Lithium battery question...

[SANGESF]

never mind lol we seem to be talking about different things entirely. I think I will stick to my sla but thanks for all the help

The original question you asked was how well will lifepo4 handle a draw compared to sla or NiMH.....
There is no comparison... Lifepo4 handles it better by a longshot...

My SLA would drop (sag) voltage. From 37.8 to 34.5 or by 3.3.
My lifepo4 would drop voltage from 38.4 to 36.6 or 2.2
Both at 20a draw

Difference is that lifepo4 holds the voltage throughout the entire ride as where the SLAs voltage will drop continously and to even lower voltages.

 

[SANGESF]

Dude, it's time for a hub motor..
Spend the $200 on a hub motor setup with all the controller, throttle, etc, etc and you'll have a MUCH MORE EFFICIENT setup.
I bet you'll at least DOUBLE your milage, with your current setup of batteries.
If you get rid of a heavy push trailer (if you're using one), get a lithium battery of the same AH rating and I bet you'll TRIPLE your mileage.

 

[motorbiker]

Ping has a good rep so I kinda pay attention to his battery specs.
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24v 20 ah

24V 20AH LiFePO4 Electric Scooter E Bike Ping Battery! - eBay (item 320565554322 end time Aug-22-10 01:33:48 PDT)

Specifications
Fit 24V Motor Wattage: 200 Watt to 450 Watt, 300 Watt Suggested
Voltage: 24 Volts
Capacity: 20 Amp Hours
Dimension: 200x105x150 mm ( 7.9 x 4.1 x 5.9 inches )
Weight: 4.70 kg ( 10.30 lbs)
Charging Voltage: 31 Volts
Charging Current: <5 Amps
Standard Charging Current: 1.5 Amps, 10 Hours
Quick Charging Current: 3 Amps, 5 Hours
Rated Discharging Current: 20 Amps
Max Continuous Discharging Current: 40 Amps
Max Discharging Current (Peak): 60 Amps
Amperage Cut-off Protection: 40 Amps
Lifecycle of the whole pack: >1000 times, >85% capacity.
Lifecycle of single cell: >85% capacity after 1500 cycles, >70% capacity after 3000 cycles. (<1C discharge rate and <1C charge rate)



--------------------------------------------------------------------------------------------------------------
24v 10 ah

24V 10AH LiFePO4 Electric Scooter E Bike Ping Battery! - eBay (item 320569710688 end time Aug-31-10 09:09:51 PDT)


Specifications
Fit 24V Motor Wattage: 50 Watt to 250 Watt, 200 Watt Suggested
Voltage: 24 Volts
Capacity: 10 Amp Hours
Dimension: 100x105x150 mm ( 4 x 4.1 x 5.9 inches )
Weight: 2.30 kg ( 5 lbs)
Charging Voltage: 30-31 Volts
Charging Current: <5 Amps
Standard Charging Current: 1.5 Amps, 7 Hours
Quick Charging Current: 3 Amps, 4 Hours
Rated Discharging Current: 10 Amps
Max Continuous Discharging Current: 20 Amps
Max Discharging Current (Peak): 40 Amps
Amperage Cut-off Protection: 30 Amps
Lifecycle of the whole pack: >1000 times, >85% capacity.
Lifecycle of single cell: >85% capacity after 1500 cycles, >70% capacity after 3000 cycles. (<1C discharge rate and <1C charge rate)
--------------------------------------------------------------------------------------------------------------

24v 15 ah

24V 15AH LiFePO4 Electric Scooter E Bike Ping Battery! - eBay (item 220646892279 end time Aug-31-10 09:09:20 PDT)

Specifications
Fit 24V Motor Wattage: 50 Watt to 350 Watt, 300 Watt Suggested
Voltage: 24 Volts
Capacity: 15 Amp Hours
Dimension: 150x105x150 mm ( 5.9 x 4.1 x 5.9 inches )
Weight: 3.50 kg ( 7.8 lbs)
Charging Voltage: 30-31 Volts
Charging Current: <5 Amps
Standard Charging Current: 1.5 Amps, 7 Hours
Quick Charging Current: 3 Amps, 4 Hours
Rated Discharging Current: 15 Amps
Max Continuous Discharging Current: 30 Amps
Max Discharging Current (Peak): 60 Amps
Amperage Cut-off Protection: 45 Amps
Lifecycle of the whole pack: >1000 times, >85% capacity.
Lifecycle of single cell: >85% capacity after 1500 cycles, >70% capacity after 3000 cycles. (<1C discharge rate and <1C charge rate)
-----------------------------------------------------------------------------------------------------------------

My guess is that he uses a good bms that will protect the battery pack so that it will last a long time.


