BMS for RC Lipo

[majornelson]

I'm looking for a BMS for two 6S Lipo batteries in series. Link would be really helpful. I saw a link recently (which now I can't find) but I when I looked, the part wasn't available retail.

Any help appreciated.

Note: Just edited my original post as I am putting the two packs in serial for 48v.

 

[friendly1uk]

http://bestekpower.com/222v6spcmbmspcbforli-ionli-polymerbatterypack/

 

[majornelson]

friendlyuk1,

Thanks! That's the link. But I couldn't find it available for sale on the site and a quick google search and check on ebay and aliexpress for one of the boards didn't turn up anything. :?

Also, they listed quite a number of boards. Is it just the shape and amps required that I need to consider?

Really appreciate your help on this!

 

[dnmun]

will your total pack be only 6S long? that is an extremely low voltage so i wondered if you were going to use 2 of these in series.

 

[majornelson]

Just saw that I wrote 2P and that is not correct. (I corrected my original post - thanks!)

I'll be using two 6S packs in a series (so 12S, right?). I have the zippy 6S 5AH packs (at 48V) and, with two, think I can get about 15 miles around town with some assist. Which is fine for me... My office is only two miles away. And I want a stealthy setup...

My interest in the BMS is both safety and charging convenience.

The batteries are powering either a Cute Q100 or a Bafang K5 (forget the other letters) front drive motors on a cruiser type bike.

 

[dnmun]

if it is 12S then you need a 12S BMS. http://www.bestekpower.com/444v12spcmbmspcbforli-ionli-polymerbatterypack/

lemme know if you are interested in buying one because i am about to pay for my order to henry and i can include you in the order if you wish.

 

[majornelson]

I'm in. I think I'll be mounting this in a wooden crate on the rear (I think/hope it will look better than it sounds...)

I'm completely new with this (read - don't know what I'm doing. I assume that I need a 20A BMS is appropriate (I think my controller will draw 17A with a soldered shunt- haven't crossed that bridge yet)?

I have this controller:
http://www.greenbikekit.com/index.php/motor-controller/250w-36v-electric-bicycle-hub-motor-controller.html

Would this one be a good choice for 20A BMS?
http://www.bestekpower.com/444v12spcmbmspcbforli-ionli-polymerbatterypack/PCB-D165.html

If 15A would work, it would be better. They're much smaller (though looks like slower charging, which is fine). Here is one I saw:
http://www.bestekpower.com/444v12spcmbmspcbforli-ionli-polymerbatterypack/PCM-D122.html

 

[dnmun]

both will work at 20A. i have put 25A through the 3 FET configuration that is limited to 15A like that D122. both are 84mA balancing current. the first one includes a heat sink and is made for higher current for longer periods. but the D122 should handle your controller fine.

you might wanna consider going to 14S too. see if you can add a pair of 8S to make it 14S2P. that allows you to charge with the regular 48V lifepo4 charger.

that is where i am now gonna focus. i ham talking to him about increasing the balancing current on the D126 14S lipo i am ordering for me and richard. i am hoping to get the balancing current to 132mA.

 

[eva-michael]

We manufacture both LiFePO4 and LiPO BMS.
If you can not find one, we can custom made one 6S LiPO BMS for you. That's something only 16usd for a 20A.
The size will be like this one
http://www.evassemble.com/index.php?main_page=product_info&cPath=6&products_id=209
And connection will be similar as below.
http://www.evassemble.com/pdf/BMS/Resistor%20Bleeding%20balancing%208S%20BMS.pdf

Via post office is 6usd shipping and via express shipping is 18usd.

Michael

 

[cwah]

I'm looking for a BMS that can avoid situation like this:

Which bms is better for good auto-bleeding? Bestekpower BMS only starts when cell reach 4.2V right? So it's not very efficient?

 

[eva-michael]

Generally release voltage for LiPO cell bleeding will be 4.1V. Single cell ending will be 4.2-4.28V.

 

[cwah]

Generally release voltage for LiPO cell bleeding will be 4.1V. Single cell ending will be 4.2-4.28V.

How come the cells voltage are all around the place then?

 

[dnmun]

Generally release voltage for LiPO cell bleeding will be 4.1V. Single cell ending will be 4.2-4.28V.

How come the cells voltage are all around the place then?

do you have a BMS on your lipo pack? do you use a balancing charger?

 

[eva-michael]

Generally release voltage for LiPO cell bleeding will be 4.1V. Single cell ending will be 4.2-4.28V.

How come the cells voltage are all around the place then?

There is a range of voltage difference which activates bleeding of the higher voltage cell.

 

[cwah]

The current BMS I'm having is useless because I have 4.2V and 3.8V cells......

 

[dnmun]

that is a useless statement. what kind of BMS do you have? how can it balance the pack if the voltage is not enuff to fully charge it?

 

[eva-michael]

The current BMS I'm having is useless because I have 4.2V and 3.8V cells......

Are these cells new? I will say LiPO is easy to keep balance as they have a good consistence(Manufacture).
Is there LED in the BMS which will light when the corresponding cell is bleeding? This will let you know if the BMS help cells balance.
Generally the balance current is about 60-80mA for LiPO BMS. If the internal resistance, real capacity, voltage of energy level of cells are too different, BMS may be not easy to balance them.

 

[dnmun]

the BMS cannot balance his pack because he doesn't have enuff voltage to fully charge it. it should be obvious.

 

[999zip999]

You balance the pack befor you install the bms. Charge all to 4.1v or 4.15v Then install bms and use the a charger set at the right voltage.

 

[dnmun]

no, the BMS will balance the pack but he has to charge it to 4.2V/cell minimum. why is that so difficult? the BMS will not turn on the balancing transistors and resistors until it gets to 4.2V.

 

[cwah]

It's a no name bms. The charger is set to 42V, but bms shuts down the charging process as soon as 1 cell reaches 4.2V.

This pack was not mine, I found it like this after 1 year of usage from someone else...

In this case, the bms auto-bleeding is quite useless. I don't think the bms from bestech power shows which cell is bleeding

 

[999zip999]

You would like to balance the cells befor you hook up the bms. Why do people start with a out of wrack bunch of cells and hope over time the bms will balance. It's a lot easier to start with balance cells install the bms. Yes the bms will take the cells to 4.2v for balance. But to many people just install a bms on a pack of cells unbalance. It just takes to long. At 4.15 v is just a cleaner start.
What a cell at 3.6 and 3.8v and one at 4.2v and just hook up a bms ? Nonsense.

 

[dnmun]

no, he said the battery came like this already assembled. without more info there is no way to know what is happening if it turns off when one cell hits 4.2V and there is no picture to guess from. i would be balancing it manually if it is 20% outa balance like that though.

 

[cwah]

Pack was already like that when I received it. Initially the lady was able to do 25km range, and then over time she could only do 5km max.

She asked me for help so I opened the pack and discovered the issue.

Obviously the pack was initially balanced as she had full range, but now it isn't anymore.


Of course, I'm now balancing it manually, but my hope is that she shouldn't need anyone to balance it for her??

 

[agniusm]

Obviously it bleeds the high cell and when threshold is met, charger should kick in. If you want BMS to balance it leave charger on for 48 hours at least in safe environment. Another thing to consider is a bad cell/s if it went out of balance that much with bms.
If you still want bms, there are capacity transfer ones and they are a lot more expensive. Cheapest 24s I found was 120usd.