Battery Voltage Testing
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Road Master
Joined: Nov 2018
Posts: 860
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From: CA
Battery Voltage Testing
My battery on my sportster (2019) seems to be on its way out. It is a little over 3 years old.
So, testing with a volt meter:
1. After a couple of minutes with the ignition turned on... then turned off: 12.3
2. With ignition on: 11.95
2. While cranking over: 8.7
3. While idling and/or throttle @2000 rpm: 13.87-13.90
So, it seems I definitely need a new battery. But while idling voltage should be 14-14.7 correct? My reading was around 13.9... so wondering if I have a problem with my stator or regulator? Or maybe I am seeing an underrepresented voltage reading from any variance that may be associated with my meter?
So, testing with a volt meter:
1. After a couple of minutes with the ignition turned on... then turned off: 12.3
2. With ignition on: 11.95
2. While cranking over: 8.7
3. While idling and/or throttle @2000 rpm: 13.87-13.90
So, it seems I definitely need a new battery. But while idling voltage should be 14-14.7 correct? My reading was around 13.9... so wondering if I have a problem with my stator or regulator? Or maybe I am seeing an underrepresented voltage reading from any variance that may be associated with my meter?
Last edited by cj24; Mar 8, 2023 at 08:07 PM.
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,586
Likes: 6,435
From: Honah Lee
My battery on my sportster (2019) seems to be on its way out. It is a little over 3 years old.
So, testing with a volt meter:
1. After a couple of minutes with the ignition turned on... then turned off: 12.3
2. With ignition on: 11.95
2. While cranking over: 8.7
3. While idling and/or throttle @2000 rpm: 13.87-13.90
So, it seems I definitely need a new battery. But while idling voltage should be 14-14.7 correct? My reading was around 13.9... so wondering if I have a problem with my stator or regulator? Or maybe I am seeing an underrepresented voltage reading from any variance that may be associated with my meter?
So, testing with a volt meter:
1. After a couple of minutes with the ignition turned on... then turned off: 12.3
2. With ignition on: 11.95
2. While cranking over: 8.7
3. While idling and/or throttle @2000 rpm: 13.87-13.90
So, it seems I definitely need a new battery. But while idling voltage should be 14-14.7 correct? My reading was around 13.9... so wondering if I have a problem with my stator or regulator? Or maybe I am seeing an underrepresented voltage reading from any variance that may be associated with my meter?
Your 12.3 is very confusing. Mainly why I am surprised your other test are good ..
I am surprised it cranked.
That idle test should be at 2000 rpm. Over 13.5. Under 15 depending on battery condition and charge.
Your battery is badly sulfated or worn out.
Charge it on a milliamp maintenance charger 24 hours. Kill the surface charge with headlights on and off. Key off, should be 12.6-12.8. Cranking no lower then 8.7.
Aways test fully charged. All test on both lead of battery and wire
Never load test on bike .
I would replace it if it fails what I suggest. You don't want that last start being at home after removing it from a maintenance charger.
All just my opinion and as a suggestion. Just what works for me.
Last edited by Jackie Paper; Mar 9, 2023 at 07:42 AM.
Seasoned HDF Member
Joined: Sep 2017
Posts: 12,254
Likes: 4,946
From: England
A load tester I have seen will pull maybe 100Amps. As the starter motor probably pulls more than that what harm does it do or what won't be proved if the tester is used whilst the battery is connected?
Last edited by Andy from Sandy; Mar 9, 2023 at 07:37 AM.
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Tourer
Joined: May 2011
Posts: 469
Likes: 158
From: Alberta
Charge the battery up, check the voltage and then let it sit for 24 hrs. If it reads 12.5 or lower resting, after the 24 hrs. replace the battery.
You can only get good accurate charging readings off of a good healthy battery with the bike running. If you do the tests on a weak battery your voltage readings will be low. From your readings I would replace the battery.
You can only get good accurate charging readings off of a good healthy battery with the bike running. If you do the tests on a weak battery your voltage readings will be low. From your readings I would replace the battery.
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Road Master
Joined: Mar 2013
Posts: 817
Likes: 380
From: Central Ohio
You expect a battery that is designed at 12.6v to not even lose .1v after 24hrs?