# LiPO:s for a MX motorcycle.



## lasse55 (Nov 24, 2011)

I am EV-converting a Honda CR (motocross). It’s equipped with a 5kW 48V 100A motor (15kW 300A peak). 
LiFePO4 batteries that can deliver 300A are too big (they get damaged in all the crashes that are obvious on every MX-bike). LiFePO4 with a size that suits (can be protected) deliver too low current.

So I plan to use 8pcs of LiPO 5000mAh 6s (2 in series x 4) because of the large current they can deliver, the low weight, small size and lower cost.

Mileage has a low priority. Output high.

"You don’t use LiPO in a vehicle, you must use LiFePO4" (TS), battery-dealers say. I ask them "why"? 
No one of them can give a proper answer.

So I ask you, why should LiPO:s not work in a MX bike?

I know the disadvantages of LiPO:s. 
I mount them protected in a removable tray, and charge them outdoors at good weather. Handle them carefully and so on.
They are supposed to be fragile, but I have seen RC-cars and buggy’s on YouTube……
Jumping like madness and crashing into the ground. Rolling, flipping over and loop. 
I can’t think of a more violent way to treat them.

I can’t see why they don’t fit my MX

This is my project, with two borrowed LiPO:s. 
To protect the LiPO:s, the controller is limiting current to 100A. http://www.youtube.com/watch?v=sMjffhBHw8o


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## Yabert (Feb 7, 2010)

Lipo can be more dangerous if you don't use correctly. They will need more care and attention, but I think it can be interesting to use it in small quantity for a toy. (your MX...)

Take care of the low voltage and high voltage and go for it. If not, you can watch for headway cells or A123 20Ah. Both are LifePo4.

But, a such small battery pack will give you less than 3 mins of riding at peak power.


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## lasse55 (Nov 24, 2011)

Yes, my bike is indeed a toy project.........
I am deeply impressed by your Suzuki DRZ SM 2005 electric. I deal a lot with different inventions and can see you put a lot of work and knowledge into your bike. Respect.

I have looked at Headway, and made a lot of measurements on my bike to fit them in.
As I want at least 16s/2p, there isn’t enough space to mount them in one "row".
I must have at least 2 "rows" (beside each other in their length axis) and then they poke out to much, and will be destroyed in the first of overturn.

However, a Chinese dealer promises that their Headway 40160 is capable of 90A cont and 250A peak (5 sek x 6 /minute). 
I don’t know if I believe those data. 

Should i?

If so, it is enough with 16 pcs and I’ll be able to mount them in one row (inside the frame, nothing pokes out).


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## Yabert (Feb 7, 2010)

From my knowledge, the voltage of 40160S cell will drop under 2v at 250A (16C).

2v x 16 cells = 32v x 250A = 8 kw from the cells.... so probably less than 9 hp at motor shaft! It's not a lot of power, but for a 500$ battery pack it's not bad.
If your controller can take 2 more cells (58v nominal), your peak power will increase. What is your controller?


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## Jozzer (Mar 29, 2009)

Lots of people DO use Lipo in vehicles, and in motorcycles especially it makes most sense. All you need to do is make sure the cells don't get overcharged, overdischarged, or punctured and you will do fine.

You will also find it's possible to buy a good stiff pack of LiPo (brands like Turnigy) for around the same price as cheaper LifePo4 (like Headway).

Although the risks of a badly maintained LiPo pack are higher than a LiFepo4 pack, they are actually much easier to keep in shape, and have to be a lot further out of balance before cell damage actually occurs.

Discharge power is much higher, so the vehicle can run full power on a surprisingly small pack. I have an Aprilia RS125 fitted with 6KW/H of Turnigy, the pack could manage an astonishing 120KW, or even higher for short bursts..

