Range

[starway]

I have not tested my range out fully but I have a latest gng mid drive chain version running at 48v I believe it runs at 450w at this voltage. If I have a 48v 15ah battery that equals 720 watt hours , people say they average 20 watts per mile that means I'm looking at about 36 miles ? Does that seem right ? Or is that without always full throttle, I know hills matter and everything else but whenever you go up the hill your bound to go down it.


Any thoughts ?

Starway

 

[dogman dan]

I'll just say that while 15-20 wh/mi is not hard to achieve, It's also hard to not let the throttle creep up to closer to 25-30 wh/mi.

And then there's hills, weather, what you are wearing, and if you tuck or sit upright. The speed you travel matters the most If you cruise 25 mph, It will pull more than 450w.

I never ran a gng kit, this is from hubmotors. That size battery running 25 mph would get me about 20 miles, at 18 mph about 30 miles, and up to 40 miles if I went really slow and pedaled harder.

I see no reason at all why the ranges on your gng would be much different, unless you ride a more aerodynamic bike like a recumbent.

 

[arkmundi]

I have a Watt's Up meter. Cycle Analyst is better but more expensive. Something that will collect and display the data for you. Not theoretical, but actual. Its different for every eBike, rider, location & terrain, as all those factors will effect your performance. So for old fatto me with a gimp leg and hilly terrain, and with an A123 36V 20ah 12S8P 26650 battery pack, and running a Cree LED constantly, my actuals, averaged as a rule of thumb are about 1 mile per amp-hour.

 

[dogman dan]

Yep, I use the same 1 ah per mile for 36v. At 20 25 mph. That's not absolute range, but rather a good starting point for estimating what size battery can do a given commute distance.

.75 ah per mile for 48v.

Once you start to think in watts, or watt hours, then it doesn't matter what voltage it is.

Re the up and down hills, you might still lose some range going up and down if it's fairly steep hills. But later on you will know what your typical wh/mi is including the hills. I can hit 25 wh/mi pretty easy riding in town, but If I go ride San Augustine pass, I tend to average about 35 wh/mi.

I tried regen and interestingly, regen all the way down the 4 mile long steep hill only put enough energy back to ride a half mile. You can coast farther than that by not using regen.

 

[dnmun]

if you have no BMS on the pack there is the risk you will damage the battery attempting to drive as far as possible. i use cellogs on the critical channels to warn me in advance when the voltage drops below 2.9V for lipo and 2.2V for lifepo4.

 

[Drunkskunk]

Ignore your motor's watt rating. A 250W and a 5000w motor will pull the same wattage at the same speed on level ground. But the 250 watt will melt much sooner.

You'll need some kind of baseline to make any estimates from. a cheap watt meter will do. a normal ~500 watt kit bike can be rode sedately and get as good as 9 watts per mile, or rode like a psychotic teenage lunatic on PCP and pull 100 watts per mile.

My typical ride at around 20mph I pull 18 watts. On a bad day with high winds and a few hills I may pull 30 watts. But I've also done the 9 watts and the 100. In general estimating 36 watts per mile will give you a rough idea how far your battery can take you in any weather, with a good probability that you could go further if you have to. Anything else is just a guess until you measure and monitor your power usage.

This can all be summed up with: YMMV.

 

[MadRhino]

if you have no BMS on the pack there is the risk you will damage the battery attempting to drive as far as possible. i use cellogs on the critical channels to warn me in advance when the voltage drops below 2.9V for lipo and 2.2V for lifepo4.

Cell log monitors can be set, and you should set them to warn you much sooner, for discharging RC lipo at 2.9v is not good at all. 3.7v is the point that you don't want to go lower, 2.7v is the discharge point that can kill most lico cells very quickly.

Then, it is right that if one wants to know his true range, he has to monitor his cells and ride. Every bike, terrain and rider's habits are different; and don't forget to count a fair safety margin for windy days.

