What does it mean if you have a 350 Watt-hour battery?

[tjcooper]

I have seen discussions before but no one has really gone into the EUC definition of battery capacity that I know of.   I have (amoung other EUCs) a MoHoo that has a battery rated at 350 Watt-hours.  I have tested the original battery and a new replacement from China for it.  But from a full charge (using Dr. Charge) to full discharge when it starts to lift up the petals to get me off and issues a ChinEngilsh warning of "low voltage", my total re-charge on both batteries is only 95 Watt-hours.   That is no where near the 350 Watt-hour label on the battery and advertised by the EUC vendor.

It is my "guess" that 350 Watt-hour is the total charge capacity if I drove the battery from 4.2 volts/cell as fully charged down to zero volts in a battery-killing discharge, then I might get 350 Watt-hour.  Does anyone have ISO definitions of what a battery capacity is defined as?  I have put an electromagnetic amp meter on the EUC and measured "average" amperage during 8 mph trips down the street.  The outcome was that the 95 watt-hour is a realistic value to bring the battery down to 3.05 volt/cell at the end of the trip.

What have other "measurement feaks" found as the drop in capacity from full charge to must get off the petals?

     tjcooper

[nute]

You also need to bear in mind that the control board may well seek to limit the performance of the wheel as the battery charge decreases. Inmotion certainly do this and I assume others do aswell.

It's a safety precaution which seeks prevent you from asking more (performance) from the wheel than it can provide by activating tilt back at lower levels as charge decreases. 

[Keith]

6 hours ago, tjcooper said:

It is my "guess" that 350 Watt-hour is the total charge capacity if I drove the battery from 4.2 volts/cell as fully charged down to zero volts in a battery-killing discharge, then I might get 350 Watt-hour.  Does anyone have ISO definitions of what a battery capacity is defined as?  I have put an electromagnetic amp meter on the EUC and measured "average" amperage during 8 mph trips down the street.  The outcome was that the 95 watt-hour is a realistic value to bring the battery down to 3.05 volt/cell at the end of the trip

Absolutely not, never ever. There is damn all capacity to exaggerate about between 3.3V and 0V maybe 1 or 2%.

How battery capacitor is rated and stated is well documented in various places such as http://web.mit.edu/evt/summary_battery_specifications.pdf As is the tendency for manufacturer’s to, perhaps exaggerate - not the least by stating nominal voltage as 3.7V instead of 3.6V.

However these ‘exaggerations’ will have only a few percent effect on the usable capacity.

Typically the rated capacity of a battery is at a quite low discharge rate often only 1C or even 1/10 C and at a favourable temperature. Higher discharge rates will reduce actual usable capacity somewhat.

Low temperature will have the biggest effect and below 10F (-12C) you might be lucky to get 50% of the battery capacity. http://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures

Because batteries have internal resistance, voltage off load and voltage under load are very different things, a battery protection circuit can only function under load so it has to make an assumption exactly how much current the wheel is going to be consuming and set a tilt back voltage accordingly - this is why no two articles or devices state the same low voltage cut of voltage - it can be anywhere from 3.5-2.5 volts depending on how much load the manufacturer thinks the device will be taking. However, again, this will only make a something like 10%, perhaps 20% tops, difference to capacity.

Given where you are, it is safe to assume low temperature isn’t a problem, even accumulating everything I’ve said above, other than temperature, there is no good reason for a rated 350Wh battery to give less than (say) 300Wh  - however, unless you are as light as a chimp ,10 miles or so is pretty much all most European/American weight people get out of a 340-350Wh battery before it significantly speed reduces - it is certainly all I get out of mine so 95Wh for 8 miles seems a very low estimate unless riding very very slow, it’s not much more than 12Wh/mile it should be nearer 20-25 (or much higher if very fast or heavy).

Finally, draining a battery down to 3.05V off load (?) regularly will knock your capacity down very quickly, doing it in the first 3 or 4 charge cycles will knock it down even quicker. 

