a cost benefit comparison of lifepo4 and lipo for newbs

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a cost benefit comparison of lifepo4 and lipo for newbs

Post by auraslip » Apr 01, 2011 12:02 am

In an effort to save a lot of beginners time and money I've decided to break down the real difference between lipo and lifepo4 packs. When I was new here I was VERY excited to see how inexpensive the lipo packs from hobby king were, but as I spent hours upon hours reading on the subject I realized that they were not only more expensive, but would not be convenient or even doable on my "charge anywhere" commuter bike. This excerise will show the true costs of both types of batteries on the most typical begginer bike; a 48v hub motor with a battery capable of putting out 30 amps continuously. Why 30 amps? Because that's about as much power most 48v kits are capable of.


14s lipo vs 16s ping, headway, and a123
48v packs capable of 30 amps sustained


I don't want to waste time here dealing with people saying, "you could do it for much cheaper with some little 500mah chargers and a voltmeter for LVC!" Yeah, of course you could, but then it wouldn't be at all comparable to the performance and ease of a lifepo4 pack and 5ah charger. That being said, I'll be using an hyperion 14s charger and decent power supply to charge the lipo. For sourcing the lifepo4 headway packs I've used victoria from headway for pricing. The 10ah packs are either the normal 10ah cells that are 3c (barely!) or the 8ah (9ah really) cells capable of 8c. The 15ah headway packs are made from the 16ah cells. For the 15c a123 I've used cell_man. All pack pricing INCLUDES SHIPPING AND A 5AH CHARGER.

Costs

Materials:
You'll need cell-logs to manually perform the lvc. You absolutely need cell level LVC, and don't let anyone tell you that you can use the controllers LVC. To charge in a decent amount of time you'll need an expensive charger and power supply. Sure you could do it for less, but the first time you want to ride your bike and you can't because the batteries take 10 hours to charge or your cheap charger breaks you will realize you've wasted your money. Also you'll need wiring, connectors, a decent soldering iron, heat shrink, and electrical tape, but I'll assume you already have most of that.

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You can plainly see that lipo loses every time in this power range. Lipo DOES become less expensive as you over come the initial investment, but even at 20ah the only more expensive option is a123 packs.

Time:
Building a lipo pack is easier than building a lifepo4 pack, but while the listed lifepo4 packs come pre-built, you have to build your lipo pack. It's not too hard, but it does require time and soldering. Another thing many people don't consider is the time to charge the pack. It's not as simple as plugging in the pack and walking away like it is with lifepo4. While it is trivial when using the 14s hyperion, using a smaller charger requires arranging the pack accordingly. For weekend riders who enjoy playing with their toys, it may be fun! If you're like me though and charge your bike several times a day (in several locations), It can be tire some.

User error:
Expect to mess up and break stuff. There is lots of room for error, and it happens fairly often here. Search for KFF. Even though you can't account for it, it will add to the costs. Even the best and brightest people here have had accidents, and I am of the mind that any handling of hot wires is dangerous and given enough time will eventually lead to an accident.
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Cycle Life

The cycle life of Lipo is up in the air. While some have claimed as much as 1000 cycles, others have had problems at 300. There has not been any studies done on R/C lipo, but there are quite a few done on other types of Lipo and they show %20 capacity fade at 5c and %80 DOD. It is totally possible to get 1000 to 2000 cycles out of lipo by using a very conservative discharge charge(%30-%90 SOC) schedule, but that requires a pack twice as large and removes any cost or weight benefits. No matter how you treat your lipo batteries, it seems discharging below %20 dramatically reduces cycle life. More on this later.
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This testing done by LG on lipo meant for cell phones. These batteries are discharged to %80 DOD.


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This is done at 1c and %100 DOD, but with a123 even high rates don't seriously induce cycle fade. The same can not be said for ping though.
If you use the conservative (%30-%90 SOC) with lifepo4 you can expect cycle life in the 5000 range, and even at %100 DOD it will still provide 1000-2000 easily.


Power

The high c rate(15c-90c) is the most touted feature of lipo. However, many of the people looking at lipo for it's low costs are using it in low power bikes so they have little to gain from it.
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1200w/52v = 23 amps.
This graph shows how much power a motor is capable of putting out. In practice the battery current is higher, but it still drops off considerably once you get up to speed. 15-20 amps is around the amp draw you'll see with the above kit while cruising at 25-30mph. (If you use the speed %120 mod, expect that to go up to 30 amps though) Even the lowest c-rate lifepo4 is more than capable of putting out the peak amps needed to get up to cruising speeds, so you could easily use a battery capable of only 20ah continuous if you didn't want the head room. This assumes that you don't do much stop and go riding, live in a hilly area, or ride off road. For those uses you'd really need a battery more capable of higher amp draws in the 30-35 amp range.

The low C rate ping is somewhere between 1.5c and 2c. This means the 15ah ping is happy doing 25-30 amps continuous, and the 20ah is fine with 30-40 amps continuous. This is more than enough.
The 10ah headway cells have a nameplate rating of 10c, but are are actually more like 2.5-3c. The 8ah headway cells (more like 9ah really) are the same form factor, but perform at 8c - 64 amps continuous. More than enough power for even some high voltage packages.
A123 are 15c, so even a tiny 5ah pack will be capable of putting 75 amps.


