Discharged battery(again)

[scapa]

It does not matter how much electrical equipment is fitted to the car once the engines running the alternator provides all the required power and more.

All the battery needs to do is be capable of cranking the engine over correctly if your charging system is operating correctly and your battery is servicable you wont have any problems no matter what time of year it is.

[StanC]

Originally Posted by scapa

It does not matter how much electrical equipment is fitted to the car once the engines running the alternator provides all the required power and more.

All the battery needs to do is be capable of cranking the engine over correctly if your charging system is operating correctly and your battery is servicable you wont have any problems no matter what time of year it is.

You are correct - but only to a point. Your conclusion is only valid if the car is used every day and gets a decent run of, say, 30 min with only limited equipment running.

Most modern cars have some 'residual' drain current when parked, due to the demands of equipment like the clock, radio code, alarm/immobiliser, power seat memory, etc. On my 1996 960 3Ltr the residual drain is 40mA and this seems to be a fairly typical figure. When you do the sums, a 40mA residual drain equates to 1Ah being drawn from the battery for every 24 hours that the car is parked. This is the equivalent of about SIX starts of the engine! So, even if a car is used every day, it still probably stands for about 15 hours each night and in this time the battery might lose as much as .7 Ah.

It is for this reason that certain marques such as Porsche, Mercedes and Aston Martin actually supply a CTEK charger (branded with their own logo) with every new car and they don't guarantee that the car will start if left for more than about a fortnight not on charge.

Also, although alternators are indeed sized to cover the power requirements of all the electrical equipment in the car, they tend to be specified with very little, if any, over-capacity and if you really do have everything running (as is possible in this winter weather) even a healthy alternator might struggle to power everything AND also recharge the battery from starting the car and the loss of about .7 Ah from standing all night.

Finally, cold weather does affect even a healthy battery's ability to perform and recharge (which is why CTEK chargers have a cold weather mode).

If, like my 960, a car gets used for an hour or so and then stands for a few days before it is next used, the battery soon takes a hammering, which is why I keep it more-or-less permanently hooked up to the charger.

Incidentally, I'm not employed by CTEK!!! I just happen to think that they are excellent bits of kit.

Stan.

[scapa]

I on occasions spend a fair bit of time up in Kittala Finland during the winter and as yet despite temps being as low as -35 i have never had the car fail to start or needed
the battery charging, It has never let me down, However i do ensure the cars well maintained and the battery is on spec

The low temp the UK has recently had will however find out a poorly maintained vehicle in short order.

Your point about very short trips is of course a valid one as even the best generator takes a while to fully recharge the battery

[TonyS9]

I've had problem in a Capri in the 80s with everything running (lights/wipers/heater fan/rear demister) that eventually ran out of battery power, but I'm not sure it wasn't faulty. Never had a Volvo run out of power. The 940 alternator is rated at 0.9-1.5Kw depending on model.

I agree with Scaba , an hours drive (or idle) should be more than enough to recharge the battery no matter what the electrical load (unless you have somehow connected an 800w load directly to the battery). If you need to keep your battery on charge over 2 days there is something wrong with it. The remote field control will ensure the charge voltage stays up at 14v (the regulator regulates down BTW).

I would also say that a cheap charger works fine for me. I have a cheap 4A charger, that gradually drops to <1A once the battery is charged then it maintains a trickle charge. Normally 30mins on the the charger is enough to start a dead car (unless battery is knackered). The only thing smart chargers do is charge faster (mainly) which you need more advanced controllers for. I guess there are pulse modes and stuff like that but there is not strong evidence that they really heal batteries.

I agree 2 weeks is a typical battery life for being parked up, repeated lay ups will also kill the battery.

[RealEstate]

Brenda,
If you are a member of RAC, AA etc, ask them to check out your charging system. I expect they will tell you exactly what is wrong
All the best,

[Brenda]

Hi Real Estate

I am a member off the RAC,but each call out means a lowering of my no claims discount,which is a pain, and they know it!!

Any way, its worth a try if I need to call them again, thank you

[Brenda]

Ive haD the battery on charge for a couple of days now,and the \"trickleometer\" has gone down to one amp.


The starter turns like new now, and never has done so with this battery.

I will fit a replacement alternator when the weather warms up a little and see if there is any noticeable difference.


Thanks for all your helpful suggestions so far. I will keep you posted as to my progress along the way.

This isnt the end of the thread though,please continue to help if you can.


Brenda

[RealEstate]

Originally Posted by Brenda

I am a member off the RAC,but each call out means a lowering of my no claims discount,which is a pain, and they know it!!

I didn't know there was an RAC 'no claims (call-out) discount'? Have I been missing something?

Glad the trickle charger is a help. If you decide on a new alternator, I suggest a reconditioned Bosch one available from your local motor factors. Make sure it has been fully reconditioned and not just had the brushes replaced - the trap I fell into!

[Brenda]

There certainly is a no claims discount on my membership because I had to work jolly hard to reduce this after I called them out last year twice with this battery problem.

Never mind eh?

And VJUK

How did you turn off your DRL\'s?

Brenda