Adding BMS to 12s lipo pack (2 6s)

Batteries, Chargers, and Battery Management Systems.
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Sidotian
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Adding BMS to 12s lipo pack (2 6s)

Post by Sidotian » Wed Nov 08, 2017 2:21 am

Ok so I have been charging 4 6s 16ah 10c lipos with a 80watt RC 6s charger in parallel. That's a total of 6s 62ah while charging with a parallel board. I would absolutely love to somehow wire up the pack with a BMS so that I could plug the pack in without disassembling every single time. I run the packs in my bike at 2s2p for 12s 32ah with a max draw of 22amps. Any suggestions on a simple plug in and charge idea?

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rojitor
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Re: Adding BMS to 12s lipo pack (2 6s)

Post by rojitor » Wed Nov 08, 2017 7:28 am

Lipo and bms in the same sentence give me the creeps.
Lipo is cheap and has a high C.
If you add a cheap bms you have a not so cheap battery with a low C and a risk of fire.
If you bypass the cheap bms you will keep the C while increasing the risk of fire.
If you add an expensive bms you will have a decent C and decrease (not erradicate ) The risk of fire but in that case it will not be cheap at all.....so why lipo?
Years ago we were using super expensive and heavy lifepo4 packs. Li ion were even more expensive.
Those days some of the sphere gurus did nice solutions lipo oriented. Even with the cost of Those great inventions lipo was way cheaper and lighter than any other option.
https://endless-sphere.com/forums/viewt ... oodrum+bms
https://endless-sphere.com/forums/viewt ... 31&t=36414
Nowadays li ion are cheaper and lighter than ever. Not worth it anymore I guess.
Lots of guys around are using bms with lipo lately, often cheap bypassed ones. If you google it you will find many diagrams.
Honestly I would never do that. And i do not recommend it at all.I have seen too many lipo fires around. The best you can do is making a harness and be yourself the bms. There's a few threads about lipo harness and you can even buy them done.

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motomech
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Re: Adding BMS to 12s lipo pack (2 6s)

Post by motomech » Wed Nov 08, 2017 11:42 pm

Sidotian wrote:Ok so I have been charging 4 6s 16ah 10c lipos with a 80watt RC 6s charger in parallel. That's a total of 6s 62ah while charging with a parallel board. I would absolutely love to somehow wire up the pack with a BMS so that I could plug the pack in without disassembling every single time. I run the packs in my bike at 2s2p for 12s 32ah with a max draw of 22amps. Any suggestions on a simple plug in and charge idea?
I guess you haven';t seen any of the dozens of posts I have made on the subject.
You don't need a BMS, what you need to do is bulk charge and nothing is easier to bulk charge than 2S/2P.
Use this power supply an d 4) battery Medics;
100_0016.JPG
100_0016.JPG (94.07 KiB) Viewed 118 times
Above charging a 2S/1P aux. pack. Or b elow, charging my 2S/2P 12S/20,000 mAh pack w/4)Battery Medics;
100_0064.JPG
100_0064.JPG (73.17 KiB) Viewed 118 times
For more details, search my posts using key words Multistar, Mean Well, bulk charging, etc.

This is about as close to "plug and play" as one can get w/ LiPoly. It will never be as simple as the other chem.s, because it's usually a 2-step process. But this Power supply is fast because it doesn't switch on and off like a balance charger. Say you have charged your pack to a storage cell voltage of 3.90V. To top it off to 4.10V will take about a half an hr. But you, like me, have capacity to spare and I sometimes just go for a local ride at 3.90V to 4.00V.

I'm assuming you are using your controller's LVC. The beauty of using 12S LiPoly, is it matches the 42 V LVC of most 48 V controller's so well. Right around 3.65V/cell, perfect.
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, 2.4 Holly Rollers run ghetto tubeless. 25 mph. Mean Well HLG-320H-48A
https://endless-sphere.com/forums/viewt ... =3&t=83430
'07 GT Idive 4 4.0, Q100C 201 12S LiPoly elifebike 9-FET 17A controller. 20 MPH.
https://endless-sphere.com/forums/viewt ... 8#p1237928

Sidotian
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Re: Adding BMS to 12s lipo pack (2 6s)

Post by Sidotian » Thu Nov 09, 2017 12:53 am

I'm confused as to why you say you don't need to balance charge/bms I don't have a lvc I just watch a lipo checker on my handle bars. Once the cells start to deviate from each other is when I switch off. Which is usually around 3.5v. I understand that when I hook my 4 cells to a parallel board (discharge and balance leads) that it would naturally balance. cell1 of battery one, two, 3, and 4 . But not between battery cells them selfs. I know all of the 6s plug-in RC lipo balancers are only like 40-400 mah balance rate which is pretty much useless if your actually trying to get somewhere... I just find myself carefully tapping into to the parabord 6s balance lead connector and bringing the lowest cell up by charging. Sorry Im new to such big lipos (worse mistake IV made so far is mix up series and parallel connectors 12s and 6 s in parallel your in for some smoke ) that's why I'm looking for a better way...

