Enginer PHEV automatic over/under voltage protection

[Daox]

I've started talking to a robotics guy I know from the local EV club about how we can use the balancer's warning to trigger some sort of pack disconnect. IMO this is pretty simple thing to do and can be done without cutting anything, and very minimal rewiring. I'm just not an electronics guru, so I need help to put it all together.

My current thought is to use a simple VOX circuit (microphone activated switch) that is triggered by the buzzer on the balancers. The VOX circuit will feed a signal to a programmable micro controller (the arduino is what I'm familiar with and its cheap). The micro controller will then control a relay to disconnect the pack from both the charger and dc to dc converter. This allows protection from both over and under voltage.

Once the pack is disconnected, we need to reconnet it somehow. But, with the arduino, we can do pretty much anything with it. We could wait an hour then reconnect the pack, hoping that the balancers have pulled the high cell back down and continue to top off the pack. As soon as the buzzers go off again, it would disconnect for another hour. Another alternative is that we could wait for a manual signal from the user to connect the pack again. This signal could be from another switch added up in the dash area, or even from turning the phev system of and back on (this would require tapping into the phev switch). At that point, the pack would be reconnected and ready to go.

The setup would cost less than $50.

The drawbacks of course are you are stuck with the balancer's set voltage points. Personally, I'd like to adjust them a little bit. However, this is a quick fix and I'm hoping Enginer eventually comes up with something on their own.

Thoughts?

[ericbecky]

If it is activated via an audio signal, is there any issue of other audio tones inadvertently tripping the audio activation. (The stereo, a bang when closing the hatch, the backup beeps, etc.)

[Daox]

True, that is a possible problem. You might have to hit a reset switch to get the pack to reconnect. Or, the sensitivity of course could be adjusted with the circuit posted. Another alternative is with the arduino you could even program it to ignore other noise and have the mic only listen for the beep. I think this is probably overkill. I think if you have noises as loud as those buzzers going off in the case, you have other problems.

[Daox]

I ordered the VOX circuit this morning. The current plan is to just deal with charging. This seems to be the area where we are having most of the problems due to charging unattended and not being able to hear the balancer buzzers going off.

I am thinking that I will make an additional box that goes between the charger and the wall. Inside the box is the VOX circuit, arduino, a wall wart (for 12V power), and a solid state relay. There will be leads going to the inside of the phev box to the microphone. Since we aren't charging on the go, sound won't be an issue. When the balancers go off, it cuts power to the charger. Pretty simple. Once the charger is unplugged, the arduino powers down and it operates as normal.

I'll keep this thread updated as I build it.

[banshee08]

Instead of using the balancers to trigger you cut off relay. You can use this Cell Log 8S. It has an alarm output lead to trigger external alarms. I am currently using this to monitor my cells while I am driving and it works great. And it logs my voltage difference for later analysis.

CellLog is releasing! - RC Groups

[ericbecky]

Looks interesting.
Rather than trying to sift through the 15 pages of posts, could you please tell us the price? I went to the web site of the mfg, but never found an actual price listed.
Here's a direct link to the product on the mfg's web site:
http://www.jun-si.com/EnProductShow.asp?ID=96

[banshee08]

Originally Posted by ericbecky

Looks interesting.
Rather than trying to sift through the 15 pages of posts, could you please tell us the price? I went to the web site of the mfg, but never found an actual price listed.
Here's a direct link to the product on the mfg's web site:
ÉîÛÚÊп¡Ë¼µç×ÓÓÐÏÞ¹«Ë¾»¶Ó­Äú

I got 4 of them for my 8kWh pack. They were like $30 plus shipping straight from China. Here is where I bought them at.

HobbyKing Online R/C Hobby Store : Cell-Log Cell Voltage Monitor 2-8S Lipo $27.98

[dan2l]

Originally Posted by Daox

I ordered the VOX circuit this morning. The current plan is to just deal with charging. This seems to be the area where we are having most of the problems due to charging unattended and not being able to hear the balancer buzzers going off.

I am thinking that I will make an additional box that goes between the charger and the wall. Inside the box is the VOX circuit, arduino, a wall wart (for 12V power), and a solid state relay. There will be leads going to the inside of the phev box to the microphone. Since we aren't charging on the go, sound won't be an issue. When the balancers go off, it cuts power to the charger. Pretty simple. Once the charger is unplugged, the arduino powers down and it operates as normal.

I'll keep this thread updated as I build it.

Hi Doax,
I have become tuned into the charging process well enough to be watching when it is approaching shut down. I am getting various beeps and alarms from the balancers. I am guessing that about 1/2 the beeps should be corrilated to a shut-down and the other 1/2 are false alarms. How will your system know a real alarm from a false alarm?

If you do not know if the alarm is real or false, but shut down on all alarms, then you will not know the SOC on the batteries. I would be conserned about restarting the charger on a full battery. The charger comes on pumping out full power and then takes some time to figure out to turn off.

If you have one cell at 3.75v and all the others at about 3.5v then it only takes about 5 minutes at 15.5a to put the 3.75v cell up to 4.0v where it may be dammaged. So one start of the charger on a full battery pack is probubly OK, but I would never want to do it two times.

Thanks,
Dan Lander

[Daox]

Well, I may or may not complete this project if Jack comes out with the new balancer that controls the dc to dc and charger.

In any case, there would be no way to differentiate between false and true alarms with this setup. However, if you start up the charger and the alarm goes off again, it simply shuts it down again. So, no worries there.

BTW, how do you qualify a false alarm?

[dan2l]

Originally Posted by Daox

Well, I may or may not complete this project if Jack comes out with the new balancer that controls the dc to dc and charger.

In any case, there would be no way to differentiate between false and true alarms with this setup. However, if you start up the charger and the alarm goes off again, it simply shuts it down again. So, no worries there.

BTW, how do you qualify a false alarm?

Hi Doax,
I push the button on the balancer before turning off the charger. As it rolls through the cells, the alarming cell (in my case #5) says 5 3.75H. Also the "d 0.020" number was up at 200mv-300mv. If it is a false alarm the readings will be normal and the charger stops beeping very quickly. I think it gets a false high reading and the alarm goes off, but then it corrects the reading quickly. A real alarm keeps beeping and will drive you crazy while you are trying to figure out which cell it is.

Thanks,
Dan