VOTOL EM-30S/Xiaoniu U1 Pro E-Scooter optimal controller settings/battery issue

[Sopheus]

Hello everyone,

I have Xiaoniu U1 Pro e-scooter and I have replaced original controller with VOTOL EM-30S.

Currently my hardware set up as follows:

Engine: 800W

Battery: 48V40.3AH (54.6V max. charging voltage, 39V min. charge voltage, 45 A max. discharging current, 12 A max. charging current)

Controller: VOTOL EM-30S

I'm not a techy guy and do not know much about deep modification of e-bikes, as well as electric circuits. Originally a seller of the controller helped me to set up all the data. I use e-bike to get to work and back home, the route/distance is the same each day. Originally, when I have just bought the battery, about 7 months ago, I was able to use one charge for 3 days, but recently I'm experiencing an issue when my e-bike forcefully cuts the power off when there are still 20-22% of battery charge. I have changed Undervoltage & Soft undervoltage to 39V and 41V (originally: 41V and 42V), and both Busbar current & Current limiting to 40A (originally: 45A both). But it didn't solved the problem of force power cut with 20-22% battery charge.

So I have two questions:

1. What I should change in present controller settings (see the current data on the image below. I do not have English version of the flash app, but I can help with Chinese translation if needed), any way to optimize them?

2. What could be an issue that there is a force power cut when still 20-22% battery charge left, while at the very beginning I was able to ride on one charge during 3 days and use the battery up to 0%? (need to mention that most of the times I charge the battery on the second day, when there are still 40-45% of charge left. There were like 3-4 times when I ride on one charge till 0%).

Any help would be really appreciated.

 

[amberwolf]

it's not controller settings; if it worked before and you didn't change anything to cause it, then changing them now won't fix it. (though it may temporarily mask the actual cause, and potentially cause damage to the battery).

the battery has a problem, most likely a bad cell or cells, or interconnects between them.

the cells are sagging or dropping in voltage more/faster than the other cells, cuasing the bms to shut off the system to prevent damage to the cells taht can result in a fire.

if you have a voltmeter you can open the battery enough to measure dc volts between each pair of small wires at the bms. list all of them here, in order from one end of the connector to the other. then we can help you figure out which cells are bad and need to be replaced.


if you do not want to replace the cells yet, you can first just leave the battery on the charger to try to rebalance them, which may take hours, days, or weeks, depending on how bad the imbalance is. however, it will require you to do this every ride, and at some point the cells are going to degrade enough that this won't get you the range back (if it even does so now, which it may not).

 

[Sopheus]

it's not controller settings; if it worked before and you didn't change anything to cause it, then changing them now won't fix it. (though it may temporarily mask the actual cause, and potentially cause damage to the battery).

the battery has a problem, most likely a bad cell or cells, or interconnects between them.

the cells are sagging or dropping in voltage more/faster than the other cells, cuasing the bms to shut off the system to prevent damage to the cells taht can result in a fire.

if you have a voltmeter you can open the battery enough to measure dc volts between each pair of small wires at the bms. list all of them here, in order from one end of the connector to the other. then we can help you figure out which cells are bad and need to be replaced.

Thanks a lot for such detailed explanation! Really appreciated!

Unfortunately for me, I do not have all the technological knowledge to use voltmeter and if I would have the battery is sealed by the original 3rd party seller, so I think the only way for me is to return it for checking and repair. Good thing it is still in warranty period. So I will try to send it back, though Spring Festival is coming (it is one week of holidays here in China), so probably will do it after that. Is it still safe to use the battery though? It won't explode right?

if you do not want to replace the cells yet, you can first just leave the battery on the charger to try to rebalance them, which may take hours, days, or weeks, depending on how bad the imbalance is. however, it will require you to do this every ride, and at some point the cells are going to degrade enough that this won't get you the range back (if it even does so now, which it may not).

I am not sure if this one work, since there is some kind of overcharge protection mechanism in original Xiaoniu charger itself, when it charges the LED light is red, and when it stops it turns green.

