Big testing excitement today:
1.) Under any sort of real world load it's become obvious that one of the batteries is failing. Only good for 6-8 miles now and that's without any really high current loading (no 300A blastoffs or hills.) We captured one of the failure events with the datalogger and sent the file off to Sean. He agrees it's bad and apparently it will be warranted. May swap in a battery from the other car to get this one back on the road.
2.) Load test: we went out with four people on the car. Not a long drive or any hills to speak of, but the people weren't exactly lightweight either. It wouldn't hit 45 with four of us in there. Scotty to Bridge: She's givin'it all she's got captn'!
3.) The specs for the new battery management board are pretty much set and Brian may have first prototypes available by mid month. Way to go! Update: Prototype boards arrived and are reported to work exactly as expected. Should have final parts in two weeks. Cool.
Sunday, May 31, 2009
Sunday, May 24, 2009
Always: Flies in my pudding
There's always SOMETHING...
The battery monitoring system has been acting whacky. It reports the last three batteries are continually in 'overcharge' state. The first battery (the added non-standard one) is reported as being 13.2V (which it is) while the others are at 13.4V (which they are) and that the second battery is at about 13.8V (which it isn't, more like 13.6V). Sounds like small differences I know but 0.1V is a big difference in terms of State Of Charge (SOC).
Add to which it almost always shows SOC at 100%, even when the batteries are half discharged. The current indicator shows random stuff and the temperature indication has been variable. We spent part of the afternoon re-routing wires to try and improve matters (assuming it's some kind of electromagnetic interferance problem) and putting in some quick-disconnects to make resetting the system easier. Attaching the sensor modules to the top of the batteries should help with the temp reading. We'll see how it goes.
Now add the fact the Battery Equalization system (BattEQ which is separate) has just been recalled by the manufacturer. Bummer. However this will be less of a loss than you might imagine since the large voltage difference between the first and second batteries causes it to freak out and say: "that difference is too big for me, I'm turning off" so it hasn't been all that much use anyway.
Brian Blocher has a new version of his VoltBlocher product out that is intended for Lead Acid 12V batteries. I'm going to see about getting a set of these and getting some modifications done to them to replace the BattEQ unit. More on this later, it's a pretty significant price/performance breakthrough on the battery management front.
The battery monitoring system has been acting whacky. It reports the last three batteries are continually in 'overcharge' state. The first battery (the added non-standard one) is reported as being 13.2V (which it is) while the others are at 13.4V (which they are) and that the second battery is at about 13.8V (which it isn't, more like 13.6V). Sounds like small differences I know but 0.1V is a big difference in terms of State Of Charge (SOC).
Add to which it almost always shows SOC at 100%, even when the batteries are half discharged. The current indicator shows random stuff and the temperature indication has been variable. We spent part of the afternoon re-routing wires to try and improve matters (assuming it's some kind of electromagnetic interferance problem) and putting in some quick-disconnects to make resetting the system easier. Attaching the sensor modules to the top of the batteries should help with the temp reading. We'll see how it goes.
Now add the fact the Battery Equalization system (BattEQ which is separate) has just been recalled by the manufacturer. Bummer. However this will be less of a loss than you might imagine since the large voltage difference between the first and second batteries causes it to freak out and say: "that difference is too big for me, I'm turning off" so it hasn't been all that much use anyway.
Brian Blocher has a new version of his VoltBlocher product out that is intended for Lead Acid 12V batteries. I'm going to see about getting a set of these and getting some modifications done to them to replace the BattEQ unit. More on this later, it's a pretty significant price/performance breakthrough on the battery management front.
Friday, May 22, 2009
A week of "real"
Yes there really is a back seat and we really have had real people in there. Ya stuff several of the admiring crowd in there and...it still moves, really! There's just some rubbing sounds as we have the springs set fairly 'soft' and it kinda waddles under full load.
The big news is that after we came back from a week of vacation we ended up driving it to work and many trips elsewhere for basically the entire week. A slight increase in the slack in the emergency brake cable system greatly reduced the rear brake heating. There's still a little of that so a bit more tweak may be required. Still 20 trips of over 6mi. each and four over 13mi... ya gotta say overall it's working pretty well. Good enough for the real world.
When the battery temperature is around 40deg.F the top speed is around 42. when it's more like 60deg.F it'll crawl all the way up to 44mph! Of course if there's a hill or even an incline we're talking more like 38-40. Fortunately I drop off the car-pooler during the early section of the trip to work when the max posted speed is only 30, that way I don't have to face the (mild) hills and 45mph posted sections with more than one in the car. Overall it seems to work well enough for the commute, especially (oddly enough) if the traffic is fairly heavy and thus a bit slower.
Nobody has honked or had a hissy-fit...yet.
We still have the pogo-ing front end. Sean thinks it's probably the tire. I gather the quality control in terms of roundness is, um, lacking. I put a video camera on a stick so I could hang it outside the car while moving. The video came out fine, but you can't really see anything conclusive. Guess I'll try swapping out the tire.
The batteries, charger and battery equalizer systems seem to be working OK, though there is no way you would know this from looking at the battery monitoring system. It continually complains that at least three of the batteries are in constant 'overcharge' condition and that another is 0.5V higher than the rest. The SOC meter (State of Charge - battery level) almost always shows 100%, though sometimes it will drop to 95% when we have gone 12 miles (about half the useful range) and the current sensor will still show 29Amps one minute after you have pulled to a stop. The technical term for this is "Boogered."
Gonna have to put some work into that. Having $400 worth of monitoring equipment that gives you no useful information will eventually serve as an irritant. Since we'll have the battery compartment all apart to go after this problem we should get a few useful pictures. Later.
