Recharging a car battery: sensible?

Iwannahurl

I did a brief search for older threads on this general subject, but didn't find anything that answered my query.

On a couple of occasions I have been stuck with a flat battery after the kids left one of the reading lights on in the car overnight (or even for a shorter period). It's not always possible to find someone nearby to make use of booster cables.

Today I bought a battery charger in Halfords, but after a conversation with another motorist I'm having second thoughts as to whether it's a sensible purchase.

His view was that modern car batteries are not intended for regular recharging, and if they start to lose their charge (the memory effect perhaps?) then it's easier just to replace them. Additionally he said that the cost of a new battery can be offset by selling the old one for scrap.

Does this make sense? Should I return the charger and spend the money on a new battery instead?

Car is a 2004 1.6 petrol.

EDIT: I should point out that my intention is to keep the battery fully charged, not just to charge it up (instead of using jump leads) if it goes flat. Obviously charging is going to an overnight job.

challengemaster

What does he think an alternator does?

I wouldn't be completely discharging them on a regular basis and recharging them, but on the occasion that happens it's not a big deal.

TheChizler

Think about it this way, the alternator begins recharging the battery anyway every time you use the car. Charging whenever it occasionally goes flat is hardly going to make much of a difference. As you said earlier, there's not always someone around to help jump the car, handy to have a backup. Leaving a light on will discharge an old or new battery just the same, only the time it takes is different.

Only worth changing the battery if you notice it beginning to lose charge more often, low voltage across it, sluggish starting etc (compensating for winter temperatures etc), or the interval of time between battery replacements according to the manufacturer has elapsed etc.

corktina

I agree , but if it's a regular happening your battery probably wants replacing anyway

Avns1s

Get a better adviser!!

That said, modern batteries do object to being fully discharged particularly if left fully discharged for any length of time.

L-M

Buy a new battery. They sell them in Halfords with a 5 year warranty.

IMO there is NOTHING worse in a car than a bad battery.

You could also get your alternator checked out to make sure it's doing it's job properly.

Iwannahurl

Obviously the alternator should be doing the job, but it seems the level of charge in the battery is not sufficient.

Actually the "advice" I got was second-hand. He was quoting a mechanic who said garages don't bother charging car batteries any more. I have no idea whether that's true or not.

Just found this old post on the Boards motorbikes forum:

Big J wrote: »

I have used one of these chargers for about 6 or 7 years now on a variety of motorcycle, scooter and car batteries and never known it damage a battery. It has actually brought a discharged battery back from the dead on more than one occasion without damage.

As Judas1369 points out it is an "intelligent" charger that cuts out rather than overload the battery - so it should be OK.

Just make sure it is on the bike setting, otherwise it may try and put too much juice into the battery too quickly and will damage it in that case.

Here's the gizmo on the Halfords website: http://www.halfords.ie/webapp/wcs/stores/servlet/product_storeId_11101_catalogId_15551_productId_894769_langId_-1_categoryId_212463

L-M

Aye we have something too for the vintages. It's a fine way to work things if they're leisure use cars, but having a bad battery in your main car is an unnecessary PITA.

zapata

A new battery will run down if the interior lights are left on anyway.
Nothing wrong with recharging a car battery - might be a pain if you have to remove it from the car overnight. Just remember to connect the clamps on the battery first before plugging the charger to the mains.
A quick check of the interior lights might be easier when locking the car.
Or remove the bulbs and give the kids the small cheap book reading lights for the journey.

Iwannahurl

TheChizler wrote: »

Think about it this way, the alternator begins recharging the battery anyway every time you use the car. Charging whenever it occasionally goes flat is hardly going to make much of a difference. As you said earlier, there's not always someone around to help jump the car, handy to have a backup. Leaving a light on will discharge an old or new battery just the same, only the time it takes is different.

Only worth changing the battery if you notice it beginning to lose charge more often, low voltage across it, sluggish starting etc (compensating for winter temperatures etc), or the interval of time between battery replacements according to the manufacturer has elapsed etc.

zapata wrote: »

A new battery will run down if the interior lights are left on anyway.
Nothing wrong with recharging a car battery - might be a pain if you have to remove it from the car overnight. Just remember to connect the clamps on the battery first before plugging the charger to the mains.
A quick check of the interior lights might be easier when locking the car.
Or remove the bulbs and give the kids the small cheap book reading lights for the journey.

