Moderators: robnewyork, bassiclyLouDog, gameboy

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By Headway Headquarters
#1917
Hi all,

Starting this thread on the advice of blake to have a thread dedicated for LiFePO4, shed some light and answer questions (to the best of my ability) on Li-ion batteries and in particular, LiFePO4. Do some testing with LiFePO4, put my results up here, charge and discharge curves, all the geeky nerdy stuff placed here for your entertainment!

Was reading the thread "Baby steps in reducing lead" and one of the posts was concerning the actual real dangers of Li-ion cells, but then a little misconception in stating that those dangers are for all Li-ion cell. It is true, Li-ion if abused by overcharging can "cause injury and/or damage to person(s) or property", but can't all rechargeable batteries to some extent cause injury and/or damage to person(s) or property, even Lead-Acid (LA)? I am not making light of the accidents, injuries and other horrible events that investigators have determined were caused by Li-ion batteries, but just trying to put things in a little perspective here. It would be like saying that is a basket of fruit, but in that basket there are apples, oranges, and the odd ball avocado, all fruit, but different make-ups. Here is something I found with concerns to LA, makes me not want to purchase any type of SLA (Sealed Lead Acid)!


"Accidentally overcharging a battery will boil the sulfuric acid and distilled water mix. The casing of the battery can become hot to the touch, and begin to melt or swell. Flammable hydrogen can build up inside the sealed cells of the battery, causing swelling of the casing under pressure and seepage through small vents. Once the hydrogen is introduced to oxygen, it becomes a sitting time bomb. A small electrical spark can ignite the gas and cause the battery to explode, sending plastic and lead shrapnel flying around, in addition to a caustic sulfuric acid spray. Obviously, this is the most dangerous side-effect of an overcharged battery."


WOW! No way am I going to have that around me and my family! Possibly can have a sitting time bomb? Gases? Caustic sulfuric acid spray? If proper care is taken of the LA battery then this situation most likely won't happen, agreed? The same is for Li-ion chemistry. Yes, the Li-ion (depending on the cathode chemistry) can burst into flames like a Roman Candle on the 4th of July if not properly taken care of, but if proper care is taken, then they are a great investment. Any driving force behind an electric motor is the power source, in LEV’s (Light Electric Vehicles) the power source is the batteries and they should be an “investment” that you take care of. Not have to baby, but like with any investment, proper care should be taken with them, and do your "pros and cons" homework on the type of Li-ion chemistry you are planning to purchase.

Heat is one of the biggest issues with Li-ion chemistries. Many Li-ion cells are excellent for the power to weight ratios, but many cannot withstand high temperatures. LiPo (Lithium Polymer) has some great power to weight ratios, but many of the packs come pre-assembled (primarily for the RC crowd) which means the anodes and cathodes of the individual cells are already connected and the possibility for a short circuit is there, which means heat, which means some potential problems, unless of course you are a pyro! This is the reason why 49 CFR, IATA and IMDG regulations are so strict in transporting Li-ion batteries. Remember, I am not here to bash any chemistry, just giving some information and answer some questions on Li-ion cells. Like I stated before, as with any battery, as long as care is taken, then the possibility of any potential risk is reduced dramatically. The hub-bub about LiFePO4 (Lithium Iron Phosphate) is that although the power to weight ratio may not be as high as LiPO or LiCoO2 (Lithium Colbalt Oxide), they still have a decent power to weight ratio plus the chemistry is more stable at higher temperatures (cells do heat up when they are being used!) along with a higher cycle life. The LiMn2O4 (Lithium Maganese Oxide) is up there with the safety of LiFePO4 compared to the other Li-ion chemistries, but they deteriorate at a fast pace at temperatures above 50*C or 122*F. Compared to the LiFePO4 chemistry, whose operating temperatures are -20*C~70*C or -4*F~158*F.

As far as power capabilities of LiFePO4, here is a short YouTube video of two electric vehicles in a street race. One a Tesla, the other a BMW conversion with Headway LiFePO4 cells, enjoy! http://www.youtube.com/watch?v=-gGn4smzBcM

So if you are thinking of Li-ion cells, do your homework, do some comparison. Figure out which cathode chemistry is best suited for your application. I am ready to be bombarded by questions, so fire away!
User avatar
By Headway Headquarters
#1919
What is a “C” rating?

"C" rating is a rating system for batteries which compares its rated output or input relative to its amp hour rating.

For example: If you take a Headway 16Ah cell and run it at 1C discharge you would be putting out 16 amps. 2C would be 32 amps. .5C would be 8 amps, and so on. The same applies to its charging capabilities, the Headway 16Ah cell is capable of handling a 5C charging rate, or being able to be charged at a maximum of 80A. For these reasons, the Headway cells and A123 cells are popular amongst eBike, eScooters (Vespa styles), and motorcycles and even racing and drag racing.

