Lee, Thanks for setting me straight that the backlight draws so much power that it is better not to use a zener. An ordinary buck converter can be OK if both the meter power and measurements are connected only to the pack, since then no chassis connection exists. For 48V packs the universal power supply is not a good option, but for higher voltage packs it is, I have used those with good result. I am surprised that the backlight draws so much power, they must be using low efficiency LEDs as those a cheap. OK, good to know and thus a DC/DC is recommended.
Do you know if the meter can be powered off when the car is not used without losing its memory? 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 XoIP: +31877841130 Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 -----Original Message----- From: EV on behalf of Lee Hart via EV Sent: Sat 7/25/2015 1:03 PM To: Ing. Marco Gaxiola; Electric Vehicle Discussion List Subject: Re: [EVDL] 48V Energy Meter (Lead-Acid)... From: "Ing. Marco Gaxiola via EV" <[email protected]> > the owner of the vehicle wants something that tells him in 'percentage' an > E-meter only has 4 LED lamps. It has an option to display percent state of charge on the digital display as well (0-100%). > Xantrex is the new name of the E-Meter product Yes; it was originally designed by Cruising Equipment Company and called the "E-meter". They were bought out by Heart Interface, and was renamed the "Link-10". Then Xantrex bought Heart Interface and it was renamed the LinkPro/LinkLite. Production has been outsourced to China, and numerous changes have been made to lower cost. > and yes the new one works only up to 35V *All* of them only work up to 35v. They need an 11v to 35vdc power supply good for 20-500ma (current depends on voltage and display brightness). There is a switching regulator inside, so the higher the supply voltage, the lower the supply current. The power supply has the SAME GROUND as the high voltage pack you are monitoring. This means: - If you power the meter from a grounded 12v accessory battery, you have grounded the negative of your pack! - If you plug anything into the meter's serial data output (like a laptop to save data), then you have connected your laptop's ground to pack negative! These are usually BAD things to do. That's why I build the Companion board for the E-meter/Link-10/LinkPro (see www.sunrise-ev.com) For SENSING pack voltage, there was a software configuration option to allow an external 1:1, 5:1 or 10:1 prescaler (basically just a pair of resistors) on the voltage sense input. There is a setup option to configure the decimal point to correctly reflect input. All the recent models I've seen in fact have all the options; but they don't describe them in the manual. You have to find old copies of the manual that did describe them to see how to enable them. > Damon, an isolated power supply Cannot be done by just using a Zener diode Correct. It works; but I don't think a series zener is a good approach here. It is not isolated, so you have that lurking ground problem. And because the supply current can peak as high as 250ma, the power dissipation in that series zener could be very high. A better solution is to use an isolated DC/DC converter. Perhaps the cheapest option is a "universal input" switchmode wall-wart power supply with a 120-240vac input (which typically also work on 90-350vdc), and a 12vdc output. -- Excellence does not require perfection. -- Henry James -- Lee A. Hart http://www.sunrise-ev.com/controllers.htm now includes the GE EV-1 _______________________________________________ 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)
