As an experiment I ordered a 48V 20AH LiFePo4 battery pack from Yesa and I installed in on my Evader 1000 electric scooter. It ways about 30 lbs and I used it to replace 4 SLA 12V 45AH batteries which weighed together around 140 lbs, so my scooter is now about 110 lbs lighter. One problem I have found is that when I accelerate hard, the Evader pulls more than 60A which is enough to pull the voltage below the low-voltage cutoff and the pack shuts itself down. It then stays down for some period before waking up again, it seems. I have asked Sam at Yesa for advice on what to do in this situation.
I have not done a range test yet, and thus far I have only gone a couple of miles at a time. The scooter feels much lighter and the top speed seems to be up 1-2 mph to around 33 mph.
More reports as I gain more experience.
Decibel1,
Good luck! Nice to see someone as the guinea pig! It will be interesting to see if you can get the range out of the reduced capacity pack. Price?
Les
The price was $1100 delivered to New York State. The package includes the BMS and a 3A charger.
great stuff, the more people testing these cells the better. I'd be interested to hear what the voltage drop under load is and thus the pack resistance and also how and whether the BMS works. Is the charger/bms charging the cells to the correct voltage? and does the low voltage cutoff work only for pack voltage or when any indidvidual cell fall below a certain voltage.
One solution to your cutoff problem would be to reduce the the peak current draw from the controller by reducing the restistance of the the shunt. Another would be to bypass the bms on discharge.
The voltage sag is about the same as on my SLA pack, as read on the digital battery display on the dash, but unlike my SLA pack, which was managed with powercheqs, the pack cuts out itself whereas with the SLA system the low voltage cutoff was governed by the controller. Your idea about bypassing the bms on discharge may be a good one. Thanks.
you could buy another pack and then connect it in parallel so that the current draw on each pack is halved.
its still gonna be half as much as the SLA pack... and you'll probably get a lot more range than you had with the SLAs
I just went out on a 5 mile test trip and all went well. As long as I don't accelerate as fast as I can the voltage stays above the cutoff. Interestingly, the scooter is so much lighter that I don't have to use as much current to accelerate as fast as I used to.
I've thought about adding a second pack. There's plenty of room for it.
Please post pictures of the pack and also how much was it ?? Thanks for any info. God Bless :)
Is there a Evader Dealer in New York?
That price was just for the battery pack. I got my Evader a while back from a guy in Colorado who had a few for sale at only $600. I don't even know if you can buy one anymore.
Today I tried bypassing the low voltage cutoff circuitry on my battery pack bms during discharge, and all seems fine now. I will do more testing to determine range, etc., but I got the current up to 70A briefly. So now I am relying on the controller low voltage cutoff circuitry, and that should be ample protection for the battery pack. The bms is still connected during the charging cycle (and it may be still connected during the discharging cycle. I think I just bypassed the low voltage cutoff circuit.
Another report: Today I rode 8 miles to work, charged for two hours and then took a longer route (13 miles) home. The battery pack seemed to still have plenty in the tank. This 25 lbs of battery pack stores a lot of energy!
Today I did a range test and rode 18 miles before the pack ran down. That was over typical upstate New York terrain incuding hills and flats, and the trip had many stops and starts. The range is consistent with the 20AH rating of the pack and the average current measured by the scooter's digital ammeter.
Hey decibel,
Do everyone here a huge favor and log the data you get on those batteries to an .xls
sheet. Range, voltage fully charged, voltage fully discharged, what the range is on the
very first cycle and what it is after 100 cycles, daily soc usage, average speed. I would be optimistic if you get past the 50 cycle mark without range loss.
Keep us updated.
Thanks a million.
I also purchased a 48 volt LiFEP04 12 Ah battery Pack for my stand up scooter. I have not connected it yet but will report when I do. I was going to connect to my Project Scooter with dual 48 volt 50 amp motor but Sam recommended against such a High amperage unit.I will use this pack on the single motor unit. The current scooter uses a 22 AHR SLA rated at 300 amps discharge.
My experience with Yesa was pretty positive. They shipped about when they said they would and it took only about 5 days for the pack to get to me in New York State. The cells are 20AH cells, I believe. My pack arrived with a small dent in one of the cells due to shipping, but there is no leakage and everything seems to work ok. I can't do the logging requested because I don't have actual voltage readings to monitor, only a digital bar gauge. I do have a real-time digital ammeter on the Evader, but that varies from 3A to 70A depending on condition. I will report periodically on how the pack is holding up.
how exactly did you bypass the discharge protection circuit that you mention above? I have a 48V 12AH YESA pack that is also cutting out on me under the same way yours did. I have a 30MPH Lashout scooter with the Powerpack set up on it. Under normal riding, its fine, but it cuts out if I push the scooter hard and draw a few more amps than it wants me to. I am not worrying about damaging the cells, as I only run the stock 35 amp controller.