For the Headway 8Ah cell, they are rated at 25C max or peak discharge which would be 200A from a single cell. An independent test had a 4S1P set-up (12V8Ah) had 428A (over 53C) dropped to 360Amps in 15 seconds, cells generally down to 2.26V temp 69*C. Although it is rated to be 25C or 200A, much more was able to be pulled, but of course this would reduce the life cycles of the cells, but the capabilities are there! So the high "C" discharge rate capabilities of a Headway cylindrical cell, or any other LiFePO4 cylindrical cell, ie A123 is pretty amazing, again depending on what the application is.
User avatar
By timmy2time
#1961
I want to make a 30Ah pack or two of them actually. Can I wire those hobby king Lipos parallel? Like six 5Ah together to make 30Ah? and if so will the 20C discharge rate be 240C since they are parallel? How would I charge a pack like that and not have to worry about balancing them manually?
User avatar
By gameboy
#1972
this is great info. i changed it to a sticky so the info wont get lost. as time goes by it may be changed to FAQ . if your ok with that?
User avatar
By Headway Headquarters
#1981
timmy2time wrote:I want to make a 30Ah pack or two of them actually. Can I wire those hobby king Lipos parallel? Like six 5Ah together to make 30Ah? and if so will the 20C discharge rate be 240C since they are parallel? How would I charge a pack like that and not have to worry about balancing them manually?


I am more familiar with LiFePO4 chemistry rather than the LiPo, so storm, since you say you're a dedicated LiPo man, please correct me if I am mistaken cuz I like learning too! ;)

Typically yes, you can wire the LiPo RC packs in parallel. The C rating would not change to 240C or 7200A, the C rating would still be 20C or 600A for the 30Ah pack. The C rating 'is what it is' for the cell/battery, the only increases would be the voltage and/or Ah's for increasing the series or parallel set-up.

There are a few different options to not have to worry about balancing the battery packs individual packs manually. Some type of BMS/PCM that has balancing functions integrated in the circuitry. Wire the JST-XH balancing plug from the individual packs together for one balancing plug to use with the ever popular iCharger series that has a plethora of different options as far as charging, discharging, balancing, storage charge etc. Depending on how you wire it up, you could also use something like this http://www.tmenet.com/products/lithium-charger/xtrema-balancer or with the whole sha-bang-a-bang like this http://www.tmenet.com/products/lithium-charger/xtrema-charger.

Hope this helps, and storm, if you have any other input on LiPo chemistry, chime in!
User avatar
By tww
#1987
How do they last being stored over time, such as winter? How do they stand up vs sub-freezing temperatures and 120+ heat? yeah, we get both here :|

What happens if they're punctured, torn or opened?
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By Headway Headquarters
#1993
tww wrote:How do they last being stored over time, such as winter? How do they stand up vs sub-freezing temperatures and 120+ heat? yeah, we get both here :|

What happens if they're punctured, torn or opened?


There is a little controversy on storage of LiFePO4. Most all of the manufacturers state that the voltage will drop about .3 volts or less every 12 months. There have been individuals who’ve had LiFePO4 cells in storage for over a year and when compared to a new cell of the same size and manufacturer, there was a drop of about .001V after over a year of just being stored.

For temperature ranges, recommended storage temperatures should be at -20*C/-4*F and between 35*C/95*F~45*C/112*F. These are the ranges for storage that are recommended by most of the manufacturers of LiFePO4 chemistry. Again, these are the recommended storage ranges, but it should be noted that many have used the LiFePO4 chemistry in extreme cold such as in Quebec, Canada -39*C/-38*F along with using them in the Mojave Desert in 49*C/120*F weather without any problems.

With the casings of many of the LiFePO4 cells being made from either a high industrial strength polymer/plastic or some type of metal, it is very difficult to puncture, tear, or even open a LiFePO4 cell. If the LiFePO4 cells are punctured or cracked open, the electrolyte material that also contains free Li-ions floating around in there (commonly a salt, LiPF6, that is dissolved in some kind of organic solvent) will leak out. It should be noted that this is what is flammable. Here is a YouTube video of a few abuse tests on a cylindrical LiFePO4 cell :twisted: http://www.youtube.com/watch?v=52h8IK0IdqI Just remember, these abuse/torture tests were done in succession on this cell!
By COS
#2002
What prices can you offer for the HEadway cells? I am looking to build a another battery pack but the cells I am looking at are from...
http://www.evassemble.com/index.php?mai ... ucts_id=18
and are $16.00/cell for a 10AH cell. Can you beat these prices?

