Not starting , nearly dead battery.

The Disco is a big old lump to start. If you do put jump leads on, it surely will take a bit of time and some revs before the Disco battery will have a proper go at starting. The batteries these days also don't tend to give much warning before packing up. One minute fine, the next time- click click...nothing.

One thing I'd advise is getting a good quality battery if you need to, not the cheapest. False economy.

pedros said:

The Disco is a big old lump to start. If you do put jump leads on, it surely will take a bit of time and some revs before the Disco battery will have a proper go at starting. The batteries these days also don't tend to give much warning before packing up. One minute fine, the next time- click click...nothing.

One thing I'd advise is getting a good quality battery if you need to, not the cheapest. False economy.

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jump starts are to start the engine with the other cars battery, not a way to do a fast recharge

trax said:

jump starts are to start the engine with the other cars battery, not a way to do a fast recharge

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Yes, it's a way to start the vehicle, not charge the battery. But it still holds true that you have to give it some time connected or it won't work, especially with crappy jump leads.

with a good set of jump leads, you don't even need a battery there! just onto the terminals would do! i personally wouldn't though!

OK battery has been on charge for 4 or 5 hours and is now fully charged, remains to be seen if it will hold the charge for long but I will find out in due course.

Suggestions that the root of my trouble could be either the alternator or starter motor will have to be investigated, unfortunately the car is out on the road not the drive making it harder to work on in the dark so will have to wait till next weekend.

ClassikFan said:

OK battery has been on charge for 4 or 5 hours and is now fully charged, remains to be seen if it will hold the charge for long but I will find out in due course.

Suggestions that the root of my trouble could be either the alternator or starter motor will have to be investigated, unfortunately the car is out on the road not the drive making it harder to work on in the dark so will have to wait till next weekend.

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Hi CF, did you measure the voltage on the battery (after it had rested for at least 1 hr), after charging it? If you did, what was the result?

Dave

12.5 volts but my meter is a bit vague.

ClassikFan said:

12.5 volts but my meter is a bit vague.

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Well assuming that reading is accurate, it's at the very bottom end of acceptable.

I would leave it on charge overnight and then check it. Irrespective of what your charger might say, it won't be fully re-charged after just 4 hours.


Dave

thebiglad said:

Well assuming that reading is accurate, it's at the very bottom end of acceptable.

I would leave it on charge overnight and then check it. Irrespective of what your charger might say, it won't be fully re-charged after just 4 hours.


Dave

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a long slow charge is better than a high fast charge

The only reliable method of determining the state of charge of a lead-acid battery is by measuring the specific gravity of the electrolyte. The SG for a fully charged cell should be around 1.26. The specific gravity rises in an almost linear fashion from about 1.1 for a fully discharged cell. Battery hydrometers are fairly cheap and readily available.

Sadly, with the advent of sealed, gel and maintenance free batteries this method isn't always an option.

The terminal voltage isn't a reliable indicator because of the one of the most useful characteristics of the lead-acid battery; its ability to maintain a near constant voltage over the bulk of the discharge period.

During discharge, the terminal voltage remains almost constant at about 2.0 volts per cell, dropping to 1.8 volts at the very end of the discharge cycle. While it's on charge, the terminal voltage will remain at about 2.2 volts per cell, rising to 2.4 volts at the very end of the charge.

The only other method of "guesstimating" the charge state is to monitor the charging current during the recharging period. The actual charging current will depend on the capability of the charger, but generally the current will be very high when first connected falling to a steady level for a number of hours. When a significant drop in the charge current is noted, the charge cycle is nearing or reached the full charge.

Lead-acid batteries are generally more suitable for slow charging over 8-12 hours rather than fast charging, although that will depend largely upon the design of the battery.

A "drop test" whilst not reliably indicating the state of charge of the battery, it will often show a battery which is nearing the end of its useful life.

This is all good info, but the battery is not a problem. There is something more to it. Hope it is just a loose connection. These dark nights leave no time to try and fix it so it is off to see my friendly LR mechanic tomorrow.

Official diagnosis is that the starter motor has failed. New one coming tomorrow, hopefully that will be the end of this little episode. At least it chose to fail outside my house and not in the middle of nowhere!

All fixed, no sign of any current drain, so we have a clean bill of health again.