Third Drive of 120V System

Well, I don't know why we put it off more than a week, but we finally gave the new & improved 120V Civic a 3rd test drive. Mostly I guess I was afraid something else would go wrong.

But finally, tonight Alisa and I drove a closed 1.7 mile course starting from our house, three times around for a grand total of 5.1 miles, with an elevation change of about 140 feet from the lowest point on the route to the highest. That's 420 feet of rise & 420 feet of fall in 5.1 miles, or an average slope of 3.1%. Of course, most of the uphill occurs in about 0.5 mile of the course, and the rest of the course is level or downhill (it's a closed course!), so actually it is more like an average of 5.3% incline over 1.5 miles and 2.2% decline over the remaining 3.6 miles.

The KDH14500B did pretty well, IMO. Yes, it is dog-slow off the line, but if you have it in first gear and really step into it, it does alright. Not as good as a golf cart off the line, but then it gets up to 20-ish in first gear pretty easily, and subsequently up to 35 mph in 2nd quite easily. Haven't taken it over 40 mph yet.

But coming up the steepest part of the hill, which is from the low point on the course up the one block to our driveway, we couldn't keep it in 2nd gear. The old 72V controller would hold about 18 mph in 2nd gear. But the 14500B really wants you to shift down into first, and then it will also hold about 18 mph up the hill. Now, we did add 300 pounds of batteries and chargers that weren't there before, and it is still a 500A controller. Probably if we'd added 300 pounds into the Civic with the 72V controller, it would have had more problem with the hill then, too.

Afterwards I went around and felt the connections and battery temps and etc., and measured voltages, and everything seemed pretty copacetic. The controller and the motor were both very warm, enough that if they were any warmer at all I would have said they were hot. The starting voltage while still on float charge was 133.0V, and the ending voltage was 127.1V at rest before plugging back in. The six (92Ah) C&D Tech batteries were between 12.60 and 12.65 at the end of the drive, and the four (115Ah) Discover batteries were between 12.90 and 12.94.

And that's my report on drive #3.

Insulated Rear Battery Box

Today I built the battery box for the 4 Discover EV31A-A batteries in the far rear of the Honda. From start to finish, it took me about 9 hours, not including breaks! My wife was helping me for about the last 3 hours, too. The tasks included: Unwiring the 4 batteries and removing them from the car. Cutting a 1/2" styrofoam sheet to go under the 4 batteries. Wiring up the 4 heater pads and the thermostat. Mounting the heater pads in the car. Replacing the 4 batteries. Cutting and fitting the styrofoam walls of the box. Fitting a lid. Wiring the batteries all back up. Mounting the thermostat. Cleaning up.

Now all of my battery racks are running at a nice toasty 90'F!

Some pics:

The box, about 1/2 finished, putting together an inside corner.

The corner after it's been slid into place

Buttoned up with the cover.

[Yes, I remembered to get the scissors out! :-)]

The thermostat hides under the block sticking out. Hot water heaters place their thermostats under the insulation, so that the entire body of the thermostat heats to temperature. I mounted the thermostats on the batteries the same way, surrounded and covered by insulation.

Battery Cost Analysis

I've been encouraged to post my recent evaluation of the cost of various models of traction batteries for EVs. I basically ran the numbers three ways, to answer three different questions:

1) What is the cost per mile to use a particular type of battery? This is answered by the "Total, cents/mile" row under the "System Detail" section. I didn't include the cost of support systems such as charger or battery balancers because, although they may cost more for one type of battery than for another, they are a fixed cost and don't need to be replaced when the battery pack is replaced.

2) What is the overall cost to use a particular type of battery for 120,000 miles? This is answered by the "Cost, $ (incl. electric)" row under the "120K miles" section.

3) How far can you drive on a particular type of battery before you exceed the cost of buying Lithium batteries at today's prices? This is answered by the "Total Miles" row under the "Equal Lithiums" section.

The Range figures were obtained from EV Calculator, using a '92 Metro, ADC FB-4001A, Kelly controller, battery specs available online, Range calculated to 80% Depth-of-Discharge, and a driving mix of 85% @ 30-40mph in 2nd gear and 15% @ 60mph in 3rd gear.

Here are my calculations. I'll let you interpret the numbers as you like. Sorry it's showing up triple-spaced; I can't find a way to correct that.

Cost	Battery Mftr / Model
Analysis
Prices as	Optima	Trojan	Discover	Sky Energy
of 6/15/09	D34M	T-1275	EV31A-A	SE100AHA
Battery
Detail
Chemistry	SLA-AGM	FLA	SLA-AGM	LiFePO4
Cost, $	188	200	490	121
Source	amazon	batteriesin	batteries	evcompo
	.com	aflash.com	direct.com	nents.com
Voltage, V	12	12	12	3.2
Weight, lbs	43.5	84	74.1	7.04
Capacity, Ah	55	150	115	100
System
Detail
#(batts)	12	10	12	45
Voltage, V	144	120	144	144
Pack cost, $	2256	2000	5880	5445
Capacity, Wh	7920	18000	16560	14400
Weight, lbs	522	840	889	317
Range, mi	25	40	35	60
#(cycles)	600	600	600	2000
Miles/pack	15000	24000	21000	120000
Electricity, $	428	972	894	2592
(@9¢/kWh)
Total, ¢/mi	17.9	12.4	32.3	6.7
120K miles
#(packs)	8	5	6	1
Total miles	120000	120000	126000	120000
Cost, $	21469	14860	40645	8037
(incl. elec.)
Equal
Lithiums
#(packs)	3	3	1	1
Total miles	45000	72000	21000	120000
Cost, $	8051	8916	6774	8037
(incl. elec.)