How Battery Chargers Kill Older Lead Acid Battery Packs

[4LivesPerGallon]

This information comes from a battery guy in our group who has been on TV and magazines for his 'impossible' battery innovations.
https://www.flickr.com/photos/10670363@N05/2612151162

When lead acid batteries (Gel, AGM, or flooded) get older, their capacity diminishes. Measuring remaining capacity (Amp Hours) is a complicated and difficult process. We own several, costing from US $125 to $450 each, and each one either specialized for a type of lead acid battery, or requiring a selection for battery type. All are computerized, and all are easily destroyed by reverse polarity, so we don't lend them out.
http://www.midtronics.com/shop/prod...idtronics-pbt-200-professional-battery-tester

Lead acid batteries are destroyed by fast charging, unless it is a very expensive type that requires a high charge rate. To our knowledge, only the very expesive Hawker Genesis has the lead purity for high charge rates, i.e. minimum 4C. We had one experiment scooter with the Hawkers (Cdn $600 for 48V, 16AH) and it worked very well, full charge in 35 minutes, and could sustain high discharge continuously, without "running out of breath" unlike other Sealed Lead Acid batteries.
http://www.evalbum.com/4413


HERE IS THE PROBLEM: As capacity diminishes, the charger should reduce its charge rate also. Unless you have Hawkers, the charge rate should be no more than 1C rate. Illustration of the problem: On a 48V pack, if the remaining capacity is only 12AH, a 4amp charger will charge at a 3C rate.

Years ago, we charged a high-discharge rate (not cheap, but not Hawkers) 24V Ego scooter pack, tested remaining capacity 25AH at 15AH. Yes, it worked, but after about 30 full and partial charge cycles, the battery started to "run out of breath", and needed 20 minute rest periods.

ALSO, lead acid battery chargers should have selection buttons for Gel, AGM, or Flooded type of battery.

In summary, with batteries, nothing is simple, even with lead acid.

There are some retired BC fishermen who know how to keep flooded lead-acid batteries running for 20+ years. They did not share their secret to us, unfortunately.

There are some Chinese devices that claim to "desulfate" lead acid batteries. Motorino in Vancouver sold one that is easy to attach, inline.
http://www.motorino.ca/motorino-XPseries-owners-manual-01.pdf

We also have a "smart" Chinese battery charger that uses "reverse voltage"(?). Came from ebay, no English at all, no instructions, but seems to prolong battery life. Only 2 sets of AGM batteries used up on a 2008 Motorino scooter, which was also connected to the Motorino desulfator.

LOOKS LIKE THIS ONE, BUT 48V, NOT 36V:
http://www.aliexpress.com/store/pro...battery-charger-of-NPT/810452_1788851241.html

UPDATE: Here is another Chinese supplier, with all voltages. Note that this battery charger takes longer to complete charging.
http://www.ecvv.com/company/ultipower/products.html

 

[Nobuo]

Thanks for the interesting info!

HERE IS THE PROBLEM: As capacity diminishes, the charger should reduce its charge rate also. Unless you have Hawkers, the charge rate should be no more than 1C rate. Illustration of the problem: On a 48V pack, if the remaining capacity is only 12AH, a 4amp charger will charge at a 3C rate.

I think in that case the rating is indeed 0.33C. 3 hours at 4A to charge 12Ah.

I'm agree with that idea. Chargers nowadays should always do the longest charge possible, in any chemistry, that doesn't bother your common use. I use to recommend in lithium-ion chemistry between 4h - 5h for a real healthy charge rating.

There are some Chinese devices that claim to "desulfate" lead acid batteries. Motorino in Vancouver sold one that is easy to attach, inline.
http://www.motorino.ca/motorino-XPs...as also connected to the Motorino desulfator.

Reverse voltage it really harm a SLA battery. Maybe it means reverse sulfation.

Appart from other deterioration conditions (Corrosion, water loss, short, sheeding, Dry-out, Acid Stratification), the case of sulfation has the only reliable solution of overcharge.

