Truck #1 (Nicad)


11jan2011 22648 miles, recharged pack, +4.98kwh, 11.88kwh total, no o/c time. Refilled bearing reservoir with Mobile1.
10jan2011 Flattened entire pack. Jumpered redtop cells.
10jan2011 drove deep discharge, -6.90kwh.

Watered entire pack, 22627 miles, many cells very low. 3.7 gallons H20.

Set charger to 2 minutes of constant voltage time.

10jan2011 22627 miles, watered entire pack. Many cells very low. 3.7 gallons H20.

09jan2011 Drove, deep discharge, -6.93kwh, recharged 2.77kwh, 9.70kwh total. Pack was very stiff during charging and driving.
09jan2011 Recharged flattened pack, +5.88kwh, 11.18kwh total. 20 cells appeared shorted. After 30 minutes of charging they all appeared normal. Cells are marked with a red circle on their cap.
08jan2011 Flattened entire pack, -5.30kwh, 18.9ah, 19.1miles, 11:35pm.

07jan2011 Recharge.+2.94kwh, 8.73kwh total.
06jan2011 Drove deep discharge,-5.79kwh

06jan2011 Recharge, +2.18kwh, 6.53kwh total.
05jan2011 Drove deep discharge, -4.35kwh

27dec2010 Added 10 used and tested nicad cells to pack. 251 total. Set charge voltage to 400vdc.

16dec2010 +3.86kwh (8.3ah) on recharge. 11.19kwh (35.7ah) total recharge.

15dec2010 +4.55kwh on recharge. 11.59kwh total recharge.

15dec2010 -7.33kwh (27.4ah) @ 30.1 miles, 244.3wh/mi, dry, sunny, warm. Errands, highway and city driving. Heater. SJ loop.

14dec2010 -7.04kwh @ 27.7 miles, 254wh/mi, raining, cold, dark, no no heater. SJ loop.

241 cells installed. 2 shorted green top cells removed. 24 Redtops watered. 3 clear tops watered.

27nov2010 -4.55kwh, 20.3 miles, 243wh/mi

26nov2010 -4.13kwh, 15.55 miles, 265wh/mi

I’ve been working like a dog on making an electric vehicle system for a guy on the east coast. It’s been assembled for days. Runs too. But it has this kind of miss to it. Almost like it’s got one bad spark plug wire. It just runs rough. I’ve not seen that kind of problem before with an AC electric vehicle system.

Also have the spot welder nearly assembled. It just needs some finishing. I hope to create a process to spot weld braided flat cable to lithium battery cells. The cable allows flexing without breakage. Mostly for our combat robot buddies. For automotive use it’s not really necessary. But it will be a great process to have under my belt.

After this system gets shipped, I have gathered all of my hand drawn individual schematics, and will create one large schematic for the entire Dolphin main board. I have almost every square inch documented. Just a little remains. But even a mostly completed schematic will be helpful in debugging. I’m still deciding what cad package to use.

Lead acid battery’s are the most expensive technology in our vehicles on a $/mile basis. If a good lithium pack could be assembled, it would make for a lighter and far more efficient vehicle.

In the near term I’m building Lithium modules from ten A123 cells in parallel. That’s a 23ah module. Not much harder to make a 20 cell/46ah module. I’m guessing based on my records, that my truck could go 40 miles max on 23ah since the pack would be so much lighter than even the nicad that I currently have. 70-80% of 40 miles is 28-32 miles. That’s a reasonable range for my city driving needs. Each 10 cell module will run about $125 in just cell costs. That’s $3250 for 154lb bare pack. There still has to be a housing of some kind designed to hold the module. It will use up just one half of the battery box. Leaving the other half for another pack as funds allow. Factory packs weigh from 1400-2200lbs. Can you imagine the range and efficiency increases from loosing up to a ton of pack weight??

CAD model of 20 cell A123 module. Displaces 2 flooded BB600 nicads.

Right now the large format cells that most EV folks are using, have very poor regen capabilityof around 0.3C. On a 100ah cell, that’s only 30 amps of regen allowed. Our vehicles have up to 200a with stock settings. 250 amps with modified settings. A 10 cell module can handle 100 amps of charge/regen current for 15 minutes at a time. So I can easily see them handling 200 amps for 5-10 seconds when regen kicks in with modified software, under specific conditions. In other words they are very low impedance cells that can handle our regen needs nicely.

