Another app is developing world motorbike taxis. Electric could replace some ICE bikes, but fast charging may be critical to viability.

That is a whole new problem. A system that is made to run 24v, will only lack performance when fed lower voltage. The on'y mod that could restore original performance, would be a larger wheel and higher Amps. You should build to achieve target performance with the 22.2 v nominal battery that you want to use. At this low voltage with the kind of bike that you plan, I would build a friction drive, because small RC motors are high Kv, cheap, lightweigh and easy to replace on such a system.

High capacity RC lipo is used in drones. That is the market where you can find them in a pretty wide variety of quality. Racing drones are known to require batteries with low resistance, high C rate that can charge fast and discharge aggressively. For that purpose, they can be found locally in dense population areas, only at higher price though. I find best to deal directly with a Chinese manufacturer, where the best price and quality has a different cost, in shipping complications and delays. That is good only when you are ahead of your schedule, willing to spend time in negociations and complying with bureaucracy regulations.

I made my own lipo battery pack from AliExpress single cell lipos 3p 12s with a powerful well made bms and the whole setup works great, I’ve made a 18650 pack for an ebike a while back 10p 22s works well don’t get me wrong but the lipo pack is best still early days so I can’t say about its long term use yet but from the experience with the two types of of cells, my guess is it all comes down to the BMS get a really good one and lipos will be your friend for life never above 4.2 never below 3.7.

Also had the lipos under compression between 2mm carbon fiber plates using m3 bolts, the compression helps lipos preform better as the anode and cathode are forced closer

Volts said:

I made my own lipo battery pack from AliExpress single cells...

... my guess is it all comes down to the BMS get a really good one and lipos will be your friend for life never above 4.2 never below 3.7.

Also had the lipos under compression between 2mm carbon fiber plates using m3 bolts, the compression helps lipos preform better as the anode and cathode are forced closer

Click to expand...

Some things you need to understand about RC lipo, and LiCo chemistry.

Making your Lipo battery from single cells, does require proper equipment to achieve equal quality with factory made lipo bricks. It is unlikely that you are taking full advantage of your cells. And, you are not saving any money.

No Rc lipo will ‘be your friend forever’. It has about the shortest life expectation of all battery chemistries. They are a bad choice when long life is a priority. Their purpose is to supply high power surges, and a lot of compromises are made to achieve so.

A BMS, no matter its quality, can be the most dangerous addition to a RC lipo battery. First, Rc lipo is not safe at rest if it is plugged on anything. Second, Rc lipo are not safe to charge when nobody is with them watching and monitoring. Third, a BMS is hiding weak cells from your consciousness.

Then, while it is true that compression does help
Lico cells to perform more constant and eventually improve their life expectation, it does make them much more dangerous when they fail. Round lico cells are compressed. They are the same chemistry as Rc lipo, but manufacturers spec them much lower C rate because compression is making them at higher risk of explosion.

Rc lipo safety does require individual cell monitoring. Nothing in their assembly should keep them from being monitored at individual cell level. They must be kept at storage voltage at rest, unplugged off anything. Compression should be low enough to let them expand 15% before any gas leakage could occur.

Some forums claim the Lico chemistry allows 12% increase in power and claim max charge of 4.35v, my seller told me that 4.2v is the max for the type of cell I purchased from him, and about not using the max out of the cell, I don’t know about that dude, there is another guy doing what I did only on a larger scale his post Is high power lipo battery build I paraphrase but it’s some thing like that look it up in the forums, and his been doing it since 2012 with no complains from his customers?

Volts said:

Some forums claim the Lico chemistry allows 12% increase in power and claim max charge of 4.35v, my seller told me that 4.2v is the max for the type of cell I purchased from him, and about not using the max out of the cell, I don’t know about that dude, there is another guy doing what I did only on a larger scale his post Is high power lipo battery build I paraphrase but it’s some thing like that look it up in the forums, and his been doing it since 2012 with no complains from his customers?

Click to expand...

4.2v is the full charging voltage for all lico cells. Yet, it is not uncommon to overcharge RC lipo. If you don’t care much about how long they last, if your cells are low resistance, high C rate, if you monitor them carefully... it is pretty safe to charge them prismatic lico cells to 4.35v

The main factor is temperature. As long as they don't go starting building heat, they can be abused without any risk, other than faster wear. Monitoring temp, does make it possible to abuse their C rate as well, fast charging especially. Top quality cells that are carefully nonitored, can be charged in 5 minutes.

Round cells are another story. Since they are compressed and enclosed in a hard shell, it is dangerous to overcharge them, or to abuse their C rate. Add the fact that it is common practice with round cells to assemble them by parallel blocks, thus much more prone to dramatic failure. Round cells must be used conservatively, strictly within manufacturers specs.

The problem with hobbyking battery packs is they are 1p stacks, paralleling them with other stacks is why they fail

Volts said:

The problem with hobbyking battery packs is they are 1p stacks, paralleling them with other stacks is why they fail

Click to expand...

You souldn’t do that. Proper assembly is to series them first, then to parallel the strings. Remember: your battery must be capable of individual cell monitoring.

It is not safe to parallel lico cells like it is commonly done with other, safer chemistries. To assemble a series of parallel blocks, does make cells hide each other within blocks.