CR-E “250” Project

Bike I recently picked up and looking to make it even better than it is.

2017 CRF250R
18” rear, and 250X forks
QS138 V3
72V BAC8000
Home made 72V 34ah battery

Gearing is currently 12/63 using a 428 setup, which I think I want to change. I have a 12T 520 front sprocket that came with the bike and multiple 48-53T rear sprockets as I use the same rears on my 450

Bike is super clean, chassis etc is perfect. I picked it up for an extremely fair price as is, turn key ready to ride.

Im setting the bike up for cross country riding and racing. Most the events around here are between 5-25 miles long

Battery is way too small. Currently I get about 12-17 miles out of it depending on how I ride. I really need about 25 miles of range.

I’m thinking move to 96V 50ish ah battery if I can get something that will fit. And maybe to a Votol controller, I’ve read the ebmx is better but just not in my budget at the time.

I see lots and lots of 72v bikes but seems to me since I need a new battery anyway, may as well move up to 96v unless there’s some reason why I shouldn’t??

Here’s a few pics to enjoy

Sharp CRE, looks like a great place to start from versus from scratch.

Nice build.
Thanks for sharing your current range.
What kind cells in your 72v/34ah battery?
In middle of my build and shopping for a battery.
Found good deal on a 72v molicel p42b battery 20s9p.
Such a good deal that has me contemplating grabbing two and just swap out.
Thinking of going with that as a stage 1 build until I can find a high performance quality 96v battery.
Went x9000 v3 so can handle the volts ok at 96v.

What vendors for a 96v batts have you been checking out?

Airboy808 said:

Nice build.
Thanks for sharing your current range.
What kind cells in your 72v/34ah battery?
In middle of my build and shopping for a battery.
Found good deal on a 72v molicel p42b battery 20s9p.
Such a good deal that has me contemplating grabbing two and just swap out.
Thinking of going with that as a stage 1 build until I can find a high performance quality 96v battery.
Went x9000 v3 so can handle the volts ok at 96v.

What vendors for a 96v batts have you been checking out?

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P42A cells

I’d suggest 45B

Most likely having Amorge build my battery and after some research I actually think I’m sticking with 72V and probably doing a 20S14P which with 45B cells should net me around 72V60-63ah

Built my mock up battery using some specs here. Make sure it fits then get with Amorge

@Struggle:
Is that a hand operated rear brake? Cool if it is!
So you have a home made battery whose capacity is roughly 2.5 kWh but you want to use a bigger one. What are you going to do with that smaller home made one? WIll it be used as a swappable battery to extend the range of the new one?

Theo said:

@Struggle:
Is that a hand operated rear brake? Cool if it is!
So you have a home made battery whose capacity is roughly 2.5 kWh but you want to use a bigger one. What are you going to do with that smaller home made one? WIll it be used as a swappable battery to extend the range of the new one?

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Yeah rear hand brake

I’m going to a larger battery yes and will either sell this or use it on another project….which I don’t want to afford lol

Great project. I look at the aluminum welds, and laugh, they look like mine. The only good looking aluminum welds on my builds are in spots you can't see. But they have all proven to be solid.
Great choice on the X9000 V3 controller. I am going to try one of those soon. They have many great features. What type of riding do you plan on doing. I just finished this 2005 CRF for a friend. He wanted range so we put an Amorge battery in with 20S13P Samsung 50S cells. That gives him 65AH, (range) but not quite the current (power) for motocross tracks, he loves it. Amorge can build whatever you want for a battery including size shape voltage and cell quality. The Samsung 50S cells are medium priced, here is a price list from back in July and the shape they made for me, for a few Hondas CRFs I have done. This size and shape works in 2014 YZFs and newer too. The flat top gives you a little more working space above the battery.
Phillip did a little article here on this forum, on the last Honda I did. Don's lightweight conversions
If I can help you in any way, just ask. I am retired and love building these things. Here is an article from MXA they just happened to get of me at the World Vet nationals a couple months ago. 50K views · 846 reactions | Check this thing out! Don't Cox builds home-made E-Bikes with this one roughly getting around 45 HP. | Motocross Action
And here is a YouTube of part of one of the races. The electrics are more than competitive with the ICE bikes

DonCox said:

I just finished this 2005 CRF for a friend. He wanted range so we put an Amorge battery in with 20S13P Samsung 50S cells. That gives him 65AH, (range) but not quite the current (power) for motocross tracks, he loves it.

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So those Samsung 50S cells, compared to others of similar price, are more energy dense and less power dense. What happens if someone for example uses that bike in a MX track and asks for current above the value rated for continuous delivery for too long? Will the cells overheat and will the controller or the BMS notice that and limit the current?

Theo said:

So those Samsung 50S cells, compared to others of similar price, are more energy dense and less power dense. What happens if someone for example uses that bike in a MX track and asks for current above the value rated for continuous delivery for too long? Will the cells overheat and will the controller or the BMS notice that and limit the current?