I'm a LifePO4 pack builder. I've built many packs with Thundersky and Sky Energy (CALB) cells. Can you post your prices?

Thanks
User avatar
By Headway Headquarters
#2004
gameboy wrote:1 word...



why?



now i do like this video. http://www.youtube.com/watch?v=4Uhp0Fhi-XY&NR=1


From what I gather, it's one of the things this person does, try out different cell chemistry's to see the types of abuse they can take for personal satisfaction on if he deems them to be safe or not.

COS wrote:What prices can you offer for the HEadway cells? I am looking to build a another battery pack but the cells I am looking at are from...
http://www.evassemble.com/index.php?mai ... ucts_id=18
and are $16.00/cell for a 10AH cell. Can you beat these prices?

I'm a LifePO4 pack builder. I've built many packs with Thundersky and Sky Energy (CALB) cells. Can you post your prices?

Thanks


Hey COS, I'll send you a PM on this, I want to try and keep this thread for education and keep away from prices and such.
By COS
#2008
To piggyback on this post, it is very important that every pack that is built has a PCB/BMS in it. Some see this as building a "limitation" to the pack but it is a device designed to manage and protect the pack for LVC/OVC & OC and improves the life and range of the pack. How you design the pack depends on the limitation you design into it. If you want a higher C rate you want cells that can deliver this at no higher than 2C. Maybe 3C but remember, high current draw has inversely proportional effect to the life and "range" of your pack.
User avatar
By gameboy
#2022
could you send me a PM too? i wouldnt mind knowing prices also. thanks
User avatar
By Headway Headquarters
#2030
COS wrote:To piggyback on this post, it is very important that every pack that is built has a PCB/BMS in it. Some see this as building a "limitation" to the pack but it is a device designed to manage and protect the pack for LVC/OVC & OC and improves the life and range of the pack. How you design the pack depends on the limitation you design into it. If you want a higher C rate you want cells that can deliver this at no higher than 2C. Maybe 3C but remember, high current draw has inversely proportional effect to the life and "range" of your pack.


Good call COS, I completely agree, having some type of cell monitoring for a Li-ion pack is very important, no matter if it is a PCM/BMS or a simple CellLog LVC set-up. Like I said earlier, cells and battery packs are an investment, and to protect your investment having some type of cell monitoring during charging and discharging is essential to the life of you battery pack.

To touch a little more on COS's point about the C ratings, cell manufacturers typically rate the cell according to a .5C discharge. Although cell manufacturers "advertised" a certain amperes per hour rating, cells typically fall just slightly under the "advertised" ratings because of the testing done at .5C. Here is an example: I've tested a brand new 16Ah cell straight from the box with no top off charging at 1C (16A) and the tested capacity was 15.707Ah and total time of the test was 58' 47". I charged and retested the same cell at .125C (2A) and the tested capacity was 15.866Ah and total time of the test was 7h 55' 58".

Well said about the effects of high current draw on the life and range of a battery pack. The capabilities of some Li-ion cells are there if you need it for high discharging current capabilities, but as COS points out, and I pointed out in an earlier post, continuous high discharging will cause the cells to loose their life prematurely and you will not be able to get the "advertised" quantity of cycles from them.

Thanks for the input help COS!

gameboy wrote:could you send me a PM too? i wouldnt mind knowing prices also. thanks


Done!
User avatar
By storm
#2103
I had three packs of Yesa life cells 2 x 24v 10Ah 1 x48v 10Ah which have a steel cans, what a great investment they were...not, they started leaking electrolite shortly after ariving, many cells needed regular replacing after flatlining 0v, Yesa wanted me to pay $30 shipping each time. Many cells puffed from drains above the recomended C (sure my fault there) I eventually gave up on them and moved to Lipo, I've used a few different brands now and the cheapest are to be avoided for sure but I'm much happier, I would also like to try the A123 prismatic some day.
User avatar
By Headway Headquarters
#2141
storm wrote:I had three packs of Yesa life cells 2 x 24v 10Ah 1 x48v 10Ah which have a steel cans, what a great investment they were...not, they started leaking electrolite shortly after ariving, many cells needed regular replacing after flatlining 0v, Yesa wanted me to pay $30 shipping each time. Many cells puffed from drains above the recomended C (sure my fault there) I eventually gave up on them and moved to Lipo, I've used a few different brands now and the cheapest are to be avoided for sure but I'm much happier, I would also like to try the A123 prismatic some day.


Hey storm, sorry to hear about your LiFePO4 experience, but am glad to hear that the LiPo's are working out for you! I wasn't too impressed with Yesa either, and what you said applies to any battery chemistry IMHO, "the cheapest are to be avoided for sure"! 'Great deals' doesn't always mean 'a great buy'! I've heard a lot of good things about all the types of batteries A123 manufactures.
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By ignatiustbarfat
#2506
Interesting. Thanks for the FAQ.

