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V8F vs V8S - capacity versus maximum|peak discharge current?


rcgldr

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I can find specs and|or info for V8F 18650 batteries, max continuous discharge current is 10 amps, peak discharge current for 4 seconds is 17.75 amps. The only specs I can find for the V8S LG 21700 batteries (they may also use another battery) is max continuous discharge current is 7.275 amps, and I have yet to find any claim for peak discharge current.

I'd also like to know what is a reasonably safe max peak current for the V8F. V8F and V8S both have 30 amp blade fuses. Based on the specs for blade fuses, these are in effect 33 amp fuses, since they are spec'ed to run 100+ hours at 110% current, which would be 33 amps. At 40 amps, the minimum blow time is 0.75 seconds. My guess is that over 33 amps, the fuse could get partially melted. Compounding this issue is the V8F and probably the V8S don't have peak current alarms, only power. I have to use EUC World to set a peak current alarm setting, and there's a delay or other issue, where the actual peak current may be significantly greater than the set alarm current. For example, I have peak current set to 20 amps, today I managed to trigger the alarm while accelerating around 14 mph on a smooth slight incline with a 20.1 amp peak current. On a prior test with a bit less charge on that same incline, peak current was about 24 amps. Also today, I got a warning and a peak of 23.4 amps, but that was due to a one inch bump spike at the crest of an incline.

I posted another thread about the maximum peak current any rider has seen and one rider reported a peak of 38.7 amps, recorded on a EUC World tour. Link to the tour. The wheel statistics, which include peak current takes a few minutes to show up and you may have to sign in just to enable them.

https://euc.world/tour/601301165433104

 

Edited by rcgldr
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Update - links to test data. V8F - LG 18650 MJ1 - spec shows 10A. V8S - LG 21700 M50T - spec shows 7.275A. However, in the test at 10A, the MJ1 has about 0.1 volts more sag than M50T, and at 15A 0.2 volts more sag. The 15A tests were run for a bit over 5 minutes before stopping the tests due to battery temperature. For a battery pack at 72% => 78 volts at 30A, MJ1 sags to 64 volts, M50T sags to 68 volts, 6.25% less sag.

https://lygte-info.dk/review/batteries2012/LG 18650 MJ1 3500mAh (Green) UK.html

https://lygte-info.dk/review/batteries2012/LG 21700 M50T 5000mAh (Gray) UK.html

Both V8F and V8S have a 30 amp fuse which is really a 33 amp fuse, and even at 40 amps, it takes 0.75 seconds minimum for the fuse to blow, which is supposed to protect the batteries, circuit board, motor, ... . The only protection in the V8F (and I assume V8S) is peak power, which will sound an alarm and tilt back. I've never experienced this.

So the V8S has more range, and a bit more margin for current than V8F.

Edited by rcgldr
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  • 1 month later...

I needed to get under the battery compartment of my V8S and accidentally also took out the screws that keep the compartment shut, so got a peek at the batteries :)

Could just make up "Samsung INR21700-50..." so I'm assuming they're these ones: https://lygte-info.dk/review/batteries2012/Samsung INR21700-50E 5000mAh (Cyan) UK.html

I'm no battery expert so can't interpret everything, but it's looking like this cell has a higher discharge capacity than the LG M50T :clap3:

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On 4/12/2022 at 6:12 AM, marcelsamyn said:

I'm no battery expert so can't interpret everything, but it's looking like this cell has a higher discharge capacity than the LG M50T 

The Samsungs are rated higher, but the graphs for 15 amp load (per cell) show a bit more sag (lower voltage) with the INR21700 than the M50T, and a bit less sag than the MJ1. Although the INR21700 was tested with a 20 amp load (translates to 40 amps for a battery pack), the V8F | V8S use a 30 amp blade fuse, which is rated at 100+ hours at 33 amps, but minimum blow time at 40 amps is 0.75 second. The V10F is supposed to have a 40 amp fuse (so rated at 100+ hours at 44 amps), so a V10S with 21700 cells instead of the MH1 cells (same as V8 not V8F), might be a future product.

Edited by rcgldr
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7 hours ago, mrelwood said:

Just to make sure, have you considered that there must be a different amount of parallel cell groups between the 18650 and the 21700 packs?