[FreeRide]

Reputable cylindrical 18650 cell manufacturers rate capacity using roughly 0.5C discharge. Data sheets with testing parameters are available for Panasonic, Samsung, and LG.  They list the cut off voltage, such as 2.5V for GA cells, but as pointed out the energy difference from 2.5, 2.8, or 3.1 is not huge in a fairly high discharge use case.  Specialized high drain cells may use different test parameters than general usage cells. 

Now how the manufacturer of the wheel is rating their battery pack is another matter. Are they rating it in terms of how it performs in their device under some realistic conditions, or just stated the theoretical energy of the pack based on the cell manufacturer's specifications?

As stated your mileage may not be too far off, sounds low to me, but weight and speed are huge factors. Also note that almost all the devices currently reduce their top speed as the pack is discharged, so you may need to just slow down to get the last 4-5 mies out of your pack. 

The simple answer to you question "... what does it mean...? "; it's way too small. 

[Bob Eisenman]

Well..roughly speaking....it means that the number of miles that you can ride (without the battery management system taking over) are considerably less than ....let's say a 1600 watt hour battery. I recently rode my Gotway Monster while recording on WheelLog.

More specifically:

The averaged output WheelLog graph (each data point on the graph is the average of the preceding 100 values) is shown below. 

 

 

[Bob Eisenman]

12 hours ago, tjcooper said:

350 Watt-hour

For EUC battery packs a 'practical use range' estimate under ideal conditions of temperature, rider weight and surface type has been posted elsewhere in the forum. Dividing the wh rating of the battery by 16 gives an estimate of the kilometers of riding the battery can deliver.

1600 wh/16 = 100 km ideal estimated range

My cold weather use for the Gotway Monster is about 50% of the ideal range estimate. Range in summer temperatures (80s F) has not been determined. 

While the absolute can't go any farther range fits the ideal range estimate a bit better most riders refrain from using the EUC in the battery management mode since low speed of operation and tiltback can dissuade the use of the EUC under those circumstances.

For the Ninebot One E+ with a estimated max range of about 18 miles, the battery management system takes over below about 6 miles remaining in the battery....so an ideal riding range is limited to 12 miles or less (perhaps 10 miles at moderate speeds and hill grades). Assuming that you are planning a round trip (on a single charge) to and from your destination on a Ninebot your range is maximally limited to about one half the 18 mile battery range.

If you dig into the available literature with Google you'll find different battery chemistries not described in the description 18650

 

 

 

 

[Mono]

On 4/15/2018 at 12:31 PM, Keith said:

Finally, draining a battery down to 3.05V off load (?) regularly will knock your capacity down very quickly, doing it in the first 3 or 4 charge cycles will knock it down even quicker. 

Justin Lemire-Elmore from Grin Technologies though found that 0%-60% cycling is better for battery life than 20%-80%. Probably not many people know this. I am not sure he told us what voltage 0% refers to though.

Regarding the OP, under regular conditions (10-30ºC) you must get more than 100Wh out of a 350Wh battery after a full charge. Among other reasons, I could well imagine that the specification is an outright lie.

 

[tjcooper]

Keith,

my computer died mid-typing so I could not respond.  The 95 watt-hour is the TOTAL loss of power when my 350 watt-hour pack went from FULL CHARGE down to point where the internal electronics of MoHoo said I had to get off the petals (and shortly there after did the petals up trick to force me).  I have a Dr. Charger meter to measure how much energy I put back in to come to full charge again.  That was 95 Watt-hour.  The battery is reasonably new with about 10 cycles on it.

 

I do alot of RC flying so I am very familiar with LiPo charging capacity.  For my airplanes, the new capacity is full charge down to 3.0 volts/cell under load.....and then pops up roughly .3 to .4 volts/cell when resting.

I normally get 90-95% of my watt-hour out of my packs when flying.  But the unicycle is giving me like 27% of my full charge capacity.  So why am I not getting 95% discharge rate until the BMS tells me I have to shutdown?  I was wondering of EUC use a different terminology for battery capacity.  Is the battery just "hurting".  My old battery for the MoHoo gives me very close to the same results......it has like 40 cycles of 50% useage on it.

