PROMISSORY NOTE

$131,800.00                                                        July 27, 2001


     FOR VALUE  RECEIVED,  in the  manner,  on the dates and in the  amounts  so
herein stipulated, the undersigned,  Tanisys Technology, Inc., ("Borrower"),  at
12201 Technology  Boulevard,  Suite 125, Austin, Texas 78727, PROMISED TO PAY TO
THE ORDER OF CHUCK COMISO, individually ("Lender"), at Austin, Texas, the sum of
One Hundred Thirty-one  Thousand Eight Hundred and 00/100 Dollars  ($131,800.00)
in lawful money of the United States of America,  which shall be legal tender in
payment of all debts and dues, public and private,  at the time of payment,  and
to pay  interest  on the unpaid  principal  amount  from the date  hereof  until
maturity at a fixed rate  ("Stated  Rate") equal to Ten Percent (10%) per annum,
not to exceed the maximum non-usurious interest rate permitted by applicable law
from time to time in effect, as such law may be interpreted,  amended,  revised,
supplemented or enacted (the "Maximum  Rate"),  provided that if at any time the
Stated Rate exceeds the Maximum Rate,  then interest  hereon shall accrue at the
Maximum  Rate.  In the event the  Maximum  Rate  applicable  to this Note should
subsequently  be changed,  then interest  hereon shall accrue at a rate equal to
the  applicable  Maximum Rate until the aggregate  amount of interest so accrued
equals the aggregate  amount of interest  which would have accrued at the Stated
Rate without  regard to any usury  limit,  at which time  interest  hereon shall
again accrue at the Stated Rate.  The principal  amount of this Note and accrued
interest are payable as follows:

     The earlier of August 6, 2001 or upon the closing of the private  placement
of Borrower's Preferred Stock.

     If not sooner paid, the entire outstanding  principal balance of this Note,
together with all accrued but unpaid interest shall be due and payable on August
6, 2001.

     In the event of  default  in the  making of any  payment  herein  provided,
either of  principal  or  interest,  or in the event this Note is declared  due,
interest shall accrue at the Maximum Rate.

     Borrower hereby agrees to pay all expenses incurred,  including  reasonable
attorneys'  fees, all of which shall become a part of the principal  hereof,  if
this Note is placed in the hands of an attorney for  collection  or if collected
by suit or through any probate, bankruptcy or any other legal proceedings.

     Interest  charges will be calculated on amounts  advanced  hereunder on the
actual  number of days these amounts are  outstanding  on the basis of a 360-day
year, except for calculations of the Maximum Rate, which will be on the basis of
a 365-day or 366-day year, as is applicable.  It is the intention of the parties
hereto to comply with all applicable usury laws; accordingly,  it is agreed that
notwithstanding  any  provisions  to the contrary in this Note, or in any of the
documents  securing  payment  hereof  or  otherwise  relating  hereto,  no  such
provision  shall  require  the payment or permit the  collection  of interest in
excess of the  Maximum  Rate.  If any  excess of  interest  in such  respect  is
provided for, or shall be  adjudicated to be so provided for, in this Note or in
any of the documents securing payment hereof or otherwise relating hereto,  then
in such

<PAGE>

event (1) the provisions of this paragraph shall govern and control; (2) neither
Borrower,  endorsers  or  guarantors,  nor their heirs,  legal  representatives,
successors or assigns,  nor any other party liable for the payment hereof, shall
be  obligated  to pay the amount of such  interest  to the extent  that it is in
excess of the Maximum  Rate;  (3) any such excess which may have been  collected
shall be either  applied as a credit  against the then unpaid  principal  amount
hereof or  refunded to  Borrower;  and (4) the  provisions  of this Note and any
documents securing payment of this Note shall be automatically  reformed so that
the effective  rate of interest  shall be reduced to the Maximum  Rate.  For the
purpose of determining  the Maximum Rate, all interest  payments with respect to
this Note shall be amortized,  prorated and spread  throughout  the full term of
the Note so that the  effective  rate of  interest  on  account  of this Note is
uniform throughout the term hereof.

     The laws of the State of Texas shall govern the provisions of this Note.

     Borrower  acknowledges  that the  principal sum of this Note is composed of
$95,000 in back salary, $6,800 in Federal tax penalties, and $30,000 advanced on
behalf of the  Borrower  to pay down its  obligations  to the law firms of Smith
Underwood and Perkins and Howard, Rice, Nemorovski, Canady, Falk & Rabkin.

     Each surety,  guarantor  and  endorser  agrees that this Note and the liens
securing its payment may be renewed and the time of payment  extended  from time
to time, without notice and without releasing any of the foregoing.

     Borrower and any and all  endorsers and  guarantors of this Note  severally
waive presentment for payment, notice of nonpayment,  protest, demand, notice of
protest,  notice of intent to accelerate,  notice of acceleration  and dishonor,
diligence  in  enforcement  and  indulgences  of every kind and without  further
notice  hereby  agree  to  renewals,   extensions,   exchanges  or  releases  of
collateral,  taking of additional  collateral,  indulgences or partial payments,
either before or after maturity.

     Borrower  may prepay this Note,  in whole or in part,  at any time prior to
maturity without penalty, and interest shall cease on any amount prepaid.


                                            TANISYS TECHNOLOGY, INC.


                                            By: /s/ Terry W. Reynolds, VP
                                                -------------------------------
                                                Title: Vice President and CFO
                                                -------------------------------


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