lipo and daily commuting

[rbelisle1]

I have two ebikes that I swap back and forth for my daily commute of 7.5 miles one way, 15 miles total. I run three 12v 12ah sla's. I charge religiously asap at work and at home. I even charge inside overnight, as the weather is getting down into the 50's in the mornings now. I am starting to see a drop in top speed at the end of my ride now on both bikes, so I figure that the SLA's are getting near the end of life. I have about 200 charges on each bike. So, before I go a spend a bunch on more SLA's or maybe even a Ping pack, I wanted to know if anyone was using Ping/LiPo for their daily commute???? If so, how is your pack doing?????

some further information..

bike 1. converted EVg ebike, running 36 volts, with a 24volt 30 amp brushed controller into a Heinzmann 20amp 400 watt brushed geared motor. Along with the stock 24 volt headlight and Led tail light.
bike 2. cruiser bike with the WE BL36 brushless "600" watt motor. "50" amp controller and an MR16 12volt 20watt homebrew headlight.

thanks in advance

bob in phx.

 

[gregben1]

Do you have a DMM (Digital Multi-Meter)? You can learn a lot about the condition of your batteries by monitoring
voltage. After a full charge, each battery (measure each battery, not all three in series) should be around 13.7 V
under no-load conditions. As soon as you put a load on the battery, voltage will drop to somewhere between about
11.8 and 12.8V depending on load current. The higher the current, the lower the voltage.
Measure the battery voltage after a run (7.5 miles in your case). I consider 11 V to be 100% DOD (Depth of Discharge)
meaning fully discharged. I don't have a good rule of thumb for what voltages between 11.0 and 13.7 relate to in
terms of DOD. It can be tricky to do the measuring since battery voltage will start to recover immediately after the
load is removed, even when the battery is completely discharged.

Take a look at:

http://www.bb-battery.com/productpages/EB/EB12-12.pdf

to see some battery discharge curves and other specs. This particular battery is
a 12V/12AH battery designed specifically for small EV use.

 

[rguy56]

Oh, man!

I was just thinking about where to get rid of my sla's...2 banks of 4, for 2 48v. systems, used one season, when I read your post. Those batteries are cheap, and do the job for a little while, but they belong on a barge.

I just got a 36v limn battery from ebikes.ca, and the weight of it is simply amazing. The hammering that my carrier was taking was bending the struts into a "C" shape with the sla's. If you can afford the change in technology, then do it. You could spin this 36v. pack on the tip of your finger.

Bob

 

[BikeFanatic]

HI,

I Have a ping pack, and have been commuting 10 miles R/T to work in very cold weather lately, like 15 degrees the other day and 22 F.
Ping pack performs very well to excellent in the cold. I keep the pack inside at night and inside at work as well.
I charge it every night, but not at work. I would say it outperforms my NIMH batts, but lead I don't have much experience with lead powering my ebike, but lead does ok on my MR11 light. I use a separate 12Volt for lighting and 48 volt ping for my bike. You may want to think about upgrading to 48 volts if you can, ( more speed).

 

[dogman dan]

Since my commute home is so long and uphill all the way, I have noticed about a 25% reduction in range with my Ping 36v 20 ah in the colder weather. So if it gets windy and I lose another 20% I'm screwed. My bike is in the cold garage, or may even get super cold if I put it on the car bike rack for a few miles to shorten my ride in the morning. Kinda silly to ride the bike home, and then get in a car to go to the grocery store, where I just was, so if I am facing a windy day, or need to shop more than I can carry easy, I take the car as far as the stores and ride to work from there. Get a Ping for sure, it does get affected by cold, but not as much as sla's. And where you live, the lifepo4 tolerates heat better than lead for summer. I haven't tracked cycles accurately, but I think I average about 12-13 miles per cycle, and am just about to hit 2000 miles since last may. Last time it was 80 degrees F, I did a range test, and still have no noticable loss of range from when it was new. At 40 F, range is down about 25%.

 

[snowranger]

I've got 600 miles on my Ping 48/20 in two months with the only problem being a failed charger at one point. Commute is 14 miles RT over hilly terrain. With my BMC hub and xtracycle and pedaling, I am getting about 45 miles per charge. I charge every other day at 75% DOD.

The watts-up meter is telling me that the pack does balance itself at the end of charging, so I think it is a good idea to keep the charger on overnight for maximum capacity.

 

[JinbaIttai]

I commute with my ping 36V12ah. My experience is probably not much help because it's only few months old. I ride to work and back, 13.2 mile round trip, and this includes a 900 foot hill climb. I ride most of the time at half throttle while pedaling, even up the hill. But I never sweat and never pant :lol: .

