Car battery question

[Spinney]

A few weeks ago I was working away from home, with tools in the back of the estate car, so I thought it was a good idea to leave the ignition on and listen to the car radio while I worked. After about a day of this, the battery went flat. It surprised me that running just the radio would do that, but it did. (Stupid Spinney!)

Rescue service called out, started no probs with their booster widget, then the car went in for a service (already planned). In the three weeks since then it's had a 200 mile motorway run, a few short journeys, and at least 6 days in a row sitting unused on my drive.

Then we did a four day walk, leaving my car at the beginning. When we got back it wouldn't start - battery flat. I hadn't left any lights on. Jump leads out, etc, and it would only start with my friend's car revving very high. But it did eventually start, go home OK, and this morning testing it, it started OK again.

So the question(s):
- can draining the battery completely flat damage it in some way so it doesn't hold a charge?
- why would it lose all charge between Friday morning and Monday evening when it had been left for longer before?

Just asking for thoughts, really, as taking a car to a garage with an intermittent fault can end up being expensive!

 

[Racing roadkill]

It's a lead acid battery, the plates eventually start to crumble, this leads to micro shorting (a build up of crumbled lead plates, bridge the inter plate gap). That's the end of the battery.
It's very easy for the garage to check whether the battery has indeed had it, if not, there could be a short somewhere in the car's loom. Again this is easy to check, although not so easy to find. If it's an older type battery, you could try taking the little screw caps off of the top, topping the battery up with Deionised water, then taking the car for an 'Italian tune up'.

 

[simon the viking]

I'd say battery on way out or an alarm fault but money would be on battery. if its not sealed you can get tablets you drop in the cells and top up with distilled water but you would only be prolonging the agony.

If you use a decent garage they should be able to test the battery to make sure as it could be..... Alternator or lazy starter as well...

 

[raleighnut]

^^^^^ Wot he said.

 

[Broadside]

Yes it can damage it, they are not designed for deep discharge cycles. The battery may have been on its way out already and using the radio all day may have tipped it over the edge and now you have some damaged cells.

 

[Profpointy]

if you flatten the battery and charge it up straightway- should be ok, but if you leave it flat, it'll be ruined.

That said, from what you describe I suspect your battery is on it's last legs. I'd stick a new one in. At worst you'll have wasted some money in eliminating the most obvious cause if fault really is elsewhere

 

[Paulus]

Batteries can die without warning, normally the first frosty day in winter/autumn. The fact that the battery was drained has probably helped yours on its way.

 

[I like Skol]

Nothing kills a battery quicker than a total discharge. A newish battery might appear to recover ok but it's total capacity will be affected, just possibly not enough to notice. Do this to a battery that is a few years old and the chances are you will do enough damage to make it unserviceable. My suggestion would be to replace the battery, but first get someone to check the voltage at the battery when the engine is running, this should be around 14volts depending on vehicle. If it is only around 12volts then it's possible your alternator isn't in great shape either and replacing the battery isn't going to sort that.

 

[Globalti]

Whatever you do, don't go along to one of the high street tyre and battery places; take the car to a proper independent battery specialist for the right diagnosis and replacement. While at it, ask them to check the condition of the earth strap that connects the negative terminal to the chassis as this can corrode internally and lose capacity.

If you are anywhere near Bury I recommend Delta Batteries.

 

[Spinney]

The car is only 5 years old (10 registration) - does that affect opinions on likely death of battery?
It's a Skoda Octavia, so was hoping for some VW reliability (but as has been said, the problem is probably at least partly due to my own stupidity).

Thanks for all the comments - gives me some questions to ask. Can get out the multimeter to check the battery voltage myself - presume that's accurate enough @I like Skol?

Locating a battery specialist sounds like the best bet - I'm between Bristol and Gloucester, so will have a search. Luckily I work from home and OH cycles to work, so not desperately urgent to sort out!

 

[mybike]

I would have expected the rescue service to check the battery, after all if they could sell you a battery .....

It does, of course, depend on the sort of battery you have, I suspect that some of the batteries fitted in the most recent cars will not stand up to quite so much abuse. Leaving the ignition on will cause a higher drain than simply the radio of course. My car battery died two years ago, on a 06 registration. Perhaps the fact that the car giving you a jump start had to rev so high indicates you may have a few shorted cells. As above, check the voltage, engine running & otherwise. All the above advice looks good.

 

[simon the viking]

The car is only 5 years old (10 registration) - does that affect opinions on likely death of battery?
It's a Skoda Octavia, so was hoping for some VW reliability (but as has been said, probably at least partly due to my own stupidity).

Thanks for all the comments - gives me some questions to ask. Locating a battery specialist sounds like the best bet - I'm between Bristol and Gloucester, so will have a search. Luckily I work from home and OH cycles to work, so not desperately urgent to sort out!

Has it got a start/stop function? if it has, the life expectency is on only about 5 years (and not much more if it isnt start/stop but can last 10 years)

 

[I like Skol]

The car is only 5 years old (10 registration) - does that affect opinions on likely death of battery?

Not really a factor. I killed the original battery in one of my Merc vans just after 3yrs, but it had had a lot of cycling due to extended periods sat outside properties with hazard lights on while unloading and playing the radio when working outside nearby. On the other hand, my current car a 2005 VW Passat (built in 04) is still using the original battery and my previous car, an astra estate was sold on with the original battery at 106k and 10yrs old so I tend to be kind to batteries in general.

 

[Spinney]

Has it got a start/stop function? if it has, the life expectency is on only about 5 years (and not much more if it isnt start/stop but can last 10 years)

No - it's a basic model, no start-stop.

 

[Falco Frank]

Just the radio running during the day probably wouldnt drain a good battery but turning the ignition on would. It energises all the car systems for starting.

As had been said, for a battery of any age, replacement is the easiest solution providing all other factors have been rules out. Motor factors are often good places to deal with or as had been said battery specialists.

If in a hurry or for online use I can thoroughly recommend these guys:

http://www.mdsbattery.co.uk/