Do I need a new battery?

[NickC]

Still trying to positively identify this fault. Have just borrowed a spare battery and after 20 seconds of cranking was getting the following readings:
Starter: 6.5v
Battery: 7.5v
Maybe both batteries are faulty, that is why it was laying around as a spare.

Is it possible to have a fault on the starter which causes it do drain too much current? Am I looking too far into this, perhaps I should just change the battery as it is the cheapest component to replace.

[rbgosling]

I'd say 9V under cranking was pretty normal - cranking uses an enormous current, so the voltage at the battery drops (due to the battery's own internal resistance), and more is lost through the wiring.

My gut feeling at the moment is pointing towards the starter. I've had a couple of previous old cars (MG, Triumph) when I've had symptoms like this and it's turned out to be the starter. I believe it is possible to refurbish the starter yourself, but on both of these cars they were off-the-shelf Lucas units for about £35 for a rebuilt one, so I never bothered.

Cheaper than replacing the battery, in these cases (but more work!). No idea how much an Excel starter runs to, however...

[amarshall]

Any decent local garage or motor factor (not a major chain one!) should be able to do a proper battery test using a load. I've never yet been charged for one and it only takes a minute or two to perform.

It's quick, it's simple and it doesn't involve taking anything off the car from awkward to reach places.

[NickC]

Battery tested ok on a voltage drop tester when I tried it. Then took car to Kwikfit and their Bosch battery tester apparently showed as battery unserviceable. Therefore bought new Bocsh battery.

Unfortunately, it wasn't the battery. She was very slow to turn over again this morning, second and subsequent attempts were then fine again.

[Lotus-e-Clan]

KwickFit are clearly taking the p*$$!

I don't know if they employ wide boys by default or that training / commission puts pressure on them to try to make business out of thin air?

Get yer money back or sue them!

[NickC]

Well actually I got the battery from Costco, it was half the price of Kwikfit. Still at least I know I have a nice new top quality battery, I think the old one was over eight years old.

[NickC]

Finally solved - it was the battery to chassis earth strap connection at the chassis end. This is surprising because I had cleaned this connection last winter, it was still smeared in vaseline. However taking it off and cleaning it up with a bit of sandpaper seems to have done the trick, now starts fine again.

[rbgosling]

Glad you managed to track the issue down in the end!

[alanmoss]

Re earlier comments on type 075 or 088, the 088 doesn't fit under the fixing bracket or cover on the standard UK cars. I understand that the 088 was specified for some (colder0 markets to give higher capacity and cranking capacity.
I have found that the type 027 will fit with the standard locating bracket and just goes under the cover. This has the advantage of 63ah rather than 60ah for the 075 and better cranking capacity. CCA on the 075 is 540 but on the 027 is 610. This might be useful for those who cannot attach a battery conditioner and/or have to leave their cars outside.
I have just replaced my battery with a Varta Silver 027 as my previous Halfords was just starting to lose it after 12.5 years. I sourced it from Express Batteries who were competitive on price and very efficient with next day delivery if you order by 2pm.

For those interested in dimensions the 075 is 242mm long, 175mm wide and 175 mm high. the type 027 is 242x175x190. The type 088 is 260x172x225.

[NickC]

Thats the type I ended up using as well. In my case a Bosch S5 005 which as I understand it is their type 027 equivalent.