Looking at the Batt Bridge circuit: http://www.evdl.org/pages/battbridge.html You can see that it connects to the pack at 3 points: bottom, mid and top. So, in order to cut the current, you need to disconnect at least 2. This can easily be done adding a reed relay in series with the two resistors so the pack+ flows through the resistor, then through the contact of the reed relay, then to the red and/or green LED. From the bottom of the green LED, you go through the contact of the second reed relay, then through the second resistor and to pack-. The two coils of the two reed relays can be connected to IGN (Ignition) and ground. Make sure they are 12V reed relay coils.
Note that the resistors are suggested to be dimensioned for 20mA. That was a good value for older, low efficiency / low brightness LEDs. Today you can buy LEDs that you cannot look at directly, lest you risk eye damage at 20mA. So you may need to design for a lower current through the green LED. One way to do this is to add a resistor in parallel to the green LED, so most of the current bypasses the LED and the LED will be less bright. You can also increase the resistance of the two resistors R1 and R2 but this makes the circuit less sensitive to imbalance because there is less current change per Volt of imbalance. This sensitivity can be improved again by adding a zener in series with the resistor, but now we are starting to design a more complex product again... Cor. -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Kevin Trombley via EV Sent: Saturday, January 06, 2018 7:08 AM To: ev@lists.evdl.org Cc: Kevin Trombley Subject: [EVDL] Batt-Bridge questions Thank you, for the detailed info. I am not sure how to check LED's but, to check if a Batt-Bridge is assembled & functioning properly you just connect it to a battery pack & the green LED should be the only one lit. Then, if the positive lead is disconnected the negative side red LED should light up or if the negative lead is disconnected the positive side red LED should light. Like this El Moto part 33 Battery Pack Balance Monitor | | | | | | | | | | | El Moto part 33 Battery Pack Balance Monitor This is 48V Battery Pack Balance Monitor that I assembled based on Lee Hart's Batt-bridge. | | | | Another question, if I may Would it affect sensitivity or performance if a switch was added to be able to turn it off when not in use or for long term storage? I understand from personal testing that (2) leads would need to be switched. Either (2) switches or a dpst switch. If it's plausible to be switched, could a couple of relays be used, so it can be switched on & off by the vehicle ignition? Thanks again, Kevin -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20180106/6e774f9b/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
