Ben Nelson's Electro-Metro Build thread

[bennelson]

Always start a car in neutral. Gas, electric or other, never start in gear.

If I didn't make a habit of starting in neutral, the story would be much more interesting. Plus, my insurance company would have to buy me a new garage...

[MPaulHolmes]

Ben, it might be a grounding problem. Has Adam talked to you about it yet? The RS232 is basically the 12v ground. The DC-DC was off of the battery pack. So, if it wasn't isolated, the 12v ground was shared with the ground of one of the batteries in the pack. I think you need an isolated DC-DC.

-Paul

[bennelson]

Once again, we have learned that I am good at breaking things.

In fact, I usually learn best when something ends up broken. That way, I know not to do it again.

This time, I managed to fry the logic board in the Open ReVolt "Cougar" Controller. It all stems from hooking up a tablet computer to the controller to use for reprogramming and data-logging.

I got the tablet computer for free, but it doesn't have a battery. Instead, it needs to run from 12V DC to a 12 to 20VDC converter, and into the computer.

I didn't realize that the RS232 port has so much grounding in it, and I somehow managed to push over 20 volts to the ReVolt 12V in.

The other night, I got to stop over at Tom's house (for Robot Night) and I pulled out the multimeter and soldering iron to figure out exactly what parts I broke.

We tracked down that R1 and D2 were both smoked. R1 was easy to replace, and the controller can work fine without D2, as long as you have a known good voltage going to the controller.

Further bench testing showed that the ATMEGA chip was either fried or had a bad case of amnesia. Fortunately, I had a spare one of those from when I did a software update a while back.

UNfortunately, replacing the ATMEGA chip did NOT make the controller work properly again, although it does seem to prove that everything on the POWER board works fine, it's just the LOGIC board that's all messed up.
The 12V DC/DC converter tested out OK, as did the doo-hickey that converts 12v to 5v. However one or two other 5v components may be bad, and I have no really good way to test them.

Paul Holmes offered to help me out by mailing me some spare parts, and possibly even soldering up a fresh logic board.

So, my car isn't running right now, but I sure am learning a lot by poking at electronics with multimeters!

Another thing I learned about the Open ReVolt controller that I thought is kinda cool is that it's much easier to bench-test than, say, a Curtis controller.

For example, a Curtis controller usually has come sort of voltage range, like 48-72V. That means you need at least 4 batteries just to power the thing up (if you, like me, do NOT have an adjustable bench power supply.)
You then need 4 12V light bulbs, or a spare motor, or something similar to use as a test load. It starts to be quite a setup.

On the other hand, the ReVolt only requires a 12V battery for logic power, and almost any voltage you want for the power section. The test load can be a single 12V light. All I needed for bench testing was a 12V battery and lightbulb, a few jumpers, and a pot. That's it! Even I can handle that.

More next time, once I get this thing on the road again.

-Ben

[jackbauer]

As a suggestion you might try one of these:
UNIVERSAL LAPTOP/NOTEBOOK CAR CHARGER/DC POWER ADAPTER on eBay (end time 08-Feb-10 21:13:04 GMT)
use one myself for running a laptop in the car no problems.

[MPaulHolmes]

Hey Ben! My wife and son are going to Oregon this weekend to help my brother in law in his environmental science class, and so my mother in law can see him. It's been like 2 weeks! That's way too long for her to wait to see her precious little baby. hahahaha. No wild little 2 year old around for 1 day! Whatever will I do? Oh yes, now I remember: I'm going to solder the new board on Saturday/sunday. haha

-Paul

[dave koller]

Just a quick hi Ben!

Saw you at MREA.. am just putting your name to that!

Been wading thru Paul & Sabrina's DIY controller

Been on DIY forum too much...

Getting rid of PCM in Saturn - DIY Electric Car Forums

Not really my build thread but look at end posts - !!

[TheSGC]

Is the Metro back up and running?

[bennelson]

The Metro is back up and running.

Right now, it's running at 72V. 5 batteries in the backseat box, and one under the hood, which leaves my cargo area as stock, which I like. I do like the power of higher voltage though.

I have kind of a mixed batch of batteries right now. My range is pretty poor. I am sure that one (or more) of the batteries is somewhat bad, and really lags under power.

Unfortunately, I don't have a really good "monitor every battery individually at the same time" battery monitoring system at this time. My friend Tom has been working on a little monitoring system that uses LEDs as a little bar graph and monitors 4 batteries at a time. It's very small - something like one inch by two inches, so three of the displays in a row would monitor a dozen batteries and still barely take up any dashboard space.

I also still need to reprogram the Cougar controller. It's still running the software stock. I don't have a USB to Serial adapter anymore, as the one I was using broke!

I may end up dragging my wife's old tower computer out to the garage.....

[dave koller]

Ben
what Operating system are you using - I think I have another usb serial cord but not sure where driver went - XP will grab it - let me know...

[bennelson]

Yep, I'm using Windows XP.