Reliability

It seems the biggest argument against lifepo4 packs is the bms. I do tend to agree that a cheap or abused BMS will be unreliable, but I think the number of reports of bms problems are skewed for a few reasons. The first being that bms users require no knowledge of the system and that trouble shooting bms requires in depth technical knowledge. So when a BMS fails, people almost always post asking for help. OTOH, when the various parts of a lipo pack fails, it's easy to see what has failed and how and simply order a replacement with out posting here. A well designed BMS will work flawlessly just like the BMS in your phone, laptop, and millions of EVs around the world.

To be perfectly honest, you are a 100x more likely to damage your lipo through user error than have a BMS failure. Even the best and brightest users here have destroyed packs and equipment through a moment of human error. It seems almost inevitable that you'll be tired and inattentive and BLAMMO, bad stuff happens. Compare that to a lifepo4 setup where my grandma could figure out how to charge the pack.

Repairing pouch and tab welded cylindrical packs is a big pain and out of most peoples league. I would certainly be nervous cutting open a pouch pack or taking a soldering iron to a cylindrical pack, and it's a valid concern. OTOH, other users have reported quality control issues with lipo packs from hobby king and this makes a certain economic sense. Even when faced with shipping back to the warehouse in the states, waiting a month or two for them to inspect the battery, and then waiting for them to send you a new one most people will probably just order a new pack and be done with it. If you have to ship back to China, the shipping alone is usually more than the battery. This means hobby king has little to lose from lax QC. Compare this to a battery pack seller who uses ebay or paypal. Losing even one paypal dispute can wipe out all profits for the month. Getting a paypal dispute and being forced to ship a replacement part or having the battery pack shipped back and repaired would destroy any profit made on the battery pack. This is why a good seller will thoroughly test a battery pack before shipment.

Weight and volumetric density

Lipo weighs ~%25 less than lifepo4. However in the 5ah, 10ah, 15ah, and 20ah packs this comes out to only a 1.25lb, a 2.5lb, a 3.75lb, and a 5lb difference respectively. This is not very much at all on an ebike.
Lifepo4 has 2/3rds the volumetric density of lipo. This means it's bigger and bulkier. It can be problematic to fit a large lifepo4 pack on a bike. The 16ah headways are too long to fit length wise in the triangle and still pedal comfortably. The 10ah headways are fine, but still a bit bulky. Ping is also bulky, and 48v20ah pack is hard to place in the triangle or in small trunk bags(although I've made it work just fine). Full suspension frames pose the biggest problem for lifepo4; seatpost mounted rear racks aren't secure enough (although some have found ways to mount racks to the rear swing arm) and there is no room in the triangle for a decent sized pack. A lipo pack on the other hand is easily split up and mounted anywhere on the bike you'd like.

Modularity and upgradability

A lipo pack is easy to take apart and reconfigure. It's a lot of fun to experiment with different voltages. Upgrading a lipo pack is almost as simple as ordering the new packs you need. Since it has a high C-rate you won't need to upgrade the capacity of the pack either. It's very simple, and this is huge plus for a lot of people.
Ping packs, having a low C-rate, aren't really able to handle the currents that a high voltage system is capable of. Basically once you get a ping, you might get pigeon holed at that voltage.
The 10ah headways would also suffer the same fate. However, it wouldn't be too much of a challenge to upgrade the voltage of the pack as well as the capacity to 20ah. If you're using the 8c 8ah headways, you won't need to upgrade the capacity. The headway pack building components are modular and easy to work with, but it's no where near the modularity of lipo.
A123 packs are tab welded. Physically adding more batteries to the pack would be out of the question for most, but upgrading capacity or voltage is as easy as ordering the new booster pack, bms, and wiring harness and putting them all together. Even small a123 packs should be capable of handling high currents and voltages.

Conclusion:
If you want an ebike because you enjoy riding or you need it to commute, a lifepo4 pack is the way to go. If you enjoy diddling with batteries and buying new toys and upgrades, Lipo can be a ton of fun. You can pinch pennies and get the absolute cheapest lipo setup, and save $100-$200 over a comparable lifepo4 pack. It'll perform exactly the same as a lifepo4 pack when you're riding it, but when it comes time to charge it you're going to be spending a lot of time diddling. Time that you could be riding, working to save up for a bigger better battery, or doing what I should be doing right now - homework.
Last edited by auraslip on Apr 03, 2011 9:01 am, edited 1 time in total.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by neptronix » Apr 01, 2011 12:22 am

Wow. Too much FUD in this article to even start to address. There is obviously a clear bias here. Cmon dude. What experience do you have with lipo other than finding every possible negative thing about it online?
auraslip wrote:but when it comes time to charge it you're going to be spending a lot of time diddling.
I will contest this thought because it is the most misleading, here is my charging procedure:

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Oh god, what i would do with all those extra hours in the day.. :lol:
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by Ricky_nz » Apr 01, 2011 12:34 am

When comparing lipo and LiFeP4 you mention weight but the big difference comes when you compare volume. A Lipo brick is half the size for the same watt hours.

