Emax s110 scooter with 60v lithium batterie

[nicosp]

Hello everybody

I am new to this forum and new to messing around with e scooters, so please go easy on me

I have an emax scooter s 110. It comes with very heavy lead acid batteries, so i dicided to put in a 60V29ah lithium battery in it. ( i used a 60V29ah lithium ion battery from a niu scooter). The scooter is now +-100kg lighter and drove very great for a little time.

First day everything was great a rode about 10km no problem. Once i tried the max modus (it was used the get this heavy model uphill) the scooter shut down and didnt awnser for about 2 hours. Then i tried again and it worked fine. I figured not to put him in max modus anymore and i would be fine.

I drove another day again +- 15km without any problems. But now, the 3the day, when i drive in normal modus and reach a bit above 40km/h its shuts down but restarts imidiatly after and this while im driving...

Does anyone have an idea what could be the problem and how i could solve this ?
the sevcon gen4 controllor should be able to take 69V so i dont thing overvoltage is a problem.

 

[john61ct]

Likely a low voltage cutout, sagging under heavy load or at lower SoC

then recovering a bit, then dropping again, etc

 

[amberwolf]

The most likely issue is as noted above--voltage sag under load.


What was the current limit on the scooter the battery came from? The general info I found for Niu is they are about 2kw.

What is the current limit on the scooter the battery is in now? The general info I found for Emax is they are around 4kw.

If the former is lower than the latter, then the battery is unlikely to be designed to handle the demands you're placing on it, and will either need to be rebuilt to do so (changing out the cells, perhaps also the BMS depending on it's ratings), or paralleling a second battery pack of the same voltage (same chemistry, number of series cells) that can handle the rest of the current demands of the scooter it's on now.

If the general info I found is correct then the battery you have isn't meant to supply even half the power you need.


Another possibility is that the battery is not balanced, and some cells are so low that under load it shuts off to protect against overdischarge and damage that can lead to a fire. This type of problem indicates cells or cell groups that are old or damaged and would need to be replaced to fix it. Leaving the pack on the charger for at least overnight, and sometimes for up to several days or even weeks, may fix the imbalance temporarily, but only until it is discharged far enough to become imbalanced again.

 

[nicosp]

Thanks for the reply's !

As you both suggested i believe it could be a low voltage cut off

What is the reason the battery is limited to 2kw? Is it the size of the conectors and/or cables?

Might the problem be that i welded the small cables for the battery on to the big ones, and the small ones cant handle the current needed for the motor?

If i find a way to connect the big cables directly on the battery might this help ?

Thanks for the suggestion of the 2nd battery, but since this is a hobby project I'm working on, I would like to avoid having to invest in a 2nd battery

thanks a lot

 

[nicosp]

Hello everybody

I am new to this forum and new to messing around with e scooters, so please go easy on me

I have an emax scooter s 110. It comes with very heavy lead acid batteries, so i dicided to put in a 60V29ah lithium battery in it. ( i used a 60V29ah lithium ion battery from a niu scooter). The scooter is now +-100kg lighter and drove very great for a little time.

First day everything was great a rode about 10km no problem. Once i tried the max modus (it was used the get this heavy model uphill) the scooter shut down and didnt awnser for about 2 hours. Then i tried again and it worked fine. I figured not to put him in max modus anymore and i would be fine.

I drove another day again +- 15km without any problems. But now, the 3the day, when i drive in normal modus and reach a bit above 40km/h its shuts down but restarts imidiatly after and this while im driving...

Does anyone have an idea what could be the problem and how i could solve this ?
The sevcon gen4 controllor should be able to take 69V so i dont thing overvoltage is a problem.

Some suggested a low voltage cut off. The battery i used was designed with max power 2300W, my moter is 4000W
Might the problem be that cables inside the battery are to small and cant handle the current needed for the motor?

Thanks!

 

[SlowCo]

BMS (Battery Management System) that is protecting the battery for too much current draw?
If the battery you are now using is for a maximum power of 2300W and you try to extract 4000W then the current is too high and the BMS will protect the cells by shutting down. You'll have to program the controller with a lower maximum amp limit if possible.

 

[SlowCo]

That is really a very bad soldered connection especially the negative wire
Why not solder them both directly into the connector?

 

[amberwolf]

What is the reason the battery is limited to 2kw?

The usual reason is that the cells can't safely handle currents higher than what a pack is "rated" for, without potential for damage, overheating, lowered lifespan, and sometimes even fire if current draw is high enough.

Some BMS's can protect against overcurrent, but they may not even attempt to do it until it's so high that it's already caused damage to the BMS itself (shorting the FETs from overheating, and thus preventing the BMS from being *able* to shut off output). Those FETs have a resistance, and so any BMS has a limit to the amount of current (and power) it can support, without overheating and damaging it.

