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Power problems with a nissan altima 1999

So my battery was sitting at 11.90 volts and should be steady at 12.50 volts or higher and nothing is wrong with my battery as there is no corrosion and it is somewhat new. so i looked at the alternator and it was black so i thought it was going out. So i popped a new alternator from auto-zone on and it still stays at 11.90 volts so that got me, electrical connection is hooked up, positive is tight on as well as the negative, all the bolts are tight on there, and the belt tension is correct according to the owners manual. It is definitely not the new alternator because it came brand new out of the box. With it staying at 11.90 volts the car jerks a lot due to not enough power being supplied, it is having a hard time starting due to lack of charge to the batter, and the only way to start it without any jerking is to give it gas. Is there anything i missed? Any help would be appreciated, thanks in advance!

How old is the battery? A fully charged battery should read 12.6 volt and should stay steady when headlight are turned on.I think your battery needs replacement or at least get it tested by your local mechanic.They will use an ampmeter to check cranking power.

I mean a new battery and charging system check is in order, but the car should keep running, I think you have additional problems besides the battery. Any Check engine lights?

I check my own battery, my battery is fine. There was no check engine light on, but i figured it out. It was a faulty 3 dollar fuse. By changing the fuse the battery shot up to 13.20 volts, and the car no longer jerks. So lesson learned check your fuses first.

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Could you elaborate on this?

Where exactly were you measuring 11.9 volts? directly at the battery or somewhere else? Because a battery reading that low would be bad, irregardless of any fuse.

Get a 12V meter that plugs into your cigarette lighter. If (when?) that fuse blows again, you’ll know immediately.

Thanks for the advice.

BillRussel their is a fusible link between the alternator and the battery. if the battery reads 13.20 on the meter it is going to drop regardless to 12.50 because depending on your battery it can only hold a certain amount of volts. When you turn the key the car uses the electricity from the battery to start the car then it runs off the alternator. So basically you can unplug the positive while the car is running and it will still be on. So if the fusable link is broken then their is no way for the alternator to charge that battery the way it should. So that is why it will not pass 12 volts. Your battery acts as a backup if your alternator goes out you have at least 10 to 15 minutes before your battery is drained. So if your battery reads 11.90 do not automatically think the battery is bad, because you will be wasting money on something that worked in the first place like my alternator.