Slow cranking speed

[area51]

My W168 (A160) suffers from slow cranking speed on first start-up from cold, after this cranking speed is no problem.

The battery is a one year old genuine MB 62 Ah (correct for the car), recharged using a Ctek charger 5 days ago. Car has been used once since.

Using my trusty multi-meter: Battery voltage= 12.3v. Voltage drops to 10.3v on cranking and starter speed is slow for the first 1 second(ish).

Where do I look next? Is it possible the battery is no good, although it did accept charging ok? All suggestions gratefully received, thanks.

 

[Will]

It might be discharging slightly since you fitted it. 12.3v isn't too bad but I'd expect higher from a freshly recharged new/newish battery 12.5/13v perhaps. You need to check if the alternator is charging - what's the voltage with the engine running, should be 13v+ (probably something like 13.8-14v from memory)

The cold weather never helps though - acid is less potent at low temps hence battery is weaker, engine is cold so the oil is thicker, etc.

Maybe re-charge the battery again, leave it overnight (disconnected from the car) and try again. If it's still bad the next day it could be battery, if it's ok then you might have a drain. That's if your alternator is charging ok

 

[area51]

It might be discharging slightly since you fitted it. 12.3v isn't too bad but I'd expect higher from a freshly recharged new/newish battery 12.5/13v perhaps. You need to check if the alternator is charging - what's the voltage with the engine running, should be 13v+ (probably something like 13.8-14v from memory)

The cold weather never helps though - acid is less potent at low temps hence battery is weaker, engine is cold so the oil is thicker, etc.

Maybe re-charge the battery again, leave it overnight (disconnected from the car) and try again. If it's still bad the next day it could be battery, if it's ok then you might have a drain. That's if your alternator is charging ok

Thanks Will, the alternator seems Ok (charging is 14.4v). I will try recharging the battery as you suggest and see what happens..