Help identifying battery (and bms inside)

[Radek]

Planning to upgrade a small e-scooter. Evercross ev650. And need help identifying the stock battery.

Does anyone recognise this? It’s the max amp of the BMS I’m after, as I’m planning to upgrade the controller from the stock 17Amp one to whatever the battery BMS will allow.

Sticker on the battery says:

Battery: YLD367.8
Li-ion Power Battery Pack
Model: YLD367.8
Nominal Voltage:36V DC
Charging Voltage: 42V DC
Rated capacity: 7.8 Ah/280.8 Wh
Cell: INR18650
ISO9001/Authentication enteprise
Polly No: 12503023901763969985

CE
IEC62133
SN/YLD367. 8-240804001
MSDS UN38.3
Manufacturer: Anhui Yonglida New Energy Technology co.,Ltd

Your guess is welcome. As even If I open this up to find the BMS, whatever is written on it will likely (like the battery model nr) not give me any useful google results.

 

[Chalo]

17A on that pack is a touch over 2C discharge rate, which is probably as hard as you should consider beating on the cells. Even if the cells can take a little more, the interconnects may or may not be able to take it.

If you want much more power, use a battery pack that's built for more power. What size battery compartment are you working with?

Also note that if you only add amps, you'll get more torque but not higher top speed. To go faster, you will need higher voltage. But either one is a dubious idea on a crippler scooter like that.

 

[Radek]

Thank you for your answer Chalo.

Are you basing the 2C max discharge on anything specific? Honest curiosity, not doubting you.

I could switch out the BMS, if that remedies the ‘weak interconnections’. Not sure if you ment BMS or cell to cell.

I was hoping to switch motor to higher kv/and upgrade the controller to a 30 amp one. Though neither sure of BMS max discharge current nor cell max discharge on this pack.

 

[Chalo]

Are you basing the 2C max discharge on anything specific? Honest curiosity, not doubting you.

2C is a common spec for max discharge of both cylindrical cells and packs made from them. Here's a more detailed explanation. There are higher limits for "power cells" than for "energy cells" (subject to the limitations of pack construction, of course), but e-bike and scooter packs tend to use energy cells while cordless tool batteries tend to use power cells. There's no reason to believe that an original equipment manufacturer would spend extra for cells or reduce the vehicle's range to provide a battery that can supply much more current than the vehicle uses.

I could switch out the BMS, if that remedies the ‘weak interconnections’. Not sure if you ment BMS or cell to cell.

I meant the nickel or steel strips that make the power circuit for the battery. The smaller/more resistive they are, the more they limit the current capacity of the pack.

 

[Radek]

Thank you Chalo! Again.

Been tinkering with low voltage DC electronics since the nicd-days in rc aircraft and cars. But these ebikes bring new terminology and standards.

Regarding the battery compartment, I could fit another one of these batteries and a larger controller. Likely the bike was designed for larger components.

As a plan B I could get a hold of another one of these exact same batteries quite cheap, rewire them in series with a new bms and buy a 72v controller. It’s just that those cheap 72v controller don’t really tell on the specification what current difference is in each ‘speed mode’. That is, if I was to lock it in ‘slow’ I could only hope it won’t draw more than 2c. After buying it..

 

[docw009]

The C number for a battery is its AH rating divided by 1 hour. Just change that 7.8AH to 7.8 amps. The C rate depends on the characteristics of the internal cells. Use 2 for generic chinese cells. So if this is a 2C battery, then it can safely flow 15,6 amps, Yes, there are cells which are rated for 3C, even past 8C. The Molicell P45B is 10C, if you can keep it below 85C. You pay extra for those cells, and they're not to found in a blue shrink wrapped pack,

Might be a current label on the BMS, in chinese. On these inexpensive BMS, there is a short circuit current rating of 40-50A or higher. At that current they open the ground pin. Usually there is nothing else to prevent you from flowing 25A if your controller asked for it, except the transistors may overheat, Those transistors also have a open circuit voltage rating. maybe 70 volts.

If you wire them in series, that would be 84 volts peak. Your BMS transistors would need to be rated higher than that to do series,.

 

[lnanek]

Opening up the pack might let you see the cells. If they are Samsung 25R INR18650 then they are actually high discharge rated vape cells that can do 20A each according to their spec sheet:

Samsung 25R 18650 2500mAh 20A Battery

Buy Samsung 25R 18650 batteries at 18650Battery.com. 2500mAh capacity and 20A discharge for reliable power in flashlights, tools, and more. Trusted power—shop now!

18650battery.com

If the pack is then 3p configuration to reach 7.5Ah, that means the pack can handle 60A. Assuming the interconnects are thick enough they don't overheat at that load - which can be checked with a thermal camera. And assuming the BMS isn't set to click off at a lower max amperage which can be seen with a test load.

 

[Radek]

A colleague that had the same bike and received a battery replacement, today gave me that replacement as his kids had lost all interest in the bike anyway.

So, I now have two of these exact same packs, both lightly used, and opened one up to see the Bms:

’Superflow 10S20A sp-c10-007.. something smudged’ is all I can make out from the sticker. As previously mentioned, it’s a 36v 7.8ah battery.

Didn’t open it enough to see the cells but very much doubt these are anything but cheap. Meaning bms replacement for a higher max amp will likely beat the cells unnecessarily.

Wiring these two packs up in series would as Docw009 mentioned likely overload transistors. So unless there is some ‘Bms-Bms:er’ I could wire both existing pack bms’s to, using these packs as is, looks (with my limited knowledge) like a dead end for increasing voltage.

 

[E-HP]

You shouldnt run packs in parallel or series based on the level of knowledge you’ve demonstrated on this thread. You need to do a lot more reading. There’s plenty of existing info on this forum to increase your knowledge on the subject since it’s discussed quite often.

 

[Radek]

You shouldnt run packs in parallel or series based on the level of knowledge you’ve demonstrated on this thread. You need to do a lot more reading. There’s plenty of existing info on this forum to increase your knowledge on the subject since it’s discussed quite often.

Your right, and I really was looking for a quick solution here rather than making this bike-upgrade a project. Realizing it won’t be, so will hold my horses here and research this thoroughly instead.

Thanks

 

[E-HP]

You want to avoid something like this, and this happened despite having loads of experience, and only one battery.

Dogman Dans E bike burns his house.

First of all, an apology for just vanishing like that. I told the moderator crew what happened last February, but I was hesitant to talk all about it until I had money in hand. And I had quite a lot to do, with a good dose of PTSD. The short version, my cheap ass shipped illegally 18650 48v...

endless-sphere.com

 

[lnanek]

Kind of strange he talks about the battery and BMS so much, but not the charger. Also says he planned to manually turn it off, but forgot and went to bed.

Makes me suspect he was using something like a LED power supply that never stops and not a charger, which would have been another later of safety.

At our electronics workshop at work every outlet is on a little dial timer too. So you can't even leave a soldering iron or power supply on permanently anyway. You have to dial in a set number of hours before it turns off automatically. Still have had the fire department in a couple times over the years. Probably a good addition for any charging setup.