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Battery

Passion, instruction, buying, care, maintenance and more, any form of vehicle discussion is welcome here
Paupertas
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Battery

#303173

Postby Paupertas » April 25th, 2020, 12:34 pm

I know little, if anything, about cars.

In the present situation I have been charging the cars every two weeks or so. They were not showing any problems but I thought that it couldn't do any harm.

Someone has suggested that a) this is not necessary and b) could do some harm in some way. I don't think that the person who I spoke to knows much more than me, so can anyone confirm that situation please.

Thanks in advance.

dealtn
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Re: Battery

#303177

Postby dealtn » April 25th, 2020, 12:46 pm

Paupertas wrote:I know little, if anything, about cars.

In the present situation I have been charging the cars every two weeks or so. They were not showing any problems but I thought that it couldn't do any harm.

Someone has suggested that a) this is not necessary and b) could do some harm in some way. I don't think that the person who I spoke to knows much more than me, so can anyone confirm that situation please.

Thanks in advance.


Are these batteries in petrol/diesel cars, or an electric vehicle you are talking about.

Paupertas
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Re: Battery

#303180

Postby Paupertas » April 25th, 2020, 12:51 pm

Both petrol

sg31
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Re: Battery

#303186

Postby sg31 » April 25th, 2020, 1:16 pm

I'm not an expert on battery technology but the way I look at it is the battery loses some charge when it isn't used and modern cars have some systems that never turn off even when you turn the engine off and remove the key. I don't know the percentage of charge lost to these causes on a weekly basis so as a precaution I leave my vehicle on a trickle charger if it isn't going to be used for an extended period.

In the current circumstances my vehicle and my wifes vehicle tend to get used alternatively once per week so they each sit idle for 2 weeks. I've not bothered with the trickle charger so far but if we were looking at 3 or 4 weeks of none use I would do so.

I also move the vehicle a few yards once each week to change the tyre position.

I don't think you will go far wrong doing what you are doing.

(An expert will be along shortly to explain why I'm wrong) :D

PinkDalek
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Re: Battery

#303194

Postby PinkDalek » April 25th, 2020, 1:42 pm

Paupertas wrote:I know little, if anything, about cars.

In the present situation I have been charging the cars every two weeks or so. ...


Similar recent topic over at DAK, which has plenty of advice on batteries etc and may be of use:

viewtopic.php?f=9&t=22377

DrFfybes
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Re: Battery

#303205

Postby DrFfybes » April 25th, 2020, 2:37 pm

I'm about to test MrsF's BMW which has just sat onthe drive since it was SORNd at the end of last month. It is usually fine for a month, but getting to the battery to charge it is a bit of a PITA (and the conditioner that connects to the fly-leads I fitted is on my car which is in storage).

I gather the best thing to do is to connect the charger to the battery before switching it on. Some cars have sensitive electrics these days and if the charger is 'live' and the battery low you can get sparks which cause surges into the car.

Otherwise, charging for a few hours every week or so should be fine - a modern charger will not 'overcharge' the battery.

Paul

Paupertas
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Re: Battery

#303206

Postby Paupertas » April 25th, 2020, 2:39 pm

Thanks for the link PinkDarlek, I'd forgot about the tyres

Otherwise, charging for a few hours every week or so should be fine - a modern charger will not 'overcharge' the battery.


Exactly what I'm doing.

Itsallaguess
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Re: Battery

#303209

Postby Itsallaguess » April 25th, 2020, 2:46 pm

I've had my trickle-charger on once for a couple of hours.

My battery is fine, but a few years old, and just coming out of a long dark winter doesn't seem to offer it the best chance to then sit around idle for days on end, and I noticed a week or so ago that it was just beginning to wince a little on starting. I measured the voltage with the car off and it was on the low side, so it seemed daft not to give it a bit of a top-up.

Usually, so long as your battery is generally healthy, then a well-tuned ear will notice if it needs a top-up, and I'm not surprised to hear of so many people choosing to offer theirs a little TLC at this time with their own trickle-chargers...