KFF can happen on any large batter. lead, NiMh, LiFePo4, Lipo so not relevent to the discussion
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by auraslip » Apr 01, 2011 1:27 am

KFF can happen on any large batter. lead, NiMh, LiFePo4, Lipo so not relevent to the discussion
Yes, it can. But not if you only have to plug the battery to the charger and to the controller with the polarized connectors found on pre-built packs. KFF typical happens when people plug and unplug their packs for series and parallel charging.
Wow. Too much FUD in this article to even start to address. There is obviously a clear bias here. Cmon dude. What experience do you have with lipo other than finding every possible negative thing about it online?
Nep, I've seen you give out incorrect and wrong advice to many newbs. Instead of just calling out my "FUD" and "obvious bias" with your opinions and limited experience, perhaps you should take the time to research the things I've written and then get back to me. Wait, lets up the ante, I dare you to prove me wrong with real scientific studies and not just some stuff gleaned from dudes posting on message boards.
I will contest this thought because it is the most misleading, here is my charging procedure:
Thanks. I have a charger. I know how it works. You left out the part about unplugging all the separate connections to series and un-series the pack. You know, the diddling part?

I'm sorry if I seem like I'm being a dick, but it's frustrating to have to tell you the same thing all the time. You refuse to comprehend anything, even when I put the information right in front of your face.
Last edited by auraslip on Apr 01, 2011 1:30 am, edited 1 time in total.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by auraslip » Apr 01, 2011 1:29 am

When comparing lipo and LiFeP4 you mention weight but the big difference comes when you compare volume. A Lipo brick is half the size for the same watt hours.
This is actually true.... to the extent that lifepo4 has 2/3 the volumetric density of lipo.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by neptronix » Apr 01, 2011 2:11 am

auraslip wrote:Thanks. I have a charger. I know how it works. You left out the part about unplugging all the separate connections to series and un-series the pack. You know, the diddling part?
What diddling?

That's how i charge my pack every day.
That's how my 20AH pack gets charged too.

You can do that up to 14S and as many AH as you want, no problem, no disconnecting or reconnecting serial or parallel connections.
auraslip wrote:I'm sorry if I seem like I'm being a dick, but it's frustrating to have to tell you the same thing all the time. You refuse to comprehend anything, even when I put the information right in front of your face.
You are being a dick and you do not fully understand how lipo works. Many of the problems you mentioned with lipo are also problems with lifepo4 such as KFF ( shorting out a connector ), dead cells ( even more of a nightmare to repair on a ping pack or something like a A123 pack with multiple dozens of cells )

You used a motor power/efficiency curve calculator from ebike.ca to talk about batteries. huh?
You are using a amp draw that would show no difference between the two batteries. That would be like claiming that a prius is just as fast as a porsche up to 10mph. BTW 18FET 'unlimited' would be over the 100 amp zone or above so you obviously do not have a non-limited 18FET. In fact i don't think there is a way to turn off the current limiting on an infineon controller in the first place.

Weight does matter on an eBike especially when you are mounting things on a rear rack, have to carry your bike up a flight of stairs, or plain out just appreciate a bicycle that feels like a bicycle.

You don't need cell level LVC at all. If you have a dead cell, that cell needs to be fixed. If you discharge to empty ( 3.6v per cell ), then you stop. Cells don't get disbalanced until they drop below 3.6v. Actually the same exact thing happens with lifepo4; there are variances in those cells too.

As for cycle life for the A123 you have no definite numbers or source for numbers but you say "This is done at 1c and %100 DOD, but with a123 even high rates don't seriously induce cycle fade." So it sounds like you're just inventing that.

There is more but i am exhausted.

Why do i waste my time? Oh well, keep posting FUD and we will take turns pointing our your errors.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by dogman dan » Apr 01, 2011 6:38 am

Actually I agree with much of what Auraslip wrote regarding cost.

Unless people start their question with "I have a 5304, or I have a 40 amp controller" , I still recomend the pingbattery. Good quality controll and response when it's not ok is not free, so the bit more you pay for that is worth it. Every battery seller sends out packs that develop a problem later, so don't start that "all bms is crap" stuff. But you won't see me running an inexpensive signalab bms on any larger controllers either.

I agree that a typical lifepo4 pack like a pingbattery can provide years of easy use, provided you don't flog one to death. They can be amazingly durable. I had one of mine fly over my shoulder and land in the dirt 10 feet ahead of me once, after a huge bump broke my steel battery box. My two pings have never failed to have the bms work. Yesterday in fact, I had a huge headwind. I ended up resetting the bms 5 times to milk the last watt out and get home. No worries, I know I can trust this particular bms to work. Charging is easy as pie, and you can easily carry the charger around. I don't recomend it, unless you isolate it from road shocks by putting it in a backpack, or on a good FS bike. But for the typical 15-20 ah ping, you still want a wimpy controller.

On the other hand, this thread compares cost benifit of ping vs headway, lipo etc, for a 30 AMP DISCHARGE RATE. Well, there ya go, you don't see me recomending any 2c cell pings for a 30 amp controller. Some are doing it succesfully. Till I have done it, I won't suggest it. Probobally OK for those using 20 ah size, but not for 15 ah size.

Auraslip talks about how much hassle charging lipo is. It can be. But doesn't have to be. It depends a lot on the set up. I wouldn't want to carry around too much stuff either. But if you are bulk charging with a meanwell and a board from TP Packs, I totally fail to understand why it would be harder to do than carrying around a 5 amp ping charger. Ok, that kind of rig is likely beyond the skill level of many, especially noobs with no electronics knowledge. But there are sooo many different ways to charge lipo, and not all are a big hassle. I still haven't tried it, but fail to see how it coluld harm a lipo pack to partialy charge it with a sla or lifepo4 charger. So you could pump in a few watthours to a 14s or 15s pack while at the starbucks. I wouldn't walk away from it for the day though. Same thing goes for a naked meanwell, As long as you are sure it won't completely charge, you could give a lipo pack a little more charge.