Steve


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## lasse55 (Nov 24, 2011)

Yabert:
Thank you for sharing your knowledge that the voltage of 40160S cell will drop under 2v at 250A. I didn’t know that, though a lot of reading. 
This makes it even harder for LiFePO4 to deliver the power I want, as I can’t fit in 3p (or 4p) in the frame. 
My controller is an Alltrax AXE4844. Programmable overvoltage (max 60V). I don’t know if I can disable this limit, I don’t think so.
I have been thinking myself about making the voltage closer to 60. 
As with two serial LiPO 6S I get only 44V nominal. If I add 3s more in series I get nominal 55,5V.
But as the voltage of fully charged cells is around 4 volts, the voltage will be around 60. I guess there is a risk that my controller won´t start because of overvoltage?
Maybe I should add 2s instead?


Jozzer:
Good to read that there are people using LiPO:s in motorcycles. It encourages me.
How are the LiPO:s mounted in your bike? Are they split apart, so that the speed wind can cool them, or are they mounted together? The two LIPO:s I borrowed (total 12s/1p) run warm, around 40 degrees. But they run at 20C almost all the time (5Ah 20C limited to 100A in the controller).


A downside with many (12) LiPO packs, as I see it, is a bit trickier charging (many connectors for balancing and mains, and charging in rounds as there is no charger for all packs).


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## Jason Lattimer (Dec 27, 2008)

I just found a link on this site that advertises as Headway Headquarters. They have a special order 20c cell rated at 8 ah. They claim to be able to run 160amps continuously. Looks like a cool cell to check out.


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## Jozzer (Mar 29, 2009)

Hi,
The LiPo's don't need any cooling in my use, I mostly expect a half hour ride miniumum, and usually more like an hour, so the average C rate is low. Peak current is about 12C on most of the vehicles I've built with them.
Usually about a 10C temperature increase after a hard ride.. 

For charging, it is exactly the same as any other EV pack, I just plug in the Zivan.
The sub-packs are all paralleled at cell level inside the main pack and connected to either the BMS or the LVC/HVC protection boards, both of which will cut off charge when first cell hits max voltage (or cut of the throttle when LVC is reached).

For packaging, we make 3mm aluminium boxes, and pack the cells tightly inside, with added insulation then fit a waterproof lid. On most bikes, to get the best capacity possible, several boxes must be made, each holding a bank of cells in parallel, that then get placed in series with the other boxes.

The brand we use were fitted to a great many of the motorbikes in the electric world series this year (both TTXGP and FIM), and despite a great deal of abuse and a few track spills (including a completely wrecked bike), there were zero problems. I think they can take the inertail abuse much better that "can" type LiFePo4 cells (like headway), which actually get a lot of abuse to the cell teminals when shaken badly. We certainly saw problems caused by this to packs back when we used LiFePo4.

I also remember the trepidation of using LiPo the first times in a big pack, but now I wouldn't use anything else in a performance vehicle (at least, not anything I can afford!)

Edited to add..
You shouldn't try to overvolt your alltrax, they don't like it! Which motor do you have? Can it take a higher voltage? If so, upgrade to a higher voltage controller.. 

Steve


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## drgrieve (Apr 14, 2011)

Hi Jozzer do you have a build thread for your MX-5? Are you running the Kostov 11" @ 300V now?


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## Arlo (Dec 27, 2009)

If used properly lipo will be the best. One of the mods over on endlessphere makes a paralleling board for up to 6s pacs that sends a LVC signal at 2.7v and a HVC at 4.29v This is a back up save your ass set up.
Im building a cell level charger to charge to 4.2v a cell every charge!


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## Jozzer (Mar 29, 2009)

drgrieve said:


> Hi Jozzer do you have a build thread for your MX-5? Are you running the Kostov 11" @ 300V now?


 Not quite, last pack is now ready, we've just got to weld up a frame to hold them under the bonnet. Few more days....


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## Arlo (Dec 27, 2009)

This is the link to the sale thread for the protection boards. http://endless-sphere.com/forums/viewtopic.php?f=31&t=32460

I havwe been using 8 pacs of 6s turnigys for 2.5 years till recently I over discharged 2 cells and hurt my pack bad. So now I have some of these boards comeing for my next batteries.


