car battery, limited use, newish not taking a charge

[misterroy]

Hi, I have a car that is not used much. I bought a new battery last easter and moved the car when I took the battery home. About a month later I went to move the car again and the battery was dead, no ignition light. I cant r emember how I charged it. The two subsequent times I have tried to move it the battery has had to be charged and I have used a fancy charger borrowed from a friend because my bog standard charger cant put charge into it at al l. Is the battery likely to be knackered? Is it my fault for leaving it for a month to loose the charge? ta

[John Rumm]

Modern car batts don't respond well if deep discharged - so there is a fair chance it well on the way to knackered.

[Tim+]

Alas probably yes.

If you're using the car that infrequently it may be time to think about alternatives. Hiring a car once a month would be a lot cheaper that keeping/taxing/insuring/replacing the battery on a car used that infrequently.

Tim

[newshound]

The other solution, unless it is parked on the road, is to keep it wired up to a small trickle charger. A motorbike one would be enough.

I have a small van which is sometimes left for a month or so, and it has a small battery which is readily flattened if the lights are left on (e.g. in a shopping centre car park: being a very basic van it does not have a "bleeper"). My "fix" for that is to keep something similar to this in it. (Also comes in handy as a phone charger). These hold their charge for ~ 6 months.

[bert]

Car batts ever have responded well to being discharged. The op may well find that something like an alarm or immobiliser is slowly discharging the battery. If you are leaving it unused for some time best disconnect one lead.

[T i m]

Or a small solar panel on the dash (depending on which way it's facing of course). ;-)

Cheers, T i m

[Dave Liquorice]

yep, all manner of stuff is quietly running when the car is "off". Mine apparently is aware of this problem and if the battery voltage gets too low (FSVO "too low") it goes into a really deep sleep and has to be opened manually, via the one door that actually has a (hidden) key hole.

Or do as I did when I left my car unused for the last month. A small solar panel(*) on top of the dash board facing SE, connected to the battery. Car opened and started without a hint of a flat battery. Not conclusive, one would need to leave it for a month without the solar panel and see if it went into deep sleep, that's not going to happen.

(*) Halfords/Maplin £15 15" x 5" ish, 12 V, 1.5 W, 86 mA at max power.

[harry]

NOT a good idea on some modern cars. The on board computer may loose it's program if disconnected.

[The Natural Philosopher]

Do you have a car alarm or something that is draining the battery?

[charles]

[Brian Gaff]

Yes even when the car is just sitting there some do use quite a bit out of the battery as people soon find out to their cost. The old dodge of disconnecting it is no good as somemany bits of the car seem to lose their memories when you do that, according to a breakdown guy over the road who seems to be one of those loud voiced blokes who lets his wisdom flow loudly. Lets just say its yet anothreason why I'm not bothered by not being able to drive.... Brian

[Scott M]

Is there, literally, anything you're not wrong about?

[The Natural Philosopher]

Well to be fair SOME onboard computers may lose SOME of their

*configurations*

Examples are: car radio anti-theft kicking in and needing the code to be re-entered.

*some* immobilisers kicking in, and the car won't start

*some* other systems losing their marbles. ISTR that sometimes window warning lights come on until various resets establish where 'window closed' is..

[Bob Eager]

Not to mention the spelling and grammar errors!

[GB]

I was thinking you'd need the radio's code if you disconnected the battery for that long. OTOH the OP has tested all this by running the battery right down, and he hasn't complained about the radio not working or the immobiliser stopping the car working.

[Dave Plowman (News)]

You'd need to contact the maker and see how long they reckon it can be left without use. Remember reading of one where the makers said it couldn't be left for three weeks while going on holiday...

[Dave Plowman (News)]

OBC usually refers to a user 'computer' on the car that does things like MPG and journey times, etc. The ones which control the engine etc more commonly called an ECU. (electronic control unit)

It's quite possible a flat battery can cause some things to be lost. Maybe the radio station memory. But a very poor design if it is anything important.

Many ECUs do 'learn' how the car is driven to some extent. But should default back to the factory settings if the battery is disconnected for some time. And quickly learn again. The ECU controlling an auto gearbox being the obvious one. But in any case updates quickly if you alter your driving style.

[Tim+]

*Tsk*. Lose not loose and its, not it's. On board should either be one word or hyphenated. The rest of it's bollocks too. ;-)

Tim

[Capitol]

Fit a battery isolating switch. Battery should stay up for about 3 months minimum.Would then need recharging. Alternatively fit a plug in trickle charger. I have to do this on one of our cars.

[Capitol]

IME these don't charge sufficiently.