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Good question, yes they produce more heat. They are not good for more than 25A without creating heat, so I have been told by Amorge. But in this configuration 20S13P is about 325A (13 x 25A) , I set his Mode 3 and Sport at 350A, and you would have to hold the throttle wide open for quite a few seconds to het them up.
He and his neighbors like his Honda 250 CRF electric so much his neighbor is buying one of my other builds, my old YZ250F Electric. Same parts except 20S12P Molicels P42A battery.

DonCox said:

Good question, yes they produce more heat. They are not good for more than 25A without creating heat, so I have been told by Amorge. But in this configuration 20S13P is about 325A (13 x 25A) , I set his Mode 3 and Sport at 350A, and you would have to hold the throttle wide open for quite a few seconds to het them up.
He and his neighbors like his Honda 250 CRF electric so much his neighbor is buying one of my other builds, my old YZ250F Electric. Same parts except 20S12P Molicels P42A battery.

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Ok so 350 A @ 72 V = 25 kW as a peak power. The voltage is 72 V because 20 • 3.6 V = 72 V. ASAIK, thoug, the real voltage of the battery depends on the SoC and according to a datasheet I've just found, for each Samsung 50S cell it ranges from 2.5 V to 4.2 V. So, in theory, you would have 84 V and 29 kW at full charge and 50 V and 18 kW when discharged. I think I've read somewhere that the first Altas felt more powerful when fully charged and that then they changed this and the newer ones got into a limited power status only when the SoC was lower than like 20%, that's what I remember, I may be wrong. For the Stark, I've never discharged it to less than 14% if I recall correctly and I've never felt any power reduction, but maybe the battery is so powerful that with my power usage and power settings it didin't need it; faster riders reported a power reduction below something like 20% or 10%.
How is this handled in your converted bike or in a converted bike in general?

DonCox said:

Great project. I look at the aluminum welds, and laugh, they look like mine. The only good looking aluminum welds on my builds are in spots you can't see. But they have all proven to be solid.
Great choice on the X9000 V3 controller. I am going to try one of those soon. They have many great features. What type of riding do you plan on doing. I just finished this 2005 CRF for a friend. He wanted range so we put an Amorge battery in with 20S13P Samsung 50S cells. That gives him 65AH, (range) but not quite the current (power) for motocross tracks, he loves it. Amorge can build whatever you want for a battery including size shape voltage and cell quality. The Samsung 50S cells are medium priced, here is a price list from back in July and the shape they made for me, for a few Hondas CRFs I have done. This size and shape works in 2014 YZFs and newer too. The flat top gives you a little more working space above the battery.
Phillip did a little article here on this forum, on the last Honda I did. Don's lightweight conversions
If I can help you in any way, just ask. I am retired and love building these things. Here is an article from MXA they just happened to get of me at the World Vet nationals a couple months ago. 50K views · 846 reactions | Check this thing out! Don't Cox builds home-made E-Bikes with this one roughly getting around 45 HP. | Motocross Action
And here is a YouTube of part of one of the races. The electrics are more than competitive with the ICE bikes

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I know you’ve built a few of these and have a good bit of knowledge. I also know you don’t know me from Adam

With that said I find it a bit funny to dog someone’s welds, mind you I didn’t build this bike nor weld those spots, however the guy there did…whom I also don’t know other than meeting him to buy the bike and reading his posts on another forum did these welds about 4 years ago…..before many people on this page even dreamed of building such a bike.

Now with that off the table. I’m new to this e bike thing. I ve been riding for my whole life, short as it has been at only 46, but I currently ride mostly adventure stuff on my 450RL, and I ride cross country, with it a little and my XR200, which I also race in a vintage series.

I’m planning to do cross country races with this e bike. I’m looking to get to the 30ish mile range, most races are 60-120 mins so 30 miles more than covers is.

I’ve emailed amorge, Annie there a few times with some solid specs, used a drawing from here for a battery and I’ll say I’m less than impressed with her replies. This doesn’t mean they don’t offer a great battery at a fair price but so far she’s been less than desirable as a sales person. Especially since I came to her with all the specs up front.

Anyhow the bike functions awesome, I’m going to gear it a little taller. It’s currently running a 428 chain… 12/63 gearing. Very short for hard enduro. I’m going to 15/63 to give it some room to breath.

I’ve debated 520 setup but really not sure it needs it.

@DonCox I respect your builds and I’ve read all your posts. As well as dave daum and others. You guys have tons of r&d into these things and it’s respectable.

Hey Struggle, Sorry you took that as dogging on someone's welds, but I knew that you bought it that way, and didn't do it. I am just as bad on my aluminum welds. I would recommend going to the 520 sprocket setup and when you get a good sized battery, you can run 13, or 14, / 50, and still have a whole bunch of power. I run 13/51 and a friend runs 14/50. This gives you good top end when you need it and still good low end. A 20S12P P42A Molicel cells ( a 50.4AH battery) battery will give just about 30 Miles of single track, and about 12 laps on most tracks. There are better cells, and more expensive cells to give you more range. If you plan on going with 20S14P and you want range more than power, go with the Samsung 50S cells ( 20S14P Samsung 50S cells, will give you 70AH). That will give you more range, more like 35-40 miles, but you can't ask for 400As for very long without overheating the cells. The Molicels can handle the higher current, but are more expensive. Here are some prices from Amorge on a 20S13P battery and the cost differences per cell .
I hope you have better luck at Amorge. I work with Allen there. (Allen@amorge.com) He has taken care of me there

Sorry for the misunderstanding on my part.

