Battery light

Clark's son · September 17, 2017

The battery light is coming on in a very dim way it's actually difficult to see in the daytime.

Before starting it has the normal brightness so nothing wrong with the bulb.

The brightness reduces when accelerating

The brightness reduces when the ac headlights and other Electrical equipment are turned on.

The brightness reduces while accelerating and at around 2000 rpm beguin to flicker and at 2500 disappear completely but comes back when the rpm is reducing.

Recently the battery light was fully on and the problem was detected as the alternator so tryed to buy a new one but company told it would take 2weeks plus to bring it down so the Coil was wound at a local electrician. When we were on that we also put a new alternator belt not a company as it was not available at the time. Then a month later this happened.

The car was driven 200+km with this dim light issue but still no sign of the battery not charging even the magic eye in the battery is green

Need some expert advice

Davy · October 11, 2017

Let me address each point:

On 10/11/2017 at 3:37 AM, Premio said:

Battery health can be checked only using battery tester which shows voltage drop with load! Simple test i will tell you, just take a battery which is in discharged condition, now voltage is surely below 12V, by good battery or a charger, connect (-) to (-) and tooch (+) terminals for few minutes. Then check the voltage,it will shiw you voltage above 12V. Will this be able to perform? Voltage is only an indication. Power is multipication of Ampere×Voltage.

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A "battery tester" is no different from a fancy voltage meter. The gauge on the tester is basically a voltage range with green being used for "normal" voltages and red being used for "out of range" voltages. A multimeter does the same thing and I've been using them for years to test batteries. They're always spot on. You can do a perfect diagnosis if you have a workshop manual with you because it will have all normal voltage ranges specified. Of course you can't check the battery at the terminals and lave it at that. You need to test the voltage on load as well and it should still indicate a stable, healthy voltage. The multimeter can even be used to check each cell of a battery if it's not a maintenance free one. You simply have to open up the cell (being careful not get acid burn) and insert the + probe of the multimeter into it while using the - probe to touch the - terminal of the battery.

Just watch the video below. If as you say "voltage is just an indication", the multimeter in this video should have just shown a constant 12V throughout. But notice how it drops down to just below 10V when the starter motor is drawing a high current. Your P = VI argument isn't valid because P is never constant in a car. With each electrical accessory you turn on and off, P changes and therefore I (amperage) changes and V needs to compensate for those changes. So this is a good indication as to how the charging system is working.

On 10/11/2017 at 3:37 AM, Premio said:

Charging indicator is dissapered in higher rpm, and comes back in low rpm again.At low rmp, inducing voltage is same, the variable is current, so when you getting low current, the rest required part draining from battery, so system voltage slightly dropping, charging indicator will appears. When acceleration, more current produced,voltage increased , lamp dissapered.

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I think you contradicted your own argument here. My point is that there is a fault in the current flow from alternator to battery (i.e. charging circuit). There is simply no way the battery indicator can light up just because your battery is low. That's just not how it works.

Also, all alternators have a voltage regulator to make sure that a stable DC voltage is output regardless of what the engine RPM is. By your logic, the alternator outputs one voltage at idle and increasing voltages as the RPM increases. Again... doesn't work that way.

Rumesh88 · October 11, 2017

On 10/9/2017 at 1:43 PM, Premio said:

First of all you simply visit a battery shop. They have meter to check battery by loading it shows the battery health. Green zone and red zone. It is available in many service stations too. If it shows battery bad condition, just request them to fit a battery and check whether your battery indicator still on! If it has dissapered, your battery is need renewal. Green light indication shows electrolyte level. It can't say anything about battery cell condition.

Another thing you mentioned, it is dissapered in higher rpm, and comes back in low rpm again. Most probably your battery condition deteriorating! Time to change battery. It will cause to incresing fuel consumption too!

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No. Never. When that happens most probably it is the alternator brushes but it can be a diode or the regulator in some cases. The point that Davy is trying to emphasize is wen you have a dashboard indication you should begin diagnosis from the alternator. However, faults like alternator brushes wearing out does not happen overnight and you wouldn't get any indication for sometime. Meanwhile you continue to run with an undercharged battery resulting in battery cells getting covered with hard lead sulfate and eventually reducing the battery capacity. But still when you have a battery indication you must begin your diagnosis from the alternator. As for battery indication on low RPM well that is how it indicate a alternator brush failure or a failure in a single diode.

