EV Q&A: range, cycles, when do I replace the pack?

[Bruce {EVangel} Parmenter <BruceDP@iname.com>]

EV Q&A: range, cycles, when do I replace the pack?

{As POSTed to the ELectric Vehicle List}
[on a conversion EV using lead-acid flooded wet cell batteries]

- Yes, range will decrease toward the end of the battery's cycle life.
  The Escort EV uses US125 EV batteries which similar to the T125.
  You have a 17 mile trip to your work.

 The EVbatt report link http://members.aol.com/brucedp/evbatt.txt
 I POSTed [ref: http://www.crest.org/ev-list-archive/msg01128.html ]
 states:

Bat.    20 AH   Wt. pack   pack  range  Cycle  miles  miles X cycles
type     rate  Lbs. volts   Wt.  miles  life   /Lbs.  /Lbs.

T-105    217   61     96   976   59.4   754   .06086   45.89 \
                     120  1220   74.2                         |
T-125    235   66     96  1056   64.3   650   .06089   39.58  | 6 volt
                     120  1320   80.4                         >
Batteries
T-145    244   71     96  1136   66.8   625   .05880   36.75  |
                     120  1420   83.4                        /


 Cycle Life test - T105 Wet cell battery
Capacity
100%-     .  .   .                                              -100%
    |   .   |          .     .      .       .     .
80% - .     |                                           .       - 80%
    |       |                                           |
60% -       |                                           |   .   - 60%
    |       |                                           |   | .
    |       |                                           |   |
    |       |                                           |   |    .
    |       |                                           |   |
    |       |                                           |   |      .
----------------------------------------------------------------------
  New      100    200    300    400    500     600     700     800
Cycles


 Extrapolating for a T125, at 600 cycles you would be at 80% capacity.

- As I had POSTed [ref:
http://www.crest.org/ev-list-archive/msg01015.html ]
  and it now states on my Escort web page:
   http://members.xoom.com/BruceDP/escort/
  * range: 45 miles @ 55 mph / 35 miles city (worst case driving)

  80% of 45 miles is 36 miles. At the end of cycles, your range would be

  36 miles.

- 80% capacity would be 600 cycles. A full cycle would be more than the
  amount you are using to go to work and back (17+17=34). But as a worse
case,
  let's assume each commute you make is one cycle. By your calculations,

  * you would have two years of use at that capacity.

  If you were to able to have access to an 120 VAC at work, you could
extend
  the time to replace the pack as you would not be depending on a 80%
  capacity. Your commute would be 17 miles.

- No. The number of charges does not equal the number of cycles.
Example: If
  you were to make a short 5 mile trip the store and then recharge. That
is
  not a full cycle. Since each charge would be for a different amount of

  a cycle (or amp hours put back into the battery), it would depend on
your
  driving to how many charges you would perform.

- The Escort was *optimized for the speed limit at the time, 55 mph.
  As with a gas car, the faster you go, the worse the range (or mpg). I
have
  experienced that at 65 mph, the battery current meter reads 200 amps
vs
  100 amps at 55 mph. Your range will be less.

- Yes. Eighteen 6 volt batteries connected in series: 6 * 18 = 108

- No. As Gary of www.innevations.com had stated in his POST:
  [ref: http://www.crest.org/ev-list-archive/msg01010.html ]

A 108V system with flooded batteries needs to charge to at least 135V!
Each 6V battery is charged to 7.5V x 18 = 135V.  This is an easily
understandable mistake since 18 x 6 = 108.  After charge the batteries
should settle down at rest to about 119V.  During driving when the
batteries reach 108V when NOT under load you are more than half way
dead.

...
  The charging voltage must raise higher than the pack voltage to
reverse
  the current flow and charge the battery. As Gary had stated, the
charger's
  finishing voltage will be higher than the rate 108 volts. This has to
do
  with the battery chemistry, and is described in the EVbatt report
  (mentioned above). The Escort's onboard K&W charger is set to charge
  a 108 Volt pack. All you have to do is plug it in and it will do the
rest.


--[edited]
Date: Wed, 29 Dec 1999 11:21:37 -0800
From: Philippe Habib <phabib@us.oracle.com>
Subject:  Escort

-I'm under the impression that the range will decrease as the batteries
age so I'd like to have enough of a buffer in the range that I can make
my commute for 3 years with those batteries, not just for another year
or so until the batteries start to age.

-Do you know how far the car can go now and how far it ought to be
able to go in about 3 years?

-If we assume 6 charges a week (5 times to work and once on the weekend)

for 48 weeks that adds up to 288 charges per year.

-Is it reasonable to expect 800-900 charges for batteries?

-If the car has the battery capacity and I'm willing to sacrifice range,

can the top speed be raised to about 65 from the current 60?

-How are the batteries connected? Is it 18 batteries in series?

-If so, then I guess the charge voltage is 10A at 108 (nominal) volts.

Thanks.
--