Don

@DonCox no worries as I said and you know I personally didn’t do the work, but it has held up for along while.

However I basically bought the rolling chassis, just so happens it’s also a running bike. And fun at that.

I picked it up with full intentions to make it better in many ways, from functional to appearance.

Im going to make this post too long lol

I would like to ask some questions, as I understand gearing, final drive ratios etc on ICE bikes. But the way electric makes power and tq is obviously very different. Right now at 12/63 428 it’s 5.25 with like a 12.3 final drive which is way too short for the racing I plan to do. I “think” I need my final drive in the 8-9 range. I don’t care much for having more than 50 or so mph top speed but I need the mid range. Right now it does hav a lot of tq and I tuned the throttle ramp back a little to make it more rideable which has helped. But what it’s missing is the power at say 10-20mph being able to lift the front end over a log, hole etc.

Now batteries, I think I want 55-65ah curious if the drawing you showed above allows for more or less capacity than the drawing I’ll attach here.

And I think I’m going to stick with 72v for now and maybe even my BAC8000 controller. I can’t really find a reason to go to 96v for my application.

Then with cells I have been confused between the Samsung 50s the molicel 42s and 45s. I had been leaning toward the 45s but I’d like to hear more about the additional range the Samsungs would provide vs the 45s because the price difference is big! And how much “power” I’m losing by going that direction. I’m looking for 250-300 4T power no need for 450 power.

Thanks for the help as I said for the last two weeks I think I’ve read every dang build thread here and at endless-sphere as well as the electric Facebook pages

Scott

I am kind of curious that this bike doesn't wheelie quite easily, With that low gearing. I am about 9 to 1 on mine . Yes between 8 to 9 to 1 is the right range. I have very little experience with the BAC 8000 controller, but the Votol has 3 modes and then Sport mode. In Sport mode and with the the most responsive throttle setting the front end will come up. Also you need between 300 and 400Amps. Does your homemade 72V 34AH battery put out 300A. Do you know what cells are in it? If they are Molicels you might have 300-350A for a short while. The battery shape I sent a picture of, with the flat top, can get 20S13P cells in it. The other battery you pictured, can carry a few more, but there is no space on top of the battery to interface all the cabling.
Cells are tough to choose the perfect all around best cell. You can't go wrong with Molicel P45B cells. Good range, and they can carry the big current (45A per cell) , with no heat buildup. they are very reliable. The Samsung 50S cells will give you 10% more range, but are only safe at 25A. Anything higher will cause heat build up. The EVE 40P cells will give you less range than the P42A cells, and can carry 40A, and are inexpensive.
The range is a product of the mah the cell contains P45B have 4500mah, the Samsungs 50S have 5000mah, the EVE 40P is 4000mah. The other component is how much current the cell can supply without heat buildup.

They are molicel 42s in the battery, as to what it puts out I really don’t know. But the bike will wheelie, it will do just fine as lower speed.

Maybe im asking too much of it to power wheelie over stuff at speed. I’m used to my 450RL I suppose. The power curve just seems to really flatten out. And I’m thinking maybe taller gearing will keep the motor in a better spot for longer.

I need to record some data and see what sorts amps it’s actually pulling and go from there.

Either way I need more battery as 15 miles give or take a couple isn’t going to cut it for me.

I don't know the BAC8000 controller, but I just love the Votol EM260S controller. I have used them on most of my builds, I can program it, and it works. A Votol EM260S controller is $400 . I can send you a complete harness tune to put on your bike and it works. I don't have a spare EM260S, or I would send it to you. I have a few EM150Sp/2 which work on smaller bikes ( KX35, YZ 85 etc) but it is only good for about 200A
I think you mentioned you are thinking of buying a X9000. That is a good choice, but it is expensive. They have a tune for your motor, and good tech support.

Yes I’ve really looked at using the Votol instead. It’s much more affordable. I want some sort of digital dash I know that. And I think I’ve seen your builds having something like that.

Does the votol have a display that can be seen using iPhone or even an android? I need to get this battery figured out. While I’m waiting for that to come in I’ll probably pick up a votol…which one is the best? That way I can learn to tune it while waiting on my new battery.

Now….is there a benefit to 96v? Considering my application. Zero motocross….heavy trail use, fast cross country racing etc. now is the time to swap if theres a benefit.

I went for 96 volt thinking I could drop the power level to conserve battery. In the end I think 96 volt consumes more energy as my range isn’t the same as 72 volt. So if you are looking for range I think 72 volt is the better option.