How to use bad lead batteries

[slomobile]

What is the best way to charge and use bad lead acid batteries so that they are useful for something as long as possible?

Lots of us have old batteries that are no longer good enough for our primary chair, but might serve ok for a backup chair, pathway lighting, emergency backup power, hoist batteries, 2nd vehicle battery, water pump, whatever. The use case boils down to discharge duration @ current draw.

They may be gel, AGM, SLA (maintenance free), even flooded vented batteries requiring added water. Battery type and original nominal capacity (Ah).

They might have died from deep discharge, overcharge, frequent short cycles, long time between charges unused, overheat, freeze. Cause of death.

There are a few different reasons batteries go bad, shorted cells, sulphated cells, low electrolyte. Condition of death.

Assuming we have a good hobby charger and can customize a profile for a particular battery, what are some best practices for extending the useful life of "bad" batteries?

For example, if we suspect a battery has one or more shorted cells because it's voltage is down an exact multiple of single cell voltage, can we set our hobby charger to lead profile of fewer cells to power lower voltage devices.

Desulphating charge profile. Is it complete BS, or are there specific combination of conditions where it sometimes helps? Conditions where it never helps?

If a battery is already sulphated, is it better to push a lot of amps into it fast, or trickle charge for a long time? What kind of load can draw the most energy from a sulphated battery? Low discharge current over a long time? Or high discharge over a short time?

Is there anything we can learn about a bad battery by comparing its original nominal Ah to its present Ah measured by a hobby charger?

Do specific causes of battery death lead to specific conditions of death?

[Burgerman]

Desulphating charge profile. Is it complete BS, or are there specific combination of conditions where it sometimes helps? Conditions where it never helps?

When a battery is discharged, the electrolyte gradually turns to a weaker more water solutution as the sulfuric acid is turned into lead sulfate that coats the plates. The plates are not flat lumps of lead but a grid, that has super fine ground up lead mixed with some electrolyte"pasted" into the grids. Much like buttering your toast... This lead sulphate is returned to the electrolyte when the battery is recharged. This is why its imperative that the battery is FULLY recharged. And that takes at least 16 hours to 99.99% sort of level. This does not tend to happen as most chargers stop too soon. The remaining lead sulfate that coats the plates and also every lead paste partical inside the grids, turns from a ultra fine light grey coating that conducts electricity, into a white larger crystal NON conducting permanant sulfate. Yes everything conducts at some level, but the conduction is so low that it is not possible to reverse the situation.
Crystals that form permanant sulfation happen faster when:
-WARM. Store batteries in cool places!
-WHEN DISCHARGE LEVEL IS HIGH. Recharge as soon as practicable.
-CHARGE TIME TOO SHORT. You need at least 8 to 12 hours CV at the correct voltage. Depending on charge algo, battery type, discharge depth, how long it has been discharged.

So provided your charge profile is correct and includes a float stage, thats is exactly what it is designed to do. Return the sulfates back to the electrolyte. And after say 1 week on float charge theres really nothing more that can be achieved.

A "special" profile to remove sulfation is what a correct charge profile should be doing already. But sadly most chargers DO NOT do this properly.

So a neglected battery that has a level of build up that you want to attempt to recover that is still removable sulfation, and not permanant sulfation can be partly recovered or improved for a few months, by discharging the battery slowly down to its fully discharged state. Of 10.5V. Then using a low current, a CONSTANT CURRENT charge, of around 0.5A for a 50Ah battery, for as long as it takes to reach 150% of its rated capacity. So in this case 150 hours. The voltage should be monitored, and stopped if the voltage exceeds 16V.

If a battery is already sulphated, is it better to push a lot of amps into it fast, or trickle charge for a long time? What kind of load can draw the most energy from a sulphated battery? Low discharge current over a long time? Or high discharge over a short time?

Above. Load? Sulfated batteries, older batteries, and discharged batteries all have weaker acid/water electrolyte. They cant do high currents, and when you try peukert values are much higher than when healthy and new. So only low currents.

Is there anything we can learn about a bad battery by comparing its original nominal Ah to its present Ah measured by a hobby charger?

