Battery voltage?

[gotboost55]

I have the new apexi turbo ,and it shows the o2 reading and the A/f and it also reads the battery voltage.When i first got it it read 13.8-14.0 for the battery voltage and now in hot weather it goes down below 13 ,and the car also has a hard time starting? Is it time for a new battery?? or alternator ?help would be greatly apreciated!

 

[Korndogg]

with the car off, you should have approximately 12V across the battery.
with the car running and a minimal load on the battery/alternator (lights, wipers, AC, ect, off) you should have about 14.5V across the battery(/alternator). the more things that you turn on, the lower your voltage is likely to be.. but it should NOT drop below 12V with the car running.. it shouldn't even be below 13V, really.
if the voltage has been dropping with the car running, it's probably your alternator.. but could also be the battery.. personally i think i would replace the battery with just about any cheap-o battery. if that doesn't help, put a new alternator in. if it was just the alternator, you'll now have a new battery also and your car should start up with the effortless flick of a key every time

 

[Blk95gs]

my apexi unit reads 11.8v all the time, but my datalogger shows 13.5 and above. its probably a crappy reading or something. i trust the datalogger over the tt

 

[philipkrotch]

my turbo timer reads like 13.8 at startup, then once i get movin its around 14.3.