 

[dnmun]

hey, you can do what you want, but don't lecture me about it. i can hear the cellog go off and know to let up on the throttle to let the lifepo4 pack push more current back into the lipo pack. you do what you want, but don't pretend it is better than me. you have no knowledge of my battery pack at all.

 

[arkmundi]

I went on a longish ride today since it was sunny & warm and folks were out in force all around, kids in the playground, the soft serve truck on the park. Had a great sit down with the http://wp.wpi.edu/touchtomorrow/the-challenge/ folks on basic design. So over to Honey Farms, through Institute Park, to Technocopia, down Main Street to Da Lat Vietnamese restaurant, to & around Elm Park around 5 times, then back up Highland home. Only 5 amp-hours I'm always amazed how l little energy it takes. The point being that's a mere 25% of capacity. Its my strategy and it works great. To remain BMS-free is to NOT discharge close to empty, to remain in the sweet spot of 80%<SOC<20%, not fully charged, not fully discharged. I've been very actively monitoring the pack since its new, but I'll be relaxing that as I've got confidence the pack is self-balancing quite well.

 

[dnmun]

but for me i have to get the maximum charge from the pack to reach the maximum range. so i go from 98% charged to 10% charge in order to get to the maximum range. but i have three batteries in parallel, 21S lipo/24Slifepo4/72V SLA so i have to control the discharge from each battery during the entire range test by turning off the BMS.

i drive 35 mph for the entire time, back and forth on a long section of road in a less traveled area and can avg 25 mph including the hills and stops. so i have to be able to know when to turn off the lipo and then when i am at the end of the SLA and lifepo4 packs together. i decided to stop the tests when i got it up to 96 miles on one charge.

 

[arkmundi]

That commute and the battery to make it are awe inspiring. You got a wiring diagram posted?

 

[dnmun]

no commute. that was my range testing on the new battery pack i added to my ZENN car.

battery capacity for the three packs estimated 13.5 kWh, 144 Wh/mile avg.

 

[MadRhino]

hey, you can do what you want, but don't lecture me about it. i can hear the cellog go off and know to let up on the throttle to let the lifepo4 pack push more current back into the lipo pack. you do what you want, but don't pretend it is better than me. you have no knowledge of my battery pack at all.

OK, sorry for that, I did not know about your unusual battery configuration.
Yet, you have to admit that one has to be careful about recommendation to a newb to discharge RC lipo to low level.

 

[dogman dan]

That's why my crude rule of thumb for a commute estimate, 36v -1ah= 1 mile is definitely not a 100% discharge estimate. Ideally, its not much deeper than 85-90% most days

Even though 5-6 days a year it may leave you 2-4 miles short of getting home, when the headwind sucks that bad. But at least you can ride home into 10 mph wind, and make it every time.

 

[rborger73]

2.9v for me on lipo would only be in an absolute emergency. Running 40Ah of 12s lipo on my bike now and very rarely is it below 3.8. Takes weeks or a month for me to have to balance and furthest out I've seen my cells go would be a .05 variance from highest cell to lowest cell when I had 72 cells going. With 96 cells I expect at least a month before having to balance. Charge to 4.15 to 4.18, discharge to 3.8. The meat is in the middle, the more capacity the longer more dependable battery life from my experience so far. Just hit 1500 miles on this bike which was on the road first time towards the end of March in NW Pa winters, and I think I've only individually charged and balanced the packs 3 maybe 4 times now. I bulk charge and check to make sure all cells are still balanced.

With 40Ah I can do 25 mile runs without any worry at all. Any visit over 20 miles I just bring the charger with me in my pack if I'm stopping someplace for a few hours. Which I'm bout to shop for a smaller charger for 12s just too heavy with the Thunder 1220 plus psu. But 25 mile range is the minimum I can get on my pack even with the hills around here. I average a rolling speed of 20 to 22mph with the terrain around here on a flat 30mph. Thanks to the Hills I've hit a high speed of 42 once and 39 several times. Most days I hit 35 or 36mph on a ride. I expect I could do 60 to 80 miles at 15mph and pedaling with little worry.