The ES forum is filled with posts about what li batteries will do without a bms or with a simple bms.

I am more interested in what they will do with a good bms.

 

[motorbiker]

To make a long post short.

A good ping 24v 20 ah LiFePO4 battery with a good bms made to protect the battery and give long life has a suggested use rating of 300 watts and amperage Cut-off Protection: 40 Amps.

24V 20AH LiFePO4 Electric Scooter E Bike Ping Battery! - eBay (item 320565554322 end time Aug-22-10 01:33:48 PDT)

or just type in "ping battery" on eBay.

 

[deacon]

Dude .....

I have a good hub motor and controller sitting in the corner of my shop. I would rather walk than ride it. Okay, I have said a dozen times I have tried a hub motor and find it not to my liking. But thanks for the advice all of you ....

Just so you know I find the hub motor too anemic for my taste.... I want something with some bite to it.

File this under different strokes.... ... I have all the information I need now.

 

[motorbiker]

Dude .....

I have a good hub motor and controller sitting in the corner of my shop. I would rather walk than ride it. Okay, I have said a dozen times I have tried a hub motor and find it not to my liking. But thanks for the advice all of you ....

Just so you know I find the hub motor too anemic for my taste.... I want something with some bite to it.

File this under different strokes.... ... I have all the information I need now.

My advice would be to only use a li battery with a good bms.

If you have a 24v motor rated larger than 300 W then you might need a battery pack larger than 24v 10 ah because the bms can cause the battery to cut off to prevent damaging it.

And I would not want to use a li battery without a good bms.

I know a lot of people do but I would rather use my SLAs.

I have read many very long ES threads.

 

[jdcburg]

Hi folks – I would like to continue this discussion. I think most of us who have gone to lithium tried lead first. Some of us converts get the fever but I know there is nothing that turns me off a religion or a technology faster than proselytizing, so I’ll try to avoid that. I’d appreciate it if others would too. On the other hand, when comparing I prefer data/numbers and facts, not hearsay and feelings.

I’d like to define the terms a little. First, there are several types of lithium batteries: Lithium Polymer (LiPo), Lithium Cobalt (LiCo), Lithium Manganese (LiMn) and Lithium Iron Phosphate (LiFePO4), to name a few. Commercially they are used in everything from cell phones to laptops to power tools. The reason they are popular is that they are considered safe and reliable and they have a high energy density compared to other batteries, not only in size but also in weight. It would be hard to imagine an electric drill with an SLA on the handle. But there are many solar homes that keep banks of lead for backup. The Toyota Prius uses NiMH not lithium. Even among the different types of lithium, there are significant differences in energy density, safety, C rate, charging requirements, even nominal voltage. So ANY generalities regarding lithium batteries are so vague and wide ranging that they are essentially useless.

Also some caveats: I am no expert. I’ve read some and found out things by trial and error but you should put YMMV after everything I say. My only direct experience is with 12V 12ah SLAs and 20 ah LiFePO4s from Elite Power Solutions. Finally, I am NOT trying to sell anyone on lithium batteries. I don’t want anyone to go out and buy anything on my recommendation. I would like to get people to think about the technology with an open mind. I would love it if people would actually put up some of their numbers so I and others could compare apples to apples. I’ll give you some of mine in another post - jd

 

[jdcburg]

Part 2 - I have a digital speedometer/odometer that calculates trip distance and average speed for each ride. I use a Turnigy WattMeter to collect electrical data. It calculates other data and displays the figures. The most useful for comparison are amp-hours (ah) and watt-hours (wh). From those I calculate ah/mile and wh/mile by dividing ah and wh by the number of miles in the ride. Well Excel actually does that part. You can probably guesstimate ah if you know the amps of your charger and you pay attention to how long it takes to charge your pack. Multiply ah times nominal voltage to get wh. The WattMeter uses actual voltage so it’s a little different.

OK so here are some figures for my 350W 24V pedal assist ebike for the past dozen rides. All are averages with the range in parentheses: avg distance - 13.5 miles (4.7-27.9), average of the average speed for each ride - 13.8 mph (11.1-15.6 avg mph/ride), avg top speed - 30 (27.8-34.2), ah/mile - 0.64 (0.46-0.86), wh/mile - 15.26 (11.64-20.95), peak amps 28.03 (27.42-28.46), peak watts - 659.23 (644.1-682.4). Interesting this is from a nominal 350W motor. The 20ah LiFePO4 are rated 2C, so my max (28 amps) is 1.4 C, well within their capacity. That same 28A would be 2.33C for my old 12 ah. It's no wonder they sagged under that load, especially on some of the long hills around here.