KFF. Yup, I've done it more than once. Only because I'm stubborn and want to keep my setup changeable since I have 6 ebikes. Even a noob can be walked through the procedure to build some charging adapters to safely make the switch from series to paralell to charge. Then a meanwell and a 300 watt charger can do the job relatively fast, especially for a 12s 10 ah pack.

Soldering. I suck at it. I have 25 ah of 100 v lipo rigged up and running very succesfully for my racing bike. I haven't soldered one single thing on the whole set up. Crimping is a skill that takes some practice to learn, but I learned it easier than learning to solder better. BTW, I still use a cheap 15 buck crimper.

LVC. I trust my pingbattery bms. But I didn't trust it blindly like many who have killed a ping have. I very cautiously watched with a voltmeter untill the bms had proved itself functional. Now that I know it works I trust it completely. With the lipo I take a different approach. Lipo has a less flat discharge curve, and simply watching a voltmeter or the whole pack voltage is quite effective as a fuel left guage with lipo. Combine that with experience, and I have a darn good idea what my range is, and when to turn for home. I should remember who said it the other day, but don't. It was said " A pack with a low cell in it was dead meat anyway" or someting like that. Right on, cell level lvc is not going to make a slacker cell perform. With lipo, you simply chuck that pack, and maybe save the good cells to repair another pack if you have the skills. But in the end, whether using a bms, or no bms with lipo, if you have too small a pack, only a bigger pack is going to cure that. Easy to fix small with lipo, just paralell on another 5 ah later.

In the end, I still agree with Auraslip that lipo may not be the best solution for commuters. But there is no one best way to do anything in life. Each user has his own particular needs, and those needs will determine what's best to do. A benefit analysis based only on cost is not considering enough of the variables to be valid.

I do agree that lipo is not particularly cheap when you consider packs of the same size. But if you need amps, there is no cheaper solution when you look at the cost per amp. If you don't need huge amps, like a 30 amp or smaller controller, then lipo can still be cheap if you don't need range. I have one bike that is a joy to ride with a 12s 5 ah pack. I can't go far, but for the short run to the convenience store, it's a dream to ride with a superlight small battery.

For my daily commute, I NEED range. And the best way for me to get it is a big heavy 15 pound pingbattery. Charging at work is simpler with a simple lifepo4 charger. And I expect I will get more cycles than lipo would. I have two pings now that have paid for themselves, and expect years of free riding to come.

Bottom line, different tasks require different tools, and what's cheap to do one job may be expensive to do another.

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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by TylerDurden » Apr 01, 2011 8:02 am

dogman wrote:...But there is no one best way to do anything in life. Each user has his own particular needs, and those needs will determine what's best to do. A benefit analysis based only on cost is not considering enough of the variables to be valid...

Bottom line, different tasks require different tools, and what's cheap to do one job may be expensive to do another.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by wineboyrider » Apr 01, 2011 8:39 am

+1 on what Dogman said. I love both lipo and lifepo4 together! I love my solid as long as you don't abuse it 36v 20ah ping pack for long trips and ability to charge at 5 amps at my friends house. I love to volt up with lipo and ride. But, on long long rides I series my lifepo4 and lipo and for around 80v nominal dial down the CA and ride! Too many people take sides for this or that. I have definitely killed small ping packs, fried lipo, received crap lipo, fried lvc boards, KFF all of it. Again love them both. :D :D :D 8) 8) 8) 8) 8) 8) 8) 8) 8)
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by auraslip » Apr 01, 2011 12:26 pm

BTW 18FET 'unlimited' would be over the 100 amp zone or above so you obviously do not have a non-limited 18FET. In fact i don't think there is a way to turn off the current limiting on an infineon controller in the first place.
Nep, you are showing your ignorance here again. You can only draw so many amps at a certain voltage with a certain hub motor. It doesn't matter what controller you use. I've has a 9fet - a 12fet - and an 18fet controller and they've all been more or less limited to the amp draw from the motor. And yes you can turn off current limiting in infenion controller with parameter designer or you can solder the shunt to draw more current. It doesn't matter really though because at 48v with a 9x7, 35-40 amps peak is about all your going to get. 30 amps is about all you can get continuously, and that's with speed %120 enabled. At speed %99 my amp draw at 48v is more like 20-25 amps.
As for cycle life for the A123 you have no definite numbers or source for numbers but you say "This is done at 1c and %100 DOD, but with a123 even high rates don't seriously induce cycle fade." So it sounds like you're just inventing that.
I'm really not. A123 cells have been studied to death by the scientific community. Since you don't want to take the time to research them, I'll spend some time doing it later today and get back to you.
Weight does matter on an eBike especially when you are mounting things on a rear rack, have to carry your bike up a flight of stairs, or plain out just appreciate a bicycle that feels like a bicycle.
5lbs of difference is the same as 3x 24 ounce water bottles. Or my water bottle, my u-lock, and my tool kit. It's really not that much weight on an ebike. And if we were comparing the small 36v20ah pack you have, the weight difference would be even less.