 

I will try the same test on my Ninebot E+ (just got a replacement) and so it is a new battery with like 1 cycle on it.  I am curious if I will have the same decrease percentage wise.

    tjcooper

[Chriull]

6 hours ago, tjcooper said:

The 95 watt-hour is the TOTAL loss of power when my 350 watt-hour pack went from FULL CHARGE down to point where the internal electronics of MoHoo said I had to get off the petals (and shortly there after did the petals up trick to force me).  I have a Dr. Charger meter to measure how much energy I put back in to come to full charge again.  That was 95 Watt-hour.  The battery is reasonably new with about 10 cycles on it

There could be several reasons for this like the battery pack has wrong Wh advertised, the pack/some of cells are bad, your moho stops too soon or the moho takes too much current from the pack (way over max nominal current of the pack)

with too high loads the battery pack will reach much faster the ~3V threshold and recover then more as with normal discharge and by this „release“ less Wh.

One could test that quite easy by measuring the voltage directly after the moho stopped and about four hours later once the pack recovered.

if i remember right you once measured battery current while operation? And also have some „power resistor“ to empty the battery controlled (and estimate the delivered energy by linear interpolation of the voltage/current. As it seems assuming a linear voltage drop over time while nominal/normal discharging until around 3V should be accurate enough. Measuring the voltage/current every ~15 mins and doing a nice interpolation should be no real prob too). I‘d assume the charge doctor could be used to count the delivered Wh with an appropriate resistor attached, too.

so you should have everything to narrow down the cause of this problem.

 

[US69]

10 hours ago, tjcooper said:

Keith,

my computer died mid-typing so I could not respond.  The 95 watt-hour is the TOTAL loss of power when my 350 watt-hour pack went from FULL CHARGE down to point where the internal electronics of MoHoo said I had to get off the petals (and shortly there after did the petals up trick to force me).  I have a Dr. Charger meter to measure how much energy I put back in to come to full charge again.  That was 95 Watt-hour.  The battery is reasonably new with about 10 cycles on it.

 

I do alot of RC flying so I am very familiar with LiPo charging capacity.  For my airplanes, the new capacity is full charge down to 3.0 volts/cell under load.....and then pops up roughly .3 to .4 volts/cell when resting.

I normally get 90-95% of my watt-hour out of my packs when flying.  But the unicycle is giving me like 27% of my full charge capacity.  So why am I not getting 95% discharge rate until the BMS tells me I have to shutdown?  I was wondering of EUC use a different terminology for battery capacity.  Is the battery just "hurting".  My old battery for the MoHoo gives me very close to the same results......it has like 40 cycles of 50% useage on it.

 

I will try the same test on my Ninebot E+ (just got a replacement) and so it is a new battery with like 1 cycle on it.  I am curious if I will have the same decrease percentage wise.

    tjcooper

Hy tj,

 

this is absolut no normal behaviour....you should at least be able to consume about 3/4 of the announced watthours...so that your chargedoctor Shows you about 250wh....

Is the Charge port of the moho protected by reverse voltage? You can find out if you ONLY attach the ChargeDoctor(CD) to it.

The CD then should Show you the actual voltage of the battery. Mohoo is 15 or 16cell System? Depending on 16 a empty voltage "empty" should be about 53 Volt (67V full), on a 15cell System 0% is about 50Volt (62,8full)

 

What is also possible: I have read for 9b very often that in the U-States the Charger only goes to 60Volt....and if thats the case on your Mopoo, too, that would mean that you are always just starting with "real" 80% (60V instead of 63V)  (while even then only 95wh would be to less)

 

So my advise would be to check the voltage on your Mohoo by plugging in the Charge doctor (or when starting to Charge)....and also check for the "full voltage" when charged up!

then we will find out whats going on :-)

[tjcooper]

churill and US69,

sadly I don't have the voltage measurement when I started to recharge after pack was empty.  I remember something like 56 volts but I could be wrong.  My MoHoo is a 16 cell system to go to 67.2 volts at peak which I do remember being when the DC said it was full at 95 Watt-hr.

My old MoHoo battery has the ability to measure current while it is being ridden.  I would have to do the extended power wires to get the new pack to do that.  With the old pack I was getting something like 3amps to 6 amps as I was gently riding up and down the street.  I don't have any data now for the new pack.