I'd say it weighs about 9 pounds. One benefit I take advantage of is not needing to charge it right away. I only charge at work so it saves some money. I do the same with my flashlight batteries. I just leave the ping partially charged at home, even for a few days at a time.

I wish I had chosen a 36V16ah or a 36V20ah, as that is a more properly sized battery. With one of those I wouldn't have to restrict myself to half throttle most of the time (keep from exceeding 1C discharge rate that would reduce battery life).

 

[mvadventure]

Being unemployed for the past 14 years I don't have a daily commute. I do however use my bike for 90% or more of my personal transportation with my normal trips between 6.5 & 18 miles. For the past year I've been using a 48 volt LiPO4 from Aten Energy. I noticed no difference last winter between cold and warm days. My son contracted a brief but fatal illness last month which necessitated our being out of state for five weeks. The battery sat in an unheated garage, mounted on my bike, and maintained a full charge with NO variation from the time we left until our return.

The use it's had since my return has indicated no difference in power or range in a year and I'm no lightweight, 240 pounds dressed for cold weather. The bike has about 1,800 miles on the batteries.

However a friend with a 36 volt Lithium Ion battery in his bike left it unattended for about five months this past summer. When he returned to Florida in October he found the battery dead and unwilling or unable to accept a charge. It had 2.4 volts left it it (I measured it) and he wound up burning his charger up trying to make it come back. Since he has a bike designed for his battery pack he is kind of stuck buying OEM replacements unless I rewire for him and he likes the sleek, stealth look from the factory. Right now he is saving his shekles.

When using SLA's I took every opportunity to charge when out and about. It's a genuine relief and pleasure not to have to do that. Quite frankly I would consider a mo-ped before going back to SLA.
Mike

 

[electricridefl]

View attachment 1View attachment 2hi i commute 10 miles each day, 5 miles each way...I buy early ping 36v10ah for 20amps, 3 of these, I run 2 for 80v 10ah, I,ve had no problem...I went a couple times 3 trips or 15 miles on some charges, and then get cooler and fight wind and at about 14 miles something shut off for a bit...I had to turn off and then back on and rode home...I never charge at work...I use 2 separate chargers now so take about 4hrs for 10 mile recharge....and lately I have been blazing..it take me 11-14 minutes, or same time as car...I take it kind of easy, unless I'm late like last couple of days...then I get nice exercise and pedal along against wind...my 36v10ah I turned into 80v5ah, then cell went bad...then I bypassed a cell in other half of battery to make 72v5ah, 22cells lifepo4, charge in parallel with sla 36v charger, or chargee each half separate too , then I ride bike for 5 mile trip to store and lbs owner across from store wanted to see my bike, so I went to hess and on way across bridge of sidewalk, run over big chunk of glass and hear air, then get to store, park electric bike in front of cop car and then roll over to bike shop, buy patch kit and find hole with glass through shwalbe big apple rear tire, then let lbs owner go for ride (with 8lb, 72v 20amp battery...so of course he come back real happy and say that is the way to go bike riding....so then I ride home and bike get kinda slow, for a while I even downshift one from top gear....whenever I had to do that in the past, I had a fault in a battery cell...so I come home to check and one side voltage way down...so these cells are just too much for me to work on....My 40v10ah w bms work great...yes bike feels noticebly sluggish in cold....I long ago redid my front brake mount and work perfect now, and front end and rear end perfect suspension....but now my left wrist area goes numb after first four miles to work....that's one of the best 15 minute time period of my day....so I feel benefit of little bike ride in morning...makes my whole day better...I really miss it when I drive car....so today I ride home from christmas party with the best smoked ribs, a large vegetable platter, full, and box of cupcakes and my man purse in my basket with tiny bungee over top and cruise...on road go at least 33mph w/ 409 26" rwd and so much fun...The power is just right for pedal assist, so fun to take off through the gears and pedal and yes I get to where I am going with no waste of time for stop signs, red lights, or traffic...on a mission...to ride like motocross race or paris-dakar...but my path not limiter to roads, sidewalks, or even pavement....rain has not been an issue for bike operation...I have been riding this bike several years have many flat tire, broken spokes regular, some connection go bad, like today when I running late to timeclock and lean bike on trashcan, then bike not run, and I looked and find end connector brkoen off contrller neg wire ( yes I put the connector therre)...so motor feels like some play, and some little noise at slow speed, and after trip motor get very hot everytime, so everything working just right...the new batteries so easy to secure on bike because of less density...and bike easy to lift with 16lb battery...and great power...well 20amps is 20amps...just nice to be able to count on it all time....and so, I have no reason to doubt claim of 2000 cycles or whatever it is... I have this battery, it is fine, now no more concern for any problem for very long time....I mean its just not the same when I have my ebike project working great and reliable and the best it can be...and just ride ....so then ebike not hobby any more...just my ride....hmmm...I need a new hobby...