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motomech
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Re: Adding BMS to 12s lipo pack (2 6s)

Post by motomech » Thu Nov 09, 2017 1:33 am

I'm confused as to why you say you don't need to balance charge/bms
Simple, when used correctly, LiPoly, especially the Multistar, seldom needs balanced.
By correctly, I mean;
1)Don't exceed the constant C rate for the LiPoly used.
2)Observe the 80% Depth of Discharge (DOD) rule.
3)Don't constantly "break the string" to charge. LiPoly has a bit of a memory and doesn't like to be disturbed.
4)never discharge a cell below 3.65V/cell. There is little energy left and this is where the cells really start to stray.

On those very rare occasions I need to balance, I do it w/ my Battery medics.

That doesn't mean I don't ck the cells, I do every time, usually at the end of the "storage" charge. But to tell the truth, I can't remember the last time I had to balance any cells on my main pack. They are always between a .01V to .03V variance.
Possibly, your controller is over discharging the comfortable C rate of the Multistar, which is considered to be around 40 Amps constant for a large pack. Most certainly, letting some cells get down to 3.50V is inviting imbalance.
Last edited by motomech on Thu Nov 09, 2017 9:28 am, edited 1 time in total.
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, 2.4 Holly Rollers run ghetto tubeless. 25 mph. Mean Well HLG-320H-48A
https://endless-sphere.com/forums/viewt ... =3&t=83430
'07 GT Idive 4 4.0, Q100C 201 12S LiPoly elifebike 9-FET 17A controller. 20 MPH.
https://endless-sphere.com/forums/viewt ... 8#p1237928

Sidotian
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Re: Adding BMS to 12s lipo pack (2 6s)

Post by Sidotian » Thu Nov 09, 2017 2:18 am

My lipos have gotten as far as 0.040v between the highest and lowest is that acceptable? Where would I get a 12s bulk charger? According to the controllers Bluetooth app I draw 20amps at full throttle. My batterys rated capacity is 12s 32ah total that battery's are rated at 10c. And also will a identical battery other that the c rate for example. same mah different c rating last longer/more milage per AH?

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motomech
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Re: Adding BMS to 12s lipo pack (2 6s)

Post by motomech » Thu Nov 09, 2017 10:13 am

Sidotian wrote:My lipos have gotten as far as 0.040v between the highest and lowest is that acceptable? Where would I get a 12s bulk charger? According to the controllers Bluetooth app I draw 20amps at full throttle. My batterys rated capacity is 12s 32ah total that battery's are rated at 10c. And also will a identical battery other that the c rate for example. same mah different c rating last longer/more milage per AH?
My lipos have gotten as far as 0.040v between the highest and lowest is that acceptable?
That's right around I start thinking about balancing. I would probably go w/ it and ck them next charge cycle.
Where would I get a 12s bulk charger?
For 12S, you would want the Mean Well HLG-320H-48A. It's a 120 Volt input LED lighting(Like a store window display) power supply and avail. from many industrial electronics suppliers. Just Google it. It's super high quality and shuts down at the finish Voltage that you set. You will need to add a mini Voltmeter(to adj. the Voltage/Ebay) and add connectors on both ends. Make sure you get the one w/ the suffix A. It will be the last "charger" you will ever have to buy.
According to the controllers Bluetooth app I draw 20amps at full throttle. My batterys rated capacity is 12s 32ah total that battery's are rated at 10c.
20 Amps is fine for Multistar. For some reason, I thought you had a BIG controller.
And also will a identical battery other that the c rate for example. same mah different c rating last longer/more milage per AH?
No, the Multistar trades a high discharge rate for smaller size, lighter weight and lower cost. For ebikes that don't need a high discharge rate, it's the best LiPoly. Although I still like the Turnigy 20 C for bricks not avail. in the Multistar.

A word about Battery Medics- A few years ago, clones started to appear. They are the Black ones and some blue ones. They are junk! Right now, I only know of one vendor for the original, high-quality Battery Medics, they are;

https://www.amazon.com/Targethobby-Disc ... discharger

They are a little pricey, especially when you need 4 of them, but trust me, these are the ones you want. Plugging the balance taps onto the B.M.'s can be a little tricky, they tend to get stuck. I use 6S balance extensions(Hobby King, Ebay, Progressive RC, Hobby Partz) and file the locating nubs off to make them easier to plug-in/unplug.

So, in the end, you will need to spend some bucks to get set-up, but you will love the results, I promise.
Just don't let your cells get below 3.65 Volts :lol:
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, 2.4 Holly Rollers run ghetto tubeless. 25 mph. Mean Well HLG-320H-48A
https://endless-sphere.com/forums/viewt ... =3&t=83430
'07 GT Idive 4 4.0, Q100C 201 12S LiPoly elifebike 9-FET 17A controller. 20 MPH.
https://endless-sphere.com/forums/viewt ... 8#p1237928

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