Why do you not supply batteries with your used defibrillators

We have a vast experience of over thirty years with defibrillators and we feel that since it is a life saving item of equipment and that we have no knowledge of the history of the batteries with a used machine we will not pass the risk of a battery failure on to our customers. Batteries have a finite life anyway and may be expected to fail anytime after they three to four years old, many go on to last much longer of course but we can’t judge which. The lights on some batteries help but we are not prepared to risk reliability in the field.