Battery Discharge Rate... Old vs. New ??

[billt460]

I have a general question for those of you who are well versed in automotive electrical systems, as I'm not. About how much more of a drain do the newer vehicles place on the battery, with their advanced computers and alarm systems, that the older vehicles did not have, when they are sitting?

I've often wondered if you took say a 70's pickup in good electrical shape, and a new 2018 model, and placed them together with identical capacity, fully charged batteries, how much faster would the newer model drain the battery if both were just sitting?.... Or would it?

What got me thinking about this, is my neighbor has a really nice late model Nissan pickup, and he drives it very little. And when he does it is only for very short trips. The other day they came and hauled it away on a transporter... Dead as a doornail. I talked to him about it, and he told me it had been sitting for over 2 weeks. The dealer called him and said the battery was gone. They then inquired about his driving habits, and told him the car wasn't being driven enough to sustain the battery. (There were no shorts or other electrical problems with the vehicle). They told him to either drive it more, or else get a Battery Tender for it. Or the same thing would occur.

I try to never go beyond 3 days without at least a 20 minute run on my newer vehicles, (2015 & 2018). And at least once a week for my 1991. I've never had any issues in regards to battery life. In all of my past vehicles they seem to last as long as anyone's out here in the Southwest desert heat. Usually 2 Summers, then you're on borrowed time.

 

[supton]

Short trips, so the battery never got topped off. I bet an older car would do the same thing. But newer cars do have parasitic loads.

IIRC, my VW would turn off more of those loads if wasn't started in say a month, so as to attempt to not drain the battery any faster than usual. [Blinking alarm lights would stop blinking, that sort of thing.]

Not sure what the longest sitting is but I do go sometimes two weeks between starting my truck. It's managed.

 

[JHZR2]

That's relative. My mechanics, diesel Mercedes cars power nothing but a quartz clock in one, that plus radio memory on another. Maybe a fraction of a mA.

Any car, regardless of age, will deplete a battery of given Ah, in a given amount of time, with a given mA draw.

The newer cars have more computer modules that can potentially not go to sleep/low power mode. But assuming we're talking vehicles with fewer than all the fanciest doodads, getting them to less than 30-50mA is doable. Until it isn't. Computer modules and wiring harnesses with high resistance shorts are an issue. But older computer modules drew more power for less capability, so they can be problematic too. This isn't a 2018 issue per se.

No alternator truly charges a battery full. Some new ones have more elaborate charge controls and can slow the process further. Short trips were never good on vehicles.

Dome lights, courtesy electronics operating after a car shuts off, etc are all a recipe for shorter life. Lead acid batteries must be at 100% charge or else they will sulfate. Pulling those minor loads shortens the time reserve before these conditions begin.

 

[SilverSnake]

I never have a problem with my batteries even on infrequently used cars like my toy car (2016 Charger Scat Pack). I monitor the batteries health with my Midtronics PBT300 (check them all at least once a week).

https://www.amazon.com/Midtronics-PBT300...ords=midtronics

If a battery reads below specs (CCA/Voltage), I hook up the CTEK and give it a ful charge. Easy as can be.

https://www.amazon.com/CTEK-56-353-12-Volt-Battery-Charger/dp/B000FRLO9Y

 

[djb]

It varies quite a bit between vehicles.

Modern alternators (anything from the mid-1980s onward) do a better job of charging, but older vehicles tend to have lower off-state current usage

Very basic old vehicles use essentially no off current. Mechanical clocks use more than you expect, but there were few other sources of current drain.

Modern vehicles have modules that 'sleep' with very little current draw, rather than being switched off. This usually works great, until something keeps a module from going to sleep. They generally wake up, or remain awake for another few minutes, with every message on the communication bus. An occasional message on the bus from a rogue module can quickly drain the battery with no way to figure out what happened.

 

[billt460]

How do the new electronic odometers maintain their memory when the battery goes dead, or is changed?

 

[billt460]

Originally Posted By: djb
Modern alternators (anything from the mid-1980s onward) do a better job of charging,.....


I know RAM offered a 180 Amp alternator on their Cummins Turbo Diesel RAM 2500 in 2017. I remember it wasn't that long ago if you had a 65 Amp alternator, that was considered big.

 

[dogememe]

My 97 Suburban can sit for over a month, be run for 5 minutes to move it around, sit for another month, and still start right up.

 

[maxdustington]

Originally Posted By: dogememe
My 97 Suburban can sit for over a month, be run for 5 minutes to move it around, sit for another month, and still start right up.

GMT400 = truck perfection.