If you have SLA with 45Ah for 10 hrs discharge you need 40/65 (this is the Peukert Problem) * 45Ah for Li- which equals to 28Ah. Otherwise you get the problems you experience.
I assume the amperage cutoff problem was simply fixed with a "shunt" wire across the boards' battery-in load-out connection?
I'm not sure why they put amperage protection on these boards - the batteries should be matched to the application to start with; the motor controllers always have a amperage limit, for truly excessive discharge rates (aka short-circuits) you have a simple gadget called a fuse or circuit breaker.
I bypassed the voltage and current limiting circuit by simply connecting directly to the battery (-) point on the board. I did not change the charging circuit at all.
Also, I ordered a second 48V 20AH pack from Yesa and installed it in parallel to the first, again bypassing the voltage and current limiting circuit. Thus I am now relying on the controller to provide both functions. I am now charging the pack with a 48V, 8A 3-stage SLA charger, which seems to work ok (I should probably tweak the charging voltage up a bit), but it's been so cold and snowy in Rochester that I haven't had a chance to get out for any test rides.
This may seem a bit extravagant, but I only paid $600 for the scooter so I figure I can use it for some expensive experimentation :>)
Thanks for th tip. I may go ahead and try it.
I talked to another Lifepo4 supplier, and they said the reason for the protection is to increase the charge cycles of the battery pack, and also because discharge rates above a certain level actually affects the capacity of the pack. A 20AH pack may perform only like a 14-15 AH pack at higher discharges above whatever the cut off was set for. On my 48V 12 AH pack, the thing was nor designed to discharge continually above 2C-which I think means 20 amps continual use. If I bypass the cut off, I may get less distance on the pack by 20-25%, not even counting the increased amps the motor is taking.
I just went and bypassed the BMS on discharge and ran a test. I also hooked up a voltmeter to the pack and ran it to my handlebars so I could see the readings under power, and ran the scooter with and without the BMS. the voltages readings were erratic with the BMS removed, which makes me believe it may be doing more than just limiting maximums/minimums. I think I will use this pack on a slightly lower powered scooter I have been testing it on where it doesn't cut itself off with the BMS intact, and get a higher capacity pack for my 30MPH Lashout. It sure is nice that the LiFepo4 packs are not affected by cold temperatures, and the fact that the scooter weighs significantly less can be felt when riding (and when having to pick it up!)
Boy are you crazy - SLA charger for Li?
In the best case the BMS cuts the Voltage in the worst case you blow up the whole thing.
cheers
"Boy are you crazy - SLA charger for Li?"
Actually, the nice thing about LiFePO4's is they use exactly the same charging protocol as lead acid. For example, a 16 cell system can be charged with an ordinary CC-CV charger for 48 volt lead acid pack - CC charge until a pack voltage of 59-60 volt (i.e 3.7 per cell); CV charge at 59-60 volts until less than 0.1 amp; float at about 55 volts.
But of course, you should carefully watch the voltages the first time you charge the pack to be sure. I'd also check that every cell has the same voltage while charging the first few times to make sure the BMS is working - it's from China after all.
LiFePO4's is they use exactly the same charging protocol as lead acid.
PJD, yes I've seen this before. But aren't the cutoff voltages a little different?
The 3.7v per cell doesn't fit evenly into 48v for example. So at the very least you'd need to find an SLA charger where the voltage cutoff's are adjustable. Right? Hm, but LiFePO is 3.2v per cell and that does fit evenly into 48v, but 3.2v per cell doesn't fit evenly into 60v.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Actually, it works out pretty well for 48 volt and 60 volt packs anyway.
A "48 volt" lead acid pack contains 24 cells - while the "48 volt" LiFePO4 pack is typically built with 16 cells. I know, 48/3.2 = 15; but, their rating of 3.2 volts per cell isn't quite as conservative as the commonly accepted 2 volts per cell for lead acid - so they use 16 cells to assure the "48 volt" pack will really be 48 volts under even multi-C discharge rates - plus it allows the use of ordinary 48 volt lead acid chargers as well. It works like this...
