Tell tale signs of bad Alternator?

[Lapister]

Was driving up the twities today enjoying the drive when all of a sudden the Battery, ABS, and Brake lights all came on. Kinda got worried but after about 30 sec all went out and car never wavered from performing well. Then about 20 min later same thing but car just died. Could not restart it. Gave all indications of bad battery. Clicking solenoid and all electronics going haywire. Windows trying to go up/down a short margins spoiler going up down. Fortunately, the tow driver had a carry bout jumper pack that started the engine and stayed running. So, is my alternator the culprit here? Soon as he unplugged the jumper it died?

I put a charger to the battery and started car. It only shows 11.8vdc. Would even a bad battery actually show 13.8vdc if the alternator were working?