Average speed is one that is interesting. Whenever I look at the speedo it’s in the high teens to low 20s and that’s where I would have guessed my average was. But I have a drive-through-the-derailleur system and I shift down for the steep hills. So I go slower up them. I think because I spend more time going slower up the hills than fast down the hills, it brings my average speed down.

In part 3 I’ll talk about how I built a combination BMS/pack charger that keeps my pack balanced while charging and warns me if any cell is getting dangerously low while in use. The whole shootin’ match is pretty simple and cost me under $75 + s&h – jd

 

[Sahevaan]

Since i am into aeromodelling ,
I would suggest you to check out the Lithium Polymer battery packs with the highest C ratings (or Discharge ratings) .
Maybe you are aware that if your Li-po cannot suffice your needs and draws a higher current , the battery could explode .

Cheers ,
Sahevaan

 

[SANGESF]

I know for a fact that either way you look at it, the lifepo4's really are the best bang for the buck/safety.

Deacon's hub motor that has no "bite" must be a low voltage/wattage one.

Just today, I went to the local bike shop and picked up a 36v 750w one and DAMN! What a difference it makes from my 24v 250w one that I was pumping 36v into.

Initial torque is amazing... I can go from 0 to 20 in about 10sec with a max amp pull of ~30 or 900+ watts and that is with a total of 345lbs being ridden.

I don't understand the need (re: ineffeciency) of a push trailer or non hub motor setup with antiquated (re: SLA or NiMH) battery types.

It's like saying, I'll stick to my old pre 2000 motorola flip phone that runs on NiCad instead of using my iPhone with it's li battery.. It really doesn't make sense.

To each his own, I guess...

All I know is that with my own particular setup, I get 80 miles travel at 20mph with at least 20miles to spare (at a slower speed of course).

Yes, it cost me $500 total for the two batteries (2-36v LiFePO4)---- $200 for the bike and another $250 for the other motor, for a grand total of about $1000

However, it will last me at least 3 years and still have 100% of my speed/distance.

 

[motorbiker]

My thing is I like to pedal most of the time and don't hit the switch very much.

I can go well over 20 miles distance without even hitting the switch on the Ezip.

My Heinzmann hub will freewheel but none of the others will and they are hard to pedal with the motor off.

The Ezip currie motor will freewheel too. That is the one I tend to travel on most.

The heavy sla batteries tend to build up the legs making for much longer distances.

I have lost alot of weight riding that bike too and it is faster than ever !

 

[jdcburg]

Part 3 – I agree with MB on BMSes – Li packs benefit from them. BMS simply stands for battery management system. In a practical sense that means all the cells get charged to their maximum without overcharging and no cell gets discharged below its minimum. My understanding is that most packs that use multiple batteries have a BMS of some sort. That includes NiCad tool packs, etc, not just Li. Some ebike packs come with them but if you are making a pack or buying individual cells, then you have to devise your own. There are also aftermarket ones and long threads discussing the relative merits of factory-built vs aftermarket on Endless-sphere. Problems arise when a BMS fails, as then the BMS may prematurely shut down a perfectly good pack or, more importantly, a rider may ruin an expensive pack by overdischarging or by overcharging it. Some argue that for various reasons (poor soldering, poor quality parts, rough shipping) factory-built BMSes are more prone to failure.

I bought my LiFePO4 packs without a formal BMS, as some riders propose that LiFePO4 are the most forgiving and that, with care, a rider can be his own BMS. While that may be true, I use a pair of relatively inexpensive devices to be my BMS and they seem to work well. The first is a Celllog 8M, which is essentially an 8 channel voltmeter with fully adjustable alarms for high voltage (pack/individual cell), low voltage (pack/cell) and differences in voltage between cells. The alarm beeps and the affected cell indicators flash when the alarm is triggered. The Celllog also has an external alarm circuit that will trigger a louder alarm or LED. The alarm circuit can also be used to turn off the charger when any cell or the whole pack reaches a preset limit or turn off the controller if a cell or the pack gets too low. As I use an 8 cell (24V) pack, I use one of these. I don’t bother with the external alarms/shutoffs at this point. If I know I might be running low, I keep a closer eye (and ear) on it while riding. They are under $15 from HobbyKing Online R/C Hobby Store : Cell-Log 8M Cell Voltage Monitor 2-8S Lipo. It requires a 9 pin JST-XH connector. I got 5 connectors for $10 (inc s&h) on ebay.

