On 15 Jul 2015 at 5:59, Willie2 via EV wrote: > This one: http://www.rc-electronics-usa.com/meter-applications.html is > slightly intriguing, but it looks like it may run demand current > through 14 ga wire. I could probably use one per battery.
I have one of those "Watts Up" meters. It works nicely, within its limitations. It's US made (!), and appears to be really well built. I use it a fair bit. However, the specs claim a current capacity of 50 amps continuous and 100 amps peak. I think that's wildly optimistic. The shunt is built in, and you're right, the lead wires are only #14. I wouldn't use it at over 10-15 amps continuous. Even at 15a, I keep a fan blowing on it. I originally intended it as a small EV "fuel gauge," but for that it turned out to be a bust. The problem is the that the numbers you really want for use as a "fuel gauge" don't don't display continuously. The display shows voltage, current, and power all the time. A 4th "slot" rotates among AH, WH, maximum current, maxiumum power, and minimum voltage. I can't just glance at it and see how many AH I've used; I have to wait for the number to appear. That's not so good when you have to take your eyes off the road! I keep it in my EV toolbox, though. It's great for checking small battery capacity. I've considered using a makeshift prescaler with it. If I can accurately measure the total resistance of the internal shunt and connecting wires (the shunt is in the negative side), I should be able to add a parallel shunt of 1/9 the resistance. Then for a 100 amp load, it would display 10 amps. The trick would be calibrating the external shunt. I usually don't buy shady Asian stuff, but this here's one with an external shunt, and features that might enable it to work better as a small EV fuel gauge. It was cheap enough that I ordered one to try out. Ebay item # 161751430848 $31.20 (includes shipping) DC 120V 100A Voltage Amp Power Capacity Meter ... I just got it and haven't even had a chance to connect it yet. It claims to work at 10-90v (0-120v with external power) and up to 100a. It can supposedly be set to display your choice of 2 parameters, using front panel switches. It also has a calibration mode. I'm not sure whether that's a bad sign or a good one. :-\ As a first impression, the meter and connection board look OK. Soldering looks decent. However, the shunt looks like junk. It's kind of crooked, and stinks of chemicals (probably the gunky black stuff they slathered on its middle). There's also no mounting bracket for the shunt, so I'll have to make one with phenolic or something similar. More when I get a chance to actually try it, if anyone's interested. David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ 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)