 

[amberwolf]

leaving the charger on will still fix an imbalance issue. the charger shuts off not because the pack has reached full voltage, but because current drops below a certain level.

that happens in two cases.

the first case is when the battery voltage is at full, so the charger and battery are so close in voltage that there's very little current flow.

the second case is when the bms of the battery shuts off input because a cell or cells ahve reached the hvc, or high-voltage cutoff, usually around or a bit above 4.2v for common lithium cells depending on chemistry.

that's what's happening in your case, most likely. so most of the cells are full, but some of them are not yet. so the bms drains the full cells down a little bit while charge is stopped, so that it can then restart charging to fill up those low cells. if they re more than a little bit lower than the fullest ones, it will take multiple cycles of this to fix.

so what happens when you disconnect or turn off the charger as soon as it goes green is that never gets a chance to fix the problem at all, so every ccharge/discharge cycle teh cells get more and more different, gradually creating a problem where range gets less and less, and/or using high amounts of throttle causes cutouts, stutters, or much poorer performance than previously..

leaving the charger connected instead will let the bms rebalance the cells. since each of those cycles only fixes a tiny imbalance, it can take quite a while for a big imbalance to be fixed.


since you have lost more than a fifth of the accessible capacity, that's a very large imbalance, so it'll take a while to fix--potentially days or more. so it might nto fix in just one charge cycle.

i would just leave it on the charger the entire time you are not ridng it, so it can rebalance. it'll probably mprove a fair bit the frist time, then the next time there will be more improvement, and then mroe, etc.


the reason this happnes is most packs are made of unmatched low-quality cells. so when they're fully charged they more or less operate around the same, but as they get emptier and emptier, they act less and less alike, especially at higher current rates. similarly, the older they are, the more used they are, the worse the problem gets to be.

if the packs were instead built of cells that were well-matched to each other (whcih costs more) and thsoe were good quality to start with (whcih costs mroe), then this particular problem would take a lot longer to show up (though it eventually happens to all of them; good ones will often take years to start the process).



anyway, try leaving it on the charger whenever you're not using it. if the range goes back up, then this is what's wrong with the system.

if not, there's some other problem, or the cells are just bad enough that they cant' be rebalanced, or the charger is a type that does not restart once it's shut off.

if it's the latter, you can unplug the charger from wall and battery, wait till ligths all go out, then plug back in after say, 30 minutes (to give the bms time to rebalance). when it shuts off again, do that again, and just keep doing that until it doesn't restart charging anymore. then the pack is as balanced as it can get.


it's unlikely that antyhing will happen if you continue to use the scooter, other than that range will continue to drop as the imbalance gets greater, if the above doesn't fix it or if you don't try it out.

no guarantees, though.

.

 

[Sopheus]

leaving the charger on will still fix an imbalance issue. the charger shuts off not because the pack has reached full voltage, but because current drops below a certain level...

Man, really appreciated your time and reply (why I haven't found the forum earlier...)!

I think what adds to the problem I have is that it is recommended to fully deplete battery charge once in a month and charge back to 100%, but I didn't do it each month, and charged the battery each time when there is still 45%-50% charge left and end up with that imbalance. If only I knew all that earlier...

 

[amberwolf]

well, a full charge/discharge wouldn't necessarily prevent an imbalance either.

the only thing that will definitely do that is using better cells that are well-matched to each other.

the next best thing is to leave it on the charger long enough to rebalance, every time it is used.


if all the cells were already well-matched, then a full discharge would leave them at about the same state of charge, so that a full recharge would recharge back to the same balanced state.

however, the same would be true of any other discharge level, from just a little to mostly to completely.


if the cells are not well-matched, then a full discharge is actually going to make the problem worse every time, unless it is also recharged and left on the charger long enough to rebalance.

but, again, the same is true of any other discharge level--it's still got to be left on the charger long enough to realance, howver long that takes.

additionally, cells of various kinds have various amounts of charge/discharge cycles that they will last thru, before degrading enough to need replacment. some of them are only a hundred or two cycles, some are hundreds, or even a thousand or two. this isn't all cost-dependent, but cost does factor into it. usually the stuff in the cheap packs is well, cheap, so.... anyway, what it comes down to is taht any battery pack has a limited number of full charge-discharge cycles. if a manufacturer recommends "using up" some of them, there should be a really good reason for it, that they can tell you.

the less full a cell is charged, and the less empty it is discharged, the longer it lasts. there's other factors too, but those have been shown to be fairly important, dependign on the cells. in large-ev packs like cars and whatnot, they'll generally use electronics that restrict the cells from being charged above some point, or discharged below it, so you don't get the full capacity from the pack, but it generally then lasts longer by enough to make that worth doing.

in small evs like scooters, etc., they can't carry enough battery to necesarly make that practical...especially on the cheap ones.



so...i don't know what they intend to happen by a full discahrge, but it won't actuallly do antything good that i can see, unless they havea specialy and very unusal bms that bottom balances by fully discharging every individual cell never seen one on a common bike or scooter pack...it would be more complex and require it's own specific development and design, unlike the common top-balancing bmses that are everywhere, and based on the same root designs. that makes it more expensive...and these thigns are all about being as cheap as possible.


you might, for curiosity, ask them why they want their packs to be fully discharged on a regular basis. my guess is they can't actually answer sensibly.

