Dead battery?

[Dali007]

Hi guys,

I have a weird issue that happened the last couple of times that I used my engine.
Run for 1 hour then quit, tried to start it and the battery was dead, switched to house battery and it started.

If the battery is not holding charge, should it matter? I mean once the engine is on it runs on gas and the alternator charges the battery, my engine should not stop working due to a faulty battery or what am I missing?
My mechanic recently checked the alternator and he said it's working properly.

Thanks so much!

[Ando]

Get a second opinion on the mechanic’s stmt maybe? Or test the alternator yourself.

[sastanley]

Depending on how your electrical system is set up, the alternator probably only charges the battery which corresponds to the 1-2-ALL switch.. If you have to switch over to the house to start the engine, the start battery probably is not getting charged back up when the engine is running. If you are careful you can usually switch between batteries when at idle, but it is usually advised to make sure you do not go thru OFF when switching or it can fry the diodes in the alternator when in a no load state. (Personally, I have heard varying stories about this..it seems more 'dangerous' when the alternator is working hard, but less likely to do any damage if the alt. is not pumping out lots of amps.)

Also, putting the selector on ALL is not always the answer either...a bad battery can suck the life out of a good battery in the ALL position.

Did you check the water level in the battery or put a meter on it yet ?

[Al Schober]

You need voltage at coil + to make spark. A 12V test light (or a meter) will tell whether you have voltage. The alternator won't put out anything until the engine is running.