If the sulfation is reversible (crystals still capable of dissolve) the process is to 24h of overcharge to the battery after it is fully charged, between 2.50V and 2.66V overcharge per cell (16V on a 12V battery). During the process the battery must reach around 60º centigrades in order to help crystals to dissolve. After this process (harming for a healthy battery) the battery will recover a huge percent of the looses it has accumulated everytime it were not fully charged.

On the other hand, if the battery were below 20% during a month or more, not a restoration is possible, the battery is officially dead :|

 

[4LivesPerGallon]

You wrote, and I emphasize: "After this process (harming for a healthy battery)"

In other words, the desulfation process should not be used frequently, or not used, at all, on any healthy battery.


We just rechecked the "reverse voltage" Chinese charger. It was outputting over 58V (on a 48V pack) for hours. The pack was fairly depeleted, down to 12.1 volts per battery. After six hours, we unplugged it, as it was going on too long. The ending battery voltage was 54.4, or over 13.6 per battery. That's too hard on a good battery.

Based on the last results, I do not recommend this battery charger, for regular use:
http://www.ecvv.com/company/ultipower/products.html

 

[dogman dan]

Looks like some "dogman dan math" happened there.

FWIW, for a sulphated up lead battery, .33c charge could easily still be too fast for it's own good.

But for a fresh 12 ah sla, I would never recommend a charger more than 2 amps myself. Slower the charge, the mo bettah, for lead brah.

Faster charging of lithium is one of the reasons that lead is dead, for EV's.

 

[spinningmagnets]

The off-grid guys still use flooded lead acid, giant ones. They occasionally do an "overcharge" enough to get the liquid bubbling with hydrogen and oxygen (no smoking please). This re-invigorates the liquid electrolyte (sulfuric acid and water). Because sulfuric acid loses some of its hydrogens and oxygens over time from the constant separation and re-uptake of sulfates (Sulfuric acid = H2SO4). This overcharge electrolyzes some of the water into H2/O2, so the cells must be topped off with fresh pure water before and after. SLA has a gel electrolyte, so you can't help it with an overcharge.

Without enough hydrogen and oxygen to complete the chemical reaction, some of the sulfur gets left behind on the plates (lead oxide plates + lead DI-oxide plates). Less plate area = less range and peak amps when fully charged.

There are two reasons for reduced capacity in a FLA, sulphates have built up on the plates and reduced the amount of surface area exposed to the electrolyte for potential chemical reaction, and...

Plate erosion. charging and discharging a FLA/SLA will dissolve a little bit of the plates (deep-cycle batteries have plates at thick as your little finger, while car starter batteries have very thin plates to pack as much plate surface area as possible into a fittable package). Near then end of the batteries life, the plates will get so thin that holes begin to appear. Motorcycle starter batteries often have clear sides, and the dissolved plate residue can be seen to build up in the bottom. A vehicle starter battery has the plates sized to allow a small space at the bottom of the case for the lead residue to build up without shorting the plates.

For FLA/SLA, charge it up frequently, and charge it to full (two shallow charges are much better for long life, than one deep charge). Low charge rate is helpful, and heat is bad. Also freezing is bad.

If you use more than half of the FLA/SLA batteries between charges, then...in the long run, you would be better served by a pack of Lithium.

 

[4LivesPerGallon]

Hey, SpinningMagnets, I agree with you.

Let me add, re: "dissolved plate residue can be seen to build up in the bottom"

That residue causes "high self-discharge". This is why lead-acid batteries, in a multi-battery pack, go out of balance.

To check for "high self-discharge", check the battery 24 hours after a recharge, and again, 48 hours after a recharge. These will need to be removed from an EV pack.


A small point about "SLA" definition: SLA includes: AGM and gel batteries.

Do not do the "boil off" methods on these.

 

[neptronix]

Yup. IR for all batteries i've seen goes up with age. IR gets crazy exponentially high if you have a battery that is overdischarged.
Too bad these chargers don't account for that, huh?

I have brought a few car batteries back to life from 3 and 6v using an iCharger 1010b+. 0.1 amps is too much for them at that point :lol: You have to baby them until you see 10 volts and it will take hours to get there, but some can be saved.