The car is serviced annually, but iirc my regular mechanic has never drawn attention to the battery.

I'll have to check the manual for the recommendations concerning battery replacement.

A question about batteries and alternators has just occurred to me. Assuming that no lights are left on to drain the battery, will the charge decrease significantly over time anyway?

Obviously the alternator can only recharge the battery when the engine is running. Thing is, my car sits on the driveway over 95% of the time*. Could it be the case that the charge is dissipating faster than the alternator can charge it, given the very limited use of the car? It might be used for ten minutes per day during the week, occasional longer trips on weekends.

Does the engine have to be run for a minimum length of time in order for the alternator to keep ahead of the 'passive' discharge of the battery?




* Might even be close to 99% these days.

L-M

How old is the car/battery?

TheChizler

How long is a piece of string? Cells can self discharge by themselves, through internal electrical leakages, or ongoing chemical reactions in the battery. This varies with state of charge, charging current, temperature, drawn current and a million and one other things. In some batteries the rate of self discharge can actually reduce with age, due to layers of chemical buildup on the electrodes (so a new battery won't necessarily be better!) However age deteriorates them in other ways so new will probably be better. Basically if you notice the problem happening more and more, time for a new battery. Check the voltage across the terminals daily maybe as an experiment for yourself to see how fast it discharges!

Del2005

Iwannahurl wrote: »

The car is serviced annually, but iirc my regular mechanic has never drawn attention to the battery.

I'll have to check the manual for the recommendations concerning battery replacement.

A question about batteries and alternators has just occurred to me. Assuming that no lights are left on to drain the battery, will the charge decrease significantly over time anyway?

Obviously the alternator can only recharge the battery when the engine is running. Thing is, my car sits on the driveway over 95% of the time*. Could it be the case that the charge is dissipating faster than the alternator can charge it, given the very limited use of the car? It might be used for ten minutes per day during the week, occasional longer trips on weekends.

Does the engine have to be run for a minimum length of time in order for the alternator to keep ahead of the 'passive' discharge of the battery?




* Might even be close to 99% these days.

A battery will discharge over time but once it's good to start with it'll easily last a couple of months in summer, cold is hard on batteries so winter will be less.

If the car is sitting for ages and then only gets short runs your slowly killing the battery. A better option, if at all possible, would be to get a trickle charger instead of letting it discharge. Plenty of bikes are constantly hooked to trickle chargers due to infrequent use.

You need to get in the habit of checking to make sure that all the interior lights are off before locking the car, as the kids are bound to leave them on where you can't access a plug or find someone to jump off.

Garages don't charge batteries as their business is to make money, charging a car for several hours won't make much and will tie up a bay.

wexie

Iwannahurl wrote: »

Obviously the alternator can only recharge the battery when the engine is running. Thing is, my car sits on the driveway over 95% of the time*. Could it be the case that the charge is dissipating faster than the alternator can charge it, given the very limited use of the car? It might be used for ten minutes per day during the week, occasional longer trips on weekends.
* Might even be close to 99% these days.

That's definitely not an ideal situation for a car battery. Proportionally you're drawing a lot of power starting the car and then not giving the alternator a lot of time to recharge the battery. This shouldn't be a problem every so often but if this happens five times a week the battery may well be pretty low towards the end of the week.

You could always invest in a decent charger that can be wired in the car. They'll charge the battery, then trickle charge the battery once it's full and the really good (expensive) ones can even condition / recondition batteries.
CTEK do a good range, I have one for a car that doesn't get driven often and rather than moving the battery around (it's a freakin heavy lump) I have the charger wired in.

Iwannahurl

I actually don't know how old the battery is. It generally works fine, but the most recent reading light experience, plus the father-in-law's flat battery due to having a car sitting in a garage for many weeks, has made me wonder whether a regular 'external' charge should be routine for cars that are used only occasionally.

Clearly there is a market for such chargers. Here's an example, the Ring Automotive RSC512 12V 2/4/8/12A Smart Charger, as mentioned in this Boards thread that I've just found: http://www.boards.ie/vbulletin/showthread.php?p=82923184#post82923184

Halfords provide a battery testing service (I don't have the means to do it myself) but I guess they have an interest in selling me a battery.