Thanks for the injection of sanity dogman. I totally agree with the different tools for different jobs. I'm not saying either setup is better, but for an absolute noob like I was a year ago there is no way a lipo setup would of been cheaper or easier. The point of this was to show that for the most typical beginner kit (9c and 20-30 amp controller) lipo doesn't really have any benefits in performance or costs. You really need to be running high voltages or be willing to use the cheapest charging setup possible for lipo to cost competitive.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by Jethro56 » Apr 01, 2011 12:50 pm

It's the demand for technology that funds developement for better chargers, better battery packs, better BMS's. If no-one bought LIPO batteries bigger than 200 maH would we have 500-1000 watt microprocessor controlled chargers? I'm sure the OP's argument was going on when SLA's were king and NiCad was the too expensive/dangerous/not for Noobs. Time for a new paradigm.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by wesnewell » Apr 01, 2011 12:57 pm

dogman wrote:But there are sooo many different ways to charge lipo, and not all are a big hassle. I still haven't tried it, but fail to see how it coluld harm a lipo pack to partialy charge it with a sla or lifepo4 charger.
OK, I've done this. Actually, one of the first things I tried after switching to lipo a week or two ago. I have a 15C 5ah 14s pack. My sla charger wouldn't even start charging with 54V still in the pack. Just a green light. I suspect it will start charging at about 53V, as a fully charged 48V sla pack stopped charging at ~53.8V. But I ran lipo down to 3.62-3.63V per cell or about 51V total. I hooked up a voltmeter to the pack and then hooked up the sla charger, ready to jerk it off, not knowing for sure what to expect. No problem. Voltage started slowly rising, and I mean slowly. It took about 30 minutes to reach 54.something volts. I kept checking the packs for heat and puffing, but nothing ever happened other than charging. I couldn't feel any heat variance at all. I was concerned with a cell overcharging, puffing and exploding, but absolutely nothing happened. After I unplugged the charger, I hooked the packs up to my lipo charger expecting cells to be out of balance somewhat. I was surprised to see they were still in excellent balance between 3.80 and 3.82 volts per cell. So knowing the charger won't even start charging at 54V, I don't think there'll be a problem using it if it will start charging. But I'd keep a close eye on it anyway.

As far the lipo/lifepo4 cost debate, well I'm biased towards lipo for lots of reasons. Power to size/weight being one. And cost for small packs being another. You don't need more than $50 in charger gear, regardless. It will charge your lipo, just not in 15 minutes. About 2 hours per 5ah. And you can start with a 12s pack for 48V for under $100 and not have to worry about C ratings. Don't get me started.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by neptronix » Apr 01, 2011 1:09 pm

auraslip wrote:
BTW 18FET 'unlimited' would be over the 100 amp zone or above so you obviously do not have a non-limited 18FET. In fact i don't think there is a way to turn off the current limiting on an infineon controller in the first place.
Nep, you are showing your ignorance here again. You can only draw so many amps at a certain voltage with a certain hub motor. It doesn't matter what controller you use. I've has a 9fet - a 12fet - and an 18fet controller and they've all been more or less limited to the amp draw from the motor. And yes you can turn off current limiting in infenion controller with parameter designer or you can solder the shunt to draw more current. It doesn't matter really though because at 48v with a 9x7, 35-40 amps peak is about all your going to get. 30 amps is about all you can get continuously, and that's with speed %120 enabled. At speed %99 my amp draw at 48v is more like 20-25 amps.
That doesn't seem right at all. People overpower DD hubs all the time and never say 'well gosh, this motor just won't take more current'. In my experience, motors will eagerly take as much current as you give them.

Maximum amp draw is at 0rpm and then it goes downhill from there on w/a DD motor. What amp metering device are you using?
As for cycle life for the A123 you have no definite numbers or source for numbers but you say "This is done at 1c and %100 DOD, but with a123 even high rates don't seriously induce cycle fade." So it sounds like you're just inventing that.
auraslip wrote:I'm really not. A123 cells have been studied to death by the scientific community. Since you don't want to take the time to research them, I'll spend some time doing it later today and get back to you.
You said you presented scientific studies / there are scientific studies so please show me them, you need to back your claims up if you are writing an article like this.
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5lbs of difference is the same as 3x 24 ounce water bottles. Or my water bottle, my u-lock, and my tool kit. It's really not that much weight on an ebike. And if we were comparing the small 36v20ah pack you have, the weight difference would be even less.[/quote]

When you have to haul your bike up a flight of stairs every day, yes, it does matter.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by spinningmagnets » Apr 01, 2011 1:28 pm

I appreciate the effort, auraslip. I feel this is a useful thread, but I will leave the arm-wrestling over details to others more experienced than me.

A warning to newbs on LiPo charging component selection: I started with the absolute cheapest 6S (22V) LiPo charging set-up I could find at the Hobby-King website:
https://endless-sphere.com/forums/viewto ... 16&t=23465

I knew charging would be slow with the $10 12V/5A power-supply, and the $33 7A charger set to a 5A charge, but I was curious. The 5A PS died right away from heat, so I ordered the $40 25A/14V PS with a metal case and a fan.

