# How fast should a six month old battery drain down?

#### Oro_O

Had a bad alternator that was draining down the battery. Resolved. Battery is a NAPA and purchased and installed 4/1/2022; sticker on it indicates manufacture 1/22.

After fulling charging or driving, it sits at 12.6V or a hair under. The next day it will be 12.45 or so, today it was 12.3V. I’ve been checking since I replaced the alternator and resolved the draw. I ran a desulfation routine with a smart charger on it and recharged it fully that way to offset any damage the brief period with a draw may have done.

Normal? Too much for a new battery?

#### fsdork

Someone who knows more about batteries than I do will chime in, but from my tinkering with batteries in relation to my travel trailer, I would consider the following:

1) I would not expect any measurable self-discharge from a battery in a matter of a couple/few days. My flooded lead acid batteries sit in my heated garage over the winter, and lose voltage very slowly - weeks or months before they are down one or two tenths of a volt.

2) You resolved the draw associated to the alternator issue, but have you since measured for any key-off draw that persists from other sources? If there is any draw remaining, the math could be done on that as compared to battery capacity.

3) The voltage measured immediately after engine shutdown could be subject to a false-high surface charge. After engine shutdown, if you turn an electrical load on (headlights with high beams) while the engine remains off for around 5 minutes, then turn the load off for 5 minutes to let the battery rest, you may find a significantly lower reading than the 12.6 volts you're getting now. In other words, your battery could be at, for example, a "true" voltage of 12.5 when you get home.

#### Lubener

It shouldn't drain that fast, hopefully measured with a good DVM. 12.3v is practically a dead battery. I would have the battery load tested as a first step. Measuring statically isn't the best way to determine the condition of the battery.

#### Duffyjr

I started monitoring my last AGM about 2 years before it actually started cranking slower and was replaced before winter. I normally only drive the truck on weekends during the summer so battery sits for a few days in between starts. As I was checking the voltage over that 2 years there were times when it would give me voltages below 12 but mostly low 12's but it turned the engine over like it was new 🤷‍♂️

I really don't put much stock in the voltage reading any more, my test is how fast it's cranking the engine.

#### Trav

Had a bad alternator that was draining down the battery. Resolved. Battery is a NAPA and purchased and installed 4/1/2022; sticker on it indicates manufacture 1/22.

After fulling charging or driving, it sits at 12.6V or a hair under. The next day it will be 12.45 or so, today it was 12.3V. I’ve been checking since I replaced the alternator and resolved the draw. I ran a desulfation routine with a smart charger on it and recharged it fully that way to offset any damage the brief period with a draw may have done.

Normal? Too much for a new battery?
How much parasitic drain does it have now? A brand new battery manufactured yesterday will drain down quickly if the vehicle has a higher than normal parasitic draw.

#### Rand

are you checking the voltage with a meter at the battery or using the dash voltage readout?

#### Oro_O

The draw now was pretty minimal - well under 20ma IIRC. The alt. diodes were the prior culprit. I’m going to check it again today just to make sure. Using a good MM between post and ground lead, not any instrumentation.

Tuesday night after driving and sitting a few hours (fully charged on weekend) - 12.6V
Weds, no use - 12.45V
Thurs, no use - 12.3V
Today, no use - 12.15V

I’ll check draw again but I found none on Monday.

#### Oro_O

I checked the draw before dinner tonight, 0 mA. It has been sitting three days w/o starting. Guess I’ll be getting a replacement battery tomorrow. (Warranty)

#### SC Maintenance

FWIW - I bought a cheap battery tester when they were on sale at the Bezos empire, and think it was well worth buying. I think I only paid like \$25 bucks, but I would pay a lot more than that knowing how well they work now.

#### Oro_O

FWIW - I bought a cheap battery tester when they were on sale at the Bezos empire, and think it was well worth buying. I think I only paid like \$25 bucks, but I would pay a lot more than that knowing how well they work now.
It is able to load test or what kind of test(s) does it perform? Sounds interesting.

#### ripcord

Try disconnecting the battery when letting the battery sit for a few days to ensure there is nothing drawing power. If it still drops that quickly your battery has issues.

#### SC Maintenance

It is able to load test or what kind of test(s) does it perform? Sounds interesting.
It gives cranking amps or cold cranking apps dependent on how set up, state of charge, state of health, and internal resistance of the battery. It goes through a test cycle which I assume is some sort of emulated load test since its a tiny thing. So far its worked really well. I watched a couple youtube videos that said if state of health dropped below 60% the battery is going bad. Its happened twice, and both times I took the battery in to walmart and they tested it themselves and replaced, even though they both easily started the car.

#### Oro_O

It gives cranking amps or cold cranking apps dependent on how set up, state of charge, state of health, and internal resistance of the battery. It goes through a test cycle which I assume is some sort of emulated load test since its a tiny thing. So far its worked really well. I watched a couple youtube videos that said if state of health dropped below 60% the battery is going bad. Its happened twice, and both times I took the battery in to walmart and they tested it themselves and replaced, even though they both easily started the car.

Thanks. that sounds useful. We have enough vehicles, a boat, bikes, an atv and it seems like I'm always charging or diagnosing a battery all the time. Even with use and/or vehicles on trickle maintainers. I didn't know a good tool like that was so cheap.

I got a slightly better "cheap" charger that has a desulfate mode and that has been very helpful. That tool would be a good addition to save time diagnosing.

#### Trav

I checked the draw before dinner tonight, 0 mA. It has been sitting three days w/o starting. Guess I’ll be getting a replacement battery tomorrow. (Warranty)
You must not have had the meter set right or didnt do it properly, 0 mA parasitic draw is impossible on a modern car. A 1940's car would have more than with no ECM if it only had an electric clock.

#### Oro_O

You must not have had the meter set right or didnt do it properly, 0 mA parasitic draw is impossible on a modern car. A 1940's car would have more than with no ECM if it only had an electric clock.
No, it's correct. I'm getting microAmp measurements consistent with the memory draw, I just didn't get into it. The alarm was not enabled, which is the only thing that bumps it up into mA range draw.

#### Silver

I started monitoring my last AGM about 2 years before it actually started cranking slower and was replaced before winter. I normally only drive the truck on weekends during the summer so battery sits for a few days in between starts. As I was checking the voltage over that 2 years there were times when it would give me voltages below 12 but mostly low 12's but it turned the engine over like it was new 🤷‍♂️

I really don't put much stock in the voltage reading any more, my test is how fast it's cranking the engine.
I've seen the same. I've been like, "oh no, my battery is going dead fast!" based on these charts floating around. But they crank as fully charged and have remained good for years (knock on wood!).

But this guy I think has an issue. 12.15 after three days is low even for my dismissive opinion.