Battery damage in one night of low voltage?

softdown · February 2020

My case pertains to an auto battery. But the "science" carries over to off grid batteries.

Used the emergency flashers until they cut out and died. Was too late and tired to mess with a cold midnight. Charging this morning. Charger says battery started at "25 %" charged. Slightly less than 12 volts.

I do wonder if low voltage for a short period does significant damage. I would hope that the sulfation process would be more lengthy - at least a few days. A few weeks, or even months, would be much better.

Sometimes I use my solar batteries early in the morning prior to the sun naturally charging them. It is remarkable what a little internet and TV or computer can do to cold, morning voltage. Say 49.8 drops to 49.6ish for an hour or so. It does lengthen and intensify the recharge process. So should be avoided when possible. But how much real damage took place I wonder.

FWIW a cold (30Fish) 12.4 volts is a warm 12.5 volts. Or a cold 49.8 volts is a warm 50.2 volts.

TLDR: battery damage with 8 hours of low voltage?

Dave Angelini · February 2020

When you number is up it is up! How many other times have you done this? It is cumulative but I don't think you can equate a car battery with a large offgrid battery. Cats and 9 lives work with car batteries. Does it have water in it?

48 volts and below without a load are not good numbers for long life. You are not near that.

softdown · February 2020

The problem with the Prius 12 volt battery is disassembling much of the rear to get at it. Watched a youtube video and found how to charge from the fuse panel. Would have been an ordeal at midnight - was exhausted from towing a car though black lengthy ice conditions. Unnerving really.

How many times? Once - that I recall.

You are talking at an elementary level: "48 volts and below without a load are not good numbers for long life. You are not near that"

I was asking about "an hour of reduced voltage" for off grid batteries. Or 8 hours for an auto battery.

Photowhit · February 2020

softdown said:

- was exhausted from towing a car though black lengthy ice conditions.

While I often lament on how difficult it is to freeze a lead acid battery....
...your's might have frozen. You shouldn't try to charge frozen battery.

BB. · February 2020

In my humble opinion, taking an older (say older than 1 year) FLA car battery "dead"--Even if you get it recharged and running, it can very easily die again in 1-14 days at any random time. I have seen cars started in the morning, drive to the store, sit for an hour, and then simply not even crank over the engine.

If you can live with the "unreliable battery" (have AAA available for jump start, carry some sort of Jump Start Battery, etc.), and don't want to spend the money time at this moment... You can try the old battery and see how things go.

If you need a reliable car and cannot get afford to get stranded/delayed--Get a new battery.

-Bill

softdown · February 2020

It didn't get below 32F last night. Was a cloudy night.

The electronics seem to have shut down the battery drain at ~ 12 volts. I measured 12 volts when I started charging. "Charger says battery started at "25 %" charged. Slightly less than 12 volts." Edit: I measured 12.2 volts after ~ two minutes of charging. So 11.9 or 12 volts prior to charging is the estimate.

After charging I can put a decent battery tester on it and have a pretty good idea of its health. While asking advice on the internet often seems like a good idea - and often is - the responses have been a bit dramatic considering 12 volts for ~8 hours. Internet responses due tend to the dramatic.

I'm betting it will be fine and look forward to the test results.

My Explorer with the 2019 battery sat in a more declined state for a few months. It was obviously damaged but passes the tests as a decent battery. I'm sure it would be dead if made a few years earlier.

4 amp charger has brought it up to 12.9 volts so far. I suspect this charger will continue charging it for another 4-6 hours. Other chargers would have called it a day by now.

The Prius 12 volt is a fairly newish battery - I am told. Toyota chose to pretty well bury it in the back.

Tester: https://www.amazon.com/ANCEL-BA101-Professional-Automotive-Motorcycle/dp/B01M0ARG3X/ref=sr_1_6?keywords=ancel+battery+charger&qid=1582154409&sr=8-6

Got a feeling this whole episode is headed for comment deletion. It was pretty questionable to start with. Towing on black ice is exhausting. Exhausted takes awhile to recover from.

BB. · February 2020

I have no problem with this discussion...

If the car's systems shut down at ~12.0 volts--Probably much less damage to the battery. It being cold, and charging the next morning--All good things.

Watch the battery charger... I had a cheap 1 amp trickle charger cube I put on a truly dead battery (10.5 volts or so). And after a few hours, it overheated and split the case wide open. Still works--But not a lot of confidence in that charger.

-Bill "moderator" B.

softdown · February 2020

My feeling is that newish batteries can handle deeper and longer discharges much better than old batteries.

Healthy batteries take longer to charge and to discharge. The fact this it is charging for so long is heartening to me. Though 4 amps is not a powerful charge. Also - Prius batteries are ~33% smaller than typical V-8 batteries. Still costs a fairly similar amount. Maybe $20 less.

mike95490 · February 2020

Battery damage is cumulative. There is "damage" from chemical processes, plate shedding materials, and other damage from sulfation.. All are cumulative. At some point, 5% here, and another 5% there and there, the battery can no longer function.

