Re: [Electric Boats] China bike motors and batteries

 

Hi Ned,

I use the BMS from EV Works.  http://www.evworks.com.au/index.php?category=6

It consists of cell modules which sit between the poles of each LFP cell and monitor the voltage and take action when it gets too high or too low.

When the voltage is in range - which is between 2.5 and 3.84 volts - one greed LED is lit.

When the voltage is above 3.84 a red LED lights, and the internal shunt begins to burn off power. If the voltage exceeds an upper limit, which is 4.2 or maybe 4.25v (I've forgotten which and don't have the details with me just now) it breaks continuity on a circuit which is a daisy chain of all the cell modules.  When the circuit is broken the Master Control Unit disengages a relay which is intended to shut down the charging device, and sounds an alarm.

When the voltage drops below 2.5 volts the continuity is broken, triggering the same response at the MCU, which is to open the relay.  Both the power to the motor, and the charging device are intended to be wried through the main relay so that both are shut down for either under or overvoltage.

So far though I have used only the alarm function.

The alarm has gone off for low voltage twice now in my use of it, and on each occasion I have been able to shut down the power immediately.  i could see from the cell modules which cell had low voltage (the one with no green light) and could check the voltage.  each time this took a couple of minutes to get a multimeter onto it, and by then the voltage had risen already to 2.6 or 2.7 volts.

At the high end of the scale, because the charging is at a low rate (intermitent 2 amps) its low enough for the cell module to shunt all the excess power, and so hitting high voltage has not been an issue.

Since then I have wired a pair to each cell and then back to a board so that I can message individual cell voltages more easily than clamping the multimeter leads to the cell terminals.

I have now aquired a relay to use on the main power cables to the motor so I can make the disconnect automatic.  But as yet not fitted - another of the many projects that seem to multiply on my list...

Cheers

Chris

On 21/02/2010, at 12:07 AM, Ned Farinholt wrote:

 

Chris,

What battery management system do you use?

Ned

__._,_.___

Reply to sender | Reply to group

Messages in this topic (9)

Recent Activity:

• New Members 22

Visit Your Group Start a New Topic

Switch to: Text-Only, Daily Digest • Unsubscribe • Terms of Use

.

__,_._,___