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 Battery 
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Joined: October 17th, 2017, 8:17 am
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Post Battery
Hi, my 2cv has suddenly started to struggle to turn the engine when cold, is there way of testing the battery, bearing in mind the volt meter is showing a good charge when driving, or, do you think it something else? thank you.
















































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October 27th, 2017, 5:11 pm
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Joined: March 21st, 2013, 12:04 am
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Location: Exeter, Devon
Post Re: Battery
Let the battery rest and test the voltage with the engine not running. If you have 12.5 volts, you are probably ok. Check the connections are clean and tight at both the battery end and other ends. The gearbox earth connection can frey with movement.
Roger V

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October 27th, 2017, 5:21 pm
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Joined: June 22nd, 2014, 8:09 pm
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Location: Reading, Berks UK
Post Re: Battery
Testing the battery a good idea. Also could be the starter motor is tired.


October 27th, 2017, 9:31 pm
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Joined: February 22nd, 2012, 10:34 am
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Post Re: Battery
Try some wd40 on the starter exposed shaft.
Check the cables and connections.

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October 28th, 2017, 8:51 pm
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Joined: August 31st, 2016, 12:12 pm
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Location: Hawkins County, TN. USA
Post Re: Battery
I found 2CVs seem to be more forgiving when it comes to weak batteries. Before I replaced the battery on my 2CV, mine would turn the engine over as low as 12.0 volts. By all accounts, the starter motor on any of my other cars above 2 liters wouldn't even attempt to turn over at that voltage. I guess it doesn't require allot of cold cranking amps to turn a 600cc engine over :D

A few years ago my Trabant (also 600 ccs) failed to start except in this case, it was if the battery was completely flat. Not even the dome light would turn on.

I did the usual tests. I measured voltage at the battery, starter, the resistance of the battery cables and all checked out good. Turned out the battery cables were just bad despite not showing any resistance.

I was once mislead by something. Not on my 2CV but my Fiat 124 Spider.

If you test the battery with the engine running and it shows 12.6 volts at the battery, this doesn't mean that the alternator is not working, it just means the battery is fully charged and the alternator is not having to charge it.

If the battery is constantly reading something like 14.3 volts with the engine running (such as after driving it for 10 or more miles), it typically means the battery is getting tired. But it's no uncommon to see 14.3 volts if the car hasn't been driving in a few days or weeks.

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December 17th, 2017, 11:07 pm
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Joined: March 6th, 2009, 1:40 am
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Post Re: Battery
I think you need to 'unlearn' that lesson.
The voltage regulator does not stop controlling the system voltage once a battery is fully charged.
In fact, as long as the engine is spinning fast enough, it will maintain the alternator's output voltage at 14.4 volts from here to eternity...

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December 18th, 2017, 1:20 am
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Post Re: Battery
turbofiat124 wrote:
If you test the battery with the engine running and it shows 12.6 volts at the battery, this doesn't mean that the alternator is not working, it just means the battery is fully charged and the alternator is not having to charge it.

As Ken wrote, no. The alternator doesn't "shut off" when the battery is full charged.

turbofiat124 wrote:
If the battery is constantly reading something like 14.3 volts with the engine running (such as after driving it for 10 or more miles), it typically means the battery is getting tired. But it's no uncommon to see 14.3 volts if the car hasn't been driving in a few days or weeks.

No, the battery can't have over 14 volts for days or weeks.

You have mislead a lot with battery and alternator functions...


December 18th, 2017, 12:02 pm
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Joined: August 31st, 2016, 12:12 pm
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Location: Hawkins County, TN. USA
Post Re: Battery
I'm sorry but I can't agree with those last two replies. Unless of course you guys are talking about dynamos and not modern alternators. Yes a dynamo won't react to electrical demands in the same way a modern alternator will.

I may have gotten the voltages wrong but I still say an alternator will adjust accordingly based on the load of the electrical system and the condition of the battery.

Why is it that when you turn the headlamps on, the engine speed can drop? Particularly on smaller engines below 1 liters?

A "good" battery should read 12.6 volts. I have seen voltages on higher priced batteries read as high as 13.2 volts.

Years ago I was decided to test the alternator on a tractor to see if it was even working. The initially reading was 15+ volts. Thinking the voltage regulator was bad, I removed the alternator and had it tested and the shop said it was fine.

So I checked the level in the battery and it was almost dry. So I topped it off with water and now the voltage at the battery bewteen 13 and 14 volts.

One incident I thought the starter was going bad on a car. I checked the battery voltage when the car wouldn't start and it was around 13.3 volts. Turns out the bearings in the starter motor were just worn out. So once the engine compartment cooled down, the starter would turn over.

I have noticed that if a car has not been driven for quite some time, the voltage reading will be closer to 14.3 volts. If I've been driving around all day long and check the battery voltage it's closer to 13.2 volts with the engine running and no headlights on.

I'm sure different brands of alternators can produce different voltages so no those numbers are not set in stone.

I still say the more demand required by the electrical system, the harder the alternator has to work to make up for that and also the condition of the battery. A shitty battery will require the alternator to work harder.

That's why it's not a good idea to use the car's alternator to recharge a flat battery once it's been jump started.

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January 9th, 2018, 2:29 am
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Joined: August 8th, 2012, 11:00 am
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Post Re: Battery
Sorry, but that is a far away from reality...

When your car is running, the alternator make all power to all electrical equipment. The battery is only a storage, that you can use equipment when engine isn't running, you can start the engine and also the battery is stabilising the voltage...

At normal driving conditions, no energy is taken from the battery. Period. If your car uses the battery to operate electrical devices, the battery will be flat after some driving...

Why the alternator of the car isn't a proper way to charge battery? Really? The manufacturer is designed the alternator can supply all equipment and still can charge battery to be sure you can start the car...

I think you have misunderstood the car electric system at all. Please think again... I'm not try to be rude...


January 10th, 2018, 12:44 am
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Post Re: Battery
something else to consider is, its not all about voltage. Its also about amps. ;)

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January 10th, 2018, 12:55 am
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