Sluggish start (have changed battery)

Looking for some friendly help.

My 90 300tdi defender has been sluggish to start/not starting.
I'm not using the truck that much so and so just thought the battery just wasn't that healthy in the cold and so swapped it out.

I've made sure it was fully charged before putting it in and initially all good.
It gets a good 30min drive a week, with the occasional longer run, even on the motorway with an indicated 70mph!

Initially, all good but a month later I'm getting the same issues... turns over but sluggish and then 50-50 if she starts or I drain the battery.

I've just charged the new battery with a mains charger and dug out the multimeter.

1) checked any current being drawn when ignition fully off... no vampires present.
2) getting a good 13.6V directly on the battery with ignition off
3) started the truck... still a bit sluggish but started.
4) voltage at the battery increased to around 14.6V
5) voltage directly on the Alternator a steady 14.9V

Electrics are fully working and lights inside and outside are bright with no flickering....

I don't think I've fixed it.... I've left the battery on charge for a bit (extension cable out to landie and charger sat inside. Cold and raining so come inside for a cuppa.

What else would you suggest I check/diagnose ?

Naigle

Clean all terminals on battery and starter, including earth leads to chassis and body

freelance said:

Clean all terminals on battery and starter, including earth leads to chassis and body

Click to expand...

Will give that a go @freelance. cheers

Good advice above however I wouldn't trust your voltmeter, I think it's a bit optimistic on all readings. An extra earth strap off the engine wouldn't do any harm

+1 ^^^ a battery shouldn't read 13.6 with the engine off, 12.6 would be more normal.
Do you have another meter to confirm the voltage or can you try yours on another battery?

Put an extra earth strap from the rear of the transfer box to the chassis.

update: so I used a jumper cable, directly from the negative on the battery to the engine (tried a couple of places to make sure I was getting a good connection).
Same problem. Turning but sluggish (and the battery was fully charged last night).. didn't start but didn't push it as saving what I have left in the battery.

From the above, I don't think it's an earthing issue. Next, I'll get to the starter motor and clean up the connections there.
p.s. remeasured voltages and was 12.6V before and after testing directly on the battery (last night could just have been user error as I was cold and wet).
I've also charged the old battery (charged at about 1A and left overnight)... might help later on.

really appreciate the advice... I'll update again (birthday today so might not get the chance to get mucky).

Naigle

Fixed.

Thank you all.

As suggested by @freelance > cleaned the connections to the starter motor and battery for good measure and this fixed the issue.

The main nut on the starter motor feed wasn't as tight as it should have been (wasn't what you would call lose but too easy to undo).
Cleaned all the connectors with a little wire brush and a bit of fine-grit sandpaper... did the same to the battery connections (removed to do the above) because, why not, and put everything back.
Started nice and sharp again (relative for a 300tdi).

Now to find someone local to swap a tire for me.

Cheers