Lowest cost per cycle ebike battery

[mark.curry3]

Putting costs aside for a moment, I have been researching the NMCs go in a 60V bike and the ones I found ADVERTISE a charge cutoff 71.5 and discharge cutoff at 46.75. the LIFEPO4 (20s) states a charge cutoff at 75v and discharge cutoff at 44V. To me this indicates an operating voltage range (for lack of a better term) of 24.75 vs 31 or a 6.25v difference. Will this equate in getting less travel range from NMC than LIFEPO4?

and has anyone had experience with this
https://www.aliexpress.com/item/app-48V-40Ah-Electric-Bicycle-LiFePO4-Battery-BMS-Charger-Bluetooth-GPS-control-5V-USB-Port-Pack/32784984337.html?spm=2114.01020208
battery with an app that shows capacity left.?

 

[Ianhill]

Putting costs aside for a moment, I have been researching the NMCs go in a 60V bike and the ones I found ADVERTISE a charge cutoff 71.5 and discharge cutoff at 46.75. the LIFEPO4 (20s) states a charge cutoff at 75v and discharge cutoff at 44V. To me this indicates an operating voltage range (for lack of a better term) of 24.75 vs 31 or a 6.25v difference. Will this equate in getting less travel range from NMC than LIFEPO4?

and has anyone had experience with this
https://www.aliexpress.com/item/app-48V-40Ah-Electric-Bicycle-LiFePO4-Battery-BMS-Charger-Bluetooth-GPS-control-5V-USB-Port-Pack/32784984337.html?spm=2114.01020208
battery with an app that shows capacity left.?

What it equates to is lifepo4 battery's have a wider operating voltage which is not desirable, the lower the volts go the more amps are needed for the same output wattage, So any system with a full battery is faster than one that's flat and with lifepo4 this is exaggerated but with a Nmc it holds its volts higher giving more usable power output to the end of discharge that's if the packs are comparable with capacity and voltage and both are discharged comfortably below their c rating then nmc wins every time and lifepo4 will never discharge as hard as the nmc cell so its on the back foot from the get go.

 

[mark.curry3]

Thanks. To my uninformed thinking a wider operating range seemed better. Now i get why it is not

 

[2old]

FME, whoever it is; don't consider Dillenger; two 36V, 10 a/h batteries died precipitously after a year and 50 or so cycles --- horrendous.

 

[LockH]

Looks like the car companies are going prismatic or laminate versus 18650s...

 

[Ianhill]

I think the only benefit the Tesla pack has over the rest is a greater surface area in contact with coolant so it can be used in more harsh conditions and its easy to keep its temperature stable. They work amazing in California but in a harsh cold conditions battery's fall on their face not sure on how the cars perform in real life with ice and snow but one things for sure the range drops drastically. Same as a combustion engine the charge air is more dense so there's more output available but the heat generated by the block is lost to ambient faster so the efficiency drops a little and mpg is worse in cold climates. There's loads of room for crazy new thinking with heat management systems that transfer it to where its needed or try and recapture the heat into electrical rather than dissipate it through sinks etc, That way the cycles can be extended with current gen tech just implemented better as the generations evolve with slight performance increases the way the manufactures always work keep a bit in the tank for reserve so the market has not cornered them they release a mildly moist product where competion oil pays to well not to so we have a electric focus thats only nw begins to compete with other fixed EVs at 100+ mile range while the ice version gets the focus rs drift mode and all the chilly sauce and spice bits one can handle.
Why not combine them to make a focus ERS and blow away supercars then the sauce will have steam coming off it and smoke out of your ears every time you get behind the wheel but its too much of a risk to actually blow people clean off their feet in amazement.

 

[999zip999]

The difference is you definitely definitely know when your 18650 cell pack is getting low with a lifepo4 pack it dies at the end. So know and understand your range will the lifepo4 pack

 

[Alan B]

A123 LiFePO4 is good stuff, but there are lots of counterfeits out there and finding a reliable quality cell at a good price for any cell is problematic. A lot of suppliers are not trustworthy, and even trustworthy ones can have counterfeits slip into their supply sources at times.