V8F and V8S both use 40 cells, 20S2P, and both use the same 30 amp blade fuse.

Edited by rcgldr
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16 hours ago, rcgldr said:

V8F and V8S both use 40 cells, 20S2P, and both use the same 30 amp blade fuse.

Wow, I remembered the V8F capacity completely wrong!

 The V8F is 518Wh, and the V8S is 728Wh.

So whichever cells the V8S comes with, it’s superior to the V8F. Maybe not that big of a surprise though.

Btw, you seem to prefer a 3rd party current alarm to the included power limit. Is there a reason for that, do you maybe not trust the included limiter for some reason?

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1 hour ago, mrelwood said:

The V8F is 518Wh, and the V8S is 728Wh. So whichever cells the V8S comes with, it’s superior to the V8F. 

Btw, you seem to prefer a 3rd party current alarm to the included power limit. Is there a reason for that, do you maybe not trust the included limiter for some reason?

V8S is higher capacity, but it's spec'ed at a lower continuous current rate (7.275 A versus 10 A per cell). However, in actual tests, the V8S has less battery sag than V8F. For example at 30 amps, 78 volts, V8S has 10 volt sag (drops to 68 volts), V8F has 14 volt sag (drops to 64 volts). As an analogy to overheat hill, either battery pack will overheat in about 6 minutes or so if run at about 20 A or more. The Samsung 27100 has a bit more voltage sag than the M50T 27100, but both are less sag than the V8F MJ1.

The point of using EUC World peak current alarm was to avoid blowing the 30 amp fuse. However, due to a delay between V8F and EUC World, it's useless when you need it the most, during acceleration. For example, say the peak current alarm is set to 20 amps, and during moderate|aggressive acceleration 20 amps occurs at 15 mph, but the alarm doesn't sound until 17 mph, and then the V8F has to accelerate to balance the rider when the rider stops leaning forwards, resulting in an actual peak near 27 to 28 amps (I had that happen one time). Using light acceleration, anticipating when the alarm would trigger, and due to shear luck in the timing, I've managed to get an actual peak of 20.1 amps, with a 20 amp alarm setting. The fuse is 30 amps, and a 30 amp blade fuse is spec'ed to run 100+ hours at 33 amps, so it's really a 33 amp fuse. At 40 amps, the minimum blow time is spec'ed at 0.75 seconds. 

I posted a thread hear and at another forum for the highest peak values a rider has ever seen on a V8F. The record was peak current 38.7 amps, max power 2544 watts on a 1.4 mile ride, with no alarm from the V8F. The rider thinks that maybe a small bump triggered the spikes. You have to sign in and wait a few minutes to get "vehicle statistics":

https://euc.world/tour/601301165433104

So a rider has to determine that he|she is getting close to the limits by noting the peak current and power after stopping and looking at the stats, and adjusting their riding style accordingly. The peak current alarm could be used as a way to indicate peak current alarm setting was exceeded in the last 1 or 2 seconds, but not as a warning. 

I've never experienced overlean or power limit on my V8F. I weigh a bit under 190 lbs, so I don't get too aggressive on acceleration, especially if I'm close to 15+ mph, mostly around 20 amp peaks. I could probably increase this to 25 amps, but there's rarely a need to accelerate more quickly, and the V8F brakes fairly well, better than most EUCs.

I've tested speed limit tilt back at 8, 12, and 15 mph, but concerned at 18 or 21 mph, that the tllt back could trigger wobble, so I set it to max (21.6 mph) and avoid going over 18 mph, most of the time riding at 12 to 15 mph on a local bike trail or private streets (15 mph speed limit) near my home. The speed limits on nearby streets are 45 to 55 mph, and close to a senior community so I don't ride on those streets. 

Video of a tester blowing a fuse on the second acceleration test on the V8F in a comparison video (this is what I want to avoid).

https://www.youtube.com/watch?v=hAEOnvDNaYw&t=723s

 

Edited by rcgldr
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Is the acceleration test in the link the only case of a tripped fuse that you know of? Because if it is, it should be pretty easy to avoid… Don’t dive into the acceleration like the guy did. Instead, increase the acceleration slowly. As you can hear, the wheel’s alarm did go off, but I guess Inmotion didn’t tune the warning to be fast enough for acceleration tests… on a small wheel.