What is the charging voltage for LiFePO4 cells?

I'm often trying to field charge batteries in my applications. E.g. an old car alternator (w/ built in voltage regulator) run off a tractor PTO can charge my deep cycle LAs out in the vineyard rows. It isn't pretty, but it works, particularly as the tractor is out there running the sprayer anyway. I wonder if brute charging like that would work with a ~12V pack or just destroy things.
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By Headway Headquarters
#2510
Hey Iggy,

ignatiustbarfat wrote:What is the charging voltage for LiFePO4 cells?


The charging voltage for LiFePO4 varies with the manufacturer according to the specific type of LiFePO4 chemistry they are using, but typically, the charging voltage is around 4.1V~4.2V for the prismatic and 3.65V~3.95V for the cylindrical, but both will still float down to their operating voltage range, somewhere between 3.2V~3.4V after awhile.

ignatiustbarfat wrote:I wonder if brute charging like that would work with a ~12V pack or just destroy things.


Both! :lol: Much depends on the charging capabilities of the cell. Some are rated for a .5C~1C charge while others are rated as high as 5C~6C charging. The other thing, like with all batteries, the slower charging (less A or even mA :shock: ) should give a longer battery life so blasting a charge into it may give it some life, but not a very long one!

LiFePO4 is based on the CC/CV charging method, so much needs to be known about all the other components before putting 4 cells together for a 12V battery if it is going to be recharged with means other than a charger specified for LiFePO4 chemistry. Also it is important to ensure that the cells are closely matched as far as discharge curves and charging curves. Of course there will be small variations of 'matched' cells, but the closer they are, the better off you will be, the pack is only as strong as the weakest cell!

Here's an example (with no balancing or other battery/cell monitoring system in place): If you have a 4S1P LiFePO4 12V pack (12.8~13.2V) and all the cells are matched by discharging evenly to 2.0V per cell, and when charged they are evenly charged to the 3.65V+/-.05V each (14.6V), then there should not be a problem with the battery pack and periodic testing and checking of each individual cells would be minimal to ensure the cells are still performing equally (but this is still considered cell and battery management, just not electronically!).

If you have the same set-up and one cell hits 2.0V while the others are still at 2.2V, then during charging, the cells with the higher LV will be charged faster and reach their max charging voltage than the one with the 2.0V LV. The battery would not be up to the full charge of 14.6V, and if so, then the 3 similarly matched cells would be carrying the brunt of the CV phase since the other is slow in catching up, which could very well cause the 3 strong cells to overheat and begin to deteriorate faster than normal by the higher single cell voltage during the charge. :ugeek:

Which, like COS stated above, it is always good practice to have some type of BMS in place, no matter if it is manually, electronically or anything else, as long as there is some type of battery monitoring system in place!

BTW, it is nice to see another from WA here!
User avatar
By ignatiustbarfat
#2515
Hurray for WA state!

Thank you for a terrific and informative response!

Can describe the landscape of available BMS, particularly electronic?
User avatar
By Headway Headquarters
#2637
Hey Iggy,

Been busy and not online much lately so sorry about the late response. :oops:

You're welcome, for the info. Not sure of exactly what you mean by the 'landscape' of the BMS, not a true electronics expert, so have not really delved into building or attempted to build a BMS, have relied primarily on sample testing, burning up the samples, doing what I can to see what IC nomenclature that has not been sanded off from the OEM is to do some research and that sort of thing.
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By Headway Headquarters
#2989
I finally have a little break to do some cell testing and post it here since I said I would in an earlier post on this thread!

I did not do any temperature graphing on these tests, but I did take some notes. Didn't do a real in depth test since this cell has 'been around the block', but nevertheless, it was sitting there just begging to be tested again! :lol:

Cell: LiFePO4 38140S 12Ah
Voltage at start of test: 3.307V
Ambient Room Temperature: Start of test: 17.3*C End of test 17.8*C
Color - Amperes (C Rate) - Time - External Temp
Black - 12A (1C) - 00:53:55 - 23.5*C
Red - 36A (3C) - 00:18:18 - 35.2*C
Green - 60A (5C) - 00:11:12 - 43.5*C
Blue - 96A (8C) - 00:06:40 - 59.6*C

Charger was set at 3.700V and 19A
Charge - Voltage - Time - Capacity
1 - 3.689V - 01:12:00 - 10.783Ah
2 - 3.689V - 01:04:10 - 11.086Ah
3 - 3.689V - 01:11:10 - 11.065Ah
4 - 3.689V - 01:06:04 - 10.667Ah

The voltage drop is apparent, but still being able to pull those continuous amperes from a single cell that has been the red-headed test cell (no offense to any red heads out there!) is pretty good I think. ;)
Attachments
38140S Discharge.jpg
Headway 38140S 12Ah cell Discharge
38140S Charge 19A #3.jpg
Headway 38140S 12Ah cell Charge
User avatar
By gameboy
#3854
i think you have to send him a PM. not sure if he will see this.
User avatar
By Headway Headquarters
#3865
I still lurk on here when I have time! Am testing some new cells that I received, 12Ah cells 40120S, 40mm diameter, casing is 120mm long overall length (145mm screw end to screw end) so will be posting some stuff up here on that testing.

