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Sealed Lead Acid Battery - Dead?


Nigel Heather
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Hi,

 

Do sealed lead acid batteries die if you leave them for an extended period so that they completely discharge?

 

The reason I ask is that I went to use my power panel yesterday and there was no sign of life.  That didn’t come as a surprise as I hadn’t used it for a long period.  So I checked the voltage (6V showing on a 12V battery), hooked it up to the trickle charger and nothing.  I tried my two more elaborate chargers but they both stop quickly, one reporting a broken connection and one that the lead polarity is incorrect.  Neither of these faults is correct but from what I have read these computer controlled chargers get confused if the voltage is too low.

 

The battery was new in summer of 2019 when it was used regularly.  But I haven’t flown ICE over the last two years because of the pandemic - I’ve done little flying and what I did was electric.

 

So the battery has been unattended for 2 years.

 

Is it likely to be dead or can it be brought back to life.  I’ve seen videos about taking the cover off to access the cells and topping up with distilled water and then paralleling it up with another 12V battery to force a charge but not sure whether that is a genuine solution.  I thought the whole point of sealed batteries were that they contained a gel rather than liquid acid so didn’t need maintaining.

 

Cheers,

 

Nigel

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4 minutes ago, Don Fry said:

No lead acid matter likes to be stored in any state but full charge. It’s dead. Sorry.


I’m pretty sure it is dead too.

 

But interestingly, it was stored with a full charge - it is connected to a glow panel though, I’d always assumed that they don’t draw any power unless you operate something like the starter, fuel pump or glow clip, but maybe there is a small continuous drain that flattens the battery over time.

 

Cheers,

 

Nigel

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6 minutes ago, Nigel Heather said:

it is connected to a glow panel though, I’d always assumed that they don’t

 

may be some small parasitic discharge going on.

 

or it might have self discharged, they lose around 5% charge per month when new, and two years of that would see it flat

 

ideally, they like to be stored quite full, so need regular charging, this is why there are lot of 'maintenance' chargers out there (for e.g. motorbikes or cars) that are left permanently plugged in and keep them topped up

Edited by Nigel R
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Yes they are designed to be kept on a low trickleor maintenance charge . They will self discharge over time. As yours still shows 6v then a parasitic charge is highly unlikely as the battery would show zero volts over that period if a discharge was present. 

You may be able to restore some capacity with a normal car battery charger using a 12 v indicator bulb in circuit. Set charge so that bulb glows but not you brightly. Leave for 24 hrs and check regularly. If the bulb dims and eventually goes out it will have revived but will never completely recover from a deep discharge. Worth a try but don't hold your breath.

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I used to know a bloke who bought and sold second hand lead acid batteries. They were ex fire brigade, used as emergency power sources. Fire brigade kept them connected to a fancy charger, but they were sold and replaced after about 4 years if memory serves. 
He initially sold them without warranty. Then, not getting returns, kept increasing the warranty, until he got to a year, and he still got no returns. 

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You might be able to resurrect it by connecting another 12v battery in parallel and then connecting one of the computerised chargers which should see a high enough voltage to start the charging process. I have done this and after a while the discharged battery voltage was high enough to disconnect the parallel battery.

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Names withheld. Location withheld. Year withheld


Custody unit charge office, big police station; present, custody sergeant, staff, and a well respected police surgeon (AKA, a local GP with extra training). 
 

comes the cry, “sarg, drunk in cell 1 is dead”,

 

General charge towards cell 1.

 

Police Surgeon examines body. “Sorry Sarg, he’s dead”

 

Sergeant swears mightily, with visions of a future writing long reports on short bits of paper, and kicks the corpse, who wakes up. 
 

A true story.
 

Btw, I was not that sergeant.
 

Off post, sorry, but Lazarus can walk again. Not often.

 

 

 

 

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Update.

 

I couldn’t get either of my intelligent chargers to even start and I have decided to switch to a LiPo battery nut for the hell of it I decided to experiment.

 

I created a low current 14.2V fixed voltage supply with an LM317 regulator and I have left it hooked up to the battery for over three days.  The voltage has crept up very slowly and now it is sat at over 12V.  Next will be to see whether it has capacity as well as voltage so will try connecting a load to it tomorrow to see how it responds.

 

Cheers,

 

Nigel

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I agree that the so called intelligent chargers are useless if a battery has gone a bit to flat ; whereas a constant current charger will often wake up a tired battery. Once damaged though the capacity never really recovers to original level. Gel or AGM seem to suffer far more than wet/ flooded type.

I know it's off topic but Re the wet lead acid pictured above opened up. Do you realise it's now an offence to remove the sulfuric acid from the battery? Tip it down a drain and dilute is as far as I'm aware is ok but remove it to use for anything else like anodising for example and is an offence . I think it comes under the explosives act ?

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   The battery pictured above blew up when on charge,[ not used for some time and gone very flat ] not much fun when you are just a few feet away. lucky I was facing away and my wet weather gear took the worst of the splatter.

Edited by J D 8
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1 hour ago, Engine Doctor said:

 

I know it's off topic but Re the wet lead acid pictured above opened up. Do you realise it's now an offence to remove the sulfuric acid from the battery? Tip it down a drain and dilute is as far as I'm aware is ok but remove it to use for anything else like anodising for example and is an offence . I think it comes under the explosives act ?

Only if you are unlicensed & wish to buy, receive or supply sulfuric acid that has a concentration level is above 15% W/W.

BTW a knackered battery will usually have a lower than normal concentration of acid if the electrolyte level is about normal. 

 

Edited by PatMc
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47 minutes ago, J D 8 said:

   The battery pictured above blew up when on charge,[ not used for some time and gone very flat ] not much fun when you are just a few feet away. lucky I was facing away and my wet weather gear took the worst of the splatter.

That's type of damage is usually caused by overcharging resulting in a "gassing" - an explosive mix of hydrogen & oxygen being produced. Fast charging a lead acid battery is risky.

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36 minutes ago, Nigel Heather said:

Update. Checked today, the battery voltage showing 13.5V.  Connected up to the power panel and tried the starter.  It turned fine but there is no torque to speak of.

 

So definitely dead.

 

Cheers,

 

Nigel

This sounds like a classic problem when a battery has been standing unused for an extended period.

Quote from my college notes circa 1962 AD :  The lead sulphate on the plates tend to become hard & form a white incrustation. This white sulphate has a relatively high resistance & reduces the porosity of the plates. This causes the electrolyte (acid) to be unable to penetrate as deeply as normal into the active material of the plates thereby reducing the capacity of the affected cells. The off load voltage will give a normal reading.     

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