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## Jozzer (Mar 29, 2009)

Aye, Patricks LVC/HVC boards are great. We need to talk him into making one for LiFePo4 too next


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## lasse55 (Nov 24, 2011)

Thanks Jozzer. I really appreciate that you share your experiences. Saves me a lot of trouble.
I’ll go for LiPO. Starting with 8pcs of LiPO 5000mAh 6s (2 in series x 4 parallel), and expand if needed. If I am right it should be 15c at peak.

But I am unfamiliar with charging of parallel packs, so I will do some net study to learn the basics. Not bother you with basic questions. 

I plan to use this for LVC while running: http://www.hobbyking.com/hobbyking/store/__10952__Cell_Log_8M_Cell_Voltage_Monitor_2_8S_Lipo.html
And this to use the LVC signal to turn of the controller.
http://minibms.mybigcommerce.com/products/MiniBMS-Head-End-Board.html

I use a Mars ME0909 motor 48V, so I guess I stay with 48V all the way.

I have a reeeeely bad movie of a garage test with two LiPO 6s 5Ah in series at http://www.youtube.com/watch?v=sMjffhBHw8o 


And a picture of an earlier stage: http://postimage.org/image/4mmo509lj/


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## sokon (Sep 15, 2011)

maybe this ones: http://www.hobbyking.com/hobbyking/store/__14074__ZIPPY_Flightmax_8400mAh_4S2P_30C_LiFePo4_Pack.html

Lipo like, but Lifepo. 30c continuous 0.7 $/Wh (better than 20Ah [email protected] 50$).


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## Arlo (Dec 27, 2009)

Or this http://www.hobbyking.com/hobbyking/store/__15521__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack.html
My cost is $21 a pack so $.28 a w/h pluss shipping. I have ordered 25 packs so far with no problems!


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## sokon (Sep 15, 2011)

sure, the lifepo pack is more than double the price, but

- 50% higher c rate
- probably much higher cycle life
- safer chemistry

of course everybody has to find out for himself wheter the things mentioned justify the increase in price..

best,
sokon


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## Arlo (Dec 27, 2009)

I don't use lipo because of price. I use it because its the highest performing battery available. If you look at the grams per w/h the lifepo4 is 8.25 grams per w/h and the lipo I listed is 7.13 grams per w/h

And the size in terms of cc per w/h with the lifepo4 you listed at 4.39cc per w/h and the one I listed at 3.72 cc per w/h

Not only are the batteries I listed cheaper they take up less space and weigh less helping performance! When you parallel 4 pacs the c rating is major over kill. I have personally put over 300amps on one of these batteries and its fine. I only shared the link because of price if you want better C ratings and or quality I suggest a nanotech they are now over 100c ratings and higher cycle counts as well. I personally spend as little as possible on performance batteries because battery technology is advancing like computers in the 90's!


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## sokon (Sep 15, 2011)

Hi Arlo,

as I said, if safety and cycle life is not a concern for you, then probably lipo is the way to go.

It seems that what you call performance is energy density (wh/kg and wh/l). There are better cells in terms of energy density than those that you quote (which are indeed not bad at 140 wh/kg compare with 133 wh/kg for a123 20Ah cells). Have a look at NMC cells, they have energy density of around 160 to 180 wh/kg. However, for a small battery pack as discussed in this thread, I think it is not crucial to get the last little bit of energy density...

best,
sokon

Edit: Also consider that every EV that bursts up in flames will damage the reputation of EV. It will make the laws of how to make diyEV street legal more restrictive for all of us. That is the main reason that I am not so much a friend of advertising an inherently unsafe battery technology for building/converting EV. Sure, people will say that if lipos are treated right then they will behave nicely... on the other habnd, there will always be somebody not to trat them nicely enough


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## Jozzer (Mar 29, 2009)

Worth mentioning here that of all the motorcycles racing at TTXGP this year, the only one to go up in flames used "safe" Emoli cells..


