Lifepo4 battery needed for qs138 70h v3

Tfisher309

10 mW
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Jul 3, 2022
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Hi, after reading this site for a month, thank you for all the info, I have started my first EV build. The frame is a 1967 H-D Sprint 250ss. I have installed a qs138 70h v3 motor and looking to buy a Votol EM-200/2 controller. I have room for a 72v 60a lifepo4 battery, but cannot find one with a fast enough discharge rate. Buying a EM-150 would get me closer to the batteries I am finding.

Can anyone suggest a battery supplier so I can use the faster controller?

Thanks again for all the great info. Tom
 

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For higher discharge rates lifepo4 look for A123 cells.
Or take Li-NMC power pouch cells they have diacharges rates up to 10C.
 
I have been looking for about a month and can't seem to find a good solution.

It seems most of the companies building lifepo4 batteries are for solar systems and have a 1c discharge rate. The best 72v 60ah lifepo4 battery I have found that fits my 400x250x250mm size limit has a 60a continuous discharge rate with 80a max. This doesn't seem enough power for a 3kw motor, 100kg bike weight and 120 cont. amp controller.

I don't under stand how phase currents are involved. Is this something that a battery needs to deal with?

My performance goals are low. Thirty or forty miles of city driving and top speed of 55mph would be plenty, no wheelies, burnouts or freeway driving.

Building a battery is not an option for me, can anyone recommend an American company who is building lifepo4 batteries?

I see batteries on AliExpress that would be perfect, if they can be trusted. Can anyone recommend a reliable vendor?

I appreciate any help I can get. Tom
 
After a month of looking LiTech Power has worked the hardest to come up with a battery for my bike, but I don't know if it is strong enough. I hope some of you with more experience can look at the specs and give me an opinion.

QS138 70h v3 cont 67a max 150a
Votol em-150 cont120a max 200a pulse 390a
32700 lifepo4 23S8P 48ah cont 48a max 144a pulse 240a for 5 seconds

This battery would push the size and weight limit that I set for the bike, but it would work. I just don't know if has enough power.
 

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I used 32650's for my e-moto, https://www.endless-sphere.com/forums/viewtopic.php?t=117496, so I can comment. I'm sure they're not exactly the same spec as what you're looking at, but they'll be close enough for a comparision.

I used 24s12p, and I built the battery myself. Total weight was about 110 pounds. Total bike weight was about 350 pounds. My speed and acceleration specs are similar to what you are planning for. At 12p, they're rated for continuous discharge of about 215amps, and short bursts of supposedly 700 amps. Luckily, I built it as a commuter, not a speed demon, so this is just fine with me. I can comment that while these cells technically can handle the high discharge rates, you will likely notice a bit more sag than what you will actually plan on. Again, I don't mind it, since I'm just commuting; and during normal periods of acceleration, I see average sag hover at right around 5%, acceptable in my opinion. But if I have to floor it for some reason, it sags to 10%. It rebounds back up quickly enough, and I have yet to have a situation where it sags so much that the BMS cuts off due to low voltage.

I would say with your planned 8p, you will see even more sag than that. And 23s? 24s would be better for a bit more speed. The bike is probably going to be heavier than you think.

Earlier in the post someone suggested A123 LiFePO4 pouch cells. On my next build this is what I will use as well, they are supposed to handle higher discharge rates better with less voltage sag.
https://batteryhookup.com/products/4-pack-a123-3-2v-31ah-lifepo4-cells?_pos=1&_sid=af0cd4445&_ss=r
If you used the above cells and were up to assembling it yourself (i know you said you didn't want to, but these shouldn't require spot welding or soldering), you could do 2p24s to get 72v nominal, 86V peak, 62ah, for about 4.7kwh. Weight for just the cells would be 30 kilos, call it 45 kilos with the cabling, connections, case, ect.

Can't wait to see your finished conversion. It looks so great so far, really nice starting point.
 
Tfisher309 said:
Can anyone suggest a battery supplier so I can use the faster controller?

What is the size of the battery box you're able to fit?:


Battery box size.jpg


If you can fit 20x22x65cm (8x9x26inch) then you can build a 20S2P battery out of the LG NMC pouch cells that member Tumich is selling:https://endless-sphere.com/forums/viewtopic.php?f=31&t=61608

And be able to use a stronger/higher amp controller.

LG NMC pouch cells.jpg
 
Thanks for the info. This forum has been great for a newbees.

Maximum size battery can be is 250x250x425mm, or 10x10x17. Because this is just a city commuter bike, no freeways and no long range requirements I would like to go with a Lifepo4 battery.

