36v 10s9p battery bms

[Garry Hallam]

Thanks for letting me join here. I just converted my mountain bike with Bafang 36v 350 W Mid Drive kit. I used a 17.5ah cheap chinese cell battery from amazon but being a tinkerer I soon wanted more range, and after learning about cheap chinese cells I wanted something better. I opted for a 90 cell hailong type blank pack to allow 36v 10s9p pack and bought LG MJ1 cells that are advertised as reclaimed and unused from wrongly put together packs. They came from what seems to be a reputable uk based seller whom I spoke with and he claims as I mentioned they are just from wrongly put together unused packs.
As I am sure most folk on here know they are rated 3500mah with continuous discharge of 10amp. I bought a cheap amazon BMS 36v 30A. I doubt my 350 watt will draw anywhere near that. Are my instincts correct?
Garry

 

[thelarkbox]

Check your motors controller limit iirc its 18a, so a 30a battery should have ample head and shoulder room. Quite the build? we like project pics in here.. what sort of range are you aiming for? whats the bike gonna be like to ride when out of juice???

 

[Garry Hallam]

I will upload pics a little later. I just got carried away tbh. I was needing a project. I am ex engineer (Machine shop) and not happy unless I have some kind of headache to work on. I have dabbled in electronics to some extent. I was frustrated at the fact that it seems like if you want a decent battery you are gonna have to build it yourself. I opened the 17.5 pack i bought and was horrified at the level of craftmanship inside. Lets just say it put me on a mission. An expensive one I have to say. I probably will do 50 mile round trip and I doubt the one I bought would manage that.
This pic is of the inside of what I bought

 

[Nealh]

Let us know when the UPP catches fire, it coul dbe the first time we have heard of a forum member battery fire.

 

[Bikes4two]

@Garry Hallam -what specifically was it about the OEM battery build that you didn't like? That single picture doesn't show much - there's many many aspects to a battery build that together give a quality construction.

And out of interest, as this is going to be your first battery build, what are your information sources for ensuring your build is up to standard?

@Nealh - what is UPP. Edit: are yes, forget my question Neal - UPP being the brand of battery with a recent product warning - I just seen that post!

 

[harrys]

I bought a few UPP batteries from 2017 thru 2021. All still work, but the ones with premium cells are appreciably stronger. Three 36V bottle packs, one 36V Silverfish, a 48V Dolphin and a 48V Hailong.

The Hailong 48V10Ah was the most recent pack. I didn't see anything wrong with its construction. I would have liked cell level fusing, but ypu don't get that for £190.



The UPP packs that were banned. I wouldn't have used them.

 

[harrys]

I never owned one, but would expect a BBS01B to draw around 12-14A max. I've had two BBS02B's and they were 25A and 18A respectively, so I think your BMS will be more than adequate.

The MJ1 is rated at 3.5AH, so 9P is 31.4AH, giving you over 1100 Watt-hours in theory. Wow.

 

[guerney]

I never owned one, but would expect a BBS01B to draw around 12-14A max.

The controller of my 250W 36V BBS01B can be programmed to draw up to 20A, but I don't know about the...

Bafang 36v 350

...version.

 

[Garry Hallam]

It was after reading something online. But, I'll give them the benefit of the doubt and use along with my own build battery. It is finished now and working fine.

 

[Nealh]

The controller of my 250W 36V BBS01B can be programmed to draw up to 20A, but I don't know about the...



...version.

My old bbs01 was 18a max, which almost tallied with the 630w read out.

 

[guerney]

My old bbs01 was 18a max, which almost tallied with the 630w read out.

My DPC18 display can display voltage as a number, and current level remaining via the battery icon, both sag ascending steep hills... but sadly no wattage readout. At the moment, I not inquisitive enough about it to get one to solder on. Quite enough wires on the bike already lol.

 

[Garry Hallam]

@Garry Hallam -what specifically was it about the OEM battery build that you didn't like? That single picture doesn't show much - there's many many aspects to a battery build that together give a quality construction.

