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Meters · 30 November 05
With the first EV I used this E-Meter from Cruising Equipment. It shows volts, amps, amp hours, and time remaining…but only one at a time.
Along the top of the meter is a little “gas gauge” which shows approximately how much charge is left in the battery pack. It’s a rough, well, very rough estimate and can have some serious lag.
The other downside is that you can only see one reading at a time. To toggle between volts and amps takes from 1 to 4 presses of the SET button.
I’ve started thinking about what to use for Eve. Easiest approach is to pop the E-meter in again and leave it at that. Maybe add an analog meter for showing the current or voltage, so the meter can be left on one position most of the time.
A couple weeks back I bought a new Palm Z22 for 99 bucks. I gave my last Palm to Dad a few years ago when I changed jobs thinking I didn’t need it. I really missed it, since it acts as a backup brain.
Searching for software (hex calculator, password manager, adobe reader) I stumbled across Ohler’s site.
What a great resource! He’s owned a few EVs (be sure to check out the Spyder and its schematic) and has written a couple of Palm EV apps. The one shown here, EVDash, hooks to an E-Meter with the optional RS-232 connector. This allows the Palm to show volts and amps, along with overall capacity based on both.
Great, I’ll use that!
A couple problems. #1, the Z22 is USB, not serial, so you need an older Palm model to take advantage of this. #2, my E-Meter doesn’t have the RS-232 option.
We probably have an ancient palm kicking around somewhere, and there’s always ebay, so that problem is solvable. Cruising Equipment was purchased by Xantrex and the meter is now called a Link10. Not sure if they still make it and my email to support asking about an RS-232 upgrade has so far gone unanswered.
Another option is to make my own. I’ve been learning embedded system programming and this might be within my grasp, especially since I work with smart folks that’ll answer newbie questions.
I could probably install a couple analog meters. They are very responsive and it’s faster to glance at these meters to quickly assess readings. The only downside is they typically take more room and, franky, are a little “hobby ugly.”
If I end up using AGM batteries the car will need some sort of battery management system. Lee Hart has posted a do-it-yourself battery balancer. He also had posted another idea that you can read about at the bottom of Cameron’s Battery Management page.