 But if you are seriously concerned that the V8F doesn’t have the acceleration you crave for, don’t try to figure out how to put on alarms so you can stay on the edge. Save your skin and get yourself a wheel that has what you need, without worrying over stuff like this.

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On 4/14/2022 at 6:45 PM, mrelwood said:

Is the acceleration test in the link the only case of a tripped fuse that you know of? 

 But if you are seriously concerned that the V8F doesn’t have the acceleration you crave for, don’t try to figure out how to put on alarms so you can stay on the edge. Save your skin and get yourself a wheel that has what you need, without worrying over stuff like this.

Wrong Way also blew a fuse in his V8F review (noted after he made the video), while going up an incline at 3 mph or so (but this was after abusive testing):

https://www.youtube.com/watch?v=CQFR9afWhGA&t=886s

Most youtube reviewers will push the wheels they are loaned to the limits and for the prototypes, often blow fuses, burn circuit boards, ... .  In a recent case, one of Hsiang's friends was doing a series of short acceleration | braking stress tests on a prototype S20, when it cutout under braking (a popping sound was heard, probably a mosfet failing and shorting) and started the battery pack on fire (it's not clear why a fuse did not prevent this).

https://www.youtube.com/watch?v=8h41p13e4TU&t=569s

I'm an old retired guy (70 years), with a bit over 500 miles on my V8F that I got last August. The V8F acceleration is good enough for me. I was hoping that similar to being able to lower the top speed, a rider could lower settings for PWM, power, current, ... , that would trigger beeps for more margin, in case something unusual was going on with the V8F.

Edited by rcgldr
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Kingsgong 16s (16s4p) or mcm5v2 (20s3p) are far more capable and safer wheels, while still remaining in the very portable category.

I have set a tiltback at 30 kph (19 mph) on my mcm5v2 and I don't have to worry about anything.

Overpowering the wheel will not come by accident. It will have to be a conscious effort.

Edited by Freestyler
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We should also mention that the V8S has a smaller motor of 1000W.... personally I prefer that given there are 40 cells. The question is whether it has 62V motor over driven at 84V like on the original V8. I never liked the V8F 1500W

I just posted this on another thread as to how many cells/size can be packed in a V8.

               
Edition Cells # Sur area Total Area cm^2 Cell Size Type Capacity Pack Capacity Whr
*) 57 2.5447 145.0479 18650      
V8 40 2.5447 101.788 18650 MH1 3000 432
**) 60 2.5447 152.682 18650 MH1 3000 648
V8F 40 2.5447 101.788 18650 LG MJ1 3450 496.8
**) 60 2.5447 152.682 18650 LG MJ1 3450 745.2
  40 3.1416 125.664 20700 Sanyo20700B 4250 629
V8S 40 3.4636 138.544 21700 M50T 5000 720

 

Edited by OneLeg
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On 4/15/2022 at 4:43 AM, rcgldr said:

V8S is higher capacity, but it's spec'ed at a lower continuous current rate (7.275 A versus 10 A per cell). However, in actual tests, the V8S has less battery sag than V8F. For example at 30 amps, 78 volts, V8S has 10 volt sag (drops to 68 volts), V8F has 14 volt sag (drops to 64 volts). As an analogy to overheat hill, either battery pack will overheat in about 6 minutes or so if run at about 20 A or more. The Samsung 27100 has a bit more voltage sag than the M50T 27100, but both are less sag than the V8F MJ1.

 

 

 

 

 

If i was going to build a 21700 I would go for the Samsung 50E 10A.... I would generally go for 20A cells on the V8.

I/my friends have broken a number of times in emergency and the unicycle simply failed at staying upright and fell back and landed on my arse. Quite often when this happen, the wheels goes on, an my friend has hit pedestrians twice. I think that even the 800W motor is capable to draw more than what the 10A cells can deliver specially when the pack is below 50%... or is it the motor?

I am  presently building the Sanyo20700B  20A, 629Whr pack for my V8... lets see how it does breaking in emergencies.

