Seeking battery and motor advice

Hi there!
So I built my son a 3kw kids cross which works great after heaps of help from this forum so now I kinda want to do something for myself as the 1000w scooter I have has no chance to follow my son when he drives off.
At first I wanted a trials bike like oset but after finding out their price its a hard pass.

I got myself a midsize pitbike frame which isnt awesome by any means but good enough starting bike for me. it was free so cant complain, right?

I do have a 2000w hub motor that I got cheaps in what seems to be in a good condition, it drives about 50km/h pretty okayish and tops out at around 65-70km/h when tested on a slightly bigger bike obviously flat road,no wind and fully charged 60v battery. It doesnt do hills at all, its doesnt have enough juice even feels like the 1000w scooter fairs better running uphill than the hub motor.

So I need advice, can something be upgraded on this hub motor, safely? Motor has no information aside from Swedish reseller who writes its a 2000w hub motor. Its big and heavy thou.

Goals?
60-80kmh top speed
Good torque, able to ride uphill,trials and uneven mud/gravel roads - it has to be fun! Not many flat roads where me and my son live.
Can something be done with current motor or should I change it? Can I have recommendations for midsize pitbike

Battery
I have 60V 20Ah 50A continuous and 72V 28Ah semi homemade battery by joining 4x 36V 14Ah ebike battery
I feel range is well enough with these two batteries (tested on sons smaller bike) but want a battery able to draw alot more Amps.
Been looking at 5s lipos 20Ah but they're at 250usd each + shipping to sweden, would need 4x.. its too expensive atm
But also been eyeing pouch cells? Seems alot cheaper, doesnt require spotwelding and kinda what I read is that they handle 100-200A discharge, seems awesome! Reseller
Battery hookup (are they ok/legit?)
Or is there any better ideas, websites etc to buy batteries abit cheaper?

Budget I would say no more than 1200usd i can handle more but only overtime.

Thanks in advance

These guys sell kits: https://www.electroandcompany.com/buy-kits

Quinc said:

These guys sell kits: https://www.electroandcompany.com/buy-kits

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Thank you, im sure they're great but priced way higher than alibaba and most above my total budget

Dixonk said:

Goals?
60-80kmh top speed
Good torque, able to ride uphill,trials and uneven mud/gravel roads - it has to be fun! Not many flat roads where me and my son live.

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Up what slope hill, at what speed, with how much weight total?

You'll need those to find out how much power it takes to do the work. Without knowing at least roughly what the worst case is, only guesses can be made, which are not all that likely to give you a parts list that will do the job you want.


I recommend using the simulator at http://ebikes.ca/tools/simulator.html with some of the preloaded "parts" to "build" a bike and then run it using the worst-case conditions under which you'll need it to do the work. It will at least give a ballpark idea of power required to do it.

It can also show you the acceleration curve, so you can see how quickly you could reach the desired speed under those conditions, relative to a different system (using the a/b compare mode, for instance), if acceleration is also important to you.


Side note: terms like "good torque" are very relative to the specific person stating it, under the specific conditions they'd use it under. For instance, to me, "good torque" would be enough for my SB Cruiser trike to pull a couple of tons of load on a trailer (plus the few hundred pounds of me and the trike itself) up a minimum 10% slope hill at 20MPH with a 20MPH headwind on smoothly paved roads. (I definitely don't have that yet. :lol: )

Dixonk said:

I do have a 2000w hub motor that I got cheaps in what seems to be in a good condition, it drives about 50km/h pretty okayish and tops out at around 65-70km/h when tested on a slightly bigger bike obviously flat road,no wind and fully charged 60v battery. It doesnt do hills at all, its doesnt have enough juice even feels like the 1000w scooter fairs better running uphill than the hub motor.

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The motor itself is not usually the cause of not feeling as powerful as another lower-power motor.

It's usually the controller and battery, as well as the gearing of the motor to the ground (if hubmotor in a wheel, the tire diameter is the gearing).

If the controller can't supply the phase amps the motor needs to do the work being asked of it, the motor can't do it.

If the battery can't supply the battery amps the controller needs to convert to phase amps for the motor for that work, then it doesn't matter how powerful the motor or controller are.

So I need advice, can something be upgraded on this hub motor, safely? Motor has no information aside from Swedish reseller who writes its a 2000w hub motor. Its big and heavy thou.

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There's not really much you can do to "upgrade" a hubmotor itself for significantly greater power, other than rebuilding it in various ways, such as rewinding it (a huge expensive PITA) to better match the speed you need the power at, or give it better copper fill, etc. Or ventilating it with forced-air cooling (like Cowardlyduck by building fans into the stator supports), etc. You can somewhat increase it's heat dissipation ability by sealing it really well and using either Statorade (ferrofluid) or liquid cooling (filling partly with oil, etc), but there's limits to what this can do; it doesn't change the motor's physical capabilities.

Also, the "watt rating" of a motor doesn't tell you it's real story; it is at best a general guide to the continuous power it might be able to take when used at it's rated RPM. If a motor is used at that power level but at very low speed vs what it normally spins at for a particular system, it can easily overheat, and quickly. Or, often you can use a "1000w" motor at three or four times that for short bursts, intermittently, without overheating it. Depends on the system, conditions, etc.