The identical model of charger upgraded to 10A was only $6 more (40% faster charging for $6), and also included a metal case with a desireable $3 balance lead extension http://www.hobbyking.com/hobbyking/stor ... oduct=7351

I started with a pathetic $43 (plus shipping) 6S charging system, and now I have a barely adequate $78 system. I now need 10S (37V), so I have to do the series/parallel shuffle using two LiPo bricks to charge with this very basic 6S charger.

edit: I have seen the iCharger 1010B for $160 (will charge 10S pack directly, instead of charging two 5s packs separately)
Last edited by spinningmagnets on Apr 01, 2011 1:53 pm, edited 1 time in total.

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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by neptronix » Apr 01, 2011 1:45 pm

I started out with an iCharger 1010b+ and an adequate power supply, charging 10s. When i got into lipo there was no real good information on it and it was kind of a quack thing to do. I jumped straight into it as a newbie and by asking the right questions, doing the research, and not skimping, i got the right stuff that works great for my purpose.

spinningmagnets, your story is like many. People can't wrap their head around spending a lot of money on a charger. It inflates the initial purchase price quite a bit. So you end up with some junk from HK that dies in a short time. However, many people end up replacing charger bricks and BMSes on their lithium packs over many years of ownership. I think that over a long period of time, the cost of the charging stuff really evens out. I know that dogman has gone through at least 2 ping chargers by now for example. I have not heard of anyone replacing a quality RC charger when it was used within it's specifications.

If i had my chance to get 14 20AH A123 cells, i would avoid the BMS and charge those suckers with a 14S Hyperion just the same.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by Spacey » Apr 01, 2011 3:17 pm

Auraslip,

With all due respect I wired up my first hub motor and controller by bridging the controller parts with copper solder sucker stuff.

The amps as registered with a turnigy amp monitor was 70amps at 48v, it would pull wheelies so you are wrong that the amps are defined by the motor. This was with a Magic Pie GM motor and controller....motor still going strong after 14 months.

Also your tone recently has changed, it's more aggressive and combative......any reason? Let's not make wars over different Lipo chemistry he he....

I have gone Lipo over my 20 cell 16ah Headways because of voltage sag and bulky fixtures on my bike. The headways were great, my ping pack was good for 20am conrptrollers.... But I need more grunt and other than A123 pack Lipo is the only one to give it. I hate BMS's and would rather monitor with a Cell Logger thing on my lipo.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by dogman dan » Apr 01, 2011 3:34 pm

Something else is limiting Auraslips amps I think/ guess. Wiring, connectors, hard to say exactly what.

I often see something similar to what he describes though, in my case it's simplly lack of load on the motor. Once hauling ass, amps drops to amazing low levels. I've seen this effect even when climbing fairly steep hills.

Again, I feel the only way lipo is cheaper is if you have a use for a short range pack. Awesome though, that good c rates can be equal in price to a large pingbattery. That is HUGE, to those interested in big amps.

Re one of Neptronix comments, I myself still have a hard time bringing myself to invest in better chargers for my mountain of lipo. But I'm not using it daily. Sure is nice though, to have a ton of packs around when I want to ride all weekend. Charge time matters little when you have enough to go out multiple times.

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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by neptronix » Apr 01, 2011 3:52 pm

dogman wrote:Re one of Neptronix comments, I myself still have a hard time bringing myself to invest in better chargers for my mountain of lipo. But I'm not using it daily. Sure is nice though, to have a ton of packs around when I want to ride all weekend. Charge time matters little when you have enough to go out multiple times.
Yeah i noticed that. Your setup works OK for occasional use but when you get into daily use, you need a bigger charger.
It makes even more sense if you are using geared motors like i am. 10S gets me to 25-29mph on my MAC, 14S gets me to 30-35mph and hill climbing speed on a 7% grade is about 75% of my top speed. Geared motors perform great on low voltage but demand copious amounts of amps.

Perhaps this will shed some light as to why i am such a big lipo fanboy. I don't need more than 14S, and the less voltage sag i have, the higher my top speed is. I gain about 1 mph per 2V. With RC motors, the effect is even more pronounced. That is why you will get people on here like LFP going nuts about turnigy nanotech.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by auraslip » Apr 01, 2011 4:12 pm

Something else is limiting Auraslips amps I think/ guess. Wiring, connectors, hard to say exactly what.
I use 8 gauge wiring, 8mm bullets, and now my hub has 12 gauge (compared to 16 gauge) wires running to the coils. The controller is a 12 fet lyen completely unlimited, and the battery pack is running with out the bms.

Perhaps the mods to your controller make a big difference, or maybe the magic pie is a different wind and can draw more amps. In any case, at 70 amps you'd be doing 3650watts and the motor wouldn't last long before it overheated.

30 amps is the point where you start needing to do serious mods to your bike to be safe... it's more than enough power for beginners.
Also your tone recently has changed, it's more aggressive and combative......any reason?
When I post actual data spelling out exactly what I'm talking about people call me ignorant, liar, and tell me I don't know what I'm talking about. It's upsetting to actually take the time to do the research and footwork, and then to be shouted down by people not willing to respond anything but insults.

A warning to newbs on LiPo charging component selection: I started with the absolute cheapest 6S (22V) LiPo charging set-up I could find at the Hobby-King website:
This is why I didn't list prices for a cheaper charging setup... my imax b6 doesn't correctly balance cells, and like yours, my $10 PS died right away also. Going cheap with lipo chargers is just not worth it.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by auraslip » Apr 01, 2011 4:48 pm

THANKS TO EVERYONE HERE WHO TAUGHT ME ABOUT EBIKES. I'M IN YOUR DEBT.