Timmy2time, send me a PM of the specs that you are requiring and a postal code and I'll give you some info! :D
By TheBoffin
#5921
Not sure if this is going to be the correct spot, but it is a LiFePo4 question, so here it goes :)

I work at a motorcycle shop where we sell 2 different brands of LifePo4 replacement batteries. One of them is catching my eye as a very nice alternative to the SLA batteries we currently use. The brand is Shorai and they make them in a case that resembles a traditional SLA. There website can be found here http://www.shoraipower.com/default.aspx

To those who have experience with LiFePo4 batteries, would you mind taking a look at these to see if they are worth the effort? They make several styles and sizes, and have a few 14Aheq that are the same size as the 10Ah SLA batteries. My main question, is there is not a lot of data on their site, making it dificult to do any real comparisons. They are also classified as "starter batteries" capable of delivering a high amp discharge, but what about run times? Does being a "starter battery" mean that it is not as capable of delivering the runtime as well? Anyone with some insight to this, please respond!

-Boff
By TheBoffin
#5935
OK, so I did a little diggin into the Shorai batteries, and while they produce HUGE amp capabilities, their Wh rating is garbage. a 14Ah Pb eq actually only stores [just shy of] 60Wh! While they might look good, they won't work.
User avatar
By gameboy
#5952
thanks Boffin... so what i am reading here is that even though its a lipo style battery the same school of thought holds true for both, or for this matter, all styles of batteries. starter batteries have high cranking amps, but no run time and deap cycle batteries have huge run times, but a little lower on the cranking amp... even lipo.

interesting to say the least!!!
By TheBoffin
#5959
That is exactly what i am saying. The output of the starter batteries was quite impressive and would be great for a "drag scooter" i suppose, but not for our applications.
By COS
#6032
When they are classified as a "Starter Battery", that means the have good power deliver for a short burst.
Shorai used to use A123 cells ANR26650 but went to a different manufacturer to reduce cost.

One other thing to consider is, does this battery have a built in BMS?

Consider building a DIY pack from Headwayheadquarters.
By TheBoffin
#6034
Trust me, I have contacted Headway, but sadly, I must modify the battery tray of the Schwinn before I can fit a [decent] pack in there
By erikv
#6074
A123 is now making a 12v7 style replacement (ALM 12v7) that can be used in any application that typically uses a lead acid battery. Their battery has BMS built in as well as a user replaceable fuse for overcurrent protection and can be charged with the same charger that was originally used for the lead acid battery. While the voltage is about the same, the Ahr capacity is not quite the same. In theory you'll get better overall performance under heavy load as the internal resistance is vastly less than a lead acid.

For more information:

http://www.buya123batteries.com/v/vspfiles/images/a123/406017-001_ALM_12V7_Users_Guide.pdf

I just ordered a Razor E325 and will do some back to back testing. I'm interested in seeing how well they perform compared to the lead acid batteries. Acceleration should be better, and the lighter weight should help too.
User avatar
By gameboy
#6088
thats pretty sweet. half the weight, more power... whats the price?

also it states in the pdf. to not hook more that 4 of these in series or you will damage them. so 48v is the limit with these things.
User avatar
By bassiclyLouDog
#6090
$130 each on ebay. compared to $20 for 1 sla. ouch. I man there's no comparison but geez oh man.
By erikv
#6101
So completed some testing with a Razor E325 scooter. First test was with the fully charged lead acid batteries (stated 7 AHr capacity). The test loop was 3/8 mile with some downhill and some uphill (not more than 10' elevation change), but mostly flat. The lead acid results:

Lap #: time in minutes (average speed in mph)
Lap 1: 1:51.33 (12.5)
Lap 2: 1:50.54 (12.3)
Lap 3: 1.50.76 (12.8)
Lap 4: 1.50.39 (12.5)
Lap 5: 1.51.45 (12.1)
Lap 6: 1.52.90 (12.0)*
Lap 7: 1.52.90 (12.0)*
Lap 8: 1.54.43 (11.7)
Lap 9: 2.01.91 (11.1)

* lap timing software did not trip, so lap 6/7 is split evenly from the available data.

