Even Newer 4 to 24-cell Battery Management System (BMS)

[Jay64]

Ok, I ordered two of these boards. Now I have to work on finding the "out of stock" componenets of the BOM.

 

[fechter]

There are alternate parts available for almost everything.
There are alternate suppliers too, like DigiKey and Allied Electronics.

Here's a few Mouser subs: (taken from Patriot's build thread)


- 299-4.7K-RC 4.7Kohms 1
Xicon 1/8W 5% Carbon Film Resistors
This product is expected to be in stock by 03-02-09.

Alternates:
270-4.7K-RC
71-CMF50-F-4.7K/R71-RN60D4701F

- 270-180K-RC 180Kohms 1% 16
Xicon 1/8W 1% Metal Film Resistors
This product is expected to be in stock by 01-20-09.

Alternates:
270-180K-RC shows in stock now
660-MF1/4DC1803F
660-MF1/4DCT52R1803F


- 286-6.8-RC 6.8ohms 16
Xicon 5W Small Metal Oxide Resistors
This product is expected to be in stock by 01-20-09.

Alternates:
280-CR5-6.8-RC
284-ACS5SW-6.8
286-7.5-RC
71-CP5-J-7.5 (7.5 ohm, 5W)

 

[methods]

Go back a ways and find my BOM
I listed other alternatives as well.

-methods

 

[Jay64]

How big of a output wires can be connected to this board? I would like to use 6ga wire, is that possible with this board?

 

[fechter]

How big of a output wires can be connected to this board? I would like to use 6ga wire, is that possible with this board?

I don't think the holes are big enough for 6ga. 10ga for sure.

Since only the charging current needs to go through the board, you can use smaller gauge wire from the board to the main wires or pack.

On my pack, the main wires go directly to the controller and not through the board.

 

[Jay64]

So does this not have a function to monitor discharge?

 

[fechter]

So does this not have a function to monitor discharge?

Let me try to clarify:

The BMS board needs a connection to the main pack + and -, as well as one wire to each connection between cells. All of the between cell wires won't carry much current, so they can be very small gauge wire.

The main + and - wires from the pack need to go to the controller (big fat wires) and to the charger (wire size depends on charger amps).

A picture would be good here:

 

[GGoodrum]

So does this not have a function to monitor discharge?

There's no current limit, if that's what you mean. This is not needed though. All the current goes through all the cells, so current limiting can be done at the controller level. The only reason most of the import BMS boards do current limiting is because they usually go with the cheaper LiFePO4 packs that have low "C" raings. If you have a 20Ah pack that is limited to 2C, for instance, you need to make sure no more than 40A is drawn from the pack at any time, or you will kill the cells.

There is an LVC function that does monitor the voltage level for each cell. If any one cell/cell block drops below 2.1V, it trips the output "switch", which is a ganged series of optocoupled outputs. You connect this output to either a brake switch input, or you connect it to the throttle signal line and ground. What it does is tell the controller to cut the throttle, thus removing the load.

-- Gary

 

[Jay64]

Yeah, I was refering to the LVC function. I see now that it takes small wires from the total battery, but those wires aren't needed to then go on to the controller/motor. Thanks again guys. Sorry for all the novice questions.

 

[biohazardman]

So does this not have a function to monitor discharge?

Let me try to clarify:

The BMS board needs a connection to the main pack + and -, as well as one wire to each connection between cells. All of the between cell wires won't carry much current, so they can be very small gauge wire.

The main + and - wires from the pack need to go to the controller (big fat wires) and to the charger (wire size depends on charger amps).

A picture would be good here:

Thanks for the pic that makes it easy and lets me know I am not going to screw something up. At least not if I ever get the thing together the rest of the way.

 

[steveo]

Hey Everyone,

I have (2) 24 cells boards on the way to me;

Just wanted to know if there is some sort of write up on how to convert this bms to work with lipo batteries, componets that need to be changed etc.

any links/info you could provide would be great!

thanks
-steveo

 

[methods]

Check your PM

Also search this thread for "LiPo" or "methods" and you will see all my posts with different versions of the Lipo BOM
All my parts are "in stock" as well.

-methods

 

[Patriot]

I was planning on building a small wood box with a clear plexi top, and leaving a big gap on the side for all the wires to come out. Even though a good 1/4" gap will be open along the whole side of the box, would I need to install a small fan to cool the BMS during charging?

Or perhaps just make it run all the time. If I use my 12vdc converter, I would have to leave it turned on when charging. If I set it up to run only when charging, where does one get the 12v from to make that happen?

 

[methods]

Just pop the 12V regulator off the board and wire in a beefy one.
They even have them at Shadio Rack

After I started running 100V on the BMS I dumped the on board regulator and just ran 12V from an outside supply

Any number of wall warts will give you 12V @ a reasonable current too. No doubt you have one or two. Just extend the wires, cut the regulator off the board, and wire in the new 12V. Tie the grounds together.