Cheers,

Itsallaguess

DrFfybes
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Re: Battery

#303236

Postby DrFfybes » April 25th, 2020, 5:46 pm

I just checked the BMW and it was 11.69V with the boot open (courtesy lights on) - probably just about enough to start it.

Then I remembered I bought a solar car charger yonks ago from Maplins to go in the Beemer's predecessor - abandoned as the ciggy lighter was switched with the ignition.

5 mins and a connection to the fly lead and we'll see what it is like tomorrow.

Paul

Paupertas
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Re: Battery

#303242

Postby Paupertas » April 25th, 2020, 6:17 pm

Then I remembered I bought a solar car charger yonks ago from Maplins to go in the Beemer's predecessor - abandoned as the ciggy lighter was switched with the ignition.


I remember reading about these a while ago.

Could you let us know how you go on please?

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Re: Battery

#303243

Postby Mike4 » April 25th, 2020, 6:21 pm

Paupertas wrote:I know little, if anything, about cars.

In the present situation I have been charging the cars every two weeks or so. They were not showing any problems but I thought that it couldn't do any harm.

Someone has suggested that a) this is not necessary and b) could do some harm in some way. I don't think that the person who I spoke to knows much more than me, so can anyone confirm that situation please.

Thanks in advance.


I know a bit about lead acid batteries, enough to know how much I don't know, if you see what I mean. And I have to say I agree, the person advising you sounds as though they know less than you, to be telling you those two things.

All lead acid batteries have a 'self-discharge' rate. This means if you just store it, a lead acid battery will eventually discharge itself down to zero. I think the SD rate on a car battery will typically be in the order of 1% a week. So if your car is not used, it is necessary to charge the battery to counter this effect.

Secondly, a lead acid battery will be damaged by a process called 'sulphation' if stored at less than 100% state of charge (SoC). Sulphation effectively takes away the proportion of charge capacity that is not being used, so so if you allow your battery to discharge to say 80% SoC and store it that way for a month, you will be unable to recharge it back to 100% of badge capacity and that 80% becomes the new 100%. And the process never stops - do it again and you'll lose another 20% of the remaining 80%. This is how lead acid batteries die.

So to maintain your car battery when the car is not in use, you do need to trickle charge it regularly if not all the time. The term nowadays with a modern three stage battery charger is 'float charge'. A decent electronic charger will charge the battery to near 100% with a voltage of about 14.4 then drop back to float at about 13.2V, and the charger on float is designed to be left connected permanently to counter self-discharge.

So your adviser is wrong on both counts I'm afraid. Lead acid batteries are a fascinating subject complex beyond belief. Its taken me years to get to understand them in any depth. All the basics covered in depth over at Battery University, if you're interested. https://batteryuniversity.com/learn/

sg31
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Re: Battery

#303259

Postby sg31 » April 25th, 2020, 7:50 pm

Many years ago (meaning I can't remember how long ago) pleasure boat owners took their batteries to the local chandlery every winter when the boat was laid up. The batteries were stored connected to a small bulb which would place a load on them so they slowly discharged. Every week or two the batteries were put on charge until they were fully topped up. This went on until the boat was put back into srvice the next spring.

I think modern battery technology made this redundant or maybe it just became too expensive.

DrFfybes
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Re: Battery

#303545

Postby DrFfybes » April 27th, 2020, 10:49 am

Paupertas wrote:
Then I remembered I bought a solar car charger yonks ago from Maplins to go in the Beemer's predecessor - abandoned as the ciggy lighter was switched with the ignition.


I remember reading about these a while ago.

Could you let us know how you go on please?


I connected it on Sat afternoon at 11.69V and on Sunday lunch it was 11.64V. So pretty much unchanged. The car is a Z4 coupe and the panel was on the boot floor and the car is on a North facing hill so not a lot of direct sunlight.

I put a mains charger on it as we need to move the car tomorrow for some rubble to be collected - I'll give it a 10 min run up and down our unadopted road then leave it with the boot open for 30 min to allow the car systems to shut down and measure the voltage. Then put the solar charger on the boot cover and check it after a few days.

Paul


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