The other device I use is a Turnigy Accucel 8150, $42.44 from Hobby King as well - HobbyKing Online R/C Hobby Store : Turnigy Accucel-8 150W 7A Balancer/Charger. This is a balancing charger that uses the same JST connector as the Celllog to monitor the battery while charging. It is fully programmable for charging all kinds of Li batts as well as lead, NiCad and NiMH. It monitors each cell (up to 8) while charging and brings them all up to the proper voltage (3.60V for LiFePO4) without overcharging. It requires an external 11-18V power source. I originally used an SLA and charger for its power but since have adapted an old 300W computer power supply. It charges at up to 7A, so if I use 16 ah I can get it mostly charged in a little over 2 hours, although a full charge with balancing takes longer.

Hobby King is in Hong Kong and shipping is slow and relatively expensive, or fast and more expensive. I ordered them separately and they took 2-3 weeks each to eastern US. The Celllog was about $5 and the charger was about $19 s&h. Add a few bucks for standard connectors and wire and you’re all in for under $100. If you use 36 or 48 volts, buy 2 Celllogs and divide the pack for charging.

In part 4 I’ll talk about the LiFePO4 batteries I bought. That final post should be shorter - jd

 

[Recumpence]

I will post my experience here as I have had literally hundreds of packs with various battery chemistries in the last decade in RC and E-bikes.

Lipo is the highest power density per pound and per cubic inch, period. They are also cheaper than Life Po4. A 24 volt, 20 amphour Lipo pack can be as little as $280 and that is 30C pack! That pack will only weigh 9 pounds and take up less space than two house bricks. They can be damaged by overdischarging. But, the new cells are much more stable than the older cells. You really have to try hard if you want to blow one. ALso, Lipo cells have full power (high C cells) all through the charge. They ahve VERY low internal resistance.

There is a huge aversion to lithium for some reason. However, once you go there, you will not go back.

I will admit, I have a bit more money to spend than most (I have an E-bike business). However, SLA will eventually cost you as much or more because of the lower mileage you will get out of them before replacement. Also, the added weight of SLA wears out bike parts faster from the added strain.

Matt

 

[jdcburg]

Thanks Matt. I’ve read lots of ebikers are going to LiPo. I’d heard LiPo are safer now but I didn’t realize they were getting so much cheaper. I think that’s a big part of the fear about lithium – the notion that you do one thing wrong and your $500+ investment is toast. You have to pay attention but I think in general lithium packs are not difficult to manage. I don’t think they are delicate or overly sensitive. Like any piece of quality machinery a little respect goes a long way toward making them last.

As I said in a previous post my only lithium experience (other than cell phone, laptop, camera, etc) is with LiFePO4s, specifically 20 ah Thunderskys from Elite Power Solutions. These come in plastic 4-packs with a nominal voltage of 12.8V. In fact their operating voltage in my experience is 13.2-13.3, so a 24 V motor has more pep than on SLAs. Each pack is 7x3x6.5 inches and weighs 6.6 lbs. They are rated 2C (40 amps) continuous and 10C impulse. I’ve seen impulse defined as no more than 5 seconds every 30 seconds. Obviously that doesn’t compare to the 30C continuous rating of Matt’s LiPos but it is fine for my needs. In addition, LiFePO4 is very stable – these cells can be charged at 3C (60 amps) so a 75% discharged pack could be safely recharged in 15 minutes with the proper equipment. As I said in a previous post I use a 7A balancing charger that will recharge my packs in a little over 2 hours.

I use a 24V 350W brushed Unite motor to power a through-the-derailleur 8-speed mtb with 26” tires. Level ground top speed is around 20 mph. I use a Turnigy WattMeter and a digital speedometer to collect data on my rides. The WM records data such as peak amps, peak watts and minimum voltage. It also calculates amp-hours (ah) and watt-hours (wh). I transfer that data to a spreadsheet along with distance, average speed and top speed for each trip. I discussed some of these figures in a previous post in this thread. One thing I have noticed with these cells is the relatively flat discharge curve. While a fully charged 8-cell pack comes off the charger at 28.8V, it quickly (within ½ mile) settles down to about 26.8, or about 3.35V/cell. My average ride is 13.8 miles and uses 8.8 ah (210 wh), which is 44% depth of discharge (DOD). The average ending voltage of the pack is about 26.3 with each cell at 3.29. On my longest ride (27.9 mi) I used 16.03 ah and ended at 24.37, 3.05/cell. I wasn’t at a full charge when I started that ride - the pack was at 26.88, 3.36/cell. The other rides where I have used 11-12 ah have an average ending voltage of 25.97 -3.25/cell.

