180kv outrunner powered offroad e-bike

[Alster370]

This project will probably not start till jan/feb but id like to explain my idea and hopefully get a few questions answered to make the real build as smooth as possible.

My plan is to make an offroad e bike which uses a turnigy 180kv outrunner which will be ran of 4 car batteries. I would like to use a hobbyking 200a esc and a servo tester plus twist throttle to control the motor. the frame will be a slightly modified bmx frame to support the large batteries, and I plan to modify the forks and rear assembly to accommodate larger, wider tires. It will be used mainly for use on private land and trails so top speed doesn't need to be more than 30 or so.

So to the questions:

Will the esc and motor be fine with car batteries?

can I run the batteries in this formation?

http://s785.photobucket.com/albums/yy140/Alster370/?action=view&current=Untitled-1.png

sorry if this is in the wrong place, I only signed up this afternoon.

 

[Samba]

The motors don't care much about what kind of batteries are used. That battery configuration is for 24 volts.

Regular car batteries are made for producing lots of amps for a very short time - for starting the car.
They aren't made to be discharged till nearly empty - they are kept between 75% and 100% of full charge.
They also have strong liquid acid which will leak out when the bike tips over.

Deep discharge batteries (e.g. a boat trolling motor) have thicker lead plates.
They don't put out as big a burst of current but handle being discharged deeply - e.g. till nearly empty like 25% full.

Then there are gel and sealed varieties which won't spill just from being tipped over.

 

[Drunkskunk]

Welcome to here.
It sounds like you have a plan. Thats good. Any plan is better than No plan.

But 4 car batteries are going to be huge and heavy on a BMX frame. 100 to 150 pounds, possably more depending on the size group. They also are starting batteries, so you can't discharge them much without killing them. You need deep cycle batteries to be able to realy use their capacity, and those weight a bit more.
Its also expensive. and would be so heavy as to make the bike a slug.

You would be better off with Lipo

the design you linked would be fine for 4 batteries. its considered a 2s2p arangement. 2 series, 2 parrellel

 

[Alster370]

Il probably set them up for a series configuration 48v, 40-50A. I only chose car batteries because they can be obtained for cheap at local scrapyards. I have looked at lipos but they are too expensive for me. I suppose with the amps being sub 100 I could get a turingy 80a esc for the same price as the hobbyking one.

 

[Kepler]

If $100 bucks for liPos is too much for your budget, I think you might have trouble being able to fund any type of RC type build. You need to understand that you need good good quality gear to do a 48V RC setup. 24V setup is much more economical but is mostly suited to friction drive setups. Good luck.

 

[Alster370]

oh I can spend 100$ on lipos if I need to, it would just take a month or two to source the money. would I be able to get 24v 50a from 100$ worth of lipos? because I can always add more later on when I have the money.

 

[liveforphysics]

The "200a brushless monster" ESC from hobbyking unfortunately just seems to explode inside of the first 2 minutes of anyone here using it for anything on a bicycle. Works out OK on a plane, not suitable for EVs.

Car batteries could work, but they will be destroyed after just a handful of deeper cycle trips.

The single place to put money in an EV build that absolutely pays off, and you never regret it, is the battery

 

[Alster370]

well if I didnt discharge the car batteries more than 70-75%, they would still last a while right? Kind of a short term solution until I have enough for the lipos. does anyone have any figures on the amp draw for this motor?

 

[Jeremy Harris]

well if I didnt discharge the car batteries more than 70-75%, they would still last a while right? Kind of a short term solution until I have enough for the lipos. does anyone have any figures on the amp draw for this motor?

If you discharge car batteries to 70% then you might get a couple of dozen cycles out of them before they die, if they are new and you are lucky.

The best way to think of this is to think of what happens when you accidentally leave the car lights switched on when parked, running down the battery. Do this a few times and the battery just keels over, even though it gets recharged quickly.

Car batteries are designed to deliver very high current, for very short periods of time and to be discharged to around 10 to 15% maximum.

The only lead acid batteries that will last a reasonable length of time (maybe 300 cycles or so in this application) are deep discharge, or cyclic discharge, ones. They tend to be bigger and heavier than car batteries of the same capacity, and, has someone above has already pointed out, they often used sealed construction with an electrolyte gel which makes them much, much safer on a motorcycle conversion.

Cheap Lipo cells will typically give you around 15 to 10 times their amp hour rating as a maximum current, so a 20Ah pack would be OK for around 150 to 200 amps, probably as much as you might need.

