>but you probably don't want a DC-DC converter running from the main battery all the time. If you have trouble getting power from the main battery, it'll be har

>but you probably don't want a DC-DC converter running from the main battery all the time. If you have trouble getting power from the main battery, it'll be hard to diagnose. I don't get this. If the converter stops working the 12v battery dies and your car stops working. I don't get why it would be easier to diagnose if it only charges when on. I assume you're talking about the converter charging the 12v battery? Even if you aren't it would still be simple enough to have some 12v points to supply external power. Further is it redundancy or doubling the chances of failure? You now have a 12v charger that could stop working, and a 12v battery that could stop working. Both of those break the car. If the main battery goes that's basically bricking the car and you aren't going anywhere anyway