Toyota Yaris 53 Plate

[dibble1]

Two things really, the car is my Mum & Dads so I don't want them wasting money. The battery is discharging itself very rapidly. we re-charge it and it can go weeks without a problem, no dimming, laboured starting etc, and then suddenly discharges overnight.
The alternator light isn't coming on but even though the speed of the discharge seems to rule that out.
Nothing is being left on either. I've tested the battery & it says it's ok even though it's the origional & therefore coming up to 10 years old.
My question is this; Is this common if so what is the cause, and I have been given a battery that has never been used. It is a different size but surely if it fits in the battery bay and bolts down it should be ok shouldn't it?
And finally Cyril, do I have to re-set the radio code or can I get away by doing it without breaking the circuit using jump leads?
Many, many thanks.

[oldhenry]

My view is that a 10 year old battery , even Japanese, is pretty old. The oldest battery I have ever had in motoring since 1966 is 9 years for a Bosch.
So be prepared for a new one. Some items that drain a battery and are overlooked are the interior light being left on, the boot light being left on and the radio. Also the alarm sytem uses electricity.
The charging light will go out of the alternator is fine, and do the lights dim and brighten as the car is revved up?

[tonyav]

It's not just the physical size of the battery that matters dibble, it depends on how many amps per hour it's output is.

[jasmin26]

cant tell you why but it happened to mine as well. I was out shopping left the car for ten minutes or so and it just wouldnt start . Got the AA and he tried to charge it enough for me to get home, it was charging ok but then as soon as car was started it just died again. Mine is a 53 reg as well.

[EDDIE51]

You need a new battery,10 years is too old .
As long as the other battery fits and you can connect the leads it should be ok. The only problem would be that the new battery was a lot lower ampage capacity but that is unlikedly in this case a Yaris does not need a high capacity battery.

[dibble1]

thanks all

[TWR]

Is the battery type with 6 plastic Plugs on the Top? If so check if the battery has Distilled water within, the fluid should be over the lead cells inside, I have not long replaced the battery in my own, 14year old, even the auto elect said it had lasted well.

[Hopkirk]

Old batteries get silt at the bottom which can short circuit the plates.

I would guess that as the car moves, the silt shifts so that the battery is OK for a while. Then another day the swishing around caused by driving causes it to be short circuited and discharged.

Change the battery.

[johnny37]

For what its worth my 10-y-o was doing the same. I managed to keep it going using a battery booster but eventually died completely. RAC man charged me £98 for a new top grade Exide battery which he said was £3 more than Halfords. Later found the same one on the net for under £70. Should have change it much sooner.