As LFP rightly says, skimping on batteries is not a good idea, as they make or break the viability of the whole project.

Jeremy

 

[bzhwindtalker]

I've used some lead acid batts for a while, even the small 7ah ones could produce peaks of 50amps, but two of them in series sagged to about 16v, so they only delivered 4,5 or so Ah. if you need to use sla, be prepared for some serious peuket effect, but they are totally usable for hitting the road and even get some thrill!

 

[Alster370]

so Jeremy if I got two of these http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=8582 and put them in series I would be getting 44.4v and about 100a constant?

 

[Jeremy Harris]

so Jeremy if I got two of these http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=8582 and put them in series I would be getting 44.4v and about 100a constant?

They work fine, but 100A continuously is more than I think you'll want to cope with, off road on an a bike, as it's over 4kW of power. Also, remember that if you do pull 100A all the time from that pack it will last for just 3 minutes maximum...........

In reality, you'll find that your bike will probably need around 300 to 600W most of the time (so maybe 10 to 15A average on a 44V pack) with short duration peaks up to maybe a couple of kW or so. Remember that a reasonably fit person pedalling hard struggles to put out more than around 200W or so and many can't get more than around 100 to 150W for any length of time. 1kW is equivalent to 4 or five people pedalling hard, but without the weight penalty.

This pack will get thrashed a bit at that sort of current, but it will deliver it OK. You just need to accept that it's endurance won't be great. That pack has a capacity of 222 Wh maximum, so in theory you can pull 222 watts for one hour, 444 watts for half an hour etc. My guess is that it would last maybe 20 - 25 minutes or so of off-road riding if you took it steady.

Jeremy

 

[Alster370]

Thanks for the info Jeremy Although I will consider putting the 2 packs in parallel for a longer runtime. Having large wide tires (4 1/2") wont draw that much more Amps that a regular bike tires would? Im probably going to do a 1:3 gear ratio too.

 

[damonjackson_spl]

Hi there, the biggest thing i have learened is to join the lipo gang!! Im still not 100% confident on my skill level on the charging side but new off the shelf products are making it simpler for novices like myself!! If your adamant on using lead acid forget the scrap ones you have been talking about and buy sealed lead acid (sla) absorbent glass matt (agm) I think these were developed on the back of military gear and are quite good for ev use. You can get 20ah sla agm jet ski batteries from eBay cheap enough or if you are in oz. I can send you a link to a good seller. Charging is easy you can buy 48v chargers on eBay but you'll need a good amp rate otherwise you'll be waiting agers for it to charge!! But even this option isn't cheap. $240 I think I paid for 4 batts plus charger and your still stuck with the slow discharge rate!!

 

[etard]

You're definately jumping into the deep end of the (cess) pool Alster, but welcome to the forum!

RC builds such as yours are not cheap, RC on a friction commuter build can be cheap, but not a chain driven offroad machine.

4 batteries $225
Charger and balancer $150
controller ( Castle Controller HV 85) $150
motor $115
throttle $50
Sprocket and chain reduction $100
Random BS $50

So plan on spending $1000 all in with a used bike on Craigslist.

Are you still in?

Also the KV (180) of that motor is going to put you at roughly 7000 rpm at 44 volts which you are going have to reduce the speed down to somewhere near 350 rpm at the wheel, so you will need a 20:1 reduction. Even if you run it at 24 volt, you still need a 10:1 reduction.

Hope that helps...

 

[Alster370]

Ive compiled what I think will be the final electrics list, although I still going over the esc .

motor $100 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5139
lipos $90 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9176
charger $40 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5606
esc $40 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=10331
servo tester $6 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8296

total ~£200 inc P&P

 

[Ricky_nz]

Ive compiled what I think will be the final electrics list, although I still going over the esc .
esc $40 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=10331

The ESC is not an item you should be cheap on!
These motors want a big controller and will eat/kill cheap controllers for breakfast.
I would recommend that you use the currently best recommended option of one the castle creations controller as suggested by etard.
I would say go for the 160A version though even though you wont need that much current most the time it will help with longevity

 

[AussieJester]

only rc esc for this motor for e-bike use that will work is a castle creations HV160... period. Fitting halls sensors to the motor and using an Infineon
is perhaps more suited to your budget though... Either way, your wasting your money on a RC ESC if
its not a CC HV160. I would suggest the Turnigy 80-100 130Kv motor too will require less reduction...
Speaking of reduction what is your method of attack here? ...ES Forum member Recumpence
makes some nice cnc alumnium reduction drives these motors will bolt straight onto in case
you haven't stumbled on them before? Best of luck with your build anywayz mate...and welcome
to Endless Sphere

KiM

 

[Alster370]

Il go with the 130kv turnigy then, but I cant afford a castle creations esc. People say that this turnigy 100 esc has worked on some e bikes so I might give it a try.