 

[Hyena]

On the topic of lipos, has anyone tried these from ebay ?
http://cgi.ebay.com.au/RC-Lab-4000mah-22-2v-15c-Li-Po-Li-polymer-Battery-Akku_W0QQitemZ150315565095QQcmdZViewItemQQptZRadio_Control_Parts_Accessories?hash=item150315565095&_trksid=p3286.c0.m14&_trkparms=66%3A2|65%3A1|39%3A1|240%3A1318

4 of those to make a 44.4v 8ah pack for under $150 USD delivered sounds very appealing for a super light weight short range commuter

 

[dogman dan]

I've seen quite a few posts from folks using the polymer lithium. Good price, good discharge rates, bad to charge in the house. Some folks don't mind that, but I kinda like not worrying about it getting hot while charging. Many of us going the longer distances are using ping packs. Mine should pay for itself in about 3000 miles and last for 10,000 based on the way I'm using it. So far so good, I'm getting close to 2000 miles on mine now, but cooler weather has me riding less.

 

[Hyena]

How do you guys running lipos find the voltage sag with current draw ?
I ordered 2 of the above linked batteries from ebay and they seem to sag very quickly. Running 2x 6S 4ah packs in series they're just over 50v hot off the charger but instantly sag below 40v with hard acceleration and after a minute will hit the lower limit of 36v (avg 3v/cell) if I accelerate hard up a bit of a grade. They instantly jump back up to 44+ v when I back off and when I come to the flat I can ride WOT and they'll happily sit in the low 40s, but higher current draw seems to quickly make them sag.

My controller has a max current draw of 30a (verified by watts up meter) but it usually only spikes at that for a second or so, hovering more around 20-25 when accelerating and going up hills and around 10a along the flat. They're rated for 10c continuous discharge, and I'm only pulling around 6c from them so I thought they would have held up better (allowing for exageration of the C rating)
I'm guessing they are probably only good for ~5c in reality and by exceeding ~20a this is causing the sag. Does this sound about right ?
I plan to get another 4 6S packs to make a 12ah 44.4v (12S3P) pack which should solve my current draw problems and get more range, but I just want to be sure they batteries aren't crook before buying more of them.

 

[dogman dan]

Big pack size is the answer to the sag problem I think. The cells may take a big discharge without damage but without sag may be another story.

 

[Hyena]

Ah... ok, I thought they could mystically supply their C rating without sag.
Next I suppose you'll tell me there's no such thing as unicorns

 

[kZs0lt]

Those lipos look tempting indeed. Keep us updated if you happen to get some more, I'm curious if it solves the voltage sag problem. I think the sag is coming from the internal resistance of the battery. If is high, it will sag more, regardless of the C rating, which like "dogman" said probably means only that high current draw won't affect seriously cycle life. Could you tell/measure the internal resistance of the 6S pack? By the way, how many recharge cycles are these expected to last? Did you measure actual capacity? These chinese cells can have 10-30% lower capacity than advertised.
What charger do you use? Can you recharge 22.2v packs in series(even if the 6S strings don't have the same SoC)? However, do we in general need BMS for RC LiPo cells?

 

[vanilla ice]

I can live with sag.. Its so light I'd just volt up if thats an issue.

What about lifespan of RC lipo? Whos been using it long enough to tell? How does it compare with lifepoooo? Thats a bigger issue for daily commuting.

 

[Hyena]

I've never used lipos before so I'm not sure what's normal behaviour from them.
If I get time down the track I'll look into the internal resistance of them.

Re: those ebay lipos - I've just ordered 2 more 6s packs which I'll run in parrallel to create a 8ah 44.4v pack so hopefully they'll perform better. I'll post my findings when they arrive.

Again I'm not sure whats normal with lipos but these seem fairly happy to run at 2-3C without too much sag. Hot off the charge they're 50v (12S pack) and drop down to 48-44v with around 10a current draw. As I said in my previous post any more and they quickly drop down to 40 odd and even fresh off the charge if I try to pull >20a from the pack with full throttle up a hill they'll sag to 36v (3v/cell). So unless I have a few crook cells, you can't really get 10C from them.
If I'm conservative though and keep them around 2C they seem fairly happy. I'm hoping running the second pack in parrallel will greatly cut down on my need to be so touchy with it.

