My Sherman Trials, Tribulations, and Triumphs

[bryon01]

9 hours ago, Chriull said:

Unfortionately not.

Increasing the charging current decreases the time of the constant current stage up to ~100% first time shown. At this point roughly around 85% real charge is reached - the higher the charging current, the lower the real charge.

So the second stage (constant voltage, balancing) takes longer to charge up to real 100%.

Btw: one could "optimize" this second stage if one just leave the charger with the higher voltage plugged in after ~half an hour. As all chargers have slight differences and the "lower voltage" charger limits the other one!

The numbers @Marty Backe wrote down fit quite nicely - 10p*3500mAh = 35Ah, charge (cc phase) with 8A within 4h (99.4V reached) equals about 35Ah/8A = 4.3h.

With 8A its a nice "slow" 8A/35Ah=0.2C charge.

A bit more than 2h for the second (cv) stage is also about what batteryuniversity.com states for this stage (at 1C charge about 2 3/4h)

So with all that together the cc stage with 10A instead of 8A  will reduce @Marty Backe's measured 4h downto 4h *8A/10A = 3.2h. The second stage will take some time longer as the with 8A measured 2h - so maybe something like a quater to half an hour saved?

The fan turning off seems to be a great indicator for charging finished (if really controlled by charge current?).

Letting the fan running while charging is imho a great idea, too! Takes some stress from the cells and is ?maybe a slight? safety measure.

For some estimated numbers with the Veteran:

The IR of the sanyo 18650GA is .038 ohm, so the 24S10P pack resistance is only 0.0912Ohm due to only the cells.  Lets add another 1 ohm for wires, welds, solder joints, and bars.  so 1.09Ohm.  If true and the battery is fully discharged at 75V, and you want to go to 100V, then you can only push 22.9A through the battery before the voltage appears to be 100V and the charger will go into CV mode.  22.9A through the battery is 2.3A through each cell, which is above the recommended limit by Sanyo of 1.65A but is actually safe as long as you don't overheat the pack during the charge, as it is less than a 1C charge rate.  Of course, you will be eating into the life of the cell charging this hard.  So of course you can just look at single cell charge curves for different starting currents, which luckily as the 18650 is so well regarded the data exists.  Sanyo claims full charge in 270min at 1.65A, but per lygte-info, you can see that they charged in 220min at a 1A cell charge (10A pack), or 3.66 hours per here: https://lygte-info.dk/review/batteries2012/Sanyo NCR18650GA 3500mAh (Red) UK.html  It appears to cutoff the charge at .15A since the AHr was barely increasing.  If you don't want the pack voltage to sag as it did in the chart then you need to let that CC go further towards zero but you are a few percent from full.

Point is, at 10A you can charge to 98% full in under 4 hours, and 16.5A you'd be charged in under 3 hours.  At 8A if you look at the curve for lygte, because the CV slope is almost vertical when it departs from the CC phase, the easiest way to estimate is say that the CV time is the same.  Charging at 8A would take 25% longer than 10, and the CV phase is the same amount of time, or 265min. (4.4hr)  This assumes of course 4A on a Chinese charger really means 4A and not 3.2A.

[Marty Backe]

15 hours ago, mrelwood said:

I must’ve clocked something like 1000-2000 miles on mine, and it only started to look a bit driven in. I’d imagine it would take two more winters pretty easily. I have no idea how someone could wear it out in 500 miles. Unless he means that it didn’t last longer on the wheel because he wanted to change to a different kind...

He published a picture that shows the tread almost gone. Good to hear that it must be unique to him and how he's using the tire.

15 hours ago, ShanesPlanet said:

Is this the sherman that came from NYC? Are the miles ALL miles on the wheel, or 500 you put on + theirs? Or did you snag one of your own already? Im mostly street intent for the sherman, but I do know that a 'trials' tread is not really a knobby. I keep thinking that the street tire may just be for that VERY rare person that absolutely needs a drag strip tire? How far into the 'chicken strips' does it seem the sherman has been? Love the vids marty, thanks for the efforts!

It's the Sherman from NYC. They had put 196-miles on it and I've put 390-miles on.