 

[dnmun]

i guess none of you guys ever has sag on your batteries, so yes, you should stop at 3.5V if there is no sag and the battery is at 3.5V when you let it rest after that. my battery will climb right back up there too when i turn off the BMS and let it rest while running on the remaining lifepo4 and SLA.

 

[dogman dan]

Size of the battery matters a lot too. Take a typical 12s RC lico pack in 10 ah. Below 3.5v per cell, there is literally only about a block or two of riding left, even at 10 mph.

But increase the pack size to 30 ah, and less voltage sag makes wringing that pack completely dry work better. You may actually have a couple miles or more left below 3.5v. With nearly no voltage sag, you can ride deeper into the pack with less worry. With a small pack, the sag makes you freak out and stop long before you go below 3v.

With a small pack, the sag really increases below 3.5v. But a 150w discharge doesn't sag a huge pack.

 

[rborger73]

40Ah wired properly drawing a max of 30a doesn't seem to sag much with the 4s turnigy 5000mah hard packs. 24 of them suckers is doing a wonderful job so far.

 

[dnmun]

Size of the battery matters a lot too. Take a typical 12s RC lico pack in 10 ah. Below 3.5v per cell, there is literally only about a block or two of riding left, even at 10 mph.

But increase the pack size to 30 ah, and less voltage sag makes wringing that pack completely dry work better. You may actually have a couple miles or more left below 3.5v. With nearly no voltage sag, you can ride deeper into the pack with less worry. With a small pack, the sag makes you freak out and stop long before you go below 3v.

With a small pack, the sag really increases below 3.5v. But a 150w discharge doesn't sag a huge pack.

for me the cellogg cuts in on one channel when i am climbing above about 110A current draw from the batteries. that is usually at the end of the discharge from the lipo pack at around 44Ah, but by then the 110A draw is coming from the 24S ping pouch pack and nothing from the lipo pack. in fact the lipo pack discharge essential stops at one point in the combined discharge even while tied in parallel with the lifepo4 but increases as the lifepo4 gets drawn down to about 69V so i shut off the BMS on the lipo pack when it keeps beeping under a 40A load which gives me a rebound to about 3.5V on the low cell, and usually about 3.7V if i can turn it off when i first hear it. but i have to manage the batteries carefully to get the maximum range of 96 miles. that took 7 hours to finish counting time i was broke down on the road when i overcharged the lifepo4 pack by accident. so i don't think i have quite that much range any more because i have one cell that was damaged by the over volting during the overcharge and it is acting lame. but my pack is so huge it will not be worth the time to find it now.

the overvolting on the cells was so high that i burned out one of the leds on a ping signalab BMS. so high enuff to push enuff current through that 1kR resistor to burn out the led. maybe 20V?

 

[rborger73]

Size of the battery matters a lot too. Take a typical 12s RC lico pack in 10 ah. Below 3.5v per cell, there is literally only about a block or two of riding left, even at 10 mph.

But increase the pack size to 30 ah, and less voltage sag makes wringing that pack completely dry work better. You may actually have a couple miles or more left below 3.5v. With nearly no voltage sag, you can ride deeper into the pack with less worry. With a small pack, the sag makes you freak out and stop long before you go below 3v.

With a small pack, the sag really increases below 3.5v. But a 150w discharge doesn't sag a huge pack.

for me the cellogg cuts in on one channel when i am climbing above about 110A current draw from the batteries. that is usually at the end of the discharge from the lipo pack at around 44Ah, but by then the 110A draw is coming from the 24S ping pouch pack and nothing from the lipo pack. in fact the lipo pack discharge essential stops at one point in the combined discharge even while tied in parallel with the lifepo4 but increases as the lifepo4 gets drawn down to about 69V so i shut off the BMS on the lipo pack when it keeps beeping under a 40A load which gives me a rebound to about 3.5V on the low cell, and usually about 3.7V if i can turn it off when i first hear it. but i have to manage the batteries carefully to get the maximum range of 96 miles. that took 7 hours to finish counting time i was broke down on the road when i overcharged the lifepo4 pack by accident. so i don't think i have quite that much range any more because i have one cell that was damaged by the over volting during the overcharge and it is acting lame. but my pack is so huge it will not be worth the time to find it now.

the overvolting on the cells was so high that i burned out one of the leds on a ping signalab BMS. so high enuff to push enuff current through that 1kR resistor to burn out the led. maybe 20V?