I'm begin to suspect (pure speculation of course) that the issue, if there is one, is that the car is not used often enough for the alternator to produce a sufficient 'reserve' charge. That would also explain the father-in-law's flat battery, since he uses his car only once in a blue moon.

This old post refers to a charger's "maintainer function":

rebel.ranter wrote: »

As for a battery charger/maintainer, Ring make a decent unit called the Ring RSC 512. It has a charge function (automatic or at different rates), desulphate function (for recovering damaged batteries) & a maintainer function (float charge for leaving the unit connected indefinitely).

grainnewhale

if the battery is dead, it is far better to charge it with a battery charger, than using jump leads. it will prolong the life of the battery.

Iwannahurl

Del2005 wrote: »

Garages don't charge batteries as their business is to make money, charging a car for several hours won't make much and will tie up a bay.

I thought that might be a factor. My "adviser" thought it was about the batteries.

Iwannahurl

wexie wrote: »

That's definitely not an ideal situation for a car battery. Proportionally you're drawing a lot of power starting the car and then not giving the alternator a lot of time to recharge the battery. This shouldn't be a problem every so often but if this happens five times a week the battery may well be pretty low towards the end of the week.

I think that could be the key. It's not the 'passive' discharge but the very large drain when starting. I suspect that my battery may be barely keeping its head above water, and any small incident may therefore drain it altogether.

I've just remembered that I got stuck several weeks ago after leaving the lights on outside a shop for a wee while.

coylemj

Iwannahurl wrote: »

I think that could be the key. It's not the 'passive' discharge but the very large drain when starting. I suspect that my battery may be barely keeping its head above water, and any small incident may therefore drain it altogether.

I've just remembered that I got stuck several weeks ago after leaving the lights on outside a shop for a wee while.

+1 That's exactly what's happening, the trips you are doing are not long enough to replace the charge expended in starting the engine. I do a lot of short journeys and the same thing happened me a few weeks ago when I left the parking lights on for a few hours and the battery was barely able to start the engine.

What you could do is use a multimeter to check the battery voltage and if it's on the low side, connect up a charger and charge it up.

Iwannahurl

coylemj wrote: »

What you could do is use a multimeter to check the battery voltage and if it's on the low side, connect up a charger and charge it up.

Good idea. My next question is of course: how much would a decent multimeter set me back?

With regard to alternators, I just found this with a Google search:

The alternator in most cars is typically sized to match the demands of a running car. In other words, when the engine is on and the car is running, the alternator compensates for the electrical load and typically doesn't offer much more. Sure there might be some surplus power produced at speed, but to fully charge a nearly dead 12V battery would take a 2000 mile drive at 80mph or more with everything electrical turned off. A quick 10 minutes down the motorway isn't doing anything for you.

That's why you should invest in a battery charger if you ever find yourself with a low battery. Use the grid's power supply to charge your car's battery instead of trying to overload your alternator.

http://carbibles.blogspot.ie/2013/02/your-alternator-does-not-charge-your.html

Bigus

Most ferraris have a permanent connector for a trickle charger.

Any car that's not doing long journeys during the winter will benefit from a couple of hours on a low charge,

some of the hyper milers in the USA even use chargers on an ordinary 12 v battery to reduce mpg !

I've brought countless iffy batteries back to long life with a slow trickle charge,

Also having a good 12 v plus in the battery , saves a lot of electronic gremlins in modern cars ECU's . Many's a good car I've seen throw warnings on engine lights, abs lights , electric power steering lights, misfires ,all related to jump starting rather than putting on a trickle charge for a few hours.

Iwannahurl

Bigus wrote: »

Most ferraris have a permanent connector for a trickle charger.

You have identified the most obvious deficiency in my situation: not having a Ferrari for popping down to the shops.

https://www.youtube.com/watch?v=e_4QATDVd1I

wexie

Iwannahurl wrote: »

You have identified the most obvious deficiency in my situation: not having a Ferrari for popping down to the shops.

They're most impractical, I had to get rid of mine cause the bags of dogfood wouldn't fit in the boot :mad: