How many miles per kWh do you get?

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Derby
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Using a Kill-A-Watt P4480 Graphic Timer (and a spreadsheet) I calculate the miles per kWh after charging the battery pack each night if I've ridden my C-124 during the day. It has been surprising to me to see a huge variance in my mileage.

The range has been from as little as 1.03 m/kWh to 83.00 m/kWh. These two readings were only two days apart. I know there was very little wind on the day I got the poorest mileage. And, NO, I did not drive down a long hill on the first (83.00) day and back up it on the other (1.03) day. I have not always checked the SoC gauge at the end of the day but have always checked it in the morning after the charge, and it has always been fully charged.

Does anyone else have this type of variance in their mileage?

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antiscab
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Re: How many miles per kWh do you get?

Derby wrote:

Using a Kill-A-Watt P4480 Graphic Timer (and a spreadsheet) I calculate the miles per kWh after charging the battery pack each night if I've ridden my C-124 during the day. It has been surprising to me to see a huge variance in my mileage.

The range has been from as little as 1.03 m/kWh to 83.00 m/kWh. These two readings were only two days apart.

*snip*

Does anyone else have this type of variance in their mileage?

I saw a variation like that once

In my case the battery had failed from over discharge, so the charger could not put back in what had been taken out (lead acid)

do you also measure the energy put out by the battery?

I don't think your bike has a failed battery, but the charger might be stopping early for some reason.
I suspect your charger has not fully charged the battery for one reading, and you subsequently started out with a battery that was not full for the other (this can happen in separate charge/discharge cycles)

My max variation is 70Wh/mile to 125Wh/mile, and that depends entirely upon whether im doing 70mph continuous against a head wind in the rain, or doing 35mph in still air.

Matt

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Derby
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Re: How many miles per kWh do you get?

antiscab wrote:

do you also measure the energy put out by the battery?

No, I do not.

antiscab wrote:

My max variation is 70Wh/mile to 125Wh/mile, and that depends entirely upon whether im doing 70mph continuous against a head wind in the rain, or doing 35mph in still air.

If my math is any good (it's been a long time since I've used this type of math) that translates to a range of 8 miles per kWh to 14.28 per kWh. My overall/ongoing average is about 7.4 m/kWh. That may not be too bad as fully dressed for riding (helmet, boots, etc.), I weigh in at 219 pounds.

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MikeB
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Re: How many miles per kWh do you get?

Derby,

I think part of the problem is the balancing charge. I get about 10 miles per kWh, but then I have to add in about .8 kWh for the balance charge no matter how far I've driven. Much of that energy is going to the balance shunt resistors, so it's not actually charging the batteries. That means that a short ride of 1 mile will need 0.1 + 0.8 kWh to finish charging, while a long ride of 40 miles will take 4.0 + 0.8 kWh to recharge. Your net efficiency looks much better on the long ride, just because most of the energy is going into the batteries and not the balance.

And yes, you're also going to see considerable variation based on your speed, weight, tire inflation, headwind, temperature, etc.

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Derby
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Re: How many miles per kWh do you get?

MikeB wrote:

Derby,

I think part of the problem is the balancing charge. I get about 10 miles per kWh, but then I have to add in about .8 kWh for the balance charge no matter how far I've driven. Much of that energy is going to the balance shunt resistors, so it's not actually charging the batteries. That means that a short ride of 1 mile will need 0.1 + 0.8 kWh to finish charging, while a long ride of 40 miles will take 4.0 + 0.8 kWh to recharge. Your net efficiency looks much better on the long ride, just because most of the energy is going into the batteries and not the balance.

And yes, you're also going to see considerable variation based on your speed, weight, tire inflation, headwind, temperature, etc.

The kWh used for the balance charge is something I didn't know about. However, since I've been tracking this data I've ridden on 18 different days with a full charge overnight. My average ride is 9.3 miles. Six of those rides were over the average in distance and two of the six had very low m/kWh (3.05 & 2.55). Also, five of the shorter rides were at 50% or more the the overall average for m/kWh.

Hard to know about the riding conditions as there were some windy days and terrain varied. One trip of 17 miles I took on two different days. This was the identical route. I don't recall either day being windy. First time: 3.05 m/kWh, second time: 54.84 m/kWh.

Anyway, thanks for your input Mike, also thanks to you, Matt.

Derby

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MEroller
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Re: How many miles per kWh do you get?

Here in Europe it is more common to look at fuel usage for 100km. In my case I have up till now used on average 8.046kWh for charging and battery heating /100km over a distance of 4533km and 10 months. And winter... I only record my elcectric "fuel" usage once per week as I have also been quite irriated over unpredictable extreme variations when taking readings too often.
But still my driving energy usage has varied between 5.8 and 8.8kwh/100km. Tire pressure and type have some influence too, and the time I did multiple acceleration tests I had my second highest reading of 8.6kWh / 100km. This is charging energy from the grid, with some 25% lost in the charger alone. Thankfully not much balancing is necessary, so this hardly adds to my total.