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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by JCG » Apr 01, 2011 5:16 pm

I came for the bickering :!:, but I stayed for a question! :?:
neptronix wrote:I will contest this thought because it is the most misleading, here is my charging procedure:
Image
This has been distracting me all day. Let me see if I get this, or if I have no clue like usual.

Unless I'm missing something, when the balance plug isn't used in the above example (where balance is already good), the charger becomes just a CV-CC charger (limit current as voltage is increased, stop when total voltage is equivalent to ~4.2 V/cell).

So let's say I have a 6S, 5 Ah (max discharge=25 C, max charge=4 C) Turnigy brick and it is 80% depleted. Could I do the following?

1) Check the balance status of the brick with a balance charger, and now let's assume I see all six cells are at about 3.4 V
2) seeing no real balance issue, I hook the brick up to charge on a current-limited meanwell power supply set to 25.2 V and maxes out at 20 A
3) leave the thing on, since once the cells reach 25.2 V total (4.2 V/cell), charging current should drop to zero
4) take away the charger, check balance, and go

I could deal with this situation, since I'm considering a setup of trying to charge nine 6S packs in parallel, and I don't feel like getting three of those 4 x 6S smart chargers, or having to use one smart charger three separate times. I could just keep an eye out for imbalance before charging, and if I see it, I use my one and only smart charger where needed.

How's that sound? Am I a dead man?

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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by auraslip » Apr 01, 2011 5:48 pm

If all the cells stayed perfectly in balance it would work. That's a big if though. As cells age discrepancies develop between even well matched cells. Even if they appear balanced at 3.4v some of the cells might reach 4.2v before the others and continue to climb until they damage themselves. I think it's a bit silly that he wouldn't use the balancing tap if you had the option.

You could do things like hook up the balance tap to a cell-monitor and set an over voltage alarm. Then you'd have to be near it while it charges to disconnect it when the first cell hits 4.2v

It's possible to do these type of things, but it's a pain and can be risky if your not absolutely sure of what you're doing.
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by neptronix » Apr 01, 2011 6:29 pm

JCG wrote:I came for the bickering :!:, but I stayed for a question! :?:
neptronix wrote:I will contest this thought because it is the most misleading, here is my charging procedure:
Image
This has been distracting me all day. Let me see if I get this, or if I have no clue like usual.

Unless I'm missing something, when the balance plug isn't used in the above example (where balance is already good), the charger becomes just a CV-CC charger (limit current as voltage is increased, stop when total voltage is equivalent to ~4.2 V/cell).
Yep, exactly, except i set mine to 4.15v per cell as a safety margin, and to stretch out the cell's life. With an iCharger you can set the max 'per cell' number and it will charge to that voltage.
JCG wrote:So let's say I have a 6S, 5 Ah (max discharge=25 C, max charge=4 C) Turnigy brick and it is 80% depleted. Could I do the following?

1) Check the balance status of the brick with a balance charger, and now let's assume I see all six cells are at about 3.4 V
2) seeing no real balance issue, I hook the brick up to charge on a current-limited meanwell power supply set to 25.2 V and maxes out at 20 A
3) leave the thing on, since once the cells reach 25.2 V total (4.2 V/cell), charging current should drop to zero
4) take away the charger, check balance, and go

I could deal with this situation, since I'm considering a setup of trying to charge nine 6S packs in parallel, and I don't feel like getting three of those 4 x 6S smart chargers, or having to use one smart charger three separate times. I could just keep an eye out for imbalance before charging, and if I see it, I use my one and only smart charger where needed.

How's that sound? Am I a dead man?
I wish i had an answer for you, but i have no experience with meanwells.

If you are using 12S as your voltage, i would keep the packs permanently paralleled and serialled and plug them into a hyperion 14s charger, and charge the whole unit as a 12S pack. When you need to balance charge ( it will happen, eventually ), all you would need to do is plug in the two balance leads, the power leads, and tell it to balance charge.

OR you get a high voltage meanwell and charge your pack as one large serial/parallel group. That is how the guys running big power are doing it. You can then use a few battery medics as a balancer and skip the balancing charger altogether.

see this vid:

p.s. 80% depleted is more like 3.6-3.7v.
3.6v is where the cells start to rapidly fall off a cliff. Consider about 3.5v to be 100% discharged. As a matter of fact, the turnigy and zippy batteries have about 100mAH extra built into them to account for the cliff.

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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by x88x » Apr 01, 2011 6:35 pm

Damn, everywhere I go around here recently it seems to be you two (auraslip & neptronix) bickering back and forth about LiPo vs LiFePo4. :roll:

Anyways, Auraslip, you make a few good points...but... A good chunk of your initial post is not "a cost benefit analysis of lifepo4 and lipo". Time, user error, cycle life; none of these are comparisons; they're just "here are some bad things about LiPo. LiFePo4 is better, because I say so".

For the costs, which Hobby King LiPo are you basing those on? If you're in the US (granted, not everyone is, but I am, so I'm using their US warehouse prices), 14S1P of 20C 5Ah comes to $117.83 shipped ($117.82 + $0.01 shipping).
auraslip wrote:It's not as simple as plugging in the pack and walking away like it is with lifepo4. While it is trivial when using the 14s hyperion, using a smaller charger requires arranging the pack accordingly.
While true, this is not valid in the argument, since you're opening on the assumption that the LiPo pack in question is being purchased with a 14s Hyperion charger which, as you noted, would be "as simple as plugging in the pack and walking away".