It was working fine yesterday !!!

softdown · February 2020

5-15% damage is my gut feeling. Still not worth fighting at midnight in the condition I was in. May change my mind when I have to replace it. Prius batteries are notorious for all the stuff you have to tear apart to replace it.

I would imagine the ~14' run from the fuse panel to the battery may slow down charging a significant amount. Tomorrow morning may be interesting indeed. I expect things to be fine at this time...

Marc Kurth · February 2020

mike95490 said:

Battery damage is cumulative. There is "damage" from chemical processes, plate shedding materials, and other damage from sulfation.. All are cumulative. At some point, 5% here, and another 5% there and there, the battery can no longer function.

It was working fine yesterday !!!

Bingo

The honeycomb or screen style construction commonly seen in starting batteries results in more surface area as compared to thick plate deep cycle batteries. That additional surface area provides 20% to 50% more instantaneous cranking amps compared to deep cycle batteries which have thicker flat plates with less total surface area. Thicker plates are great for more deep cycles.

All else being equal, a true deep cycle battery will gradually display a declining capacity as it ages out - giving you lots of warning. A starting battery will often suffer an unexpected catastrophic failure when the thinner internal structure thins out to where it finally collapses.

softdown · February 2020

I thought a lot of the increased cranking amps simply came from a lot more plates. Like maybe 25 plates/cell as opposed to 17ish (13? at times). I forget the numbers now.

Big reason the forklift cells tend to be so robust. The plates are really, really thick on the big batteries.

Photowhit · February 2020

softdown said:

was exhausted from towing a car though black lengthy ice conditions. Unnerving really.

softdown said:

It didn't get below 32F last night. Was a cloudy night.

Odd...

softdown said:

While asking advice on the internet often seems like a good idea - and often is - the responses have been a bit dramatic considering 12 volts for ~8 hours. Internet responses due tend to the dramatic.

Preseted the evidece I preseted a possibbility, your 'ice conditions' are differet than ours.

softdown · February 2020

Yeah - nights were warmish with good cloud cover to retain the heat. Conversely it is 8F this morning.

Pretty soon I will find if the battery is OK or toast. Should have tested the voltage before charging. I wanted to see what the charger said - I like this Duracell 4 amp charger. It rated the charge at 25% - it only offers 25 and 50 and 75 and 100%. After ~ 2 minutes I disconnected it and read 12.2 volts.

EDit: Disconnected completed charge and read 13.19/13.2 volts at 8F. Or ~13.35 volts at 80F (temp compensated). Have not put the battery diagnostics on it but betting it is fine. One night at 12 volts ought not to be a huge deal at all.

softdown · February 2020

5 hours later - still reading 13 volts. Not even going to test it. Why? Swallowed some gas and not in the mood to put on seat belts, hit the brakes and start etc prior to testing. I'm sure its fine.

And don't swallow any gas. Diarrhea is not much fun. Other than that - not too much to fume about.

wellbuilt · February 2020

If your battery was newish and you ran it down it will be ok but it has lost capacity
if the battery is 4 years old it will Probably Die soon . Just my Experience

softdown · February 2020

12 volts for one night is not that bad. Everyone is acting like it went stone cold dead. Guessing Prius has a feature that shuts off drain when flashers run battery down to ~ 12 volts.

I'd have thought led flashers would be a smaller drain. Then again, Prius employs a small battery. I suspect that capacitors spend a second or two driving up the power level when starting. It always waits a second or two then boom - instant start. Doesn't crank at all. Just hesitates then starts. Prius are a bit odd. Recommend for city driving though - that is where Prius really shines.

teopap · March 2020

I use an 100AH car battery extra in my off-grid setup. Constantly discharging it down at usually 11.3V (yeah I know it's bad but it was a great deal so I don't care dying soon), staying for 4 hours at that low voltage stage every other day and then recharged to full. Kept doing this for 6 months now (so battery is 6 months old) and there's minimal loss of capacity.

softdown · March 2020

teopap said:

I use an 100AH car battery extra in my off-grid setup. Constantly discharging it down at usually 11.3V (yeah I know it's bad but it was a great deal so I don't care dying soon), staying for 4 hours at that low voltage stage every other day and then recharged to full. Kept doing this for 6 months now (so battery is 6 months old) and there's minimal loss of capacity.

My understanding is that you might expect an ~ year of longevity in this scenario.

I think people greatly exaggerated the harm in one night.

It is a new looking AC Delco AGM - likely made by Johnson Controls. Small - only offers 200 CCA. Looks like Prius calls for AGM batteries. Must be due to the proximity of fumes from the NiMH traction battery.

Turns out the Prius starter battery is very easy to access. Seen horrific exaggerations about "inaccessibility". People often don't have a clue how to rate difficulty.

Battery damage in one night of low voltage?

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