The other major benefit I’ve found of the LiFePO4s is the relative lack of sag, or voltage drop under load. The WM records the lowest voltage of a ride as well as peak amps. My average peak amps is 28.05, about 1.4C. The average minimum voltage is 22.66 V. The WM doesn’t give the times of Ap and Vm but I suspect they occurred simultaneously. I never used the WM with my SLAs but the day I decided to buy a lithium pack was the day I had to push that same bike up the last hill of a 6-mile SLA-powered ride. When I got home I put my voltmeter on the SLA pack and it read over 24 volts. I scratched my head – that should have been enough juice to get me home. Then I lifted the wheel off the ground and hit the throttle. The meter immediately dropped below 21V and stayed there until I let off the throttle. That was with no load, just the tire spinning in the air. Those 12 ah SLAs probably didn’t have 50 cycles on them and were always recharged immediately after use, but they sagged below the point of usefulness that day after only 6 miles.

The LiFePO4 cells I bought are $120/pack. I ordered 2 packs. They shipped from Arizona and came within a week to Massachusetts USA. S&h was $20. If you add the $100 I spent for the charger/BMS system I described in a previous post you are at $360. The seller estimates 1500 cycles at 80% DOD. Many ebikers claim to get that many cycles and more from LiFePO4, so that appears to be a reasonable expectation, not seller’s hype. I don’t think regular SLAs will tolerate 80% DOD on a regular basis. Even deep-cycle lead will have a hard time with that kind of use. If you get 250 cycles to a set of 12 ah SLAs (very generous IMO) and they cost $60/set plus $25 for a charger, you’re at $385 after 1500 cycles. If you get 150 cycles, you’re at $625. In my experience, a cycle on 20 ah LiFePO4 is about twice the distance of 12 ah lead, so in miles traveled there is almost no comparison.

If you’re the kind of person who uses a toy a few times and then leaves it in the garage, you’re better off with lead. If your average ride or commute is very short or you can charge in the middle, lead will be closer but will still cost 7% to 70% more in the long run. If you’re really tight for cash, start off with lead and start saving for lithium. But if you’re likely to use your ebike long-term and want the most bang for the buck, do some research on the various forums and see what you come up with - jd

 

[jdcburg]

In case anyone is interested here is a screenshot of my spreadsheet. The averages at the bottom are for rows 34 through 45. I got the digital speedo then and that completed the instrumentation needed to compile the numbers.

Column labels that might not be clear: Vs - starting voltage, Ve - ending voltage, Ah - amp hour, Wh - watt hour, Vm - minimum voltage on ride, Ap - peak amps on ride, Wp - peak watts on ride. Ah/mi and Wh/mi are calculated by Excel. The last column of numbers is wh/mile divided by avg speed. I don't know if it has any value but sometimes I get carried away with making Excel work (smiley face here).

Numbers with asterisks are calculated because I reset either the speedo or WattMeter before the end of the ride. Any questions give me a holler - jd

 

[SANGESF]

I will post my experience here as I have had literally hundreds of packs with various battery chemistries in the last decade in RC and E-bikes.

Lipo is the highest power density per pound and per cubic inch, period. They are also cheaper than Life Po4. A 24 volt, 20 amphour Lipo pack can be as little as $280 and that is 30C pack! That pack will only weigh 9 pounds and take up less space than two house bricks. They can be damaged by overdischarging. But, the new cells are much more stable than the older cells. You really have to try hard if you want to blow one. ALso, Lipo cells have full power (high C cells) all through the charge. They ahve VERY low internal resistance.

There is a huge aversion to lithium for some reason. However, once you go there, you will not go back.

I will admit, I have a bit more money to spend than most (I have an E-bike business). However, SLA will eventually cost you as much or more because of the lower mileage you will get out of them before replacement. Also, the added weight of SLA wears out bike parts faster from the added strain.

Matt

The cost on lipo as opposed to Lifepo is a bit too expensive still for me....

I purchased my first 24v 30ah LiFePo4 battery for $220 (on ebay auction) and that's 50% more AH then a Lipo 24v 20ah for $60 less...
I bought a 36v 15ah LiFePo4 for the same price ($220) and get more power for about the same distance.
So for ME, LiFePo4 is still the way to go.

i LOVE lipo, but it's still too cost preventative for me...
When people start selling lipo's on Ebay for auctions, i'll be right there, until then i'll stick with my LiFePo4's.

 

[motorbiker]

Thanks for info guys ! Good stuff !

 

[artschool]

just going to ask has any one looked into ballistic batteries. they use them mainly for ricing bikes and air plains. there relatively cheep and super light and small

Ballistic Performance Components