For all the cars I have been until 2014 (before I switched to a hybrid) I set a target life of 4 years even with the automatic cars. Whenever I leave the car unattended for more than a week I keep the battery on a float charger. After two years of battery life, I make it a point to check the system voltage once every two weeks (or so) with all electrical load switched on and engine RPM at 2000. If the voltage is below the typical value for the car (each car as its own value close to 14V) I get the alternator checked. As for the battery health my only check is listening to the starter motor in the morning. If there is a slightest drag or a hesitation I change the battery the same day. I do not believe in battery testers in those shops but my methods never let me down.

Edited October 11, 2017 by Rumesh88

Twin Turbo · September 17, 2017

.Check the alternator belt for slipping, and bat posts for loos connectins and oxide/salt build-up.

You may have a prob with the charging system, to comfirm, get a volt meter and hold to battery terminals with the engine on , at slow speeds with the bat warning on. And see what the reading is,..

TT.

Edited September 17, 2017 by Twin Turbo

Clark's son · September 17, 2017

Thanks TT
There's no sound of the belt slipping and it seems tight enough to the hand.
And the terminals are tight enough no visible oxide too.

Davy · September 17, 2017

As TT mentioned, your charging system needs inspection. The symptoms you've described suggest a bad rectifier circuit (commonly referred to as the "regulator" or "diodes") in the alternator.

The other possibility (and the less likely one) is a fault with the charging system wiring. You can check this yourself if you're keen by removing then connector and the ground wire from the alternator and switching the ignition to the ON position. The charging indicator should light up fully bright.

At idle, the charging voltage should roughly be between 13.8V to 14.2V. Even with load (AC, headlights etc.), it shouldn't drop below this range.

Davy · October 10, 2017

On 10/9/2017 at 1:43 PM, Premio said:

Another thing you mentioned, it is dissapered in higher rpm, and comes back in low rpm again. Most probably your battery condition deteriorating! Time to change battery. It will cause to incresing fuel consumption too!

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Can you please explain how a bad battery can cause the indicator to light up on the dashboard? Also, I'm curious to know how a bad battery can affect fuel consumption. Thanks!

Edited October 10, 2017 by Davy

Premio · October 10, 2017

Once you clear the boubt about the battery you can gi forward to check the alternator.

When alternator rewinding, they are just using duplicate wires,sometimes not the proper gauge,not equal number of turns. That will cause dropping inducing voltage,dropping the output. After rewinding the alternator side changed,accordingly the regulator should change. Always original is better,trouble free,because we di not have much details how your indication system sensing.

Best is as soon as possible clear doubt about battery and go to trouble shoot alternator.

Davy · October 10, 2017

@Premio, all that but you haven't answered my question. Let me answer it for you.

A bad battery doesn't cause the indicator to light up on the dashboard. The indicator on the dashboard is not a "bad battery" or "low battery" indicator but a "charging system issue" indicator. It lights up if there is an issue with charging. You can have a flat battery with zero volts, but if the charging system is working, the indicator should go off after the engine has been stated up somehow. So no, a dim light doesn't mean that the "battery condition is deteriorating" as you've mentioned in your earlier post.

To check a battery, a simple voltmeter or multimeter can be used and a battery with zero draw and a full charge should indicate between 12.2V to 12.6V approximately. Then there is CCA (Cold Cranking Amperage). The current draw from the battery during engine start should not cause the battery voltage to go below 9.6V.

As for the charging system, the voltage between terminals while idling should show between 13.8Vand 14.2V approximately even under load. I've already mentioned this in my first reply above. A bad regulator will show bouncing voltage or something out of range.

And finally, while the alternator puts load on the engine to keep a bad battery charged, it doesn't have a noticeable impact on fuel efficiency. For a person who goes to two decimals with their km/l results might find a difference, but I doubt it will be more than that.