I do have the HUGE RESISTOR pack that I could use to put a serious drain on the battery for testing, but not sure if it will sustain a 20 amp load from FULL CHARGE down to stop voltage of 3.0volts * 16 cells.   Besides, what I really want to measure is the voltage (and maybe current) when the message comes out in horrible Chinglish that I have drained the battery as far as I should go.   I can only get this measurement by using the MoHoo in real riding mode.

In my previous tests I run the MoHoo at 5-8 mph going up and down the street to wear down the battery.  Maybe I should use my Garmin with GPS to have it tell me how many Kiliometers I have ridden from FULL to empty notices.   My guess is that I got like 8 miles of travel at something like 6 mph doing the testing.  I am heavy at 214 lbs so I load down the system.  Will try to get more measurements from the MoHoo and the Ninebot E+ in the next week or so.

   tjcooper

[Chriull]

7 hours ago, tjcooper said:

sadly I don't have the voltage measurement when I started to recharge after pack was empty.  I remember something like 56 volts but I could be wrong.  My MoHoo is a 16 cell system to go to 67.2 volts at peak which I do remember being when the DC said it was full at 95 Watt-hr.

56V would be 3,5V per cel- quite a feasable value for cells discharged to ~3v.

So my guess would be that you have ~100-120Wh pack advertised as 350Wh.

Are there 16 or 32 cells in the pack? With a 16 cell pack 350 Wh are definitely wrong, with a 32 cell pack some 100Wh are very low - do 1000mAh li ion 18650 cells exist?

Ps.: Did you get your pack from a "reasonable/serious" reseller or some alibaba/ebay source?

[WARPed1701D]

I'm not sure this will assist as it is a different device and different size pack, but for reference my Inmotion V8 with a 480Wh battery pack (20S2P arrangement) accepts 420Wh back into the battery (as measured by a charge doctor) when I used the wheel from full (balancing) charge to wheel shutdown at 0% (0% is 3.4v in the V8 firmware and I was riding a very modest 12kph at constant speed for the last 10% to minimize current draw/voltage sag and get the max possible range). That means I can use 87.5% of the manufacturer rated capacity. LG measured capacity by discharging to 2.5v at 0.5c (http://lygte-info.dk/review/batteries2012/LG 18650 MH1 3200mAh (Cyan) UK.html). These differences of discharge termination values are the likely cause of the 60Wh difference.

Your 95Wh of consumption from a 350Wh pack (27% of capacity) is highly abnormal.

[tjcooper]

Chriull,I believe when I took it apart it is 16S2 in configuration so 32 total cells.  THe vendor was on DHgate out of China but with good customer satisfaction ratings.  If this weekend is sunny and good I will charge it to FULL and measure start voltage then ride it as long as me legs hold out (at 72+years I cannot stand as long as I used to).  If I can get it to deliver the Chinglish message of "low voltage" then I will immediately measure the voltage.  Then do the recharge with DrCharge.   Hopefully with my Garmin Vivoactive I can measure my distance at the same time.  I have a little more confidence in the unit now that I have taken it twice to EMPTY and not had the nasty "face plant" I have experienced in the past with the wheel locking.

   tjcooper

[Chriull]

7 hours ago, tjcooper said:

Chriull,I believe when I took it apart it is 16S2 in configuration so 32 total cells.  THe vendor was on DHgate out of China but with good customer satisfaction ratings.

Could be just a very bad charge you got, or he has many friends for uprating

7 hours ago, tjcooper said:

  If this weekend is sunny and good I will charge it to FULL and measure start voltage

Good Idea -> maybe your charger has a little bit low voltage and by this already some capacity is lost! There where imo already quite some reports/suspicions of chargers "lowering" their max voltage over time...

