New battery, no start?

[Lazr111]

This is a repost of my thread in the Electrical forum for visibility.

Ok, I recently got a new battery because my old one wasn't holding a charge... With the new battery, my car still doesn't want to start. I'm getting 9.5-9.8V with ignition on, engine off, and the starter just won't turn. If I jump it, it will start, but it seems slow. I'm just looking for what the culprit might be, and what I need to fix/replace.
TIA

[jlevie]

Where are you measuring that voltage? It is way too low for system voltage with a fully charged battery (should be 12.7v).

That low a system voltage implies a bad connection somewhere. Start at the battery and work forward through the power distribution system until you find the point where the voltage drops. The problem will then be between that point and the previous good measurement.

[SpecM]

sounds like loose/corroded connections to me

I agree with JLevie, voltage accros the battery should be at least 12.5v with no load

[Lazr111]

Its 9.5V with the engine off, around 13 with the engine on. My head unit has a voltage read-out, which I don't entirely trust, but its proven relatively reliable so far...

[nando]

just because the battery is new doesn't mean it is good. if you are only getting 9.5v then it's probably bad. have it tested before you pull you hair out looking for bad wires.

[kommissar]

The low voltage is weird. Here's a problem I once had where my car would not start, which may or may not help you.

When this happened to me, the positive terminal from the battery was not making good contact with the starter. As a result, the current was arcing from the wire straight to ground via a nearby bolt. This resulted in a short circuit periodically when I tried to start the car, even though the battery was fine. The solution was to clean up the dirt and carbon that built up around the starter terminal. It's worked fine ever since!

[Liam]

If the battery is good (have it tested) you probably have a drop.

Check all of your connections both hot and ground.

[Lazr111]

Back from the dead.
Had the Battery tested (group 48), tested out perfecly.

I've tightened as many connections as I could find.

What now?
Thanks

[jlevie]

Use a meter and follow the main power lead from the battery forward to find the area that is causing the voltage drop.