I know it works for you, but having 3 different battery chemistries all running on the same bike seems like quite ill advised. The weight of sla and different cell voltage of lipo and lifepo. I don't think even if I had all 3 given to me free that I'd have them all on one system. No offense and I'm sure you have reasons, but that seems oodles more crazy than just not running a bms and bulk charging lipo that most people seem to think is like keeping a stick of C4 in your pocket with a live source to ignite it. lol

 

[starway]

Ok I just want to thank everyone who replied regarding my post. I am now wondering,

I have a wattsup meter installed. Because I don't have it wired permanently on can I keep track of the ah used by keeping a mental log,

say if I got to work on my daily commute and it says 3.5ah used can I then just minus that from my 15ah capacity and consider myself to have only 11.5 ah left.? And then I can keep using it and deducting the ah used until I get to around 1-2 ah left or if it drops below 40 volts whichever comes first?

Or would I have to wire it up with a second small battery to leave it permanently on ?

My pack doesn't tell me the individual cell charges , it is a 48v 15ah lithium ion pack with key ignition it cost me about 370 quid with customs is that a rip off ?


here's the exact link http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=390851604674

Thanks again for everyone's helpful contributions
Starway

 

[Drunkskunk]

I have a wattsup meter installed. Because I don't have it wired permanently on can I keep track of the ah used by keeping a mental log,

say if I got to work on my daily commute and it says 3.5ah used can I then just minus that from my 15ah capacity and consider myself to have only 11.5 ah left.? And then I can keep using it and deducting the ah used until I get to around 1-2 ah left or if it drops below 40 volts whichever comes first?

Pretty much, if you can keep it straight in your head. Just keep in mind 15AH doesn't always mean you can use all 15AH, especially on a generic ebay battery.

 

[rborger73]

Just got back from a single charge ride of 50 miles and no cell voltage was lower than 3.78 and 12 mile winds today with gusts up to 16 or 18 and wasn't lucky enough to have much of a tail wind. Also broke my daily total of 55 miles with a nice 70.1 mile total for the day. Will be doing a 100 mile day sometime here soon. Was an awesome test today because it was beautiful out other than the wind gusts here and there and rode around the lake. 40 Ah of Turnigy hardcase 4s 5000 mah packs and a MP3. Very pleased with todays results. I know I could do 80 miles if I conserved amps a bit more. Also have Maxxis hookworms coming this week which should give me much less rolling resistance than my current tires.

Have a Bike Mechanic going to look over everything this weekend as far as the non ebike stuff. Bike was new in March and want to keep it like new. So I can say with pretty fair confidence that 50 mile range isn't much of a problem if I need it. I usually am closer to 3.9v per cell when I get back so 3.78 still isn't too bad and sure I could of slowed down and squeezed another 5 or 10 miles out of it at the end if I had not been slightly burnt on the neck and was about done. hehe.

 

[arkmundi]

Just got back from a single charge ride of 50 miles and no cell voltage was lower than 3.78 ... 40 Ah of Turnigy hardcase 4s 5000 mah packs ... . hehe.

Impressive.

 

[rborger73]

Just got back from a single charge ride of 50 miles and no cell voltage was lower than 3.78 ... 40 Ah of Turnigy hardcase 4s 5000 mah packs ... . hehe.

Impressive.

Live in a hilly area in NW Pa bout 45 mins NW of Pittsburgh in an area that had glaciers dump lots of huge rocks and made lots of hills and valleys.

Had to do a pic of the speedo hehe. The overall time is off by a lot I'm sure. Left around 1pm or so and was back by 2:30pm and charged for 2 hours and went back out around 4:30pm and came home before 8pm