7 hours ago, tjcooper said:

then ride it as long as me legs hold out (at 72+years I cannot stand as long as I used to).  If I can get it to deliver the Chinglish message of "low voltage" then I will immediately measure the voltage.  Then do the recharge with DrCharge.   Hopefully with my Garmin Vivoactive I can measure my distance at the same time.  I have a little more confidence in the unit now that I have taken it twice to EMPTY and not had the nasty "face plant" I have experienced in the past with the wheel locking.

   tjcooper

Also to get the "better" voltage to capacity "correlation" ~4 hours resting for the batteries is suggested. But with the difference of 350Wh to 96Wh this should not matter to much - just take the measurements after charging and after discharging within about the same time intervall...

Or just as the Charge Doctor shows the voltage you could note the start voltage of charging and the final voltage - so no disassembly is needed to measure the voltage of the pack. But with this method one gets a higher starting voltage as the charger immedeately pushes the voltage up. If there is no voltage protection diode in the wheel, the charge doctor maybe shows a correct battery voltage if plugged in without charger?

[tjcooper]

needed to correct a big error:  My Mohoo pack is 161S so only 16 Samsung 18650 cells.  I am charging it on Dr Charger now and will get final voltage (which I believe will be 65.5volts DC) and then do the ride along with Garmin to measure how far I go.  I know because I have examined circuit that the BMS has protection diode.  Hopefully can get the full drain done today and will reply with results.

I fear that I said that the pack was 350 Watthour when I see in the documentation that the motor is 350Watt.  I cannot find anywhere on the original pack where it gives the Watt-hour of the pack.  I see it has 62.7 v and 2.2 amps as the battery capacity.  So that tells me 137 Watt-hour if that is a meaningful definition of capacity.  I need to remove the current battery(the new one from DHgate) and see if it has some documentation on the capacity.   All the old documents for MoHoo were lost in a computer crash and Banggood no longer carrys the item.

   tjcooper

[US69]

When you only have a 16S One paralell setup with 2200mah cells, yeah, thats just about 130wh ?

Then the 90wh numbers make sense ?

[Chriull]

And with just charging to 65,5V the 96Wh shown by the chargedoctor are very feasable.

[steve454]

Be cautious riding it, that battery is tiny.  I bet any sudden acceleration would cause the wheel to cut out momentarily.

There were some good reviews of the MoHoo though.

But they can drop you without warning, as shown at 5:40 in this video I found on You Tube.

Here is the video I was originally looking for, It's called a Huanxi H1 but I believe it's the same as the MoHoo.

 

[tjcooper]

Steve454,

did you realize that the first picture you showed for stoppage was ME????   That was when I had about 6 instances of the wheel shutting down and throwing the rider.....who sadly did not know how to ride very well.    So I am very familiar with the lock down.  That is why I have done the SHUNT fix to all the batteries so that the sudden cutout does not affect me any more.   Since doing the SHUNT fix on all my packs, never had a repeat of that problem.  But there are several others that have really made we worry about EUC....like the wheel going free-wheeling every once in a long time.  Had to get a new Ninebot E+ to correct that problem.

 

Churill,

let me share some pictures and data with you that I promised earlier.  I took the MoHoo when it said it was "under voltage" and immediately started to lift up the petals.   I got 3.25 miles of gentle riding out of the pack from a full charge.  The starting voltage hot off the DrCharger was 66.7 volts DC.  But as I later show, my OEM charger and separate voltage/current/watt-hour meter showed 67.2 volts.

Immediately after the ride (probably 1.5 minutes after I got off EUC before I could measure) was 57.9 volts.  About 5 minutes later I was ready to start the recharge using Dr. Charger and the voltage had risen to 58.0 volts (which is typical for LiPo recovery after full discharge).  I then did the full charge with the Dr. Charger in the circuit until it showed 0.00 amps being delivered.  At this point the Dr. Charger voltage was 66.8 volts.  In the same picture you see my home made charger monitor (I will call it the Ted charger).  It is in series with the Dr. Charger and shows 67.17 volts and almost no current.  You can see that the Watt-hour delivered was only 78 W-hour.  I was amazed at this difference and so I plugged in the Ted charger directly to the MoHoo and left the Dr.Charger out of the circuit.   When the Ted charger finished, the voltage on the MoHoo was now 67.21 volts and the power had risen to 89 W-hours.