As for discharging, the A123 10 cell module can handle 700 amps of discharge continuously, and up to 1200 amps for 10 second bursts. Our vehicles can only discharge at 200 amps stock or 250 amps in a modified configuration. Here is the data sheet from A123 on this cell.

These cells have a very long cycle life. 1000 cycles at the max ratings listed. Double that with any care at all. The factory told Bill Dube that if a person can tolerate a loss of 50% capacity over time, then these cells can go 10,000 cycles. Most lead packs lose 50% capacity at 200-300 cycles.

For all of these reasons I’m building an industrial spot welder for making A123 modules. Not just for EV’s, but for the Combat Robotics crowd as well. They use these cells without a BMS and they still last a decent amount of time. Far less than they could, but those folks are happy with the performance and longevity.

Each bare 10 cell module will be 66mm wide x 260mm long. That’s 2.6″ x 10.24″. There has to be some kind of structure built to house the module and some stout connections designed so they can be connected together into a pack. I’m thinking of making the structure look a lot like a flooded nicad cell. In fact I wonder if a nicad cell housing could be adapted as the structure. These modules won’t need to be strapped tightly together like the large format cells require so they don’t over expand and die. These cells will never expand.

In theory, a 23ah pack would be 100 modules. This could fit into the Prizm battery tray. My truck holds 126 nicad cells in each half of the battery box. So it could hold 126 A123 modules per side, for a max of 252 modules per truck. The stock charger could not charge them up past 400v so only 100 modules would be fitted per side. A second 100 module pack could be added to the remaining side if desired, and wired in parallel.

I have a couple of dozen A123 cells and the 10,000 amp (5 ms) microprocessor controlled spot welder is under construction. I plan to make one 10 or 20 cell module to take the place of 1 or 2 nicads in my current pack, for testing.

If you have not noticed or heard, I’ve opened the US Electricar.net store for USE owners so they can get repairs and parts to keep their vehicles running. There are links on this blog to take you there. Enjoy!

Since I am swapping around complete Dolphin systems for testing, it made it very
easy to reach down and pull out a water pump brush. Was I surprised. The brush
still had about 85% of it’s length left after over 10k miles were put on it. The
originals only lasted a total of 10500 miles! What an improvement! If you look
at my photo album there are pics, descriptions and part numbers of the brushes I
bought and mdified for my water pump. They were only around $15 or something
compared to the $75+ factory brushes.

I thought for sure I’d be replacing them again. Some day I’ll pull the motor out
to check the commutator for wear since these are obviously harder brushes. Rough
math shows they will last about 60-70k miles.

Seriously. It’s freakin’ solved after 4 years of research….

One of the boards that arrived for repair last week, was by far the worst I’ve
ever seen for dropouts, and it flashed the fault indicator in a very radical
fashion. It is now perfectly drivable!! No dropouts under acceleration or regen!
I was in total disbelief!! It works? Must be a mistake!! So I grabbed the second
board in for repair. Dropped out every 15-20 seconds. Made the same
modifications to it. Now it’s smooth as glass too! Zero dropouts under
acceleration or regen!! I had a third board laying around for years who’s only
crime was having massive repetitive dropouts. The modifications completely
stopped all traces of dropouts on it too. All 3 of these boards drive perfectly
now! Am I dreaming!!?? Feels like the Twilight Zone around here!!

Three boards saved from the junk pile. I have seen many more just like them.
That feels so good!! Many owners have this problem right now.

The Dolphin hardware has component values that are just barely within spec. With
miles of driving, time, and thermal cycles, the hardware goes out of spec, and
the Dolphin starts faulting, usually without any faults shown in Dolcom/Dol7.
I’ve posted this in the past. But the faults are felt as a sudden shudder in the
drive train. An instant loss and then instant return of power lasting only a
split second. It can rattle your fillings loose!! Some do it rapid fire, one
dropout after another. It’s all the same problem with the hardware going out of
spec. I found the faulty hardware!! Finally!!

During this research, I found an old quality control document from USE. It was a
long list of things that needed to be checked on their test fixture after each
board was assembled. The items on that list were very telling. So I have figured
out the procedure for checking most of the items on that list on my test
fixture. This ensures that the board gets thoroughly checked. I use it on every
board, just like the factory did.

