I have a charger that does not need 12V to charge the 120V flooded pack, because I plug the cord directly into the charger's AC input and the charger's output is directly connected to the pack. I do use a tap on the charger's transformer to power a small 12V supply that charges my aux battery and unless that supply dies, I am not afraid that my 250Ah aux battery runs out of juice. (The aux is made of 2 spare batteries in case 1 or 2 of the pack's golfcart batteries die) The aux battery meter is the only original dash meter that is useful in my conversion, of course the pack SoC is displayed on a separate meter.
The common item here seems to be that if your EV needs to be "on" to charge, even if it is not the key in the ignition, but still contactors need to pull in, maybe fans are running and other electronics such as BMS needs to be powered, then you also need to make sure that there is supply to those critical tasks - the DC/DC needs to supply at least a standby or float level of power. If you do not like the idea of having your aux battery on a charger for long periods of time then you can consider a separate external 15V power supply running from the AC and powering the critical tasks via a pair of diodes, one supplying power from the aux battery and one from the external power supply that you can mount near the charger and run together. The dual Schottky diodes with about half a Volt drop are frequently applied for this purpose, for example to separate an RV house battery and external power or in a car with excessive audio equipment to power it from a pair of batteries that each are charged by a separate alternator. Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of David Ladd Sent: Tuesday, January 08, 2013 10:41 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Need 12V to Charge? I've done this too. Not actually with the lights on, just a weak 12v battery that would die if left unattended too long. Here's a quick tip, instead of jumping the 12v battery with 4 of your traction pack cells, just jump the terminals of the contactor that powers the DCDC. In my case it was controlled by an EV200 contactor, and a quarter jumps the terminals quite nicely. :-) Once the DCDC is powered, you have 12v to the battery, and the contactor will now stay on itself as intended. I did have the same issue where the 12v battery died overnight and shut down the MiniBMS, which shut off the charger. Bummer, but at least it happened at home. I just drove another car that day, since I had no way of knowing how much it had charged before getting cut off. I now have the DCDC always on, and don't have this problem anymore. david. http://www.evalbum.com/4021 >________________________________ > From: Mike Nickerson <[email protected]> >To: Electric Vehicle Discussion List <[email protected]> >Sent: Monday, January 7, 2013 9:31 PM >Subject: [EVDL] Need 12V to Charge? >However, I was prepared for this. I have been carrying a couple of 10 ga. >wires in my trunk for just this reason. Each cable had an alligator clip on >one end and a ring terminal on the other end. With the key on, I connected >the clips to the 12V battery terminals and simply touched the ring terminals >across 4 of the LiFePO4 cells. That was close enough to 12V. With that >voltage, the main contactor engaged and the DC-DC converter turned on. >After that, I could remove the cables because the DC-DC converter was >keeping the 12V system alive. > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use 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 For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