 

[Sopheus]

you might, for curiosity, ask them why they want their packs to be fully discharged on a regular basis. my guess is they can't actually answer sensibly.

Yeah, that is what I did, their explanation was that: "Battery cells are degrading over time, so you need fully discharge and charge again back to 100% once in a month to get more or less accurate distance estimation and charge/discharge estimation on one charge on your e-bike display".

So it is not about cells or packs, but distance estimation. But after everything you explained above, I do not see any logic in their explanation, since, to my understanding, distance estimation on one charge is being estimated by e-scooter central unit and it evaluates on data from battery, so no matter if you discharge fully or not, data should be the same. Mean data will change, but the fact you discharge/charge back won't change the way data changes.

 

[Sopheus]

Considering that my hardware specs for battery and engine won't change, what would be the best settings for the controller throttle/battery longevity wise?

Engine: 800W

Battery: 48V40.3AH (54.6V max. charging voltage, 39V min. charge voltage, 45 A max. discharging current, 12 A max. charging current)

Controller: VOTOL EM-30S

 

[amberwolf]

Considering that my hardware specs for battery and engine won't change, what would be the best settings for the controller throttle/battery longevity wise?

that depends partly on stuff we don't know about the battery, like what kind of cells are really used in it (specific brand/model) to look up their manufacturer specs, hwo they're connected, etc.

but assuming these specs are "real" (not just marketing gibberish),

Battery: 48V40.3AH (54.6V max. charging voltage, 39V min. charge voltage, 45 A max. discharging current, 12 A max. charging current

then 39v is a reasonable shutoff point (lvc), but you could change it so you are more like 3.3v/cell or even 3.4v/cell, which means for 48v pack (13s, 13 cells in series) would mean setting the controller lvc to something like
42.9 to 44.2v...but this will decrease your range at least a little.

if you could alter bms settings iw ould also change the balance start point to 4v instead of 4.2v, so it doesn't have to charge as full to do the balancing.

those two changes would, together, help the pack not have to swing as widely in voltage and state of charge, and would probably keep it balanced a little easier.

but you likely can't change the bms settings; it's probably all hardware with no programming. you can buy a new bms to replace it that does do this, but requries opening the pack to take the old bms off, and put the new one on. ther'es always risks doing that sort of thing, though minimal.


changing the charge rate to something lower, perhaps half of the present rate, would make some difference to pack life, though ti's already a pretty low rate for many cell types, so i don't know that it would be a lot of difference. would require modifying your charger; somteims tha'ts just a pot adjsutment, sometimes it is mroe complicated.



changing the discharge rate (controller battery current) to something lower, would also help, by decreasing the heat generated inside teh cells, and decreasing the voltage sag.

but...it will decrese the torque you get from the motor, and slow down your startups and decrease our hilclimbinb agility.


to maintain 800w you only need 18-19amps at 48v; if the controller is presently set for the max the battery can do 45a, then you actually get about 2000w, dependign on voltage sag.



since the battery is the heart of the system, then if it's not up to the task, the rest of the system performs poorly.

similarly, if you reduce the system's requirements like the above, it performs less well than it did before,

so, you'll get less range with the lvc/hvc changes, and less startup torque/hillclimbing with the main current change, and longer charging times with the chagre current change.

it's al a compromise, so you have to descide which things are more important

 

[vd062]

I also upgraded to this controller EM30S, However I don't know which pin-outs are serial pins.
Can anyone please share debugging material (pinouts, guide etc).
Thank you.

 

[amberwolf]

Did you get software with it from the manufacturer to do the programming/etc? If not, knowing what the serial pins are for that isn't useful.

That said, there are other VOTOL threads on teh forum, I would recommend checking with them to see if any of that info applies to your controller.