Since it’s still very cold over most of the country, now is the best time to
have the offending boards with dropout issues repaired. The cold always makes
the dropouts worse. It’s the best season to ensure that the boards work in the
worst conditions of the year. Dropouts are less common in the warm months.

Send me your board and I’ll make the classic dropout modification and put your
board through the checkout list on my test fixture for $50 + shipping. Pack your
board very carefully, like it was your first born baby.

Mike

I finally got around to putting fuses in the P12V_Bat and Key_On_In lines on the #1 truck. I tried to use 1/4 amps fuses, but the current drop was so much that the Dolphin would not boot. They measured 5 ohms on each fuse. I measured several and they were all the same. So I went with 1.0 amp fuses that measured about .3 ohms each. Very clean. I’ve done the same thing to the #2 truck. It was much easier to spend 3 minutes removing the junction boxes from the trucks and doing the work on a bench.

I also put a spring inside the 3/4 inch heater hose that was kinking. It now has a nice curve to it. The spring is just plated steel. We’ll see how long it lasts. At least this way the new high performance heater will always get adequate coolant flow to protect the heater element from overheating.

Here is the #2 truck Junction Box with it’s new pair of fuses.

This past Saturday I went to the EAA meeting expecting to plug in and charge.
Didn’t happen. The GFCI had tripped on the Dolphin. Different outlets and a few
resets were fruitless. Vehicle still ran fine, but the GFCI would fail.

Here are the steps I took:

-Plugging in at home. GFCI still failed.
-Swapped the GFCI out with another unit. GFCI still failed.
-Visually inspected inside Dolphin. Nothing unusual.
-Isolated ground on AC line with 2 prong outlet adapter. GFCI did not fail.
Charger still works.
-Removed J2, the largest connector on the Dolphin. GFCI did not fail!
-Reconnected J2. GFCI failed again.
-Started truck. Measured ISO in Dolcom. Was -130 points below pack voltage. Not
good. Oh look, the pack has all of 4 bolts holding the lid on and it rained for
2 weeks….
-Took the lid off. No puddles of water found. But had a high humidity feel/smell
to the pack. This backs up the -130 count found on ISO in Dolcom.
-Hung the 12″ fan from the bed and let it blow on the cells all night.
-Next morning GFCI stopped failing. Charges fine on 120vac and 240vac.
-ISO at -100 counts below pack voltage, but pack much dryer feeling/smelling.

Time to go ground fault hunting in the pack again.

Tonight’s test drive showed that the pack has improved. It held it’s voltage with all 251 cells in circuit, up above 310v for about 3 miles. And then declined from there. Much better, but not as good as a complete pack deep discharge. The 14 cells have not had the benefit of a major overcharge. So I’ll try to get to that this weekend.

So the next morning the pack was still soft. The voltage sagged right away. So I electrically removed about 14 cells from the pack so the charger could keep the current level up around 1-1.5 amps even at full voltage. This will overcharge the nicads and help equalize them. Flooded cells are the only ones you can get away with this. So the charger was programmed to stay on an extra 5 hours after full pack voltage, 400v, was reached. The pack was charged like this all week.

A couple of days ago, I noticed that the resting pack voltage after the charger shut off during the night, was very low. About 306 volts. This concerned me. The first day the resting pack voltage in the morning was 325v. But today it occurred to me that I may have finally gotten what I was trying to achieve. The pack’s cells are now all at the same state of charge. So the cell to cell voltage is closer. With 237 cells in circuit (14 removed), at 306 volts, that’s 1.29v each cell. That’s a bit low. Usually the cells are about 1.35v to 1.4v after sitting for hours. I am guessing that the cells hit the knee in the curve as a group, and the voltage starts to go down as the cells are overcharged. This is some fairly serious overcharging. But it shows that the cells now are more equalized.

Midweek I reduced the overcharge time from 5 hours to 2 hours.

This weekend I’ll reattach the 14 cells that were taken out of circuit and see how the whole pack is acting. Although the 14 cells did not get the huge overcharge, the pack should show improvement. I could add some overcharge to the 14 cells before closing the pack up just to try and bring them into the same state as the rest of the pack. I’ll actually make sure I do that.

The bottom line is that with 3 different versions of the same cell, they are getting worn out as exhibited by their impedance being high. This allows the pack voltage to rise artificially high and make the charger think the pack is full when in fact many of the cells are not fully charged, resulting in a sagging pack.

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