[MrRobot]

14 minutes ago, bryon01 said:

For some estimated numbers with the Veteran:

The IR of the sanyo 18650GA is .038 ohm, so the 24S10P pack resistance is only 0.0912Ohm due to only the cells.  Lets add another 1 ohm for wires, welds, solder joints, and bars.  so 1.09Ohm.  If true and the battery is fully discharged at 75V, and you want to go to 100V, then you can only push 22.9A through the battery before the voltage appears to be 100V and the charger will go into CV mode.  22.9A through the battery is 2.3A through each cell, which is above the recommended limit by Sanyo of 1.65A but is actually safe as long as you don't overheat the pack during the charge, as it is less than a 1C charge rate.  Of course, you will be eating into the life of the cell charging this hard.  So of course you can just look at single cell charge curves for different starting currents, which luckily as the 18650 is so well regarded the data exists.  Sanyo claims full charge in 270min at 1.65A, but per lygte-info, you can see that they charged in 220min at a 1A cell charge (10A pack), or 3.66 hours per here: https://lygte-info.dk/review/batteries2012/Sanyo NCR18650GA 3500mAh (Red) UK.html  It appears to cutoff the charge at .15A since the AHr was barely increasing.  If you don't want the pack voltage to sag as it did in the chart then you need to let that CC go further towards zero but you are a few percent from full.

Point is, at 10A you can charge to 98% full in under 4 hours, and 16.5A you'd be charged in under 3 hours.  At 8A if you look at the curve for lygte, because the CV slope is almost vertical when it departs from the CC phase, the easiest way to estimate is say that the CV time is the same.  Charging at 8A would take 25% longer than 10, and the CV phase is the same amount of time, or 265min. (4.4hr)  This assumes of course 4A on a Chinese charger really means 4A and not 3.2A.

So 10 amps significantly kills the battery life of the pack more than 8amps? 

[Chriull]

1 hour ago, bryon01 said:

The IR of the sanyo 18650GA is .038 ohm, so the 24S10P pack resistance is only 0.0912Ohm due to only the cells.

Exactly.

Quote

  Lets add another 1 ohm for wires, welds, solder joints, and bars.

Way to much.

52 minutes ago, MrRobot said:

  If true and the battery is fully discharged at 75V, and you want to go to 100V, then you can only push 22.9A through the battery before the voltage appears to be 100V and the charger will go into CV mode.

Yes one could push 22.9A through the battery. Even much more as your 1 Ohm assumption is way too much!

52 minutes ago, MrRobot said:

Point is, at 10A you can charge to 98% full in under 4 hours, and 16.5A you'd be charged in under 3 hours. 

No. One cannot! Just the wheel shows 100%(98%) charge, which is not true.

1 hour ago, bryon01 said:

the easiest way to estimate is say that the CV time is the same.

No. Cv phase takes longer, the higher the cc gets.

If you want to understand li ion charging read https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

1 hour ago, bryon01 said:

but per lygte-info, you can see that they charged in 220min at a 1A cell charge (10A pack), or 3.66 hours per here: https://lygte-info.dk/review/batteries2012/Sanyo NCR18650GA 3500mAh (Red) UK.html

They only state 4h for standard charge. All the figures are discharge stats!

Edited July 12, 2020 by Chriull

[Chriull]

25 minutes ago, MrRobot said:

So 10 amps significantly kills the battery life of the pack more than 8amps? 

No - both is something about 0.2C charging. 0.5C charging is recommender - so it's way below the recommended maximum.

[Jon Stern]

43 minutes ago, Marty Backe said:

He published a picture that shows the tread almost gone. Good to hear that it must be unique to him and how he's using the tire.

It's the Sherman from NYC. They had put 196-miles on it and I've put 390-miles on.

That's because they were too busy trying to get it to cut out and getting in to fights with car drivers to ride very far!

[travsformation]

5 hours ago, Jon Stern said:

That's because they were too busy trying to get it to cut out and getting in to fights with car drivers to ride very far!

On the opposite end of the scale, when Marty has the wheel, drivers pull over for him thinking he's a cop... 

Edited July 13, 2020 by travsformation

[bryon01]

5 hours ago, Chriull said:

They only state 4h for standard charge. All the figures are discharge stats!

That is incorrect.  Look at the last chart.

[bryon01]

6 hours ago, MrRobot said:

So 10 amps significantly kills the battery life of the pack more than 8amps? 

