Battery problems maybe ..plz help

[xMalignancy]

i have an 89 5.0 and when i start it up..the rpms seem to pulse until it finally comes to a steady idle...also the battery gauge pulses with the rpms.. their almost synchronized..im pretty sure its a bad battery but im not sure that the rpms would pulse because of that...if you have any info plz help..

 

[BlownFiveLiter]

It's probably completely unrelated to your battery. Your alternator puts out more output as the RPM increases above idle. See the Surging Idle Checklist for a list of potential fixes to your idle surging issue.