So the limitation is between the cells and the BMS, and both have to be able to fully support the higher current draw. If they both can't do it, you still have a problem. So just changing one doesn't typically fix the problem.

Voltage sag is also higher at higher currents, so under excessive current draw, the BMS attempts to protect the cells agianst overdischarge damage when the voltage drops below a certain point (LVC).

Controllers also have an LVC that's usually higher than the battery LVC, so it may simply shut off the motor when excessive current causes the battery to sag in voltage too far under load.

If the shutdowns you see leave the scooter display on, but the motor doesnt' work, then it's the controller shutting down to protect the pack. If the display turns off, too, then it's the battery's BMS. The distinction is important, because the problem is more severe (harder on the battery) if it's the latter.

If i find a way to connect the big cables directly on the battery might this help ?

Those are pretty bad connections...but they are not the root cause of the problem. Fixing them will make a *small* difference to voltage sag, but not very much unless the existing connections are *really* awful, and heating up so much that they are melting things around them from the heat, or worse. That doesnt' appear to be the case, so there shouldn't be enough power being lost in the connection to cause what you see.

Smaller wires and connectors do have higher resistance, but it's also not enough to account for your problem.

The root problem is your battery simply isn't designed for the use to which you're putting it, and it's going to damage it further to continue using it at a higher load than it was meant for.

If you want to improve the connections, try following the method I used here:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=86600&p=1610761&hilit=stromer#p1463762
Some of the pics seem to have disappeared, so if you need them I'll repost them all in this thread for you.

There are also other ways to connect two cables, including crimping tubes onto the bare wire ends, but this requires buying a proper heavy-duty crimper for the splice tubes (I forget what they are called, though I have some on the workbench in assorted sizes).

Thanks for the suggestion of the 2nd battery, but since this is a hobby project I'm working on, I would like to avoid having to invest in a 2nd battery

Your other option is to reprogram the controller to match what the battery can handle, which will cut the power of the scooter in half. If it's not reprogrammable, then if it has an even number of shunts inside, you can desolder one end of half of them and lift that end off the board so it doesn't make a connection.

 

[john61ct]

Build a battery capable of handling current/power demands at least 30-50% higher than the maximum your scooter will ever draw.

 

[nicosp]

Thanks to everybody for the reply's. Sorry for my late reaction but since this is a hobby project i dont always have the time

So i understand that the voltage drop while accelarating ( the motor needing a lot of juice) is causing my battery to shut off to protect itself.

I dont have this the first 20km because then the battery is fully charged and even with a voltage drop the BMS isnt worried?

What if i put a power resistor in between the accelerator and controlor to reduce the voltage ?

 

[marecki2r]

Hello everyone.
In my opinion, I would solve the problem as follows, you should measure the load at which this BMS disconnects the current and set the maximum current in the controller below this value to protect the battery. The second solution is to buy a second such battery to increase the capacity of the package. The third solution is to dismantle the batteries from the nue and check what batteries were used to build the package and whether it is possible to use a larger BMS. However, I would not take the third option into account due to the fact that the battery manufacturer calculates the battery life quite accurately

 

[nicosp]

so reprogramming the controler seems the best option, from what i am reading in other threads this is not an easy task

 

[nicosp]

what if i find a way to take out the BMS ?
this battery has normaly a range of +-60km, with this motor he shuts down after +- 25km, when the voltage starts dropping below 40 i think, but he should be albe to take another 15km without danger for the battery no ?
im sorry for my noobness

 

[marecki2r]

It is difficult to take any action without first measuring the battery current draw parameters by the controller while loading to cut off by the BMS.
If you focus only on replacing the BMS with a more powerful one, it may turn out that the battery will degrade faster.
If, on the other hand, you want to check the parameters of the cells used to build the battery, it will be clear what bms can or can not be used.
Bosch 3000W 60V - 2x35 Ah / EVE
NQi GTs Sport Bosch 3000W 60V - 2x26 Ah / EVE
NQi Pro Bosch 3000W 60V - 2x35 Ah / Panasonic
NQi Cargo Bosch 1800W 60v - 29 Ah / Panasonic
NQi Sport Bosch 1800W 60v - 29 Ah / Panasonic
NQi Life Bosch 1800W 60V - 26 Ah / EVE
It looks like a Panasonic cell is sitting there.

 

[amberwolf]

what if i find a way to take out the BMS ?

Then you will simply be direclty pushing the cells twice as hard as they were designed for, causing them to heat up, potentially damaging them over time, and increasing the risk of fire.