Edited by OneLeg
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  • 2 weeks later...

I've been wondering this myself since I'm a new rider on the V8 and at 220 pounds, would like as many points of data to know the headroom as possible. Speed limit is one thing but would love to be able to get a reference on "max draw".

Also noob question here but for a regular V8 is it normal to have it at full charge read around 85.5V in EUC world?

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14 hours ago, Heymelon said:

Also noob question here but for a regular V8 is it normal to have it at full charge read around 85.5V in EUC world?

Absolutely not normal! The internal voltage measurement is often imprecise, but 1.5V extra is rare. Have you measured the voltage output of the charger?

 Btw, have you ever ridden the wheel to empty and then checked the voltage?

 If the voltage measurement is simply that much off, Inmotion can remotely calibrate the measurement. It would probably be best handled through the seller.

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20 hours ago, Heymelon said:

I've been wondering this myself since I'm a new rider on the V8 and at 220 pounds, would like as many points of data to know the headroom as possible. Speed limit is one thing but would love to be able to get a reference on "max draw".

Also noob question here but for a regular V8 is it normal to have it at full charge read around 85.5V in EUC world?

I would first measure the output of your charger... with a good meter, I have seen 84.5V on the cells and it was due to the charger. Many of the chargers you can adjust. I set my inmotion ones to 83.6V

 

At 220lbs, I would not ride it up very steep hills or for a prolonged period. I have 3 x V8.... I got one which had close to 5000km and the battery showed wear, then I got another with 1100km which had been abused, crashed, it came with a broken motor.... the battery was worse than the one with the 5000km. At 3000km I just doesn't do more than 20km in range and will rebuild it with 40 x NCR20700B's. 630Whr.

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39 minutes ago, OneLeg said:

I would first measure the output of your charger... with a good meter, I have seen 84.5V on the cells and it was due to the charger. Many of the chargers you can adjust. I set my inmotion ones to 83.6V

 

At 220lbs, I would not ride it up very steep hills or for a prolonged period. I have 3 x V8.... I got one which had close to 5000km and the battery showed wear, then I got another with 1100km which had been abused, crashed, it came with a broken motor.... the battery was worse than the one with the 5000km. At 3000km I just doesn't do more than 20km in range and will rebuild it with 40 x NCR20700B's. 630Whr.

Oh well ok, I thought this was just a app misread and or within normal error range so I wasn't worried about it really but now I kinda am. The wheel reads 100% in Euc world a lot earlier then the end volt of 85.4 or 85.4 and the charger light turns green. Then I can ride for quite a bit before I get to 99%, somewhere around 5km.

I bought the wheel very cheep used and it had gone 1300km and seemed in good shape. I can ask the seller what he got but this warranty is probably way overdue so it will be up to me to check it. I don't have any measure tool and I guess if I get one I should invest in one that is pretty precise and more expensive. Bit short on cash atm so should I get that or just try to buy a new charger? I'll message the seller a well to se what he got in terms of volts at 100%.

As far as the riding at 220lbs bit I'm not that worried. I have a speed limit on the wheel and I don't push it, I think I know pretty well what it can do at this point. But if you still think this will cause so much wear and tear to reduce the battery life then that's life and I'll probably upgrade before then anyway. Thx for the response. 

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7 hours ago, mrelwood said:

 

Absolutely not normal! The internal voltage measurement is often imprecise, but 1.5V extra is rare. Have you measured the voltage output of the charger?

 Btw, have you ever ridden the wheel to empty and then checked the voltage?

 If the voltage measurement is simply that much off, Inmotion can remotely calibrate the measurement. It would probably be best handled through the seller.

No, and no. I don't have any tool to measure yet :) But ty for your input, I'll have to look into that and ask the 2nd hand seller what he got.

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  • 1 year later...

I had the v8, the v8f then the v8s yesterday.The v8 cut off easily before the safety.The v8f never cut off but had a power alert which worked quite well around 2500w.Today first v8s test in high climb with 72 % of battery, there was security (overload please go down), there was a current peak at 36A! I think we should put a 40A or 35A fuse or a v10 motherboard.

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