No, but the harder you charge from the deeper you charge is always a life limiter.  You will get great cycle life with 1.65A per cell, or 16A per Veteran.  Charging and discharging fast causes damage to the anode.

[bryon01]

5 hours ago, Chriull said:

No. One cannot! Just the wheel shows 100%(98%) charge, which is not true.

No. Cv phase takes longer, the higher the cc gets.

If you want to understand li ion charging read https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

They only state 4h for standard charge. All the figures are discharge stats!

That isn't true.  You can look at the single cell data I posted.

Yes, CV gets longer, but total charge time gets shorter, you are incorrect.

I understand how to ION charge, I work for Tesla.

You are also wrong on your last point.

[bryon01]

5 hours ago, Chriull said:

Yes one could push 22.9A through the battery. Even much more as your 1 Ohm assumption is way too much!

It was an example, it doesn't matter and you miss the point.

[MrRobot]

Anyone want to list the 1-10 Amp full charge times one by one? 😅

Edited July 13, 2020 by MrRobot

[bryon01]

I have Sanyo 18650 cells, I am happy to charge them 1 by 1 and post the results which can be scaled up by the voltage and the number in parallel.

[travsformation]

On 7/12/2020 at 2:07 PM, Chriull said:

Afai read it's recommended to use both ports (each limited to ~5A) for 10A. If you have a 100.8V 10A charger (1kW!) you should use a split cable to plug in both ports and the charger.

I just found this, shared from a post of Jason's (source)

On 7/9/2020 at 8:18 PM, Shield said:

Charge Ports & Charger: the Sherman is being shipped with a 5A/100V charger as standard equipment. There is also the option of getting a 100V/8A charger with some enhancements like a Wh/Timer screen, variable amperage output in 2A increments & partial charging support. Charge ports have been upgraded with 2x wires for each +/- to support 8A from one port. It is not recommended to charge the Wheel above 8A, so please do not use both chargers at once!

 

Edited July 13, 2020 by travsformation

[FreeRide]

Charging at 10Amps should take very close to 3.65hrs or 219-220min on with a good solid charger and no BMS interference.  How does this compare with what Veteran is saying? 

Update: See Above Veteran is saying 8A max charge rate.

 

So basically we're stuck with slow charging or turtle charging. This is likely because they route the charging through their BMS which may further limit the charge rate (for some reason such as temperature) or just reduce it slightly as a result of the internal resistance it adds for monitoring and control.

Edited July 13, 2020 by FreeRide

[Chriull]

10 hours ago, bryon01 said:

That isn't true.  You can look at the single cell data I posted.

You'r right. I overlooked the last graph for charging.

The charge time is lower because this cell just has 3.25Ah. Seem to be quite a tolerance in capacitance and 3.5Ah the exception (if ever reached)?

10 hours ago, bryon01 said:

Yes, CV gets longer, but total charge time gets shorter, you are incorrect.

Yes. As stated before only cc stage time gets proportionaly shorter. By the longer cv stage duration it still gets shorter, but as for the first example (8A vs 10A) just marginal.

10 hours ago, bryon01 said:

I understand how to ION charge, I work for Tesla.

You are also wrong on your last point.

Sorry for my disrespectful and shallow post!

[meepmeepmayer]

2 hours ago, FreeRide said:

So basically we're stuck with slow charging or turtle charging.

8A is now slow charging... I like this new generation of EUCs

[bryon01]

2 hours ago, Chriull said:

The charge time is lower because this cell just has 3.25Ah. Seem to be quite a tolerance in capacitance and 3.5Ah the exception (if ever reached)?

Sanyo Li-ion cells are typically rated from full to 2.5V, at 0.1C discharge rate.  It gives a higher capacity at the expense of lifetime.  Unlike others, they typically do hit what they say it will do, versus outright number inflation of some other manufacturers. You will never see that much in your wheel though, as Gotway and Veteran cutoff the voltage at ~3.125V.  (I think Gotway is 3.3?)  You can see from the same site going down to 3.125V, with an average current pull of between 1-2A (10-20A for the pack) you are only going to see ~3.05Ah.  Any burst of power you use will reduce this further.

If you look at the energy graph near the bottom, you can see with the same constraint you are only going to get 11Wh out of each cell, or 2.64kWh usable from the pack in normal use which is quite different than the advertised 3.2kWh.  All manufacturers do this though.

