Replacing battery with one of a lower AH (amp-hour) rating?

blip · 30th November 2018, 10:58

My Grand i10 1.2 Petrol AT battery is due for replacement. I checked the OEM battery which is 40 ah. But none of the dealers are having 40 AH batteries, including online portals like batterywale etc. They all have 35 AH batteries only.

My question is, is it safe to go ahead with a 35 AH battery? Will I encounter any problems?

blackwasp · 30th November 2018, 11:19

Ah will just give you an estimate of how long a battery will last at that current level. eg. the 35Ah battery will supply 35A for 1 hr before the battery drains out while the 40Ah will supply 40A for 1 hr. This doesn't mean the batteries can't supply higher current, it's just that they will last for a lesser time on a full charge.

If you don't have any electrical accessories that would require the higher juice battery (eg aftermarket music system), it should not pose a problem keeping all other parameters of the batteries same.

You will also have to consider not using music system (or reducing the time) with the engine off.

sagarpadaki · 30th November 2018, 11:44

The battery is mainly used for starting the car and supply power in case the power demand exceeds the alternator capacity. The battery also acts as a surge protector absorbing any power surges by the alternator. So if you have a bone stock car with no 100/90 headlamps or Aftermarket amplifier and stereo, you can go for the lower ampere battery without issues.

For example, if the alternator is rated @ 120Ah, from the moment the car is started, all the power needs in the car is provided by the alternator including charging the battery. Now if the sum of the electrical load exceeds 120Ah then the excess demand is provided by the battery. In such a case, the battery is in drain-in-progress condition.

However, if you are someone who uses the stereo with the car turned off, in such case the amount of time you can use the stereo before the battery charge reaches below the minimum threshold to start the car will be less. Say, with 40Ah battery, you could use the stereo with the engine turned off for 1Hr before the battery charge reached the minimum threshold. In the case of 35Ah, you can use the stereo for 45 mins by the time the battery reaches the minimum charge threshold.

Note: The minutes/hours are just indicatory for the example.

blip · 30th November 2018, 11:56

Quote:

Originally Posted by sagarpadaki

The battery is mainly used for starting the car and supply power in case the power demand exceeds the alternator capacity. The battery also acts as a surge protector absorbing any power surges by the alternator. So if you have a bone stock car with no 100/90 headlamps or Aftermarket amplifier and stereo, you can go for the lower ampere battery without issues.

For example, if the alternator is rated @ 120Ah, from the moment the car is started, all the power needs in the car is provided by the alternator including charging the battery. Now if the sum of the electrical load exceeds 120Ah then the excess demand is provided by the battery. In such a case, the battery is in drain-in-progress condition.

However, if you are someone who uses the stereo with the car turned off, in such case the amount of time you can use the stereo before the battery charge reaches below the minimum threshold to start the car will be less. Say, with 40Ah battery, you could use the stereo with the engine turned off for 1Hr before the battery charge reached the minimum threshold. In the case of 35Ah, you can use the stereo for 45 mins by the time the battery reaches the minimum charge threshold.

Note: The minutes/hours are just indicatory for the example.

Thanks, I forgot to mention in my original post i am running a Dashcam and TPMS (Tire pressure monitoring system). Both are connected to the two 12V sockets in my car. Hope that isn't an issue with the lower Ah battery.

vikram_d · 30th November 2018, 12:55

Why don't you try the next bigger size if it fits in the battery bay/box?

dhanushs · 2nd December 2018, 09:34

^^ +1

Like vikram_d said, if it fits in your battery box, its always better to go for a higher ah battery. You never know when you need those extra cranks.

30th November 2018, 10:58	#1
blip BHPian Join Date: Jun 2008 Location: Bangalore Posts: 45 Thanked: Once	Replacing battery with one of a lower AH (amp-hour) rating? My Grand i10 1.2 Petrol AT battery is due for replacement. I checked the OEM battery which is 40 ah. But none of the dealers are having 40 AH batteries, including online portals like batterywale etc. They all have 35 AH batteries only. My question is, is it safe to go ahead with a 35 AH battery? Will I encounter any problems? Last edited by GTO : 3rd December 2018 at 09:35. Reason: Poorly typed post
	() Thanks $Received Infraction$

30th November 2018, 11:19	#2
blackwasp Senior - BHPian Join Date: Apr 2015 Location: Navi Mumbai Posts: 2,974 Thanked: 26,325 Times View My Garage	re: Replacing battery with one of a lower AH (amp-hour) rating? Ah will just give you an estimate of how long a battery will last at that current level. eg. the 35Ah battery will supply 35A for 1 hr before the battery drains out while the 40Ah will supply 40A for 1 hr. This doesn't mean the batteries can't supply higher current, it's just that they will last for a lesser time on a full charge. If you don't have any electrical accessories that would require the higher juice battery (eg aftermarket music system), it should not pose a problem keeping all other parameters of the batteries same. You will also have to consider not using music system (or reducing the time) with the engine off. Last edited by GTO : 3rd December 2018 at 09:36. Reason: Removing quoted post which has been edited
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30th November 2018, 11:44	#3
sagarpadaki Distinguished - BHPian Join Date: May 2010 Location: Bengaluru Posts: 4,213 Thanked: 5,881 Times	re: Replacing battery with one of a lower AH (amp-hour) rating? The battery is mainly used for starting the car and supply power in case the power demand exceeds the alternator capacity. The battery also acts as a surge protector absorbing any power surges by the alternator. So if you have a bone stock car with no 100/90 headlamps or Aftermarket amplifier and stereo, you can go for the lower ampere battery without issues. For example, if the alternator is rated @ 120Ah, from the moment the car is started, all the power needs in the car is provided by the alternator including charging the battery. Now if the sum of the electrical load exceeds 120Ah then the excess demand is provided by the battery. In such a case, the battery is in drain-in-progress condition. However, if you are someone who uses the stereo with the car turned off, in such case the amount of time you can use the stereo before the battery charge reaches below the minimum threshold to start the car will be less. Say, with 40Ah battery, you could use the stereo with the engine turned off for 1Hr before the battery charge reached the minimum threshold. In the case of 35Ah, you can use the stereo for 45 mins by the time the battery reaches the minimum charge threshold. Note: The minutes/hours are just indicatory for the example. Last edited by GTO : 3rd December 2018 at 09:37. Reason: Removing quoted post which has been edited
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30th November 2018, 12:55	#5
vikram_d Senior - BHPian Join Date: Jul 2006 Location: Bangalore Posts: 2,427 Thanked: 1,185 Times	re: Replacing battery with one of a lower AH (amp-hour) rating? Why don't you try the next bigger size if it fits in the battery bay/box?
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2nd December 2018, 09:34	#6
dhanushs Distinguished - BHPian Join Date: Oct 2009 Location: Chennai Posts: 4,282 Thanked: 10,181 Times	re: Replacing battery with one of a lower AH (amp-hour) rating? ^^ +1 Like vikram_d said, if it fits in your battery box, its always better to go for a higher ah battery. You never know when you need those extra cranks.
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