Test considered finished when scooter could not make it up the small hill 1/8 into Lap 10. Still a bit of juice left to limp home (about 1/4 mile).

The results with the A123 ALM batteries (stated capacity 4.6 AHr):

Lap #: time in minutes (average speed)
Lap 1: 1:36.29 (14.1)
Lap 2: 1:36.25 (14.5)
Lap 3: 1.37.34 (14.2)
Lap 4: 1.37.74 (14.0)
Lap 5: 1.37.34 (14.4)
Lap 6: 1.36.87 (14.7)
Lap 7: 1.36.98 (14.0)
Lap 8: 1.37.49 (14.5)
Lap 9: 1.38.71 (13.8)
Lap 10: 1:38.17 (14.5)
Lap 11: 1:38.34 (13.9)
Lap 12: 1:41.42 (13.6)
Test considered finished about 3/4 thru Lap 13 when low voltage cutout was reached on A123 batteries. No limping home. When they are empty, that's it.

In addition to the faster lap times, it was noticeably stronger going up the small hill on just about every lap. Performance dropped off slightly on Lap 12, but not really before that.

I'll repeat the test with the lead acid batteries again tomorrow.

P.S. If I were racing this scooter and I only needed 10-12 laps, the A123 batteries are by far the faster way to go. :mrgreen:
User avatar
By Knotical
#6103
Your data are interesting but I see some cool things that you might not have noticed.

My Assumptions:
  • the course is exactly .375 miles
  • you manually used a stopwatch with a lap feature to measure your lap times
  • you hit the lap button at exactly the same spot every lap
  • you rode the course exactly the same way every lap without cutting corners, going wide, etc.
Of course the last 2 can't really be done "exactly the same way every lap" so you get some variability that is not caused by the batteries. However, the data does show that even though you couldn't eliminate it, you did do an impressive job minimizing that variability. :D So, great job - I know that it's almost impossible to eliminate ALL weird stuff like lap 4 in the first set which has a quicker lap time but a slower lap speed than lap 5.

Anyway, I've added a column of extrapolated information to your data that I think shows something useful.

erikv wrote:fully charged lead acid batteries (stated 7 AHr capacity). The test loop was 3/8 mile with some downhill and some uphill (not more than 10' elevation change), but mostly flat. The lead acid results:
Code: Select allLap #:  lap time  lap speed       Overall avg speed (ttl dist ÷ ttl time)
===============================================================================
Lap 1:  1:51.33  (12.5 mph lap)   12.53 mph Overall avg | Overall avg actually
Lap 2:  1:50.54  (12.3 mph lap)   12.57 mph Overall avg | increases slightly for
Lap 3:  1:50.76  (12.8 mph lap)   12.58 mph Overall avg | laps 2-4. Battery or
Lap 4:  1:50.39  (12.5 mph lap)   12.60 mph Overall avg | rider? Hard to say.
Lap 5:  1:51.45  (12.1 mph lap)   12.58 mph Overall avg
Lap 6:  1:52.90  (12.0 mph lap)*  12.54 mph Overall avg
Lap 7:  1:52.90  (12.0 mph lap)*  12.51 mph Overall avg
Lap 8:  1:54.43  (11.7 mph lap)   12.47 mph Overall avg
Lap 9:  2:01.91  (11.1 mph lap)   12.35 mph Overall avg
===============
Total: 16:56.61

* lap timing software did not trip, so lap 6/7 is split evenly from the available data.

Observations:
In the first 5 laps, there is only 1.06 seconds difference between the fastest and slowest lap. Starting with lap 6, the difference gets bigger fast. Lap 8 is 4.04 seconds slower than the fastest lap and lap 9 in 11½ seconds slower. Still, in a 9 lap race if you can get a good lead in the first 5 laps, they might not catch up to you until the end. Dramatic finish.

erikv wrote:The results with the A123 ALM batteries (stated capacity 4.6 AHr):
Code: Select allLap #:   lap time  lap speed       Overall avg speed (ttl dist ÷ ttl time)
================================================================================
Lap 1:   1:36.29  (14.1 mph lap)   14.49 mph Overall avg
Lap 2:   1:36.25  (14.5 mph lap)   14.49 mph Overall avg
Lap 3:   1:37.34  (14.2 mph lap)   14.44 mph Overall avg
Lap 4:   1:37.74  (14.0 mph lap)   14.40 mph Overall avg
Lap 5:   1:37.34  (14.4 mph lap)   14.38 mph Overall avg
Lap 6:   1:36.87  (14.7 mph lap)   14.39 mph Overall avg
Lap 7:   1:36.98  (14.0 mph lap)   14.39 mph Overall avg
Lap 8:   1:37.49  (14.5 mph lap)   14.38 mph Overall avg
Lap 9:   1:38.71  (13.8 mph lap)   14.35 mph Overall avg | Interesting. Slight
Lap 10:  1:38.17  (14.5 mph lap)   14.33 mph Overall avg | stopwatch glitch?
Lap 11:  1:38.34  (13.9 mph lap)   14.32 mph Overall avg
Lap 12:  1:41.42  (13.6 mph lap)   14.27 mph Overall avg
===============
Total:  19:32.94

I'll repeat the test with the lead acid batteries again tomorrow.

