Thursday, August 28, 2014

Fuel Gauge Works!

The good guys at rechargecar are now shipping the production version of their AutoBlockAMP. This is a current sensor for an EV battery pack that drives a tachometer (tachAmmeter) with current flow in amps, an analog fuel gauge, or a computer for logging, graphing and configuration.

I had been fortunate to be a beta tester and have had several development level ABAmps installed in my evTD over the last two years. Each new version worked a little better as the bugs were sorted out.

I'm pleased to report that the production version is available now and it's sweet!

I designed the evTD dashboard to include a mini-tach between the speedometer and tach whose dedicated function is to display current amp draw. That has worked quite well since early on in the development process. Now the ABAmp also reliably displays battery state of charge on the fuel gauge.

In the absence of a functioning fuel gauge, I've been using the JLD404 Intelligent AH meter to track current consumption in amp hours and extrapolate that into state of charge. For example, if the JLD404 reads 22.35AH, then I know that I've used just under a quarter of the 100AH capacity of my battery pack. Since I don't want to discharge past 80%, then a quick mental calculation says I have roughly 58AH remaining.

 Two problems with that: I'm not so good at quick mental calculations while driving and the red digital numbers disappear in the bright sunlight when I'm most likely to be scooting around in the evTD.

With the production level ABAmp, at 22.35AH the fuel gauge shows just under 3/4 full, and I can see that at a glance. If I assume that it's fairly linear, that means that it would show empty at roughly 80AH used out of 100, giving me a margin for safety. That's something that is set up in the configuration program.

The ABAmp is installed on one of the battery pack cables. I originally had it out in the open for troubleshooting, but now that it's become a reliable device, it's safely tucked away in the box containing all the other sensors. You see it here mounted to the JLD404 shunt with a fuse and the BMS sensor downstream.

After closing the box, it looks very tidy on the component shelf under the bonnet.

Little by little, the evTD is becoming more civilized and reliable. You may note the new TCCH charger and Controller from EVTV Motor Werks. More about that in another blog entry. Stay tuned ...

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