After sitting around a few years with modest use, my collection of LiFePO4 is not exhibiting the published performance specs. There is not only a cycle limit, there are also time limits on the life and performance of cells.

Your experience with Lipo indicates some problem, that is not typical with quality product. The 20C lipo is the lowest quality available, it may contain all the cells that failed testing for higher C ratings.

I question the philosophy of trying to make an ebike battery that lasts too long. Ebikes and/or their battery packs are frequently stolen, crashed, reconfigured, killed by bad chargers, BMS's, failure to fabricate and maintain the wiring adequately, and just plain lost interest due to newer better technology. Would a 20 year battery be desirable? 10 year? Even 5 years is a long time for technology. So you may want to aim for a reasonable life at a lower cost and save the funds for something else. So frequently going for the "best" is not a good investment (especially if it results in more bulk or weight on an Ebike). In project management the phrase "better is the enemy of good enough" is commonly used. You want a battery that is "good enough" while a "better" battery may not result in a better "return on investment" and results in an increase in "total project cost". What is the "life cycle" of an ebike? Do you want the one battery to last the entire "life cycle" or would you rather upgrade it during the bike's life? Manufacturers don't rate hubmotors for all that long, they tend to develop corrosion internally (or clutches and/or gears fail) and need periodic service (that they don't usually get) or replacement, especially of operated in moist climates and bad weather. Even commercial ebikes don't seem to last many years, look at the broken ebikes on Craig's list. Even my own ebikes (and many others here on ES) end up reconfiguring ebikes periodically for various reasons.

Just something to consider when trying to make the "best" of anything, it won't be best for long, and you might want to reconfigure/improve it before you have received the value of the extra investment not fully amortized yet.

 

[999zip999]

Does the daily or almost daily use of a battery of charging discharging and recharging keep it more alive than a battery that is forgotten and charged two months later on a regular basis ?

 

[amberwolf]

To me this indicates an operating voltage range (for lack of a better term) of 24.75 vs 31 or a 6.25v difference. Will this equate in getting less travel range from NMC than LIFEPO4?

It's not about the volts, it's about the Wh.

Whichever pack has the higher Wh available to you, *at the power level you use it at*, *under the conditions you use it at*, will give you more travel range.

 

[Ianhill]

Does the daily or almost daily use of a battery of charging discharging and recharging keep it more alive than a battery that is forgotten and charged two months later on a regular basis ?

I bought a head torch with two 18650 nearly two year ago now and I charge the cells with a hobbie charger so I get to see the charging rates but not the discharge.

Personal experience when a 18650 left to sit vs one cycled once a day in a low powered head torch both still performed identical with charge capacity the non cycled battery showed a lower IR so it could still push higher amps with less strain and the cell that had the millage took longer to charge.
So keep you packs at storage charge in a non humid area at 75F temp with no sun light like vampires check at least fortnightly balance when needed and only charge when you intend to discharge.
I've heard of people freezing batterys but I've never tried it I think the science is less electrons move in the cell but every battery I've discharged in the cold hates it andnitndoes wonders for its lifespan so I say 75F throughout its life wherever whenever and your golden.
The current crop of EV battery's are used in a charge when possible fashion so it will be interesting to see the variants of distance achieved throughout the batterys complete life.

 

[Ianhill]

There is info on LiFePO4 longevity, so search for that if you'd like more (I've got A123 cells nearing 10 years old that held 95%+ at last count)... but do not mistake cheap LiFe for A123. That being said, the specs from 75-44V don't make sense for any battery unless you consider absolute minimum-- not standard operating range.
The benefit of LiFe voltage is that your power and speed are nearly constant, versus the dwindling power (assuming the battery is the limiting factor and not the controller) and dwindling speed (as voltage drops more precipitously with other types-- a disappointing experience IMO). You absolutely can estimate your capacity according to voltage with LiFe, you just have to be more precise(hundredths) and know your battery well enough to do the math. However, Wh are best.

I find with my lipo the capacity advertised is discharged between 4.20 to 3.60v, it drops to 4.05v fast then holds around 3.9-3.8v till end of discharge, there's barely 1 or 2 mph in it from full to flat and torque is good throughout but the system is well rounded nothing is struggling and the gearing just right for my torque and weight.
When I look at lifepo4 discharge graphs they appear more linear so the power is a gradual lose compared to a flat discharge steep drop off of lipo.