So in summary, don't blindly replace the battery and expect everything to work. Your brand new battery will die early if there is a problem in the charging system. This is not to say that OP's problem is strictly due to a charging system issue, but that's the most likely cause. It might even be a loose battery terminal that's affecting charging.

Premio · October 11, 2017

On 10/10/2017 at 5:34 PM, Davy said:

@Premio, all that but you haven't answered my question. Let me answer it for you.

A bad battery doesn't cause the indicator to light up on the dashboard. The indicator on the dashboard is not a "bad battery" or "low battery" indicator but a "charging system issue" indicator. It lights up if there is an issue with charging. You can have a flat battery with zero volts, but if the charging system is working, the indicator should go off after the engine has been stated up somehow. So no, a dim light doesn't mean that the "battery condition is deteriorating" as you've mentioned in your earlier post.

To check a battery, a simple voltmeter or multimeter can be used and a battery with zero draw and a full charge should indicate between 12.2V to 12.6V approximately. Then there is CCA (Cold Cranking Amperage). The current draw from the battery during engine start should not cause the battery voltage to go below 9.6V.

As for the charging system, the voltage between terminals while idling should show between 13.8Vand 14.2V approximately even under load. I've already mentioned this in my first reply above. A bad regulator will show bouncing voltage or something out of range.

And finally, while the alternator puts load on the engine to keep a bad battery charged, it doesn't have a noticeable impact on fuel efficiency. For a person who goes to two decimals with their km/l results might find a difference, but I doubt it will be more than that.

So in summary, don't blindly replace the battery and expect everything to work. Your brand new battery will die early if there is a problem in the charging system. This is not to say that OP's problem is strictly due to a charging system issue, but that's the most likely cause. It might even be a loose battery terminal that's affecting charging.

Expand

Battery health can be checked only using battery tester which shows voltage drop with load! Simple test i will tell you, just take a battery which is in discharged condition, now voltage is surely below 12V, by good battery or a charger, connect (-) to (-) and tooch (+) terminals for few minutes. Then check the voltage,it will shiw you voltage above 12V. Will this be able to perform? Voltage is only an indication. Power is multipication of Ampere×Voltage.

Fullt charged battery normally 13.2V recemond by battery makers.It is based on 6 cell ×2.2V =13.2V.

Charging indicator is dissapered in higher rpm, and comes back in low rpm again.At low rmp, inducing voltage is same, the variable is current, so when you getting low current, the rest required part draining from battery, so system voltage slightly dropping, charging indicator will appears. When acceleration, more current produced,voltage increased , lamp dissapered.

When the battery charge low, it needs constant charging, charging needs power,it gives by engine, if demand more, need higher charging rate. Normally alrernator charging is not so smooth, it is not pure sine wave rectification.

Simply, what i mean to say is just clear the doubt, start from easy way, easiest is

1) check battery health(by meter,which shows good/bad by loading)

2) if it shows bad, fit battery temporary and see the light indication going off

3) if it goes off,battery! If not check alternator .

I mention about fuel consumption, alternator overloading by my personal experience.

I just tried to give a clue.

Premio · October 10, 2017

Car battery is charged by alternator. If your battery is weak, more charging required. So alternator will be running under high load than normal. Alternator is getting power by the engine. Finally engine need to do little extra work. So the engine need little extra fuel.

Also keep in your mund, at this time alternator also getting overload. So it is affecting alternator too.

Better to change the battery always early,it can save your fuel,alternator and your valuable time too.(in case if you have Auto gear car,you have to change the battery if it stopped on the way)

Premio · October 9, 2017

First of all you simply visit a battery shop. They have meter to check battery by loading it shows the battery health. Green zone and red zone. It is available in many service stations too. If it shows battery bad condition, just request them to fit a battery and check whether your battery indicator still on! If it has dissapered, your battery is need renewal. Green light indication shows electrolyte level. It can't say anything about battery cell condition.

Another thing you mentioned, it is dissapered in higher rpm, and comes back in low rpm again. Most probably your battery condition deteriorating! Time to change battery. It will cause to incresing fuel consumption too!