One example: my SB Cruiser trike uses a "500w" ex-stromer hubmotor
https://endless-sphere.com/forums/viewtopic.php?t=86600
at a couple thousand watts during the few seconds of acceleration from a stop to 20mph...the rest of the time during cruising it's at or only a little higher than it's rating, maybe up to 700w depending on headwinds, etc. It gets hot after riding in traffic, but not overheated. I have dual motors on there (completely different kinds ATM) on the rear ~21"-22" wheels, and can climb a decent hill (phoenix, az, north mountain, 7th street northbound or southbound) that is perhaps a mile or more long at 20mph without stressing the system, with a guesstimated 600lbs of trike and me.

So...you may be able to use that motor to do what you want...if it's geared right to the ground for the speed you want to use the power at, and the rest of the system (controller, battery) can supply that power, and the usage is intermittent enough to allow cooling (or you add cooling modifications sufficient to help it out).

But you have to figure out how much power it will actually take to do the work, to even make a decent guess.


Very generally, however, the more massive a motor, the more torque you may get out of it at a higher power level for longer times without overheating it.

with only 50a continues battery check out the boma 60v 2500w motor/controller kits. or the 72v 3000w motor kits.

I have 60V 20Ah 50A continuous and 72V 28Ah semi homemade battery by joining 4x 36V 14Ah ebike battery
I feel range is well enough with these two batteries (tested on sons smaller bike) but want a battery able to draw alot more Amps.

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If the batteries were all the same voltage you could parallel them for higher current (and capacity), but since they're not, it is likely going to require buying or making a battery specifically for this new project.

Been looking at 5s lipos 20Ah but they're at 250usd each + shipping to sweden, would need 4x.. its too expensive atm
But also been eyeing pouch cells? Seems alot cheaper, doesnt require spotwelding and kinda what I read is that they handle 100-200A discharge, seems awesome! Reseller
Battery hookup (are they ok/legit?)
Or is there any better ideas, websites etc to buy batteries abit cheaper?

Click to expand...

Generally, the cheaper you go for batteries, the cheaper (less capable) you get, regardless of what is advertised.

There are some special cases, such as with used EV-grade cells that sometimes places like Batteryhookup and the like sell for next to nothing (relative to the value you get out of them). But these cells are larger format, so harder to fit on a small bike; usually you end up with a big rectangular block. (that performs way better than the arrays of small cells, but is still a big block). LIke thesedecade-old EIG C020 cells that I still use; the packs in view are 14s2p 52v 40Ah packs capable of up to 400A bursts for a few seconds in theory, and continuously capable of 200A. (I only use them at about 80A peak right now, and maybe a quarter of that continuously). Toaster oven for scale (also usable as a testing load):



The less of the capability (both Amps and Amp-hours) you use of a pack the better it will perform (less voltage sag, so more watts to the wheel) and the longer it will last (total cycles).

Batteries are...complicated, in that there are a number of factors to making the best one for your specific application...and just buying stuff and putting it together doesn't mean it will do the job; same thing with buying a premade pack that advertises it's capable of however many amps, amp hours, and whatnot. (because sellers too-often either flat out lie, or don't understand what they're selling and what the numbers mean, and get them wrong, etc., and too many cheap manufacturers use mismatched cells, or even garbage (literally untested recycled garbage cells from dead packs) to make packs from and don't test them to ensure they are well-matched so they stay balanced and work well and last long. And you can't know which makers and sellers do these things until you get and test whatever you order from them....).

Even if the cells can do what you want, sometimes the BMS can't. (or it's cheaply enough made that it causes problems itself, sometimes even killing cells by draining them constantly).

Thanks for everyones input and my late reply, being a single parent its difficult to keep track of things at time! I kinda forgot to reply!

I sold off the 2000w hubmotor and the 60v 20ah battery, I felt it was enough for my needs on flat roads on the speedside of things but it was way too weak as we have alot of uphills and bumpy roads in our area.

Im able to buy a 20s 30ah NMC cells with bluetooth bms for 800usd Inc shipping from alibaba, I have no clue if this is what you get after payment but seller says its new cells 150A continuous and 210A peak which is more than capable of doing anything I do ever want.

Qs138 70v3 550 including shipping from another alibaba seller

Is the battery and motor a good fit for a medium sized pitbike? Or is there a better motor out there for me, perhaps abit cheaper?

Im rather clueless where to look kinda have to work with the budget I have and get the best bang for the buck

Best regards

I've pretty much decided on the qs138v3 70 combo along with a FD84530 controller
However, I'm still wondering about what battery to get. How do you guys justify the cost and how long do 500-1000 cycle really lasts for occassional riding?

Stands between buying two 12s 20-32ah lipo packs from alibaba for a 24s configuration or a few smaller 5-6S similar ah packs for a serie connection either 22 or 24s, off the information I get from the internet people usually say 400-600cycles and or 1 year and paying 800-900usd for 1 year of battery is quite alot. this has a few upsides and that would mainly be its small size but obviously worried for explosions and fire risk but these should be capable at 200amps continously right? which is good!

cant really find a 18650/27100 similar pack that can push 200amps in a similar price point as with the lipos.
other option is going with pouch cells, price would be abit cheaper but at the cost of size.. as there is plenty different ones via alibaba search I'm not really sure what to get, found some A123 cells 20ah with size that's okay but at 37usd each comes out at 740usd without bms, connections and shipping.

I would prefer to get a good battery at around 1000 if possible that will last awhile, well.. it has to last awhile for me to even consider going electrical to justify its costs.

Any insights for gurus? thanks