The BMS is there to protect the batteries against exactly this sort of thing. It is doing it's job just fine.

If you fire the lifeguard, people swimming at the beach have a higher risk of dying.


If you use a bigger BMS: If the shutdown is not caused by voltage drop (LVC in either controller or BMS) but by overcurrent, then a bigger BMS will allow higher current draw before shutdown, but it is then not protecting the cells as it was designed to, and again, you've basically fired the lifeguard.

If the shutdown is caused by voltage drop, then a bigger BMS doesn't do anything but cost you more money.



You have three safe options:

--cut the controller's current limit in half to match what hte battery was designed to handle.

--add a second battery the same as what you already have in parallel with the first (so each takes half the load).

--replace the battery entirely with a bigger/better one that was designed to handle the load this system places on it.

 

[nicosp]

Great,

thanks for the awnser. i will try to find a way to change the parameters in the controler. Will this have an influence on the top speed and/or acceleration?? (it's accererating real nicely right now )

btw the battery i have was disigned for the NQi Sport Bosch 1800W 60v - 29 Ah / Panasonic
datasheet : https://datasheetspdf.com/pdf/955257/Panasonic/NCR18650PF/1

 

[marecki2r]

So If you reduce the current by 15%, you will certainly lose acceleration, but not so much that it will be drastically felt, the range will increase and it will probably stop cutting the voltage in the middle phase of the discharge, but it can happen much later, so you can already be satisfied. you won't lose too much speed, but it will take longer to reach max speed. If I were you, I would invest in a second battery, you have a lot of space there that is worth using. I have the same scooter that I converted to 72v, so far I put a 20s22p 74Ah package there, measured under a 20A load, it turned out to be 69Ah and there is space for one more such batteries. :wink:.
amberwolf also presented the solution nicely :thumb:

 

[nicosp]

Indeed there is a lot of space but the compartiments under the footrest are not easy to open, i put the battery under the seat like that i can easyly take it out and charge inside.

Im wondering if i am changing the settings on the controller, i could change the max speed ?from 50 to 70 kmh ? or will this again be a problem for my battery? or will it just reduce the range?

I found the dvt software to program the sevcon controler, and someone will rent me the ixxat can to usb cable so i will start to study how to change the settings on the controller. thanks for the help everyone!

btw if anyone is fluent in programing sevcon gen 4 controllers all info is very welcome

 

[nicosp]

Im reading the dvt manual to program the sevcon controller, but im not sure wich parameter i should change..
Do i need to change setting via the motor setup - V/F ratio or local motor limits or battery limits ?
Or do i need to change something in the baseline profile ?

 

[john61ct]

Start a new thread for the Sevcon programming issues and crosslink.

That topic gets precious few responses, not many people have such knowledge in the world, so get the keywords right out in the thread title

or maybe tack onto an existing one

 

[dialadrone]

Hi Nico, I am having the same problem as you! I have an old motobecane moped I've build into an eped of sorts with a 48v brushless motor/controller (caps are rated for 63v) My battery reads about 59v at the moment but after being under load and going about 20mph the voltage goes down and the display/motor turns off. In then won't power on until it sits for about 15 minutes. When I test the voltage on my battery it is about 25v until the bike is willing to turn on again. It is then back up to 59v. The strange thing is it ran great when my battery had about 60v. It would top out at about 33 and did great on a 5 mile ride. I'm assuming something in the bms or a low voltage sensor is tripping my battery.

If you find a work around please let me know! I know the niu scooters that generally use these batteries have two of them but considering the small frame and price of a second battery it isn't a realistic fix for me either.

 

[nicosp]

not realy a work a round im just keeping the battery fully charged for now..(got like +-30km with 45km/h untill it gets risky i think) until i rent the cable to reprogram the controler

 

[RTLSHIP]

You can get away with a somewhat incompatible battery when it is brand new, but after a while something will go wrong.
That's my practical experience. Some simple solutions are: ride slower, long time charging to correct imbalances, and testing/charging each cell w/ multimeter and cell charger. How did your scooter lose 100kg in a battery swap ? that's 220 lbs.
29 ah seems too low for something that bulky.

 

[nicosp]

thanks for the reply, it is 90kg lighter because i had 4 old lead acid batteries 12V 60 Ah that wheiged 25kg each; i replaced it with a 10 kg 60v29Ah lithium batterie

 

[nicosp]

hello everybody

i've been riding happily for one year without any issues, but now i have these random voltages drops and the scooter shuts down while riding. I know it is a voltage drop because when im driving i can see the voltage go to 18v before shut down, normaly when i drive the voltage variates between 52-64V
any one an idea what is wrong and what i could do to solve it ?
thanks