For cycle life, you use stats from a study on some other kind of lithium battery. What chemistry were those batteries? What was their rated discharge rate compared to the discharge rate used in the study? Why do you feel that they are a good comparison to Hobby King LiPo? You also provide no comparable studies on LiFePo4. Ok, you did later for A123, but what about Headway and Ping? I imagine they're not nearly as impressive as the A123 results.


BTW, in the 'power' section, that graph peaks closer to 25A, not 20A.


Reliability you're basing largely on guesswork (people not mentioning dead LiPo cells) and irrelevancies. Again you bring up user error, killing cells in the act of swapping them around. If you are truly making comparable packs, the LiPo will be wired up once and never touched again, just like the LiFePo4.


One other thing to consider is the cost of building a pack if you choose to build a second bike or even just a second pack for the first bike. I admit, LiPo has a high barrier of entry (as I have recently experienced), with the costs of the charging equipment. I didn't spend nearly that much because I already had a power supply and I got a cheaper, 6S charger (iCharger 106B+), but still. However, once that entry is met, the cost difference is much more drastic, and in the opposite direction. Yes, not immediately apparent on the first build, but if I were to, say, build two 48V20Ah (assuming 14S LiPo) packs, using the numbers in the OP. If I were to buy Ping packs, that would cost me $1,574. If I were to buy Hobby King LiPo, it would cost me $1,335. ~15% less. As with anything requiring support equipment, the cost drops drastically once that support equipment is covered.


Also, correct me if I'm wrong, but I don't remember you ever mentioning that you have actually used LiPo at any point, so forgive me if I take anything you say about it with a grain of salt. I'll stick with reports from other users (like LFP and dogman) who actually have extensive first-hand experience working with the stuff, thanks.


At the end of the day, though, it really comes down to what dogman said. Different tools for different jobs. I evaluated the options and decided LiPo would work best for me for my bike. You obviously came to a different conclusion for yours. That's fine. I don't have to buy or live with your pack, and you don't have to buy or live with mine. :P
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Re: a cost benefit comparison of lifepo4 and lipo for newbs

Post by auraslip » Apr 01, 2011 6:56 pm

I don't have to buy or live with your pack, and you don't have to buy or live with mine. :P
I'd actually probably be pretty happy with your pack for weekend riding :D

I couldn't use it with my current setup though
Image
TRUE PLUG AND WALK AWAY CHARGE SETUP
I'll stick with reports from other users (like LFP and dogman) who actually have extensive first-hand experience working with the stuff, thanks.
These guys are using lipo to build really powerful and fast bikes, and cost isn't much of an issue for them. The point of this post is not to talk them out of lipo, but people with lower power bikes who are considering lipo because it's "cheaper" and more powerful. These people don't have anything to gain from lipo unless they're pretty deep into the hobby! This is clearly a huge point of contention to most of the people in this thread; they are willing to spend hours here on forum a day, so spending 10 minutes a day messing with their batteries is no big deal. Most newbs just want bikes that WORK though, so I think it's fair to include time spent building and configuring packs as a cost for MOST people.
For cycle life, you use stats from a study on some other kind of lithium battery. What chemistry were those batteries? What was their rated discharge rate compared to the discharge rate used in the study? Why do you feel that they are a good comparison to Hobby King LiPo? You also provide no comparable studies on LiFePo4. Ok, you did later for A123, but what about Headway and Ping? I imagine they're not nearly as impressive as the A123 results.

The lipo chemistry I used is LG lipo used in cell phones. I'm not sure of the rating, but at a usage schedule of %20-%100 SOC pretty much all lipo and li-ion show pretty significant capacity fade at 800 cycles. Of course you can be more conserative and extend life by doing something like %40-%90 SOC, but then you lose the cost and weight advantage. The other day someone said hobby king rates their lipo at 300 cycles, but who knows for sure.
I should of linked to both the studies I pulled the a123 graphs from.
Image
a123 lifepo4 http://cet.berkeley.edu/dl/BatteryBrief_final.pdf
As far as ping and headway - they are both quoted as 2000 cycles at 1c with no less than %20 capacity fade, and that's pretty standard for lifepo4. Being more conservative like I am (It's hard not to be with a 20ah battery!), and shelf life becomes more of an issue!
It is really chemistry and build quality dependent though! I would really love to see more long term studies done on these headway, ping, and r/c lipo.
For the costs, which Hobby King LiPo are you basing those on?
Correct. I'm basing it on shipping from China. I believe the total price should come out near the same because the US lipo has free shipping above $100, but it's priced more.
eliability you're basing largely on guesswork (people not mentioning dead LiPo cells) and irrelevancies. Again you bring up user error, killing cells in the act of swapping them around. If you are truly making comparable packs, the LiPo will be wired up once and never touched again, just like the LiFePo4.
Well yeah, but who can withstand the temptation to put your packs in serial to for higher voltage :D

I'm also of the mind that any handling of hot wires incurs a risk. Just look at the pins on the jst-xh balance connectors; the pins on the male housings are pretty much exposed and could easily short with a really sweaty fingers!
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