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-   -   Signs that battery needs a replacement (https://www.team-bhp.com/forum/technical-stuff/22945-signs-battery-needs-replacement-5.html)

I have two questions:

1. Why do we need to crank the engine longer when the battery is nearing the end of life? Whether the battery is weak or strong, once the engine rotates, it shall fire up in the same time. Is it that the weak battery does spin the starter but at a lower speed and so it takes longer for the crankshaft to make same number of rotations?

2. Why, with a weak or dead battery, the engine switches off, especially at the idle? Once the engine fires up, the alternator shall supply to the spark plugs, throttle motor etc.

Rather than rotations, on a modern car there are other electrical components that needs to operate simultaneously to ensure that the motor fires and idles correctly, hence why you see a car with a weaker battery taking more time to fire as the starter motor puts considerable load on the battery which is also the source of power for the said electrical components.

A weak/dead battery does more harm than good i.e it persistently draws current and as the ECU and such electrical's are powered from the Battery which is powered from the Alternator, a weak battery would mean that at idle inadequate current is being passed on to the other dependent electrical's as a result of which the car stalls.

My Polo GT TSI seems to take slightly longer to crank - however the one piece I noticed is the "electronics check" (where we see all the lights/warnings lighting up on the speedo) happens even after the engine cranks. My stereo also restarts once the engine is fired up.

The car is 3 years old. I trust the above is a good sign that the battery should be changed? Also, I did a check on batterybhai - there was no GT TSI listed there. The there is only the Polo 1.2 Petrol. Will the battery for the 1.2 petrol work for the TSI as well? Thanks!

Hi guys,

The stock battery of my 2014 Swift petrol was replaced last year (6-8 months back) and is working absolutely fine. However, I found some liquid spill from the battery when I was cleaning the engine bay today. There was some corrosion on battery tray and terminals. The battery is Exide Dynex.







Is this normal or should I try to get it replaced under warranty?

The car is completely stock apart from a pair of 100/90 halogens.

Get cranking voltage measured before replacing the battery. Most car battery dealers do this test for free.

The stereo restarting after crank is normal i believe. The acc line is temporarily disconnected during cranking in most cars.

Regarding the battery spec, you can check the battery type written on your current battery (will either be xxAH or DIN xx) - xx is the AH rating of the battery or refer the user's manual.

This happened to me due to my over enthusiasm. I filled cells with excess distilled water & it boiled out while charging in my long run in highway. The boilover corroded the bottom plate & retaining screws. Had to sand & paint with black spray paint.

One thing to observe is the crank time. Mine is showing strained start, which is expected since acid : distilled water concentration is now diluted. Attack the corrosion ASAP with a layer of paint. Check voltage of battery both at rest & while running with your nearest battery shop.

Thanks for the info. As this issue has come days after I got the car serviced, maybe the workshop guys would have messed with the battery during service.

I had cleaned the earlier spill on Wednesday and it hasn't occured since then. Crank times are also normal. I will have to address the corroded battery tray though.

Hi FOW,

Can you please share which battery and from where did you install on your GT TSI.?

Thanks :)

My Ciaz ZDI is completing four years and it is taking longer to start. The SHVS system stopped working about 6 months back and the battery weakening could have been the reason. I used a multimeter to check the battery voltage. The voltage was about 12.4V in idle condition, but the moment the engine was cranked the voltage went down to 8V. It quickly went back to 13V, so i believe the charging system is good.
Is there any juice left in the battery or should i replace. My worksite is about 100kms away.

This is not a valid reason. You are presuming something without being clear about how automotive lead-acid batteries (and charging systems) work. Distilled water does not "boil" in a battery in modern cars, nor does spilling over of DW cause "strained start".

It is time you replace the battery, 8V during cranking is on the lower side. I feel it should be around 10V during cranking.

Correct.

The problem at 8V is not necessarily the starter motor not being able to turn the engine fast enough. On modern cars when the voltage drops below 10V the electronics start playing up. I have seen many cases where the engines were turning pretty good on the starter but would not catch/start. Simply because the electronics were not working due to too low voltage during starting.

Not quite sure what you mean with 12.4V at idle? With the engine switched of I guess. When an engine is running at normal idle rpm you should have at least 13.0V on the battery terminals. Anything less means the batter is not charging or there is something wrong with the battery.

12.4V is considered just about charged, but even if it drops below by a few mV you have quite the discharge. A new well charged battery usually reads a little higher, e.g. 12.6V

But the voltage dropping well below 10V is definitely the give away: that battery has had it and needs replacing.

Good luck

Jeroen

I did replace the battery, bought a 74DIN SF Sonic battery for the Ciaz Diesel, costed me 7500/ with exchange. When i meant 12.4V, it was with the engines stopped.
Did the measurements again with the new battery. The voltage dropped to 10.8volts with the new battery and then went upto 13.5V when the alternator took over. The SHVS system started working again and reinforces the thinking that the SHVS system requires a perfect battery, even though it may start your car. Another point of debate is if a bad battery can cause increased fuel consumption. The alternator will be on load for a longer time to charge the discharged battery. I felt my mileage was going down , could be some other reason also.

Well, in theory it would, but I am not so sure whether it would be noticeable in practice. Say your alternator would be pushing out 40amps continuously (not revving the engine to its max, normal driving) as you have a poor battery.

40A at 12V is only 500W. Even if it would be putting out double the current, it would only be 1kW. To put that into perspective, your car’s AC is likely to draw 2-4kW at best/worse. Depends a bit on the size of your engine of course, but the use / non use of AC can show up on your fuel efficiency. A poor battery condition? I doubt it, but perhaps other members have more insights.



Jeroen

I had my burnt starter motor replaced yesterday. The battery had been showing signs of aging since couple of months. Did get clicking sounds earlier on 2 occasions 2 months and 1 month before and the car didn't start. Push started it. Apart from those 2 occasions no other issue in starting. During the lockdown I was working so the battery didn't give any trouble. On weekends if I didn't use it for 3 days continuously the battery would run out of juice. So, I used to idle the car few minutes everyday on the weekends.

I drove through fairly deep flooded waters day before yesterday. The water caused a short circuit and the car autocranked as soon as I put the key in the ignition. What could be the cause for the starter motor to burn? The flood waters or using a aging battery for months?

Here's the report of my battery from Fiat ASS. The report says REPLACE. I don't really believe that on face value. I want to look at it quantitative ly. Do the numbers on my battery appear good to go or should I Replace?

Car is Linea MJD. 76PS. 50Ah. Stock Exide 4 years 8 months. 50000kms.