i did buy the bike at the price i expected. it is a very quiet bike tbh, much more quiet than i expected. I have not yet put it apart in any way or form. is it easy to unplug the original battery? so i can take it out to get measurements of how i need to build my own battery.
Mixing a low and a high voltage battery in paralell is dangerous, in series you just create a total higher voltage with unknown balance and internal resistance, and i think that's rather stupid. either paralell or serial connect 2 "identical" batteries, or make a completely new battery is what i think is the only 2 really viable options.
I am going to follow your thread to if you keep posting your results with the kelly controller!
The niu battery works flawlessly in parallel with the original soco battery, its exactly the same end voltage, only slightly more Ah rating. They are plenty availible on the internet for around 200 euro, for that money I can't build anything. It also slides in the slot perfectly.
The kelly controller gives a lot of juice, the bike is super fast compaired to stock, so thats a big plus, the motor is the limiting factor at the moment.
@arjan_1980 i know exactly what you mean, apart from you have no idea in regards to balancing since it runs on 2 separate bmses, but i guess it works for range exension, but how do u tackle the bms limitations? I saw claim that the original battery bms cut off at about 45A.
But i am not interested in making a 60v battery, it is too slow for me, a 21s or 22s is a good solution with a 72V controller with mosfets limiteted to about 90V. I am leaning towards getting a qs273, a slight swing extension and probably go wider, also try and find a nice front fork exchange with a wider front wheel. And with the low weight of the front end and short wheelbase i personally feel that a steering damper is not a bad upgrade for this bike. But one thing at a time, battery and controller first 😏
Balancing is meant for keeping the cells at a good level during a lot of charging cycles, otherwise one cell group could be higher, cutting out the charging cycle for the lower charged cell groups, depending on the system used it discharges the higher charged cells during charging until all cell groups are at the same end voltage. You see this a lot on the first prius cell packs, that several cell groups won't charge to a good rate anymore, needing cell group by group charging to get it back to full capacity.
In my case they are keeping the same voltage as they are parallel, that's why its so important that they are fully charged before connecting them, so they are at the same voltage.
I will put a scope on the supply of the controller to see how much the batteries are delivering in parallel, i am running at a battery setpoint of 100a in the controller and 68% of the max controller output, so getting a phase current around 140a peak during accelearion. If i go higher the bms will cut the battery supply of one of the batteries.
The first priuses used Nimh batteries, they are very different from lithium, don't compare characteristics of those solutions. One of the main faults of battery packs is when a string of cells in series will have a different amount of mAh you get it unbalanced (neglecting active or passive balancing features).
I don't buy the idea of mixing cells you know nothing about regarding conditon, it's risky imo, either build a battery pack with brand new cells matched or used cells tested in both regards to capacity and internal resistance. The original battery might be using LG m1 and the pack you bought have panasonic ncr cells, they will not perform the same, perhaps similar but not the same.
But its not my battery and everyone have their own ways i guess 🙂
Both batteries have their own bms still in place so the charging process is very simple, its nothing more then a power supply supplying almost 70v to both batteries. The bms takes care of the balancing process and charging safety.
When discharging the batteries in parallel, also the bms protects the battery if the current draw is to high.
I hear stories of people bypassing the bms to get a higher current, this is something i would not recommend.
In my case all the safety's are still in place.
I agree that you can't use different kind of cells in serie, internal resitance and other specs are different. But thats not the case with my setup.
I am wondering what is youre background?
I dont know what kind of bms it is even, does it do a standard 60mA passive balance or is it of more expensive versions? The bms have nothing at all to do with the charging process in this batteries if they end at 4.1V per cell as the intended design, the bms should be protecting each lead at 4.2-4.25V. The bms is just a safety feature that is there to stop the process if shit hits the fan. Like if you have a battery that is getting a weaker paralel string leading that string to reach max voltage prematurely, in this batterires the bms should never trigger, if it does something is wrong with the battery. The charger is the only thing that actually does have anything to do with the charging, if u have a very good and balanced pack you could safely charge it without a bms, but its like riding a bike without a helmet. As long as i don't crash, wearing it or not wouldn't matter. But if you crash, that helmet make a huge difference. And yes bypassing the bms kinda ruels out the idea of the bms. If you do bypass it, how will it be able to stop the current draw if one cell string will sag below minimum threashold?
