So looks like manufacture is ISO9001, but service is 13845, so the original fitted batteries will only be supplied to 9001...
The T34 specifications states:
Manufactured in accordance with ISO 9001;2008 and ISO 13485;2003. CE marked (in accordance with the Medical Devices Directive 93/42/EEC).
So to maintain the CE marking you have to fit parts supplied by the OEM. You can't just use parts supplied by a company following ISO 9001 and assume you have not affected the CE marking or safety of the device.