The generally recommended cutoff voltage for the lead acid cells is about 2.45 volts per cell (actually temperature dependent) or 58.8 volts for 24 cells. The liFePO4 manufacturers (Valence, Yesa) seems to recommend 3.65 volts per cell cutoff or switching voltage, or 58.4 volts for 16 cells. Most 48-volt chargers have a cutoff or switching voltage of about 58 to 59 volts, so they should work fine.
Similarly with "60 volt" 20-cell packs.
Check here: http://www.yesa.com.cn/pages.asp?id=3
Of course, alway check the charger to be sure, it is charging at the right voltage. And, come to think of it, make sure the pack builder understands that "48 volts" means 16, not 15 cells.
All of the above comments on using an 48V SLA charger for a 16 cell LiFePO4 pack are correct. Using my 8A charger for a 40AH pack is only charging at C/5, which should be fine. With my parallel 20AH packs, each pack will put out a maximum of 35A, which should help with pack life cycle issues.
I e-mailed yesa about obtaining a bare 50AH cells and a BMS to build a pack. I was not impressed with the response:
My e-mail:
I am considering replacing the existing 48 volt, 40 AH lead acid pack,
in a electric motor scooter. The existing pack consists of eight pairs
of 20AH batteries, mounted in four battery box locations. A single, or
even two, rectangular LiFePO4 packs will fit in the battery boxes, but
16 individual 50AH cells (YL48100150) mounted in the four boxes will fit.
The scooter uses up to 50 amps of current continuously, and 95 amps of
current for brief periods.
What would be the cost of 16 individual YL48100150 cells and a BMS board
for this pack?
Also, I may want to upgrade the pack to 60 volts through the addition of
four more cells in the future. Do you have a 60 volt, 20 cell BMS
available?
Thank you for your assistance,
...
THEIR REPLY:
Dear Paul Donahue,
Thanks for your E-mail.
For your application, 50 amps of current continuously, and 95 amps of
current for brief periods. That require our 50AH cell .
We are now busy developing some for E-motorcycle now, the estimated
finished date is before the end of this month.
(I DIDN'T ASK ABOUT AN E-MOTORCYCLE)
Keep in touch and I will keep you informed .
You may keep an eye on our web updating for 50AH pack.
(I DIDN'T ASK ABOUT A PACK)
www.yesa.com.hk
Any question, please do not hesitate to ask.
Any question, please contact me at
MSN: sales-yesa [at] hotmail.com or Skype me: sales-yesa
E-mail:sales [at] yesa.com.hk Lily6533 [at] hotmail.com
Website: www.yesa.com.hk
TEL;86-755-88855368 15986775944 (Cell phone)
FAX: 86-755-82379471
Yours sincerely,
Sam
Yesa Co., Ltd
PJD,
If I were you I'd simply ask again with less verbiage - the more "background" you give the more chance you have of obscuring your question. In this context the background is just noise as you specifically don't ask any questions about your intended use. I wouldn't write the guy off for not reading your first email to him closely enough.
This is what I would write:
Sam,
What would be the cost of
a) 16 individual YL48100150 (50Ah) cells
b) a BMS board for the above 16 cells
If I add 4 more YL48100150 cells in the future do you have a BMS that will handle 20 cells?
I want to build my own pack - so I am looking for the price of cells and a BMS board.
Oh, and let us know what price he comes back with. I might go with 20 cells for my XM2K. Thanks!
John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.
John H.
Agreed, but even worse, I had a typo in my verbose question.
"A single, or even two, rectangular LiFePO4 packs will fit in the battery boxes..."
Should have been:
"A single, or even two, rectangular LiFePO4 packs will NOT fit in the battery boxes..."
But, his answer seems to imply that the 50AH cells aren't available at all yet, at the discharge rates I need.
Guys,
I see one problem with bypassing the low-voltage cutoff. As I understand it, the protection is on individual cell level, not on the entire pack, mainly to protect individual cells from too deep discharge. (The second reason for low voltage protection is that even bringing a well charged cell to too low voltage hurts it, but much less than deep discharge.) With the circuit bypassed you risk damaging some cells if you discharge the pack completely.
One way to get around the problem would be to put some kind of delay on the cut-off. For example a one minute timer would help discriminate high load from low charge status. Or measuring the current, so that the circuit cuts off only when current is low. Of course all this implies extra circuits and complexity. The simple solution is to buy another pack, to give you those 70 A without tampering.
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