So this tells me that the DrCharger was putting a significant voltage drop into the charging circuit.  I gained 11 W-hours by charging directly.  You ask if the voltages and current from the Ted Charger are accurate?  I have put it on a commercial quality multimeter and a calibrated HP supply and what the Ted Charger says is the voltage and current mirrors the multimeter to the last decimal point.   So this causes me to be suspicious of the numbers given by the DrCharger.   Anyone else seen this happen?

Bottom line: My MoHoo has a 130W-hour battery and I can get 97 Watt-hour out of it if I go rather slowly.   The 3.25 miles under medium driving seems small.   I am 220lbs and was riding on clean asphault streets.   I was hoping for at least 5 miles of driving distance.

 Pictures are enclosed of measurements.

     tjcooper

[steve454]

On 5/8/2018 at 4:47 PM, tjcooper said:

Steve454,

did you realize that the first picture you showed for stoppage was ME????   That was when I had about 6 instances of the wheel shutting down and throwing the rider.....who sadly did not know how to ride very well.    So I am very familiar with the lock down.  That is why I have done the SHUNT fix to all the batteries so that the sudden cutout does not affect me any more.   Since doing the SHUNT fix on all my packs, never had a repeat of that problem.  But there are several others that have really made we worry about EUC....like the wheel going free-wheeling every once in a long time.  Had to get a new Ninebot E+ to correct that problem.

I was pretty sure that was you.  I saw that video a long time ago, and it came up when I searched Mohoo cutout.  You were riding pretty well.  I forgot that you did the shunt on the BMS.  So now it no longer cuts out.

But that small of a battery is not going to give much range.  My first wheel was a TGT3 with the 132wh battery, I weigh 210, and the range and power were terrible.  About 2 miles riding slow.  It was so under powered it was dangerous for someone my size.  You should do what I did, and recycle that thing.

But I don't know, in the second video of the low battery behavior, that Mohoo looked like a strong running wheel.  I wished I had got one instead of the TGT3, it's much better looking and has better features.

I also have a ninebot one E+ and it is so much better, faster, and longer range. 

[tjcooper]

Steve454,

your TGT3 seems close to what I am getting with 135Wh battery.   I have a special connection on the battery system that allows me to put an "out rider" on the wheel to have two of the batteries in parallel to double the watt-hour.  I will try that next week and see if I get my 6 mile riding limit.  And like you, I also have a Ninebot E+ to give me real mileage.....but it is much heavier and does not allow you to make sharp turns.

Did anyone else experience the voltage drop that I discussed above with the DrCharger monitor system?  I think most people would be disappointed to find a 12% reduction in charging capacity with the DrCharger is in the circuit.

    tjcooper

[Chriull]

12 minutes ago, tjcooper said:

Did anyone else experience the voltage drop that I discussed above with the DrCharger monitor system?  I think most people would be disappointed to find a 12% reduction in charging capacity with the DrCharger is in the circuit.

As far as i remember no one reported about a voltage drop till now - maybe just noone looked at this in detail?

Could be from some protection circuit inside? Since you call it DrCharger - is this the Charge Doctor from @hobby16or something different?

If so best would be to ask @hobby16 directly if this is normal behaviour or something is faulty.(best per email - he seems to be not really active around here) 

 

[tjcooper]

@chriull; @hobby16

This is Charge Doctor....the special one with three pin plug and Ninebot 4 pin plug.

Had not approached @hobby16 since I was hoping another "end user" had seen it.  I will include @hobby16 in this response.

   tjcooper

[Chriull]

2 hours ago, tjcooper said:

@chriull; @hobby16

This is Charge Doctor....the special one with three pin plug and Ninebot 4 pin plug.

Had not approached @hobby16 since I was hoping another "end user" had seen it.  I will include @hobby16 in this response.

   tjcooper

If you don't see the members name with the @ with a blue background in your post, it does not work out - no notification. @novazeus - one has to type the @ a first letter (or more to narrow down the search) and choose an entry from the appearing drop down box. If one just types @novazeus (not selecting anything from the box) no notifications are sent.

If one clicks on a member or such a member name with the @ and a blue background one can also see when he was the last time online - so for @hobby16 this was two month ago on march 10. So imo no chance to reach him via this forum...