Another company says they can fit 24s8p in the available space: 45ah, 2c and 6c for 10 seconds. I don't understand the battery configuration, does 24s refer to the cell layout? And how does the P value affect battery performance?

The weight of these batteries are around 35kg so I would be ok there.

Harrisonpatm: I read your build and our situation is similar. However two differences stand out. I am not as comfortable with the electrical issues as you seem to be and this bike will be quite a bit lighter. It was 225lbs with ICE and I am hoping for 250lbs with battery.

Can you feel the voltage drop when riding or are you seeing it on your display? It would be annoying If it was felt as a lag in normal acceleration.
 
Tfisher309 said:
Another company says they can fit 24s8p in the available space: 45ah, 2c and 6c for 10 seconds. I don't understand the battery configuration, does 24s refer to the cell layout? And how does the P value affect battery performance?

the series S value allows you to reach the Voltage you require (eg: 24s x 3,2V = 76,8V nominal) - the parallel P value gives you the required power and energy (eg: 8p x 3Ah = 24Ah) - total number of cells is due by S x P so you can calculate weight and cost of the pack.

this is a very high level explanation - I suggest you to search on the forum and understand more about pack layout before committing on buy cells.
 
The S value affecting voltage above is correct, and an oversimplification answer is that higher voltage=higher speed.

P value of how many cells in parallel per series connection...this typically affects your range, more in parallel means longer range. But as I was describing earlier, it's going to also affect performance in that you're going to want to pull a lot of amps when you accelerate. If you try to go uphill fast, you're probably going to pull 150amps. An 8p battery means that the 150 amps will be shared by 8 cells in parallel, meaning about 19 amps each. Thats a lot for these cells, meaning you're going to see voltage sag, which translates to lost power. It's felt a little bit as an acceleration lag, but mostly it will be not felt, but rather seen as excessive stress on the batteries.

This is just one example using made up numbers. If you actually can get your build down to 250 pounds, that would help, but its still 250 pounds not including you. So I would worry that 8p using 32700 cells is going to not cut it: in addition to performance issues, it's going to stress the cells more than you think, which may shorten their lifespan more than you'd want.

A suggestion: could you compromise on the width of the battery? Something fatter and wider, to fit more cells ? Meaning you'd have to hold your knees open more when you ride, and less aerodynamic, but could payoff by being more able to deal with high amp draw.

The second company says that they can make 45ah, 2c, and 10 seconds of 6c. This means its rated for 90 amps continuous, short pulses of 270amps. I think you'll want more than that.
 
Thanks again. This information gives me much to think about. Up until now I didn't know enough to ask questions.

I was hoping to buy the battery this fall, but with winter coming I really don't need it until spring. In the meantime I'll look into the possibility of building a battery myself.
 
I don't know if you have gotten this thing going yet, but here is some information from a bike my son and I built and I ride all the time. Batteries are Headway 40152S. They weigh one pound each, and are fifteen Ah with threaded connections. Pack is built two parallel and thirty series(2P30S). So it is a thirty amp hour/ninety-six volt unit with sixty batteries. The machine has a Motenergy ME1507 motor and Kelly 8080IPS controller. Battery pack has an ANT BMS installed for management of those expensive batteries. The bike weighs 335 pounds without rider, and the direct drive sprocket ratio is 11/49 so like 4.5 to 1.
The battery current I limited to 140 amps to increase range but if I set it to 200 amps it will wheelie. It has plenty of acceleration for a 165 pound person. Maximum speed is 65-70Mph and the range I get depending on how I ride is 25-33miles(I have kept a log of rides so I can review things like temperature and miles traveled/percent batt left). These batteries are commonly run at the 5C that I use them at during acceleration and climbing hills like harrisonpatm says there for short periods of time, but the real question is how do they perform so I think that is pretty good. Sometimes you look at the current meter and it says like three amps too.
What happens while you ride it is if the battery volts sag to a certain level for a certain amount of time the BMS will shut off the supply to the system and it stops going. From experience if you just sit a couple of minutes they recover to the level needed by the BMS and the pack turns back on and you ride away(hopefully enough to get to your charger) otherwise just like any other bike you are pushing it. What I do is set the trip odometer after charging just like you do on a gas bike and that works pretty well.
It started out life as a Suzuki GS500E. QJVA0766.JPGIMG_0809.JPG
 
I put a 20s 74v 50ah lithium ion battery with BYD cells. I wasn't looking to build a battery and I couldn't find a LiFePo battery that would fit and have a fast enough discharge rate. I am happy how it turned out.
 

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That racks got as much character as the awesome conversion. Nice work.

How's the function and range?
 
Thank you. It has been a joy to ride. Around town it is far superior to my gas bike.

I wrote up my observations a while back in another post. "End of a successful riding season".
 
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