Risks SOP, Medical Device File and auditing ISO 13485

My first question is: do I need to have a Risk Management SOP?
My understanding is that we need assess the risk on the devices associated with the medical industry (we only manufacture the batteries) and I'm already drafting up a Risk Register for ISO 9001:2015 but do I actually need an RM SOP and, if so, what needs to be in it? I'm also adding a risk assessment to the bottom of each ‘Product Change Form’, ‘Calibration – Adjustments Form’, and Corrective Actions Form to monitor any changes for associated risks.

First, instead of implementing ISO 13485:2012, you should implement ISO 13485:2016 since this is the latest version of the standard and in this way you will avid later transition process.

When it comes to risks, ISO 13485 requires organization to “document requirements for risk management throughout produ ct realization”, translated to plain English, this means that you need SOP for risk management.

I've put together Medical Device Files – neither one really takes up more than an A4 page listing the customer specs, QMS control documents, procedures surrounding how we measure/control process performance – does there need to be more? Do you have any templates/examples for something like a non-medical battery that would be used to power a medical device? (I can send an example of what I'm using?)

The standard does not defines the volume of the documentation or the mandatory elements other than the ones you've mentioned, so you are compliant with the standard in this regard. Unfortunately, we do not have templates specific for non-medical batteries, but here you can download free preview of our ISO 13485 Documentation Toolkit https://advisera.com/13485academy/iso-13485-documentation-toolkit/

I've made sure our internal audits are ‘process approach’ and documented with both 9001 and 13485 requirements but I'm unsure as to whether 13485 audits need anything extra?

ISO 13485 does not have any additional requirements regarding internal audit compared to ISO 9001, so you don't have to do anything more than ISO 9001 requires.

I've also gathered all of the regulations such as IATA and IEC 62133 that affect batteries and listed them on a controlled document to monitor for changes that may affect the business.

If you identified all legal requirements regarding your product, you are compliant with this requirement of the standard.

Is there anything else that the assessor will want to see that I'm not considering?

From your questions I see that you covered the key points of the standard, so I don't have anything to add.