# Battery or alternator **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** plymouth, voyager\ **Created:** [October 4, 2009, 4:34am UTC](https://community.cartalk.com/t/battery-or-alternator/37562 "2009-10-04T04:34:00Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![raycyrx](https://avatars.discourse-cdn.com/v4/letter/r/f07891/32.png) [@raycyrx](https://community.cartalk.com/u/raycyrx)\ **Post date:** [October 4, 2009, 4:34am UTC](https://community.cartalk.com/t/battery-or-alternator/37562/1 "2009-10-04T04:34:00Z")
Using a volt meter on the battery, what should the readings be with the engine off and on? In other words, what’s a quick and dirty method of determining if I have a battery or alternator problem? ---
**Author:** ![pgdyk1](https://avatars.discourse-cdn.com/v4/letter/p/dbc845/32.png) [@pgdyk1](https://community.cartalk.com/u/pgdyk1)\ **Post date:** [October 4, 2009, 4:39am UTC](https://community.cartalk.com/t/battery-or-alternator/37562/2 "2009-10-04T04:39:00Z")
bout 12 volts at the battery. 14+ with the engine running. some alternators only charge over 1000 rpm or so just so you know. ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [October 4, 2009, 5:20am UTC](https://community.cartalk.com/t/battery-or-alternator/37562/3 "2009-10-04T05:20:07Z")
The battery voltage will depend on the state of charge of the battery. A good, full charged battery should show 12.6 volts with the engine off but a voltmeter is not always a definitive test for either the battery or the alternator as neither one is loaded so to speak. A somewhat back yard method for checking the battery with a voltmeter is to make sure the battery is fully charged, disable the engine so it will not start, and crank it over for about 10-15 seconds with the voltmeter attached. At the end of the cranking period the voltmeter should show about 10.2 volts at a minimum. If it goes below 10 the battery is iffy. ---
**Author:** ![EllyEllis](https://avatars.discourse-cdn.com/v4/letter/e/f14d63/32.png) [@EllyEllis](https://community.cartalk.com/u/EllyEllis)\ **Post date:** [October 4, 2009, 5:52am UTC](https://community.cartalk.com/t/battery-or-alternator/37562/4 "2009-10-04T05:52:51Z")
“A good, full charged battery should show 12.6 volts with the engine off” Well, if he had a good, fully charged battery, he wouldn’t have a problem, would he?? ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [October 4, 2009, 6:14am UTC](https://community.cartalk.com/t/battery-or-alternator/37562/5 "2009-10-04T06:14:47Z")
Maybe, maybe not. A good battery should show 12.6 volts but a bad battery can show the same voltage reading. The difference between the good and the bad would depend on how quickly and how much the voltage drops when a load is applied. At this point there hasn’t been much info provided about the exact symptoms or anything else and I have no idea if any battery readings are being taken on a rundown battery or what those readings are if the vehicle even starts and runs. ---
**Author:** ![oldschool](https://avatars.discourse-cdn.com/v4/letter/o/e19adc/32.png) [@oldschool](https://community.cartalk.com/u/oldschool)\ **Post date:** [October 4, 2009, 7:38am UTC](https://community.cartalk.com/t/battery-or-alternator/37562/6 "2009-10-04T07:38:57Z")
Another Elly zinger,Elly do baterys last longer if they are providing power for a V-6 or V-8? maybe it depends on how the engines are balanced or the spacing in the power impulses.