Battery heating proved invaluable during the in part exceedingly cold winter this year, but of course added up to 4.35kWh / 100km in the coldest week. My general aim was to get a battery core temp. of +15°C, ±4 just before leaving in the morning. On the coldest morning (-19°C) the heating only managed about 8°C despite heating all night. Driving energy usage dropped slightly compared to the colder weeks before I put the heating in, which is an indication that the battery works more effectively when at or above 15°C in contrast to sub-freezing battery core temperatures. The best part about a warm battery in winter however is far more fun with the more spirited performance of the scooter :-) And having fun of course increases driving energy usage, plus the heating in this case...

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PJD
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Re: How many miles per kWh do you get?

Derby and Mike,

How long is the balance charging taking with your scooters? When the pack was perfectly healthy, mine took from 45 min in hot weather to nearly 3 hours at cold temperatures (2-3C in the partly-heated garage). However I developed a bad cell that simply would not charge over 3.35 volts , and it would have stayed on balance until the 6 hour cutoff if I allowed it. Not only does this use more electricity, it is also hard on the cells.

Derby
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Re: How many miles per kWh do you get?

PJD,

I really don't know. I am still figuring out what everything means. Most days I plug in the charger and don't look at it until I'm ready to ride again -- usually not the same day. Yesterday I took a 12 mile ride and checked the bike after two hours on the charger. It was showing two short blinks which I understand to mean it has timed out after SIX hours of balancing. I have not yet checked to see if fully charged.

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PJD
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Re: How many miles per kWh do you get?

Sure it wasn't short-long? This means balance charge.

Do you have the USB data cable and the software so you can check the BCU data and change BCU settings? If not, you should ask Current (Terry Richards) for the cable, software, and manual. It may have encountered a previous time-out condition and it remembers this error condition until a successful charge completion. The software and manual used to be available on a password-protected FTP-like "owner" web page - but it has been taken down.

If your gauge is reading "full" after charging it is probably full. Even with the cell defect, my scooter runs fine down to at least 50%-60% DOD. But, running at balance mode for 6 hours time after time is a little hard on the other cells, so I terminate charging myself via unplugging it when I see all the cells except the bad cell hit 3.65 to 3.75, or put it on a timer switch so it does not run on balance more than 1-2 hours. I have an idea what may be causing these cell defects, but I will need to get another replacement cell first. At any rate, the long balance modes would explain why you are reporting high electricity usage.

Something the scooter badly needs is a way to manually check the individual cell voltages while charging is underway. Problems like bad cells or malfunctioning BMS can be immediately detected. Having prior experience with Chinese Lithium cells and a home kit-built BMS, I learned how important this is. I understand that Current has their own diagnostic connector with a rotary switch that attaches to(presumably in line with) the BMS connector and to a voltmeter.

I made my own cell voltage voltmeter check points - it is a fairly tedious operation involving slicing 25 pigtail wires onto the BMS leads at one end and a connector at the other with 50 solder-and-shrink-tube connections. I can provide details of doing this if you want.

MikeB
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Re: How many miles per kWh do you get?

PJD wrote:

But, running at balance mode for 6 hours time after time is a little hard on the other cells, so I terminate charging myself via unplugging it when I see all the cells except the bad cell hit 3.65 to 3.75, or put it on a timer switch so it does not run on balance more than 1-2 hours.

I don't think this is correct, based on how balancing is supposed to work. A balanced cell sees no current at all, it's entirely diverted into the shunt. an unbalanced cell is simply getting charged at a slow rate. In either case, it shouldn't put any stress on the cell. It's bad for your electricity bill, but shouldn't be bad for the pack.

But you are right, it would be nice to have more visibility into your pack behavior, both on the road and while charging. The connection from the BMS to the BCU is analog, but if they eventually go digital it could carry voltages for every cell, and then the BCU could display lots more info on the dash.

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Derby
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Re: How many miles per kWh do you get?

PJD wrote:

Sure it wasn't short-long? This means balance charge.

It was definitely short/short. That is what confused me (not a hard thing to do) because I understood that to mean it timed out after six hours in balancing mode. In the instance I wrote about it had only been on the charger for two hours. I had left it on the charger and the next day it was still doing the short/short blink. I did seem to have a full charge at that point.

PJD wrote:

Do you have the USB data cable and the software so you can check the BCU data and change BCU settings? If not, you should ask Current (Terry Richards) for the cable, software, and manual. It may have encountered a previous time-out condition and it remembers this error condition until a successful charge completion. The software and manual used to be available on a password-protected FTP-like "owner" web page - but it has been taken down.

USB cables? Sure. Several of them, some standard, some with micro connectors at the device end. None SPECIFIC for use with the scooter. Nor do I have the software or any info on the BCU data or changing the BCU settings. Nor do I see where the cable can be attached to the BCU as it is entirely behind panels so far as I know. The only manual I have is the Owner's Manual but I suspect you are talking about a manual specific to the BCU software.

Today, for the first time that I noticed for certain, before I pulled the plug on the charger I noted that the LED was not flashing at all. It may have happened before but in the past, until recently, I usually pulled the plug, put in the key and then looked at the SoC needle. Does no flash with the charger plugged in mean a full and balanced charge or is it something less desirable?