I'm using a watts up meter that I use to keep a close eye on them but I'm also running one of THESE battery monitors in the absence of any BMS. It beeps when the voltage drops to below 40v (20v for that 6s pack its monitoring) so I usually back off on the throttle then, and if you let it get down to 36v (18v) it beeps constantly warning you and pedestrians that your lipos will soon ignite and tear a hole in the time space continuum :lol:
I'm only running one of these monitors on one 6S pack as a general indicator and I suspect that one of my 2 packs may not be as strong as the other as a few times now its started randomly beeping suggesting its hit 18v for that pack when my watts up still reads ~40v. For the most part its fairly accurate against the watts up though so I'm not sure if its a true reading.
They do get quite close to their rated Ah capactiy. The most I've ever got out of them was 3.8ah according to the watts up, but by that stage anything over 1C (4a) caused them to very quickly sag. The pack dropped to 33v (~2.75v/cell) for a split second when it tried to pull 10a but obviously I quickly backed off. For practical riding though I usually not pulling more than 3ah from the 4ah rated pack.

I've only put them though a dozen cycles but so far theres no signs of them going out of balance. The lowest individual cell voltage when going back on the charge has been 3.7v and the most variation between cells has been around 0.1v.

I have one of THESE cheap B6 chargers and so far its been fine. I only balace charge it around 1 in 4 charges as so far theres not been more than 0.01v difference between cells when fully charged normally (all cells 4.19 or 4.20v) If they continue this way as they get on is yet to be seen!
I usually charge the 2 6s packs in parallel too.

 

[kZs0lt]

Thanks for your very informative post. I still have some questions.
Do you know anything about how extremely cold(-10C) and extremely hot(+50C) weather can affect these cells?
About your charger:
On ebay it says 2-6 Cells 7.4v-14.8v Li-Po Battery Charger. Does it really charge at 22.2V(6cell) working from DC 11-18V?
What charge current do you use? It says it can do max 5A, but Max. charge is only over 50W.

I only balace charge it around 1 in 4 charges...

Sorry I don't know much about charging. Do you mean you can charge the batteries without the balancing function of the charger? Or you need to make a balanced discharge for balancing? (ough, little confused :? )
How much time does it take for a full charge(from almost dead) at max. charge current with your charger?

 

[Hyena]

Do you have both those temperature extremes where you live ??
I can't really comment, it's summer here in Australia at the moment and I've not noticed any real difference in capacity in the ~15-35 degrees C temperature range I've used them so far.

As for the charger, yes it does charge at 22.2v and that voltage range is pretty accurate. I have an old 3.5a 20v laptop charger laying around that wouldn't work (powered up the charger but said incorrect input voltage) Anything over 18.1v and it wont work and likewise dropping it to ~10.5 makes it cut out too. I've been using a modified computer ATX power supply to feed it 12v and its been fine.
The battery manufacturer recommends only charging around 1a with a max of 2a for the best battery life. I'm not sure how conservative that is but for the most part I'm not in too much of a hurry so I charge the 2 6S packs in parallel at 2a and it takes around 4hrs. When I was playing with it last night it wouldnt charge at more than 2.2a despite me telling it to charge at 4a, but I don't know if that was because they were already half charged. It happily charged a different 3S pack at 4a though so I'm not sure if the charge current is battery voltage dependant. I'll try again later when my 6S pack is flat and see what it can take.

And yes, you can charge without balancing - just connect up the power wires to the charger and it puts 25.2v into the 6S pack (ie 4.2v /cell)

 

[kZs0lt]

Do you have both those temperature extremes where you live ??

Well, more or less. I live in Cluj Napoca, Romania, and it's winter now. Today morning it was exactly -10°C. I'm not sure I would ride the e-bike in such a cold weather, but the temperature in the morning stays below 0°C for about 2 months in winter. The other end is a little exaggerated too, summertime the temperature occasionally rises beyond 35 degrees in the shadow, but under the sun I think it reaches 50 sometimes.(at least on the black asphalted roads with traffic). So probably a 0-35 °C range is more realistic.

Thanks for the info on charger. Clever idea to use a computer power supply.

The battery manufacturer recommends only charging around 1a with a max of 2a for the best battery life

I don't know how conservative that is, but he recommends the same for the 8Ah packs too. However charging at huge current probably shortens life. But 1A = 0.25C should be fine. And probably you won't be able to charge the pack with far more than 2A, I think the charger could be limited to 50w charging power. That could be the reason it didn't let you go beyond 2.2A at 22.2v. You could try max. current with 4 or 5 cells too, to see if this is the case.

