# Alternator and battery: I thought it was a simple question **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** batteries, alternators\ **Created:** [October 25, 2014, 3:57am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807 "2014-10-25T03:57:48Z")\ **Posts on this page:** 11\ **Page:** 2
**Author:** ![B.L.E](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@B.L.E](https://community.cartalk.com/u/B.L.E)\ **Post date:** [October 26, 2014, 3:43am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/21 "2014-10-26T03:43:25Z")
I thought that the idea behind computer controlled voltage regulation was to make the alternator do most of the charging during deceleration, when the engine is braking anyway. ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [October 26, 2014, 5:00am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/22 "2014-10-26T05:00:10Z")
For years, my Hondas have had an “electric load detector” that senses when the battery is fully charged. Then it drops the alternator output from 14.5V to 12.8V. When you lift off the accelerator, it instantly goes back up to 14.5V. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [October 26, 2014, 8:45am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/23 "2014-10-26T08:45:35Z")
Regardless of the reason, a car will stall if the battery gets too low and doesn’t provide the proper voltage, which is what I based my reasoning on, right or wrong. If the battery is so old its not taking a charge, its the same as the alternator not putting out enough. So yeah, get a new battery. Thinking of parasitic drains, my Acura has three positions for the interior lights-on, off, and door. When it is in the “door” position, the lights go on when the door is opened and shut off when the door is closed-same as cars for the last 50 years. But when it is in the door position, it has a green LED that stays on telling you its in the door position. Drives me nuts to see that light on all the time in addition to that blinking security light. It maybe doesn’t take much but still I like to see stuff off when the car is parked. ---
**Author:** ![MarkM](https://avatars.discourse-cdn.com/v4/letter/m/9de053/32.png) [@MarkM](https://community.cartalk.com/u/MarkM)\ **Post date:** [October 27, 2014, 5:24am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/24 "2014-10-27T05:24:03Z")
All of the new electric devices and the power they use is a major concern of automakers. There is a very good chance cars will be upped to 24 volts in the next decade. It’s been talked about quite a bit in recent years, but the changeover would be costly and the automakers were trying to cut costs, not increase them. Clever management of demand has let them get by so far. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [October 27, 2014, 7:48am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/25 "2014-10-27T07:48:52Z")
I heard the voltage would increase to 42V ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [October 27, 2014, 9:04am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/26 "2014-10-27T09:04:01Z")
I wonder if the lead-acid battery, after 150 years of service, is about to fade into automotive history…They will have to find a lot more Lithium for that to happen… ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [October 27, 2014, 9:04pm UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/27 "2014-10-27T21:04:05Z")
I heard 42V also, but the 42V will be for the starter, alternator and valve actuation (computer controlled solenoid actuated valves). The center cells of battery that comprise the 12v could be used for the rest of the vehicle with the ground coming from one of the center taps. The 42v would be push-pull, that is +30/-12. More expensive battery but less expensive accessories, at least at first. ---
**Author:** ![B.L.E](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@B.L.E](https://community.cartalk.com/u/B.L.E)\ **Post date:** [October 28, 2014, 5:53am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/28 "2014-10-28T05:53:18Z")
One of the biggest problems with a tapped battery is keeping the state of charge of the cells balanced. The 12 volt draw only discharges 6 of the 20 cells but the alternator recharges all of the cells thus overcharging the cells that add 30 volts to the 12 volts, unless the alternator has a independent +30 and -12 volt output which may be the case. I have a feeling we will start seeing 42 volt headlights, radios, etc. in cars eventually if this happens. Another possibility is a switching regulator to take the 42 volts down to 12 volts. They aren’t that expensive and are very efficient. I have one in my electric radio control airplane that takes the 25 volts of the motor power battery down to 4.8 volts to power the receiver and servos, eliminating the need for a separate receiver battery. ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [October 28, 2014, 7:33am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/29 "2014-10-28T07:33:16Z")
At 42 volts, they could reduce the wire size by at least half, saving a lot of money… ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [October 29, 2014, 4:01am UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/30 "2014-10-29T04:01:18Z")
By putting the 12v in the center of the battery, the cells are kept even. Tapping at one end or the other of a battery causes a problem. But I like the idea of the 12 regulator. ---
**Author:** ![MarkM](https://avatars.discourse-cdn.com/v4/letter/m/9de053/32.png) [@MarkM](https://community.cartalk.com/u/MarkM)\ **Post date:** [October 29, 2014, 12:47pm UTC](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807/31 "2014-10-29T12:47:57Z")
Different companies seem to be proposing different ‘standards’. Until they all agree we probably won’t get any change. What’s clear it that the current 12 volt system can’t do much more. [Previous page](https://community.cartalk.com/t/alternator-and-battery-i-thought-it-was-a-simple-question/87807.md?page=1)