And out of interest, as this is going to be your first battery build, what are your information sources for ensuring your build is up to standard?

@Nealh - what is UPP. Edit: are yes, forget my question Neal - UPP being the brand of battery with a recent product warning - I just seen that post!

I watched lots of battery builds on youtube. And wanted to know what was going into my pack. I insisted on 0.3mm pure nickle strip for the cell groupings as I know some are using 0.15mm nickle plated steel.

It is indeed a first build and my previous interest in building radio control fixed wing models kind of steered me into it.

I have to admit that it is not for the faint hearted.

At least we are not using lipo batteries like in the RC world. Those things always had me worried and were stored outside. Get those out of balance and theres trouble.

Anyway It has been an experiece.

 

[Garry Hallam]

Oh I meant to say that there is a very experienced ebike builder near to my house who I got to check out my work.

 

[Garry Hallam]

I really wanted to use this but it won't fit inside.

https://www.amazon.co.uk/gp/aw/d/B0CM3RDXWF/ref=ox_sc_act_image_5?smid=A32YMN8AI54ULY&psc=1

It does not replace the BMS but runs in parrallel with it to give more balance to the cell groups. And works with bluetooth.

 

[Garry Hallam]

So I have done some runs with this new battery mostly on the Canal paths with 3 sometimes 4 setting of the five available. It cuts out charging at 41.2v so must not be fully balanced or the BMS is not quite right. So far I have accumulated 50 miles and is now at 36.2v. What is the best voltage to recharge at?

 

[guerney]

Does your BMS balance charge when the battery is switched on or off? I recently discovered, contrary to the instructions supplied, that balance charging only happens on my battery when the battery is charged while switched on:

Home Ruination by Ebike Battery Fire Expulserating PreTerminator™®©℠

Consider this a trailer promoting my easy to assemble ebike battery safety contraption. Photos with details and an ever so slightly better video will follow.

www.pedelecs.co.uk

 

[Garry Hallam]

Does your BMS balance charge when the battery is switched on or off? I recently discovered, contrary to the instructions supplied, that balance charging only happens on my battery when the battery is charged while switched on:

I have no idea. As the bms does not have a switch, I assume it is always on.

DEWIN Lithium Battery Protection Board,10S 36V 30A Lithium Battery Protection Board Li-ion Cell BMS PCB Support Overcharge Protection https://amzn.eu/d/isK2fBf

Home Ruination by Ebike Battery Fire Expulserating PreTerminator™®©℠

Consider this a trailer promoting my easy to assemble ebike battery safety contraption. Photos with details and an ever so slightly better video will follow.

www.pedelecs.co.uk

[/QUOTE]

 

[guerney]

I have no idea. As the bms does not have a switch, I assume it is always on.

Due to the risk of disaster I'm not encouraging you to do so, but you could measure cell bank voltages to check balance. You'll need good eyesight and very steady hands. After doing it once, I immediately bought needle probes and a large illuminating magnifying glass.





...and added heat shrink in case of crossed probes:

 

[guerney]

It cuts out charging at 41.2v

Your DMM might be inaccurate?

Checking Multimeter Calibration at Home

One of the most important tools in an e-biker's toolbox is a multimeter (aka Digital Volt Meter or DVM). It is sometimes needed to be used to measure voltages with a high degree of accuracy, for example looking at the output of a charger to tell if it is set up to the correct voltage or not...

www.pedelecs.co.uk

 

[Garry Hallam]

I am currently waiting for ptfe cable to arrive then I will strip down the battery to replace the silicone wiring for my own peace of mind. When I do that I will check tbe cell groups and if need be connect my balance 100 10s that can balance at 1amp.

They now have an all in one unit that is BMS and active balance combined. However, I doubt that I could fit one of those into the battery case.

100 BALANCE 100BALANCE 60A 8-17S Smart BMS with Active Balancer and Integrated Bluetooth APP/UART for Lithium Battery NCM/LFP/LTO Pack https://amzn.eu/d/bGSO5L5