Yes. You can learn the new lower capacity. And sumarise that its really only fit for the bin is its down to 80 (to 90)% of original capacity. Depending on your needs. They are ok if you have a lot of them to connect in parallel or series parallel for storing power from solar etc. As long as you do not have a bad cell anywhere. Terminal voltage bust be pretty similar across all batts used, and self discharge rates must all be similar and low. Or they are no good even for solar storage.

Do specific causes of battery death lead to specific conditions of death?

???

[slomobile]

Crystals that form permanant sulfation happen faster when:
-WARM. Store batteries in cool places!
-WHEN DISCHARGE LEVEL IS HIGH. Recharge as soon as practicable.
-CHARGE TIME TOO SHORT. You need at least 8 to 12 hours CV at the correct voltage

Off the topic, but this suggests that after we do long hot chair journeys and load the chair into hot vehicles, we can help our batts live longer by turning on air conditioning and using a dumb high current single stage constant voltage charger to reconstitute the sulfuric acid enroute. An alternator in other words, using your Anderson connector technique to parallel the 2 chair batteries. Assuming the ride home is always less than 8 hours and we finish by plugging into a proper charger at home overnight.
What happens if our alternator voltage is too high or too low to suit the batteries in our chairs?

[slomobile]

Do specific causes of battery death lead to specific conditions of death?

That means, among all the bad things that we do which kill our batteries (causes of death) what are the associated failure modes(conditions of death?
Like after a hot, high mileage day in the chair we leave the chair in the vehicle and go straight to bed without charging it. That apparently leads to permanent loss of capacity through permanent crystal sulfation.

Shorted cells are likely from parts of plates breaking off and dropping to the bottom of case during high vibration or jolts when the battery is deeply discharged. Plates composed of more lead sulphate than pure lead are weaker. Therefore, whenever possible, transport batteries in a fully charged state.

[Burgerman]

Shorted cells come from plate distortion and expansion. Parts cannot break off and drop to the bottom in gel batteries because - gel prevents it. And AGM are packed together tightly like a capacitor or lithium battery. So same thing. Nohing can really fall to the bottom. This only happens in wet batteries.

What happens is that the cells try to grow because the sulfate crystals take more space. Pushing the lead pasted active materials out from the grids. They "expand". Then they grow through the seperators (the AGM mat seperators) as thin dendrites. This is caused by sulfates. But batteries age in many different ways. Including unwanted reaction from metals that are not lead (not pure enough lead is used as its cheaper ££ and why ODYSSEY survives deep discharges with strong acid and have very very pure lead and low impedance). Impurities are sometimes added for strength (Zinc, tin, copper, calcium, etc) so the grids can be made thinner so more can be fitted. These "other" metals also cause secondary unwanted chemical reactions but allow more capacity v less cycle life or higher impedance. These too can build some weird reactions producing growth that bend the plates when sulfates and other reactions build up and breakup of plates.

Overcharging (say too high long term float or too high charge voltage), causes grid corrosion on the positive plate, also causing distortion and unwanted reactions/dendrites/cells to short out etc. Theres many failures happening at once, not only sulfation.

A battery with a so called "shorted" cell may just be one that has a higher self discharge rate, or a high internal resistance or both. It reads as a lower voltage on a battery total but isnt really "shorted" to the extent that the battery could be realistically used. It remains high impedance and cannot be charged. They are junk when this happens. Total battery impedance is usually very high. With a load, the "shorted cell" boils/bubbles and voltage drops very low.

If a sealed (valve regulated) battery is overcharged, or sulfated then it gasses more than the "recombination" capability can handle. This results in electrolyte loss of water. And so it may be that an AGM battery can be topped up (drill and syringe) and be at least partly recovered. Gel, does the same but the gel shrinks and cracks so is not usually recoverable this way.

[ex-Gooserider]

What is the best way to charge and use bad lead acid batteries so that they are useful for something as long as possible?

<SNIP>

1. Find a movable object that you wish to not move (at least not as much / fast) (i.e. boats, dogs, etc.)

2, Attach rope between bad battery and object....



ex-Gooserider