Lithium battery BMS questions

[P-hack]

FYI cellog can monitor charging and discharging, it will set the alarm signal if any cell is too high or to low.

[TurnNBurn]

Originally Posted by P-hack

FYI cellog can monitor charging and discharging, it will set the alarm signal if any cell is too high or to low.

That I knew, but it wouldn't do me much good if it went too high unless I was watching the bike charger for 6 hours.

[P-hack]

[TurnNBurn]

Is there something I'm overlooking with celllog monitoring high and low voltage? That creepy M.J. GIF has me thinking there's something I'm missing.

[TurnNBurn]

Originally Posted by mechman600

Looks good to me.
Buy a 12V actuated relay to switch your 120V charging for charger cutoff.
I came up with some charging and Ah counting/fuel gauge code. It's pretty simple, actually.

Do you have a link to a 12v actuated relay? I'm thinking about biting the bullet and building this monitor. It'll offer me the flexibility I want for future updates to the bike.

I'm going to check for your thread when I get home and the search function actually works.

Also, would I need that arduino and mux shield, or would the ATMEGA 2560 suffice? It has all of the inputs for the cells.

http://www.adafruit.com/products/191

[mechman600]

The 2560 has 16 analog inputs. You need 18 if you want to monitor all of your cells, so, a mux shield. But all you really need BMS for when bottom balancing is shutting off the charger, so you really only need to monitor one cell - the weakest one/quickest to charge.

Here is the relay I bought (but haven't used in my car yet):
G8P-1A2T-F-DC12 - OMRON ELECTRONIC COMPONENTS G8P-1A2T-F-DC12 - AUTOMOTIVE RELAY, SPST-NO, 12VDC, 30A | Newark element14 Canada

[mechman600]

Here is a basic BMS/Ah counter (fuel gauge) schematic - done with 5 analog inputs.


-The battbridge mentioned above can be accomplished with the Arduino using an input at half pack
-The weakest cell is monitored for charger cutoff
-Includes warning LED (optional opto to turn on the vehicle's low oil pressure light or whatever as well) and charge LED
-Contrast ON/OFF is what turns the LCD on when the keyswitch is clicked to the first position
-Reset button kills power to the Arduino for a full hard reboot
-Voltage divider on pack inputs is 20:1
-Fuel gauge is for my car - your motorcycle likely does not have a fuel gauge

[TurnNBurn]

Originally Posted by mechman600

The 2560 has 16 analog inputs. You need 18 if you want to monitor all of your cells, so, a mux shield. But all you really need BMS for when bottom balancing is shutting off the charger, so you really only need to monitor one cell - the weakest one/quickest to charge.

Here is the relay I bought (but haven't used in my car yet):
G8P-1A2T-F-DC12 - OMRON ELECTRONIC COMPONENTS G8P-1A2T-F-DC12 - AUTOMOTIVE RELAY, SPST-NO, 12VDC, 30A | Newark element14 Canada

I must have missed that. I didn't see it only had 16 analog inputs. I got it now.

So I'm looking at the batteries and I have (obviously) the two cables from each pack. These two will go to the analog inputs on the mux shield? And from the mux shield that will be connected to the display?

What worries me is I look at that wiring diagram for that fuel guage and I know there's going to be more parts to this BMS. Transistors, resistors, transducers, etc... I'd need a diagram to study and a full parts list up front before I feel safe tackling it. Do you have a diagram for the BMS? So I can get a feel for what's required for that?

[mechman600]

Originally Posted by TurnNBurn

So I'm looking at the batteries and I have (obviously) the two cables from each pack. These two will go to the analog inputs on the mux shield? And from the mux shield that will be connected to the display?

Each cell's positive will be hooked up to an input on the mux shield (through a 20:1 voltage divider of course - see 100K/5K resistors in above diagram), withe pack negative hooked up to Arduino GND. The mux shield plugs directly into an Arduino Uno R3 or equivalent.

The mux shield hogs a lot of digital pins on the Arduino for configuration, so I would cut/solder the necessary jumpers on the mux shield to permanently set it up for the desired analog inputs to free up Arduino pins for other things. This procedure is simple and well documented in the mux shield manual.

What worries me is I look at that wiring diagram for that fuel guage and I know there's going to be more parts to this BMS. Transistors, resistors, transducers, etc...I'd need a diagram to study and a full parts list up front before I feel safe tackling it. Do you have a diagram for the BMS? So I can get a feel for what's required for that?

This diagram will not be much different that the one I posted above, as far as inputs/outputs go. Just add more inputs. Maybe remove the fuel gauge output and rely on a reading on your LCD for fuel level.

[mechman600]

Here. Everything you need:


Parts List

1 - Arduino Uno R3 or equivalent
1 - Mux Shield II
1 - HD44780 20X4 LCD Display
1 - DH06S DC-DC converter
2 - Momentary pushbutton SPDT switches
1 - 2N7000 transistor
1 - 1N4004 diode
1 - 120VAC/12VDC relay
1 - Red LED (warning lamp)
1 - Green LED (charge indicator lamp)
1 - HTFS400 current transducer
1 - 4.7nF capacitor
1 - 47nF capacitor
1 - PS2502 optoisolator
2 - 220 ohm 1/4 watt resistors
1 - 220 ohm 1 watt resistor (LCD backlight)
1 - 1K ohm 1/4 watt resistor
1 - 549 ohm 1/4 watt resistor
18 - 100K ohm 1/4 watt resistors
18 - 5K ohm 1/4 watt resistors
Bunch of - 22 gauge single strand wire