Sunday, May 3, 2009
Straighten UP and fly Left
One of the recent posts on the Yahoo group is on how well the vehicle coasts when you let off the accelerator pedal.
Hmmm, I am definitely NOT having this experience. It will coast a block on the flat (starting at 25MPH) but certainly not two.
I have been trying to diagnose what is going on:
The whole vehicle heads down the street slightly 'crabwise.'
Noticeable but not high pressure on the wheel toward the right is required to get it to go straight. (ie: it wants to wander toward the left all the time.)
The Steering wheel is not straight. Completely straightening the wheel produces a mild left turn. The opposite from what you would expect from the above.
A fairly steeply crowned road (right slope) can get it to go straight.
The front wheel/tire is not very round. Since the beginning the
whole vehicle does a hobby-horse up and down thing that is
especially noticeable around 12-14 mph. It is not the rear
tires as they have been replaced and the wheels balanced. We
have looked at the rear wheels while going to see if they
run true. I thought it might be flatspotting when parked but
the problem is still there after a 10 mile drive on a warm day.
We have checked the steering wheel vs. wheel direction. Using 6ft. long straightedge the wheel, steering wheel and vehicle center-line appear to match up.
Sean in one of his lighter moments suggested a front end alignment. Pretty funny actually.
Brake drag: There is quite a bit of brake drag (I assume) on the right rear wheel. To the point of having the wheel hub quite warm after an 8 mile drive. Being on the right the drag would cause the vehicle to caster to the right. Instead it tends to go left. If anything the drag problem is helping keep it running straight. Yes we have multiple problems.
The vehicle seems pretty stable at speed and tracks well in high speed corners (40MPH).
The investigation is ongoing.
Hmmm, I am definitely NOT having this experience. It will coast a block on the flat (starting at 25MPH) but certainly not two.
I have been trying to diagnose what is going on:
The whole vehicle heads down the street slightly 'crabwise.'
Noticeable but not high pressure on the wheel toward the right is required to get it to go straight. (ie: it wants to wander toward the left all the time.)
The Steering wheel is not straight. Completely straightening the wheel produces a mild left turn. The opposite from what you would expect from the above.
A fairly steeply crowned road (right slope) can get it to go straight.
The front wheel/tire is not very round. Since the beginning the
whole vehicle does a hobby-horse up and down thing that is
especially noticeable around 12-14 mph. It is not the rear
tires as they have been replaced and the wheels balanced. We
have looked at the rear wheels while going to see if they
run true. I thought it might be flatspotting when parked but
the problem is still there after a 10 mile drive on a warm day.
We have checked the steering wheel vs. wheel direction. Using 6ft. long straightedge the wheel, steering wheel and vehicle center-line appear to match up.
Sean in one of his lighter moments suggested a front end alignment. Pretty funny actually.
Brake drag: There is quite a bit of brake drag (I assume) on the right rear wheel. To the point of having the wheel hub quite warm after an 8 mile drive. Being on the right the drag would cause the vehicle to caster to the right. Instead it tends to go left. If anything the drag problem is helping keep it running straight. Yes we have multiple problems.
The vehicle seems pretty stable at speed and tracks well in high speed corners (40MPH).
The investigation is ongoing.
Friday, May 1, 2009
Getting up to speed
A 'basic' 72Volt Xebra SD (Sedan) is good for about 35MPH on the flat. Maybe a little more but not much and it drops to 30 on a mild grade. The GPEV (Sean) 84Volt version is good for a solid 40MPH on the flat and will hold 35 on the same grade. We wanted more of course. There are 45MPH roads on the way to work.
First thing to check was the speedometer. They're notoriously innacurate on Xebra's. We went out and checked it against a car with a known speedometer. Surprize! It's accurate within one MPH!
Second, there's some drag and tracking problems. There will be another post on that.
Third was to change the gearing (in effect) by putting on slightly 'taller' tires.
See the last part of the post below for how that works.
We took off the 145/70R12 tires and mounted 155/80R12. The new ones have about 8% greater circumference.
Results: One mile to get up to speed and then one mile with the pedal all the way down. Same course and full charge in both cases.
Before: 41-Maybe-42MPH
After: 43-Maybe-44MPH
Pretty much what you'd expect. We also ran it up our 'test hill' and couldn't see any speed difference (controller is in current limit mode). I'd say this counts as a success.
We have noticed that after it cools down from being charged the pack shows about 92-93 volts. The controller allows a maximum of 100Volts. Looks to me like there's room for another 6V battery. 90V Xebra anyone?
First thing to check was the speedometer. They're notoriously innacurate on Xebra's. We went out and checked it against a car with a known speedometer. Surprize! It's accurate within one MPH!
Second, there's some drag and tracking problems. There will be another post on that.
Third was to change the gearing (in effect) by putting on slightly 'taller' tires.
See the last part of the post below for how that works.
We took off the 145/70R12 tires and mounted 155/80R12. The new ones have about 8% greater circumference.
Results: One mile to get up to speed and then one mile with the pedal all the way down. Same course and full charge in both cases.
Before: 41-Maybe-42MPH
After: 43-Maybe-44MPH
Pretty much what you'd expect. We also ran it up our 'test hill' and couldn't see any speed difference (controller is in current limit mode). I'd say this counts as a success.
We have noticed that after it cools down from being charged the pack shows about 92-93 volts. The controller allows a maximum of 100Volts. Looks to me like there's room for another 6V battery. 90V Xebra anyone?
Subscribe to:
Posts (Atom)