Will A Bad Alternator Ruin A Battery. When it senses the battery is not charging. The best way to find out whether your car needs a new alternator or a new battery is to test both components.
There are however some concerns regarding alternators and their effect on batteries. If the engine starts but dies immediately your alternator probably isnt keeping your battery charged. I dont believe Ive ever damaged an alternator by charging a dead battery and Ive done it plenty of times.
If the alternator is producing no or insufficient charge the battery will simply run flat and this is poison to a lead acid battery.
A failing alternator can overcharge which will damage the battery. In some cases the issues with your car starting may originate with your alternators inability to recharge your battery. To test whether an alternator is draining the battery with the cars engine switched off disconnect the cars electrical system leaving the battery only. But normally they tighten the clamp when finished.