Are there any benefits charging without balancing? Maybe shorter charging time?

 

[Hyena]

Ah, of course the 50w rating of the charger would be limiting the current to 2.2a for a 6s pack, I forgot about it's wattage rating.

The benefit to me in charging without balancing is being able to charge in parallel. The total charge time for a number of batteries works out around the same but it saves having to swap over batteries every few hours and connecting up the next one. I can connect up a few batteries and walk away. At the chargers 2.2a max I can also safely give 2 6s packs 1.1a each vs 2.2v into each pack for a half the time. Finally, if I happen to need the batteries before they're fully charged I can use them and they'll both be at the same state of charge. Obviously a heftier charger would be the way to go, but for a cheap set up it's pretty good.

 

[vanilla ice]

Has anybody on ES put say, 250 to 500 cycles on any brand RC lipo, who can give us some idea of what to expect? DS mebbe? At 250 cycles is the capacity down to 85% or what.. the size/weight/cost/availability makes is soooo tempting to go with this over the lifepos'. The cycle life comparison could be that one big buzzkill tho.

 

[Hyena]

An update on the above discussed chargers and lipos:

The mystery B6 charger blew up after around 15 charges as I posted about HERE
I bought another 6S charger, a SJ swallow EQ from a local hobby shop. This one only lasted around 5 charges before it also blew up. No firey death this time, just random characters appearing on the screen when powered up. So I returned that for a full refund and fed up with pissy little RC chargers bought an 8 amp switch mode power supply to charge the pack, as done by methods and others. Charging the 4 packs in parrallel they get a max charge rate of 2a each, which quickly drops as the voltage comes up.

The lipo pack I bought in 2 halves - 2 x 4ah 6S packs at a time. The first pack has around 30 charges on it, the 2nd around 15. After I got the 2nd lot of 6S packs I've been running it as a 12S2P 44.4v 8ah pack. It WAS running well until this afternoon when it progressively ran out of juice very quickly. 4.1ah into the 8ah capacity and it was sagging to < 3v/cell when drawing 4 amps or less. I dont have a BMS, I just keep an eye on the watts up meter. The final pack voltage was 38v but after looking at the 2 parrallel 8a banks of 6S one was 22.4v and the other 16.8v. Suprisingly it was the newer of the 2 banks that died.
When I checked the individual balance taps in the 16.8v pack I found one of the cells was completely dead reading 0.5v and another 2.4v. (one in each 6S pack) All the others were >3v, some up around 3.7v. I dont know if I'll be able to recover the 2.4v cell, but it looks like the other one is totally stuffed. Time to open them up.
Bugger.

 

[Hyena]

Another update for anyone who's interested about these batteries:

I performed surgery tonight on the 6S pack. Naturally it was one of the middle cells that went and not one on the end This meant I had to essentially seperate the pack into 3 parts, which was rather difficult given they were all glued to each other. The glue was really strong and I wasnt sure how tough the foil was so I was very careful with my nails and the screw driver I was using not to puncture the foil. I'd liken seperating them to diffusing a bomb, a very slow and nervous process, knowing that any slip could result in my firey death :lol:
I had my video camera sitting there on pause the whole time ready to video the inferno should it have all gone wrong. Thankfully I didnt have to use it!

See if you can spot the dud cell. Interestingly it had a big blue pen mark along the length of it. I wonder if that was a sign it failed QC ?

It's certainly puffier than the others, although "loose puffy" rather that "about to explode puffy", which is one consolation I suppose!

Next is to start on the other 6S pack. It has a cell that's sitting at 2.4v. I tried charging it and it came up to 4.2v but as soon as I took it off the charge it started falling back towards 3v, so I guess it's stuffed. Why couldn't 2 cells in the one pack have died together!

 

[nomad85]

If your going to try Lipo I wouldn't go for anything less than zippy type packs at hobbycity.com I've tried cheaper ones and they all sucked(in my rc stuff). The more expensive ones may or may not be better than the zippys. Ebay is not a place I would buy unknown Lipoly batteries and expect good results.
If I were going to try lipo, I would get some of these, or the 15c version. Get a good charger like the iCharger 6 or 10 cell version.
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8582&Product_Name=ZIPPY_Flightmax_5000mAh_6S1P_20C_
If you want something real nice($$$) try the thunder power or polyquest batteries, I'm not convinced they are any better, but many believe they are.