Why i dont like the idea of combining with 2 different packs is that you might have 2 very different bms:s on the packs, if you change it into something that draw a lot more current the weaket bms might trigger, this push all the load on one battery pack instead. You get the idea i hope. U should watch diy solar channel where he test 2 bmses in paralell, interesting eventhou they are the same model
First thing the bms is also controlling the maximum discharche rate, so if it exceeds this it will shutdown the output.
In the first trial the 40 breaker tripped causing the extra battery to take all the load, the cutting out was constant, this is done by the bms to protect the battery.
The bms is also meant for controlling the balancing of the different cell groups, with rc cars its the charger doing this, the balancing port is then connected to the charger. As a safety but also to balance the cells, charging higher volt cells slower to asure they all end up with the same end voltage. How is not the debate here. If this balancing would not be present you will lose a lot of capacity due to some groups being half full, how good the cells are there is always a slight difference, thats why the balancing system.
The charger of the soco is nothing more then a 70v power supply, when the battery is empty it will allow 5a to go into the battery, current decreasing when the voltage of the charger and battery equalize. Off course it needs to be very stable to asure a correct end voltage.
As a last note, off course the best way would be to build a new battery with a new higher rated bms. But i have more things to do, and this works good, i will give it some drives over the next weeks to see how it behaves.
as u see, the original bms was triggered at 40A, it's a weak link in the system.
the psu is a psu with cc/cv feature, or else it's directly dangerous to charge the lithium batteries, if it wouldn't be, it would never turn off.
If one string is half full meanwhile another string is full that means something is very very wrong with the battery. it would mean that you kinda only can use 50% or less of the collected capacity b4 the bms shuts it off due to imbalance on 1 string, but balance is slow, very slow. in a perfectly balanced cell pack you don't need any balance feature at all, they should all be discharged to the same voltage at every given time, occurance of imbalance only points to poor quality or wear and tear of batteries.
But i wish you good luck with your testings! the niu pack is very interesting, and hopefully it runs a much higher rated bms, maybe even would be benefitial to run the pack alone and not interfere with the original battery at all since it's limited to 40-ish A, it's just a weak link in the system as it is for a high amp application imo.
However that battery pack you bought is interesting, i don't find it anywhere, just a lower 29Ah version. i would like to buy the same pack as you and strip it apart and test each cell to see if it is true panasonic ncr cells or just rewraped cells, if they are real panasonics it's a very good price, very good!
I have just checked e-bay and aliexpress so far, and only 1 single supplier of the 29Ah pack so far, maybe i need a better keyword when i try to find it
Check out my friends videos at diving into the inside of the TS motor, an operation to resurrect a broken original TS battery and more:
yes! i watched all of his videos, a lot of nice information and trails and errors with long term use! definately useful information when deciding how to mod and what can happen in response to your solutions and modifications, to bad his kelly controller ended up dead, but i guess it was a rather logical way to go in regards to where he placed it together with his mod to allow more air (and water...) to cool the controller
Did a nice run tonight and I am pretty pleased how it drives, i constantly pushing cars when driving away so thats a good thing, top speed is good but could be better.
The regen function is really good, i brake only this way, hardly pull the brake lever.
The controller was showing 80km radius, i drove 55km tonight and the battery showed still 20procent, so around 70km should be possible with my setup, I have to say that i pull up with full power every time and have driven top speed.
I noticed that in the last part of the drive the bms killed the power for one of the batteries for a brief moment, so I had to play with the throttle a little bit to prevent this from happening, meaning I have to reduce the power output a little bit.
For the rest its a blast to drive the bike this way, it a fairly cheap upgrade giving you way more driving fun and a bigger radius for less then half the price of a new original battery.
That is nice, 55,9 km and still 20% to go, and you are pushing a lot more current with that kelly controller compared to original too!
Out of curiousity, what is your topspeed now? and what do you think made the bms trigger? was it low-voltage cut-off or high amp cut-off?