Observations:
The first thing I notice is there is not even a 1 second difference until the 3rd lap. Then, the difference between the fastest and slowest lap is only 1½ seconds for the first 8 laps, then 2½ seconds for laps 9-11 and finally 5.17 seconds slower on lap 12.

So what I am seeing is that not only do the A123 ALM go faster and run longer but they are also more consistent in their output.

But here's the best part:
Code: Select allLap   Lap time difference
===========================
Lap 1   00:15.04
Lap 2   00:14.29
Lap 3   00:13.42
Lap 4   00:12.65
Lap 5   00:14.11
Lap 6   00:16.03
Lap 7   00:15.92
Lap 8   00:16.94
Lap 9   00:23.20
================
Total   02:21.60

That means the you with the A123 ALM will finish lap 9 before the you with the SLA starts lap 9. How you like them apples?

But does this performance come at too high a price tag? Did I read that correctly that the $$$ difference is $260 vs. $40?

Comparison: The A123 ALM is . . .
  • 16.2% faster (9 lap avg speed comparison)
  • 13.9% quicker (9 lap total time comparison)
  • lasts 15.4% longer
  • but costs 6½ times more
Unless you're racing for money or transporting live organs, it's hard to make a business case with that kind of cost difference.
User avatar
By gameboy
#6105
I was thinking the same thing about the cost, but if these batteries last 6x as long as the sla's then its a wash and you get better performance. Lets also not forget that you DONT have to buy a lithium charger and BMS system for this since it is capable of charging with a standard SLA charger and it has its own internal BMS, which is nice, so actually you might come out ahead on this thing if, IF, they last 6x longer than an SLA, which is not hard to do if you dont take care of your batteries and have any one of the miriad of problems an abused SLA can have.

Now the only real draw back i can see at this time (besides price) is a maximum of 48v is all these batts can do. :cry:

Whatcha think? Am i close?
User avatar
By Knotical
#6107
gameboy wrote:I was thinking the same thing about the cost, but if these batteries last 6x as long as the sla's then its a wash and you get better performance.

Lets also not forget that you DONT have to buy a lithium charger and BMS system for this since it is capable of charging with a standard SLA charger and it has its own internal BMS, which is nice, so actually you might come out ahead on this thing if, IF, they last 6x longer than an SLA, which is not hard to do if you dont take care of your batteries and have any one of the miriad of problems an abused SLA can have.


Those ARE good points. (Now it's time to let my ignorance shine.)

What is proper maintenance for maximum SLA life?
  • Charge after every usage/outing?
  • Charge once a month of non-use?
  • Charge the night before every usage/outing? (But only if it's been ___ days since last charge?)
  • Never drain completely?
  • something something?

gameboy wrote:Now the only real draw back i can see at this time (besides price) is a maximum of 48v is all these batts can do. :cry:

Whatcha think? Am i close?


I don't think I would call that the "only real drawback". :) From what I read, you can have an array of up to 40 batteries (four modules in series and 10 modules in parallel 4S10P). Where-in-the-hell are you gonna stow 40 batteries? Or even 16 for that matter? Plus, 16 batteries @$130 is $2,080 and 40 @$130 = $5,200.

I'm pretty gullible sometimes but even I ain't gonna believe you're gonna drop more than 2 grand on scooter batteries. :lol:
User avatar
By gameboy
#6110
Lol. Good points about the sheer cost of the dang thing and you got all the SLA points down also just for whatever reason people have they can know how to take care of them, they just dont. They get tired and put the scooter away saying "i'll charge in the morning" , kids get on the thing, run the battery down and dont tell dad so he can charge, you run it pretty hard one day and oneof the batteries goes a little farther down than the other which causes the good battery to compensate and drain more and now the good battery is as bad as the one having a problem only you dont know it till both batteries are shoeing signs of a problem.... And the list goes on

But a lot of people here like to have scooters with more voltage than 48v so for them this battery is out, but just the cost alone would put me off since i can go buy a true lipo system and a brushless motor and all the other crap that goes with this new fangled scooter i qm building for 1/4 of the cost of a decent size battery pack it would take to go ten miles.

