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1 year old battery dips to 12.1 volts.


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Hello,

I have a used 2006 Daihatsu Sirion, I changed the Battery a bit less than a year ago and also the alternator is new ( a few months old ).
When I turn on the lights, the radio, the emergency flashers the car Battery dips from 12.85 to 2.1volts and the head lights dim.

When I use the electric windows the speed they go up varies according to the rhythm of the emergency flashers lol and one time when driving in the night with the lights on + radio when I used my turn signal to turn the radio turned off and on.

I guess its safe to say I have been given a bad Battery correct ?

Thank you
Chris

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If your radio turned off when you put the turn signal on then I would be looking more toward a bad earth somewhere.

When the engine is running (alternator charging) you should not notice such things as the window speed altering as the flashers operate. You need to monitor the Battery voltage at the Battery terminals to make a more accurate estimation of the Battery condition and also to judge whether the alternator is basically OK.

A good test is to leave the headlights on for say 15 minutes without the engine running and see how the voltage holds up. A good 60Ah Battery would run headlights for around 5 to 6 hours and so 15 minutes should be easy... if the voltage falls away then the Battery is either faulty or was not fully charged to begin with. 

   

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7 minutes ago, Mooly said:

If your radio turned off when you put the turn signal on then I would be looking more toward a bad earth somewhere.

When the engine is running (alternator charging) you should not notice such things as the window speed altering as the flashers operate. You need to monitor the battery voltage at the battery terminals to make a more accurate estimation of the battery condition and also to judge whether the alternator is basically OK.

A good test is to leave the headlights on for say 15 minutes without the engine running and see how the voltage holds up. A good 60Ah battery would run headlights for around 5 to 6 hours and so 15 minutes should be easy... if the voltage falls away then the battery is either faulty or was not fully charged to begin with. 

   

I tested the Battery at the terminal with a multimeter sitting still it reads 12.85v and under the load I mentioned it dropped to 12.1v.   

I have also bought a simple cheap Battery tester from an auto store. The tests reads the Battery full when there is no load and half full under load, also testing the alternator turned out to be OK ( if you actually believe the Battery tester )

The radio turning off happened only once since I bought the Battery, the lights dimming and the window speed altering as the flashers operate happens consistently also the head lights dips when I press the brakes.

Should I return the Battery ? it still has 2 months warranty left. How much drop in voltage is acceptable ? 12.8 to 12.1v seem a bit too much for me

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40Ah is a common smaller size so I assume it is the correct one for your car. Without more detailed tests it is not possible to say if your Battery is faulty or not.

You might find this and a further post interesting:

 

 

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This forum software is very poor for linking to posts. You want the one that reads:

 

I would think some variation of this is or has become standard...

Anyhow, as an electronics tech I got curious having read this and the comment by 'Honest John' (Daily Telegraph) and so I did a little test and observation today on what actually happens with my own car. I quickly made a test lead to allow connection of a DVM to the lighter socket... and as Mr Spock would say 'fascinating'.

Cold start having stood 24 hours.

1/ Key turned to 1st position (accessories) and a voltage of 12.40 was noted.

2/ Turning on ignition resulted in the voltage falling to 12.08. I was surprised that the voltage should dip so much with what is a relatively light loading but it was what it was. I operated the windows up and down a few times to significantly load the Battery but the voltage held at around 12.08.

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10 minutes ago, Mooly said:

40Ah is a common smaller size so I assume it is the correct one for your car. Without more detailed tests it is not possible to say if your battery is faulty or not.

You might find this and a further post interesting:

Thanks for your help. What more information would help draw conclusion what more tests do you require ?

I have a multimeter, a cheap battery tester and a pretty good battery charger that can charge all types of batteries and even reads resistance. Should I bother getting a reading of the internal resistance of the battery ?

 

 

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12 hours ago, Mooly said:

If your radio turned off when you put the turn signal on then I would be looking more toward a bad earth somewhere.

When the engine is running (alternator charging) you should not notice such things as the window speed altering as the flashers operate. You need to monitor the battery voltage at the battery terminals to make a more accurate estimation of the battery condition and also to judge whether the alternator is basically OK.

A good test is to leave the headlights on for say 15 minutes without the engine running and see how the voltage holds up. A good 60Ah battery would run headlights for around 5 to 6 hours and so 15 minutes should be easy... if the voltage falls away then the battery is either faulty or was not fully charged to begin with. 

   

I just went to have the Battery load tested to where I bought it. During the load test the voltage dropped to 8v so the Battery is not good.

I got a new different brand Battery for free. So far everything looks good I will keep monitoring the Battery.