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## lasse55 (Nov 24, 2011)

Now I think I got a clue how parallel charging works. Seems like a real work saving thing. But I have found one contradiction. 
I need to get this solved before I can order a proper charger.

This is the contradiction I found:

“Correct charging of LiPO:s should be 1c. Some packs can manage 2c, _but current must never be below 0.5c. Otherwise the cells will be damaged”_

“No matter how small your charger is. The charging only takes longer time with a small charger”.

If the first sentence is correct, I need a 30A charger (8x5Ah), 660W (22V x 30A) for 1c charging. At least I can’t go below 15A 330W without damaging the cells.

If the second sentence is correct, I can use any charger that can manage 6s. The only thing is that charging time is longer_._


What is your opinion?


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## Jozzer (Mar 29, 2009)

You can charge at anything BELOW 1C. 8 x 5AH would be 40A of course at 1C anyway, so anything less than 40A will be fine.
I don't know where you found that statement that 0.5C will hurt cells, this is definitly not true..

You can use any size charger you like, as long as it does not supply MORE than 1C, or more than 4.2v X total number of cells in series.

Any cells tied in parallel at individual cell level will behave as if one larger cell.

Steve



lasse55 said:


> Now I think I got a clue how parallel charging works. Seems like a real work saving thing. But I have found one contradiction.
> I need to get this solved before I can order a proper charger.
> 
> This is the contradiction I found:
> ...


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## lasse55 (Nov 24, 2011)

Clearly answer! Thanks a lot! 

Sorry for my basic miscalculation.....


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## Arlo (Dec 27, 2009)

sokon said:


> Hi Arlo,
> 
> as I said, if safety and cycle life is not a concern for you, then probably lipo is the way to go.
> 
> ...


Yes you have a good point. we dont need EVs in flames. This is just a small off road motorcycle so not as bad but you wont have to worry about safety if you properly take care of lipo thats were Patrics boards come in. 
On the other hand yes NMC cells are totaly kick ass. But.... Where do you buy them??? They are not sold to the public the last I checked. One of the guys on ES posted a video of him beating on a NMC cell and it would not catch fire he said he also charged it to over 10v and nothing! Once they become availible yes thats what I will use but untill then. Lipo is cheep and the most logical to get my EVs built then down the road I will just change out the batteries for a new better cheeper type!


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## sokon (Sep 15, 2011)

I was in contct with somebody from

www.cleancarb.com

they claim to sell kokam NMC cells. However, I havent bought anything from the shop (yet) and cannot tell you whether it is for real or not.


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## Jozzer (Mar 29, 2009)

I'd not heard that Kokam were selling NMC yet, will check it out.
Kokams LiPo are 3 times the price of Turnigy however, even if you buy extremly large quantities (though they may well last twice as long), I expect thier NMC will be premium price too..


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## lasse55 (Nov 24, 2011)

It took five months to get the LiPo:s from hobbyking, but now they are mounted.
It was worth waiting for. The motorcycle runs really well.
Thank you guys!

http://www.youtube.com/watch?v=Wj_OjgApCEo


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## cosmo440 (Aug 28, 2014)

[/QUOTE] But, a such small battery pack will give you less than 3 mins of riding at peak power.[/QUOTE]

Forgive me as I'm a real newbie to this EV scene. How do you know, or more appropriately put, how do you calculate how much run time you'd have? I'm thinking of converting a Kawasaki KX100 (just about 100lbs. sans motor/exhaust) to 10kW 72v brushless motor, Kelly KEB72121E controller, and (4) 4S 10Ah 50C LiPo packs. I also considered running (3) 8S 10Ah 65C LiPo packs with the appropriate controller/motor. Wouldn't you need to factor in the rider weight, bike weight to know about the run time? I really want a bike that 's got some real punch to it off the line and I'm only looking for about 30 minutes of ride time. Of course nobody wants to throw their money away on an illogical project. Please help me out if you can.


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