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4691&Product_Name=TURNIGY_Sentilon100A_HV_5-12S_BESC_(Ver4

 

[Jeremy Harris]

Thanks for the info Jeremy Although I will consider putting the 2 packs in parallel for a longer runtime. Having large wide tires (4 1/2") wont draw that much more Amps that a regular bike tires would? Im probably going to do a 1:3 gear ratio too.

You can roughly work out the run time by working on the basis that you will use around the average power above. Just calculate the power capacity of the total pack by multiplying its voltage by it's Ah capacity. Once you have that number, just divide it by the power that you think you will draw on average and it'll give you the approximate run time.

For example, doubling the pack size to 4 of those packs you linked to, wired so that they form a pack that is 12S, 2P, will give you 44.4V at 10Ah, which is 444 Wh. This might extend your run time to around an hour at around 400W.

A side effect is that the pack will probably last longer, in terms of lifespan, because you're now only pulling half the current from each sub-pack. Lowering the maximum discharge rate makes life easier for the cells, and paralleling packs means you have a lower pack internal resistance, so lower losses and high peak current capability.

Jeremy

 

[Jeremy Harris]

Ive compiled what I think will be the final electrics list, although I still going over the esc .

motor $100 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5139
lipos $90 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9176
charger $40 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5606
esc $40 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=10331
servo tester $6 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8296

total ~£200 inc P&P

That ESC won't run on a 12S pack, as it's limited to 6S maximum. It will also die within a few minutes of use on an ebike, in fact it might not survive the first few seconds of use.

If you want to use an RC controller on a fairly high power bike for off road use, then I agree with Kim, go with the only controller we know that will take this sort of use, the Castle Creations HV range. It'll blow your budget, but at the moment we don't know of another controller range that will survive this sort of use.

The cheap Turnigy controllers have been found to work on low power assist set ups, used on road (like Keplers friction drive), but pretty much anyone here who's tried one on a powerful bike has found they simply cant cope with low speed, high torque operation.

Fitting Hall sensors and running on a cheap ebike controller is a good budget option, but needs some work. It does give very good results though, with excellent bottom end torque.

Jeremy

 

[Alster370]

Il have a look into hall sensors as an option, it doesn't look to complicated. I think I will go for 22.2v 10A setup with the lipos giving me about 4000rpm from the motor. then give it a 1:2.5 reduction to take it down to 1600rpm which would give me about ~31mph tops which is spot on.

 

[liveforphysics]

Il go with the 130kv turnigy then, but I cant afford a castle creations esc. People say that this turnigy 100 esc has worked on some e bikes so I might give it a try.

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4691&Product_Name=TURNIGY_Sentilon100A_HV_5-12S_BESC_(Ver4

You'll just be disappointed watching it turn to smoke, and have a $100 less money to buy the Castle 160amp.

 

[olaf-lampe]

Il have a look into hall sensors as an option, it doesn't look to complicated. I think I will go for 22.2v 10A setup with the lipos giving me about 4000rpm from the motor. then give it a 1:2.5 reduction to take it down to 1600rpm which would give me about ~31mph tops which is spot on.

1600rpm on the rear wheel?
I guess you better calculate again. Maybe you mixed rpm with rounds per hour? 1600x60=96000
-Olaf

 

[Jeremy Harris]

Il have a look into hall sensors as an option, it doesn't look to complicated. I think I will go for 22.2v 10A setup with the lipos giving me about 4000rpm from the motor. then give it a 1:2.5 reduction to take it down to 1600rpm which would give me about ~31mph tops which is spot on.

Bear in mind that 22.2V at 10Ah is still only 222Wh, so you won't get very much endurance from it, maybe 20 to 30mins at around 400W average power. If you want to ride at 30mph then you'll find that the range with such a low pack capacity will be quite modest, as I think you'll find that it will take about 800 watts to make an ebike do around 30 mph. 800 watts from a 222Wh pack will give you barely 15 minutes of endurance.

Jeremy