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PJD
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Re: How many miles per kWh do you get?

Actually, the cell always sees at least some, gradually decreasing, current to hold it at the 3.65 to 3.75 volt balance voltage. In Current's case, the charger puts out a steady 0.5 amps, and the shunt acts like the CV-part of a typical CC-CV charging protocol, shunting the balance of current as needed to hold the voltage of the cell constant. The resting open circuit voltage of the cell after charging is about 3.5 volts decreasing to about 3.3 volts it is discharged a little bit. So, while charging to 3.7 volts and allowing the cell's charge current to dissipate to a low value will assure the cell is nice and full, holding the cell at 3.7 volts for a long time is hard on the cell - not outright destructive, but it probably reduces the life of the cell at least a bit.

I know this is the case from past experience with lithium packs and BMS's. A lead acid battery works the same way.

When the pack is healthy, not a lot of shunting gets done, because as soon as soon as the BMS has all 24 or 32 channels shunting at least a little bit, (they initially turn on just a little bit) it sends a "terminate charging" signal to the charger.

PJD
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Re: How many miles per kWh do you get?

Derby,

No flash with the charger plugged in means charging is complete and the charger is shut off. Do you have an older charger setup in hich teh fan continues to run as long as it is plugged in?

What you can do to check charging is simply unplug the charger, close the charger door, turn the scooter key switch on about a minute or so, reopen the door, plug the charger in and watch it. You should see a long, long, long... flash and about 850 watts on the kill-a-watt for just a minute or so, the gauge will go to zero, and you will see short-long. But whether you see short-long or short-short, keep checking on it every 15 minutes or so, it should finish charging in anywhere from 5 minutes to an hour (the colder the temperature, the longer). If it persists for 6 hours, you probably have a bad cell.

The USB cable (USB on one end, 8 pins (i think) on the other) needs to be gotten from Current motor. If you remove the small cover from the front of the under-seat area, you will see aluminum box with a Velcro (and maybe electrical tape) cover. The BMS interface software and software manual needs to be obtained from Current and you proceed from there.

Another useful gadget is a "USB Tiny" which is used to load program updates to the BCU.

Derby
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Re: How many miles per kWh do you get?

PJD wrote:

Do you have an older charger setup in hich teh fan continues to run as long as it is plugged in?

No, Current replaced the charger in January.

I'll try the check charging routine later when done with whatever riding I do today.

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PJD
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Re: How many miles per kWh do you get?

You have a kill-a-watt don't you. I am interested in the power usage of the new charger. Is it the fanless charger?

Derby
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Re: How many miles per kWh do you get?

PJD wrote:

and about 850 watts on the kill-a-watt for just a minute or so,

Not sure what you mean here. Should the cumulative kWh meter increase by 850 watts? If so, that has not been happening.

PJD wrote:

You have a kill-a-watt don't you. I am interested in the power usage of the new charger. Is it the fanless charger?

The power usage of the charger would be what it takes to recharge the batteries. That would include any juice used by the charger as well as what is get replaced in the batteries, I suppose. That is the info I've been giving in the previous posts and what this thread is all about.

I believe the charger is fan-less as I have never heard a fan running.

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PJD
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Re: How many miles per kWh do you get?

Watts are measures of power. Power is the rate at which energy is expended (Watt = one joule per second or electrically, volt x amp). Watt-hours are units of energy - the energy the power company sells you to charge the pack.

I was asking for the wattage - in the same manner as: "Is that a 50 watt bulb or a 100 watt bulb." There is a button on the kill-a-watt meter to change the display to show the watts the appliance is drawing. Be careful to distinguish the "watts" setting from from the "VA" or volt-amps setting. They are not the same unless the appliance is just simple resistive load like a toaster or incandescent light bulb.

For the Standard model (24-cell pack) my charger draws about 820 watts charging and 60 watts balance charging.

LeThala
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Re: How many miles per kWh do you get?

I commute about 12 miles round trip each day. Last night I used 1.68 kwh to charge the bike. That includes the .16 amps the charger draws after the charging completes. So I'm getting a little over 7 miles per kwh. I have the original charger with the fan.

Derby
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Re: How many miles per kWh do you get?

PJD wrote:

Watts are measures of power. Power is the rate at which energy is expended (Watt = one joule per second or electrically, volt x amp). Watt-hours are units of energy - the energy the power company sells you to charge the pack.

This I knew.

PJD wrote:

I was asking for the wattage - in the same manner as: "Is that a 50 watt bulb or a 100 watt bulb." There is a button on the kill-a-watt meter to change the display to show the watts the appliance is drawing. Be careful to distinguish the "watts" setting from from the "VA" or volt-amps setting. They are not the same unless the appliance is just simple resistive load like a toaster or incandescent light bulb.

For the Standard model (24-cell pack) my charger draws about 820 watts charging and 60 watts balance charging.

I had forgotten about the ability to display the watts. I set it to display watts and, following your previous instructions, it went up to 1100 watts. Checked it a half hour later and it is still in the 1095-1100 range.

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