Edited July 13, 2020 by bryon01
added more specificity

[FreeRide]

2 hours ago, meepmeepmayer said:

8A is now slow charging... I like this new generation of EUCs

It always has been on a 33Ah battery, nothing has changed. We have "NEVER" had a wheel yet with fast charging, and this wheel does not even have standard rate.  

Luckily it seems like a fun ride so we accept it as is, no one wants to pay for good chargers anyway

Edited July 13, 2020 by FreeRide

[Patton250]

Sometimes when I come here and read these posts I think we are discussing aircraft, spaceships or guided missiles. Something incredibly complex like that. Then I remember it’s electric unicycles. Lol 

[Ben Kim]

5 hours ago, FreeRide said:

Charging at 10Amps should take very close to 3.65hrs or 219-220min on with a good solid charger and no BMS interference.  How does this compare with what Veteran is saying? 

Update: See Above Veteran is saying 8A max charge rate.

 

So basically we're stuck with slow charging or turtle charging. This is likely because they route the charging through their BMS which may further limit the charge rate (for some reason such as temperature) or just reduce it slightly as a result of the internal resistance it adds for monitoring and control.

“not recommended” is the wording. There is no reason two double pinned GX ports with an XT30 connector to the board can’t handle 16A unless the board limits current like Kingsong. 

The other issue is a typical outlet is only good for 15/20A max (depends on the breaker), so 10 is probably the most you’d wanna draw given other possible loads on the circuit. 

Edited July 13, 2020 by Ben Kim

[FreeRide]

1 hour ago, Ben Kim said:

.......

The other issue is a typical outlet is only good for 15/20A max (depends on the breaker), so 10 is probably the most you’d wanna draw given other possible loads on the circuit. 

That's at 120V, so 1800W,  10A at 90VDC MAX or so before CC phase is only 900W, very safe in most cases.  Someone should report the max input wattage spec from the charger, but not seeing any issue with most outlets if one has proper electrical.  Out on the road one might have to be more conservative in some places; just ask them where they plug in the vacuum cleaner or floor polisher.  I suspect the 5A charger is probably rated for only 400W max, but it would be great to know.  Maybe Marty can tell us, what it says.

Edited July 13, 2020 by FreeRide

[Marty Backe]

Overheat Hill Stress Test Results

 

 

[Ben Kim]

3 hours ago, FreeRide said:

That's at 120V, so 1800W,  10A at 90VDC MAX or so before CC phase is only 900W, very safe in most cases.  Someone should report the max input wattage spec from the charger, but not seeing any issue with most outlets if one has proper electrical.  Out on the road one might have to be more conservative in some places; just ask them where they plug in the vacuum cleaner or floor polisher.  I suspect the 5A charger is probably rated for only 400W max, but it would be great to know.  Maybe Marty can tell us, what it says.

I suspect you missed the part where I stated possibly other loads on the circuit. At home, there is very little reason to charge at such speeds, it’s use case is on long distance rides where charge speed will dictate how much distance you’ll get on a given day, where you have absolutely no clue how much load is on the circuit before you draw another 1000W from it (100.xV * 10A)

Explain where you came up with this 90VDC figure? 

PS: stock YZpower charger is rated for 450W. 

Edited July 13, 2020 by Ben Kim

[FreeRide]

3 hours ago, Marty Backe said:

Overheat Hill Stress Test Results

 

.....

WOW!!  what an adventure that was.  Jeff was a real life saver for sure.  Not sure if I would have showed that part on Camera though    In the future always wrap the chain and hook it securely back on itself, you could save yourself a lot of grief and possibly serious injury (even though you were lifting something relatively light for the crane sticking to good practices saves lives  ).

I hope Veteran can make use of this test data.  I think we heard the capacitor can roll out onto the floor when you removed the controller cover.  The smell must have been pretty bad with a sweat tinge of the capacitor electrolyte.  It would be interesting to get a better look at just what burned, maybe something other than the MOSFETS burned up because the wheel was not locked. Brush it off and give us an update.  If course if the leads melted that could also explain the no lock, or just the way they burned up.  I guess it pretty much has to be the drivers, but would be interesting to get a  closer look.