We have many auto electrical companies that use, buy and ask our advice.

We have this info to offer:

Auto electricians test their batteries for cranking power, the ability to start the vehicle. Even a battery of only half-life remaining will accept a charge and work off an alternator. A CCA test normally indicates a lack of power which is what is required to turn over an engine. Let's not forget they are used to testing start batteries, alternators, and starter motors and their CCA testers are used to test cranking power and not reserve capacity. Many are also advised on what's needed to test by the battery supplier they are affiliated with. Only if they speak to a specialty product manager within the distribution business will they be given info regarding the requirements to discharge test a battery correctly.

We are also aware of one major distributor only using a 75A discharge current to calculate capacity. Many batteries smaller than 100Ah won't even have technical data to support a discharge of this large capacity so the test results aren't accurate.

You need to visit a marine electrician or a well-trained motorhome service centre to get specific info and ensure it's a discharge test done to industry standards. If the test is free it isn't being done right because it takes time and effort to do this properly and most businesses require payment for their services.