-methods

 

[Patriot]

^^^ Would a fan even be necessary?

 

[methods]

A fan is a nice touch
It will work without it but do it if you can.

-methods

 

[flashedarling]

-- Gary

Could you post a zoomed in image of this that I could download? At least for the first 4 cells? It would really help me as I put my v2.3 board together.

 

[fechter]

Could you post a zoomed in image of this that I could download? At least for the first 4 cells? It would really help me as I put my v2.3 board together.

Look on page 2 of this post: http://endless-sphere.com/forums/viewtopic.php?f=14&t=8140
(sorry don't have it on this computer). It's big enough to read the resistor numbers.

 

[GGoodrum]

Attached is a full-resolution PDF version of the layout. You can zoom this in as far as you need.

-- Gary

 

[steveo]

Hey guys,

Just a question as per i'm still learning about this bms boards a bit more everyday, When you cut the board and seperatie them into there individual 4s bms boards; Do all the rest of the bms boards need to know what the others are running at; or does it not matter; Must the entire bms board stay in one piece in order to use the full 24s board.

I hope this make sence for you guys..

Also one more question; Will 1/2 amp be sufficent for dealing with a 10p 24s a123 pack.

thanks
-steveo

 

[manfred59]

I have a question about connecting this BMS with my 24V/10A china scooter controller.
Out of the controller there are a break conector(white /brown) and a breaklight connector for the back light, which lights up when the hand-brake is used.
Now I have cut the white/brown cables and connected the brown to GND and the white to the brake pin of the BMS . But now the back light does not work. Should I parallel the BMS wires to the brown/white and would be white the ground wire?

 

[fechter]

I have a question about connecting this BMS with my 24V/10A china scooter controller.
Out of the controller there are a break conector(white /brown) and a breaklight connector for the back light, which lights up when the hand-brake is used.
Now I have cut the white/brown cables and connected the brown to GND and the white to the brake pin of the BMS . But now the back light does not work. Should I parallel the BMS wires to the brown/white and would be white the ground wire?

If the brake switch is operating a rear light, I think you'd have to tie the LVC into the throttle line.
You don't want the LVC to activate the brake light. That would be too much load. There might be another set of wires coming out of the controller (possibly unused) for a brake switch that does not activate a light.

To tie into the throttle line, you first identify the 3 wires going to the throttle. One should be steady 5v, one ground, and one signal that varies from around 1v to 4v as you advance the throttle. To be safe, you should cut the signal wire and install a 1k resistor in series with it.
The LVC connections then go in parallel to the ground line and the controller side of the 1k resistor you installed. This will just kill the throttle when you hit LVC.

 

[fechter]

Hey guys,

Just a question as per i'm still learning about this bms boards a bit more everyday, When you cut the board and seperatie them into there individual 4s bms boards; Do all the rest of the bms boards need to know what the others are running at; or does it not matter; Must the entire bms board stay in one piece in order to use the full 24s board.

I hope this make sence for you guys..

Also one more question; Will 1/2 amp be sufficent for dealing with a 10p 24s a123 pack.

thanks
-steveo

If you split the board, you need to connect the pieces together with 6 wires. 2 for the LVC bus and 4 for the charge control (ground, 12v, all shunts, any shunt) lines. These wires can be very small and don't carry much current. There are holes in the bus traces for these wires.

500ma seems to be more than adequate for 40Ah packs.

 

[GGoodrum]

Hey guys,

Just a question as per i'm still learning about this bms boards a bit more everyday, When you cut the board and seperatie them into there individual 4s bms boards; Do all the rest of the bms boards need to know what the others are running at; or does it not matter; Must the entire bms board stay in one piece in order to use the full 24s board.

I hope this make sence for you guys..

Also one more question; Will 1/2 amp be sufficent for dealing with a 10p 24s a123 pack.

thanks
-steveo

You can break the board up into subsections, which I assume you want to use with subpacks for your setup, and connect the subsections via six wires that make up the opto bus lines, two for the LVC and four for the charger control. These are shown in yellow below.

These can be thin-gauge wire, as there's not much current to carry. The only other thing you need to do is make sure that each subsection board has the first and last connections to the first and last cells in the subpack. This is the reason for the duplicate cell connection holes (i.e. -- 5/6, 10/11, etc...).

-- Gary

 

[flashedarling]

Out of curiosity what should I look for in a charger to match with the BMS? I'm trying to decide on a 72v charger and while Zivan NG1s seem to be very popular I was looking for something cheaper. Would there be any problems matching my 24 Headway cells and BMS with this charger? http://elitepowersolutions.com/products/product_info.php?cPath=9&products_id=80