So, with that said you have no ignorant statement in my book.
By erikv
#6124
I used my iPhone and a lap timer app to record lap times, so it's GPS based (Harry's Lap Timer Pro) -- no need to hit a button. I'm trying to make sure the test conditions are as similar as possible. Also of note, the charger supplied with the scooter has a red/green light on it (red when charging, green when done). The A123 batteries get the "green light" after as few as 5 hours, while the instructions with the scooter recommend a minimum 12 hour recharge time on the OE lead acid batteries.

I'll continue to test and post results. I'm curious to see if the lead acid batteries will improve after a few cycles. I might get a few more laps, but not any more speed.
User avatar
By Knotical
#6127
erikv wrote:I used my iPhone and a lap timer app to record lap times, so it's GPS based (Harry's Lap Timer Pro) -- no need to hit a button. I'm trying to make sure the test conditions are as similar as possible.

That's a great idea. Still, I can see how the app might have a slight lag as it reads the GPS and captures the lap time - which could be causing the slightly inconsistent lap readings. I think you're doing everything you possibly can to minimize those inconsistencies. You have reached the point of dimishing returns, i.e., it would take significantly more effort to achieve minimal gains in accuracy. Not worth it.

erikv wrote:Also of note, the charger supplied with the scooter has a red/green light on it (red when charging, green when done). The A123 batteries get the "green light" after as few as 5 hours, while the instructions with the scooter recommend a minimum 12 hour recharge time on the OE lead acid batteries.

That's yet another mark in the plus column for the A123. Now if we could only get the economy of scale to kick in and bring the cost down to $60 a pop. (Or $40?) I think they would sell a LOT more batteries if they were only 2~3x the cost of SLA. Would I be a prophet if I suggested that this technology has the potential to replace SLA in the marketplace? Dunno. ;)

erikv wrote:I'll continue to test and post results. I'm curious to see if the lead acid batteries will improve after a few cycles. I might get a few more laps, but not any more speed.

Please do. I am also interested in seeing what happens. This does sound like an interesting technology. And I am happy to hear about it through your tests.
If you think of it, comment on any interesting things that happen on the laps. Especially if you think it had an impact (positive or negative) on the lap times.
User avatar
By Knotical
#6178
I heard something on the news about A123 this morning. I didn't realize before today that they had received a crapload of federal and state grants and incentives (and we have really no hope of ever seeing any benefit from that money).

Massachusetts-based A123 Systems -- which received $279.1 million in stimulus money from the Department of Energy, and up to $135 million in incentives from the State of Michigan -- boosted the base salaries of two vice presidents and its chief financial officer on February 8.

Cool, huh? :roll:

Almost 2 months ago, their stock was "at an all time low". About 2 weeks ago the stock price dropped another 50% from that "all time low".
User avatar
By gameboy
#6179
Knotical wrote:I heard something on the news about A123 this morning.
Almost 2 months ago, their stock was "at an all time low". About 2 weeks ago the stock price dropped another 50% from that "all time low".



sounds like its time to buy, buy, buy!!!!
By fresh101
#9625
Hello Everyone, I got a quick question. I am upgrading my Schwinn Electric scooter (Currie Tech) running a 36v 1000w motor to a 48v LifePO4 setup instead of SLA. The pack that I am planing on using is a 48v 15Ah LifePO4 pack but wondering what controller should I use to get the most out of the Currie 36v 1000 watts motor? Please note, I would like to go with Kelly controller but dont know exactly what amperage model should I choose, maybe KDS48200 which maximum is 200 amps or the KDS48100 maximum 100 amps. Please help, thanks
By fresh101
#9632
robnewyork wrote:100 amps will cover a 100 watt motor


Hey Robnewyork, thanks for the quick response but just to clear things out, did you mean 100amps will cover 1000 watt motor instead of 100 watt motor? Please also note that the controller mentioned above was of max amperage and the continuos amps is less (please view specs below). Thanks again

KDS48100 KDS48100E KDS48200 KDS48200E
•Peak 1min: 100A. •Peak 1min: 100A. •Peak 1min: 200A. •Peak 1min: 200A.
•Continuous: 40A. •Continuous: 60A. •Continuous: 80A. •Continuous: 120A.
By electrodj
#15961
razor e 300 moded li-ion 25V 15Ah
6 X18650 2,5Ah parallel X 6series (36 cells)

2.5 times more power
Attachments
1512810_10152474601943142_6363668015419285626_n.jpg
User avatar
By zogthegreat
#19196
electrodj wrote:razor e 300 moded li-ion 25V 15Ah
6 X18650 2,5Ah parallel X 6series (36 cells)

2.5 times more power


Where did you order them from?
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