 

[Alan B]

Just for fun I'm going to take a new cut at this. From the top.

To minimize cost, as the title requests:

Build more packs from tool and laptop 18650's salvaged from packs that have gone "bad". They won't last too long but the pricing is very low. Probably as cheap as you can go. Well, maybe not the cheapest, some techniques below might be free or even profitable...

Use Walmart car starting Lipos and wear them out before the warranty is done and get your money back. Maybe even make a small profit. (It's been done).

Buy Lipo on deep sale. By the way, a lipo pack that is lightly cycled and properly managed will last far longer than a few hundred cycles. Don't know where you got that, but it isn't correct. I've gone years with Lipo, charging twice per workday (up tp 50-70% cycle) and it was no problem, the batteries didn't die in a couple hundred cycles.

Buy LiFePO4 on clearance - prices are occasionally fantastic as people move away from them and there is some really great fire sale pricing.

Have wesnewell build your packs for you.

What not to do - buy the latest technology with the highest promised performance - this always costs more.

Also don't put your location in your data so people cannot be as helpful with suggestions about local sources. Either keep it a secret or bury it in the conversation so it gets lost and you miss out on useful feedback.

Think out of the box. Solve the problem in some other way - I solved the problem of wearing out my commute batteries by cutting out the working (and commuting) part. Now my batteries last a lot longer. Work via internet, win the lottery, retire, marry rich, trade stocks and bonds, real estate, etc. Lots of information, seminars, etc on how to do this, must be easy. Move near your work. Get a job close to home.

What really to do - buy a good commodity product that is widely used, generally something that is used for (or built from components for) a much larger market. One example might be 18650 cells like the ones Tesla uses. They have pushed the cost, reliability, safety and performance way out there and the price down. This is where the price/performance is optimized, the research has already been amortized and the best value lies.

In the particular case of the Tesla perhaps used modules are available at even better pricing. Buy a full vehicle pack and sell most of it off at a modest markup so the part you keep is free.

Make ebike batteries and sell them, using the profit to pay for your own batteries, which are then free.

Also - for commercial packs - buy from a reputable distributor that you can get service from. If a pack needs a cell replaced or a BMS you need access to that service, and shipping a lithium battery with known problems can be subject to huge fines. Buy it locally, build it yourself, prepare to deal with that in some way or another, or be prepared to discard a costly pack and re-purchase if something goes wrong.

Treat your batteries properly for longer life. Your experience and expectations for pack service life seem to be very low for some reason. Make the pack large enough that you can live in the 20-80% charge range for "normal use". Store at proper temperature and charge state. Use quality chargers that treat the cells properly. Keep them balanced. Don't charge past 80% often, and when you do, run it down right away. My commute machine eventually got an upgrade to Multistars at 32 amp hours, and the most I would use for a half-commute was about 13 amp hours. They just last and last. Plus if I have to I can make a roundtrip commute without charging. For longer trips I parallel another 8 amp hour booster pack and take it up to an even 40 amp hours at 75 volts hot off the charger. It goes a long way.

Or buy a used Nissan Leaf - get a 24 kWh pack for about the price of the batteries alone. Drive that for awhile, especially in bad weather and see if you still want to ride your ebike anymore. The range is 80 miles or so and it can carry more than my ebike in either passengers or cargo. It is warm and dry inside, the stereo is better and the seats are leather (or something like it). Used electric cars are cheap - not too many folks are buying them so a 40k$ car with a 6k$ battery is selling used for 5-12k$ or so.

I love my ebikes, but the used Leaf SL is really nice too. Tennis team practice is 20 miles each way, it is 40 something degrees out and dark, and the route is 2/3 freeway (yes, this is real). Do I take the ebike? The heated seats are really nice on those tired muscles, especially on the way home. If you set the timer the car will already be warm before you get in, at least for the outbound run.

I hope you enjoyed this. In spite of the humor there's a lot of experienced based data in this posting.

Have a great 2017!