One of the few things missing from my toolkit is a good Battery load tester, so I guess I should buy one so I do not have to guess what is wrong

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You'd just be throwing your money away buying a tool you will use once in 3 years.

Could be just a bad Battery, and new one will function as it should for years to come.

Glad it was sorted out without any issues.

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4 hours ago, furtula said:

You'd just be throwing your money away buying a tool you will use once in 3 years.

Could be just a bad battery, and new one will function as it should for years to come.

Glad it was sorted out without any issues.

The Battery went dead in less than a year, plus the tool is not that expensive about 30-50£

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I'm pleased to hear you have the problem resolved. A good multimeter would be a better purchase (imo) than a dedicated Battery test tool.

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Just now, Mooly said:

I'm pleased to hear you have the problem resolved. A good multimeter would be a better purchase (imo) than a dedicated battery test tool.

Can I load test with a multimeter ? I am not aware how I can do that.

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Also I will keep replacing the Battery as long as they are willing to give me a new one for free and then I will get a proper brand name and probably higher Ah as long as it can fit in the car properly.

I got the car used with a 33Ah 270A Battery and the one that got bad was a 40Ah 330a and the new one is the same higher specs but different brand.

My next Battery ( when the time comes ) will be a 45Ah one or better.

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You can do a load test with meter by turning on known electrical loads and monitoring the Battery voltage.

For example a pair of headlights (normal 55 watt rating) draw approximately 4.5 amps each at 12 volts. (I=W/V). So a pair draw 9 amps plus the load of the small tail lights (about 5 watts each as I recall) which add nearly another amp.

So that is around 10 amps loading which a new fully charged 40Ah Battery should run for at least 2.5 to 3 hours. It would not be 4 hours as you might expect because the capacity of the Battery is measured and calculated at a lower discharge rate.

  

 

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I use one of these cigarette lighter volt meters, which gives me real time voltage whilst sitting in the drivers seat.

Cigarette Lighter 12 Volt Meter

With the vehicle key switched to the on position, but engine not started, I can see what the resting voltage of the Battery is. With the engine switched on, I can see if my alternator is providing enough volts, and by switching auxillary things on, such as lights, rear demister etc., can see if the alternator is providing enough amps to cope with the demand. If something is switched on and the voltage drops badly, then It might signify the alternator is on its way out, or that something I've switched on is drawing current above its spec. Not exactly hi-tech I know, but for a few quid, it may highlight a potential problem.

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45 minutes ago, Mooly said:

You can do a load test with meter by turning on known electrical loads and monitoring the battery voltage.

For example a pair of headlights (normal 55 watt rating) draw approximately 4.5 amps each at 12 volts. (I=W/V). So a pair draw 9 amps plus the load of the small tail lights (about 5 watts each as I recall) which add nearly another amp.

So that is around 10 amps loading which a new fully charged 40Ah battery should run for at least 2.5 to 3 hours. It would not be 4 hours as you might expect because the capacity of the battery is measured and calculated at a lower discharge rate.

  

 

I just checked the Battery and they installed a 35Ah 270A while they previous one was 40Ah 330A.  I specifically asked for exactly the same specs Battery if not better they said OK and they installed a 35Ah one lool.

Should I bother to go change it ? I think I should go change it and get the 45A one and pay for the difference.

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Update:

 

I returned the Battery and got a 60Ah 400a and it fits just right and it looks like it belongs in the car. It is the absolute biggest Battery that can fit in the original position without any modding or for the Battery looking out of place.

I just paid 10 euros extra. So I think it was a good move, lets see how long it will last.

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I bought the below Topdon AB101 Battery tester for 34 euros:

https://www.amazon.com/TT-TOPDON-AB101-Automotive-System,Charging/dp/B07DDDDSK9

So no more bad batteries from dishonest local shops, I will be able to know right way if the Battery is not good.

 

 

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4 hours ago, Roy124 said:

I found this which appears to be very interesting: Auto Battery Monitor BM2 Bluetooth 4.0 12V Device Car Battery Tester at £25.99

As it is bluetooth you should be able to have someone monitor from inside the car.

You don't need bluetooth to monitor your Battery, plus this thing won't load test your Battery, also it looks like its on 24/7 so you will have parasitic drain.
You are better getting something simpler/dumb like this:

https://www.ebay.co.uk/itm/3in1-Digital-Voltmeter-Thermometer-12-24V-Cigarette-Lighter-USB-Car-Charger/293987781724

Also if you have a look at the Topdon AB101 it has lots of features:

* Battery test

* Charging test

* Cranking test

etc

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